Wildguzzi.com
General Category => General Discussion => Topic started by: simj26 on December 11, 2014, 10:53:37 AM
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Hi there. I'm having a bit of a problem with an ol' guzzi. It's a '92 V75 ex Italian police bike acquired as a non runner that'd been stood for a while. The problem is that it will only run on the left cylinder. I've done all the usual stuff...cleaned and set up the carbs, swapped all the ignition components over to the non running side (no improvement) even swapped the carbs over (no improvement). Removed the head on the non running cylinder to check the valves...they weren't too bad (re ground them anyway) piston n bores are good and compression is good. The one big thing is that the valve timing seems to be out. runs fine on the left cylinder but just backfires on the right. There does seem to be some back pressure through the inlet port at one point during the cycle....which does give the impression the valve timing is out.......but the left cylinder is fine?
Anyone have any ideas as to the problem......I can't see how you can have the valve timing out on one side but not the other when there's only a single cam? I haven't opened the front casing to check the cam chain or guide yet.
Any help would be much appreciated. ???
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Could be a bent pushrod , or maybe a flat cam lobe . Yes , a bit of a puzzler .
Dusty
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Checked the pushrods...they're fine. Would one cam lobe deteriorate that badly...on one side only? Must admit,this one is baffling me! ???
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Checked the pushrods...they're fine. Would one cam lobe deteriorate that badly...on one side only? Must admit,this one is baffling me! ???
Sure can, although it is extremely rare on a Guzzi.. it's certainly easy enough to check, just turn it through and watch the valve movement. Report back.
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Checked the pushrods...they're fine. Would one cam lobe deteriorate that badly...on one side only? Must admit,this one is baffling me! ???
Yes , baffling . If the valve timing is off on just one side , and the rocker arms and push rods are alright , would indicate a bad cam . Can you verify that the lift is correct on the bad side ?
Dusty
Edit . OK Chuckie beat me to it , Anyway , yes , what he said .
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Thing is, if a cam lobe is worn it would reduce valve lift wouldn't it? Considering that there is back pressure through the inlet port to the carb on part of the sequence...would indicate that the valve is opening longer or at the wrong time? ???
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Are any Guzzi cams made up of any thing other than a single unit..ie, a two part cam that's joined in the middle?
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Thing is, if a cam lobe is worn it would reduce valve lift wouldn't it? Considering that there is back pressure through the inlet port to the carb on part of the sequence...would indicate that the valve is opening longer or at the wrong time? ???
That is why we suggested measuring the lift . Kinda sounds like a lobe has gone flat .
Dusty
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Surely if a lobe has gone flat the valve will open less or hardly at all? Am I missing something here? it is the lobe that pushes the pushrod that opens the valve.....right? The valve fully closed position would still be the opposite of the lobe(whether the original lobe was worn or not) on the cam?
It seems like the valve is actually open either for a longer duration than it should be or opening at the wrong time altogether......I've checked the valves and they are definitely fully closing when they do close but am getting a back blast through the carb....in fact it has actually backfired through the carb a few times If the left cylinder wasn't running ok I'd say definitely the cam timing rather than lift. ???
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OK, let's go back to the beginning . Left cylinder runs fine , right doesn't run at all . You switched carbs side to side , and ignition . Doesn't solve problem . You state the valve timing on right side seems off . Correct so far ?
We ask about pushrods , , they seemed alright , compression seems OK . Still no answer regarding the actual overall lift on the offending side , or an actual PSI compression reading . We suggest a flat cam lobe , you basically say we are wrong w/o doing any test . The overall lift might be fine , maybe the ramp on one of the lobes has gone out of shape . The valves spend very little time at maximum lift . We are talking thousandths of an inch here , hard to discern with the eye . Heck , where is the lash set ?
Dusty
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Also, low cam lift cause by a failed lobe can cause all kind of oddball effects. Suppose it's the exhaust lobe, and the valve is opening so little that there is still pressure in the cylinder when the intake valve opens, so it puffs out that direction.
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One coil with a distributor or 2 coils with two sets of points?
I'm thinking either the wrong cylinder is using the other cylinders points putting one spark 90 degrees out of wack.
Been there, done that with an old Indian.
Use a timing light to check for points opening near TDC of each cylinder in turn.
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One coil with a distributor or 2 coils with two sets of points?
I'm thinking either the wrong cylinder is using the other cylinders points putting one spark 90 degrees out of wack.
Sent from my shoe phone!
'92 model , doubt if it has points KR .
Dusty
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'92 model , doubt if it has points KR .
Dusty
I think you're right, Carl's drawing shows an electronic module of some sort with two coils, perhaps it's fritzed but it could be still crossed over. the thing to do is see if ther's a good spark on the non running side.
Roy
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I think you're right, Carl's drawing shows an electronic module of some sort with two coils, perhaps it's fritzed but it could be still crossed over. the thing to do is see if ther's a good spark on the non running side.
Roy
Yeah , and check the ignition timing also . However , I was working with what the OP gave me .
Dusty
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So.... what kind of ignition is it running?
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It's not running.
Well, only on one cylinder.
Oh, never mind me, just wanted to be involved but don't have anything new to contribute.
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So.... what kind of ignition is it running?
The "sparky" kind ;D Sorry :-[ Good question though , did the SBs run the famous digiplex in that era ?
Dusty
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I think you're right, Carl's drawing shows an electronic module of some sort with two coils, perhaps it's fritzed but it could be still crossed over. the thing to do is see if ther's a good spark on the non running side.
Roy
Yes, the first thing to do is check for a spark on the bad side. Pull the plug, ground the plug shell to the bike's frame, and crank the engine while keeping an eye on the plug for a nice blue spark.
Let us know what you find.
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Says Moto Guzzi on the electronic ignition pick up plate. Swapped all ignition wiring and tried all combinations..good spark both sides. Looks like I'll have to remove the cam next to have a look.
The right side tries to run but just backfires. Exhaust is clear, good spark,carbs good,no short on ignition wiring, fuel good (use remote fuel tank so no fuel tap issue). This bike has only 30451km (approx 19000 miles) are Guzzi cams liable to wear at that mileage? Someone on the Triumph forum suggested the timing chain tensioner is made of plastic and can break? Sorry if anyone thinks I'm being 'smart' and telling them they're wrong...I'm just trying to gather as much information as possible as I'm not familiar with Guzzi's.....I'm a Triumph man meself! ;)
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You don't have to remove the cam to see if its lobes are OK, you just need to measure how much the valves are moving as you crank the engine. When the lobes get really bad, you don't even need to measure, you can see the problem.
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Sim , yeah I apologize if I seemed snarky , was not my intention . We are really trying to help , was simply trying to apply the scientific method . It is just so easy to get "stuck" when trying to diagnose a mechanical issue . Assuming anything can be a problem .
Dusty
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I'm putting my money on (let me know where to send it) Dusty and his ignition timing question. Shouldn't you be able to pull both plugs, crank it slowly by hand and witness a spark somewhere near TDC on each cylinder?
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I'm putting my money on (let me know where to send it) Dusty and his ignition timing question. Shouldn't you be able to pull both plugs, crank it slowly by hand and witness a spark somewhere near TDC on each cylinder?
Thanks Norm , I wasn't the only one who suggested that ... was I ? ;D We aren't there yet , just in the beginning stages of solving the issue . Besides , RK , Roper , Guzzisteve and Kev m haven't weighed in yet . And where is
Orwig, lying down on the job Wayne , wake up ::) ;D Sure I missed a few , apologies .
Dusty
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Yep done that,and timing looks pretty close (thing is with the pick up plate it doesn't make sense for one side to time correctly and not the other).....need to borrow a strobe light I think (hadn't used mine for 20 odd years and now it doesn't work).
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So far I've got nothing to add to what's already been said -- run the baseline checklist + the suggestions so far and report back. I'm no expert on early 90's electronic ignition, but I've got a fair handle on the general 4-stroke theory. Maybe with more information re: compression, fuel, timing, etc I might have a thought.
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It's been a while since I studied up on small block cams, but I remember there were quite a few issues with cam and lifter wear on the Lario. I think the V75 has the same head/cam/lifters...
IIRC...the lash would get a little out of adjustment and the it would rapidly wear the lifter...the valve springs were really high tension, so the bike would rev higher without floating the valves...but the increased tension also contributed to rapid wear. I guess the fix is to go to a progressive spring, like on the newer small blocks...
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I think the process should start with a bit of systematic observation and recording.
What is the compression/leakdown?
What is the actual ignition timing, and on what stroke does it occur?
What is the fuel flow quality and how was it determined?
What is the condition of the coils/wires/plugs (have the plugs been manually checked and gapped?)
What is the valve lash and how was that determined?
What is the cam lift and how was that determined?
If we think the problem is deep-rooted and out of the ordinary and have no eyes on the bike, then these baseline levels need to be excluded.
Don't care what has been done. Or checked. You're here because none of it worked. I do care about heading to the garage and taking an hour to fill out this list with fresh data. This is how I would handle the broad strokes on anything that came into my shop, and 97% of the problems I encounter are solved by simply a fresh run at systematically stepping down the checklist. I think the problem will be obvious when the blanks are filled in. Until then, any diagnosis is speculation.
Humor me. $0.02
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Says Moto Guzzi on the electronic ignition pick up plate. Swapped all ignition wiring and tried all combinations..good spark both sides. Looks like I'll have to remove the cam next to have a look.
The right side tries to run but just backfires. Exhaust is clear, good spark,
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Thie backfiring was what made me think perhaps the ignition was crossed over, it would fire ok on one cylinder but be 90 degrees late or early on the other. it's not the sort of misstake you would normally make but may be the reason the PO gave up on it, I'm sure it's quite easy to get it mixed that's why you need to check both cylinders.
On the Indian I built up of parts with no point of reference I timed the front cylinder points correctly for the rear cylinder plug, of course the front cylinder was way off because of the uneven firing pattern. It was just a matter of swapping the wires and re-timing.
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So.... what kind of ignition is it running?
Once again Chuck makes the most pertinent query for the most probable suspect. ;-T
92 V75. I'm guessing it is a faired Strada.
Do you have a couple of modules like this, probably under the seat?
(http://image.wikifoundry.com/image/1/0uN7KSvgXrh2phzZYpZt2A138824)
If so you have the motoplat system. Quite sensitive to poor earths. Clean and check ALL connections. If that doesn't work then swap over the modules and see what happens.
You're lucky. I normally don't help Triumph people. :P
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Yep done that,and timing looks pretty close (thing is with the pick up plate it doesn't make sense for one side to time correctly and not the other).....need to borrow a strobe light I think (hadn't used mine for 20 odd years and now it doesn't work).
If it was a BMW Boxer it wouldn't matter since the cylinders fire every 360 degrees
Looking from the front
The RH (shift side) cylinder fires at TDC (lets call that zero degrees) the other cylinder (brake side) should fire 270 degrees later when that cylinder is at TDC
Now if you have the timing crossed over with the first RH cylinder firing at TDC (zero degrees) the other cylinder will fire not at 270 but late at 450 degrees (BDC with the exhaust valve opening)
I'm sure this happens with old loops all the time after an engine rebuild.
Please post a picture of the pickup plate with the running cylinder in firing position.
How is the pick up plate driven, at half speed from the camshaft?
Carl's drawing shows of the 94 V35-75 shows 4 evenly spaced lobes on a CW rotating wheel, is that what's really there?
BTW, I do realize the spark doesn't occur at TDC but just before, I'm just trying to get my idea across (not very well), I'm assuming the previous owner pulled it apart, mixed the wiring and it never ran since.
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KR , I think you may not be thinking this through . If the "wires" are crossed , neither cylinder will fire at the correct time . Crossing the wires would cause one cylinder to fire way late , and the other way early . Unless of course the timing could be so dramatically altered that one cylinder could be made to fire at the correct time , which I don't think is possible . Am I missing something here fellas , if so , the apologies all around .
Dusty
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Not so, it might be possible to move the plate enough to get one cylinder to be spot on, the other of course would be miles out, Besides it's more likely than a cam worn away to a point it will not fire.
I think the next step is to put each cylinder in firing position and see if the ignition lobe lines up with the timing sensor.
Sent from my shoe phone!
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Not so, it might be possible to move the plate enough to get one cylinder to be spot on, the other of course would be miles out, Besides it's more likely than a cam worn away to a point it will not fire.
I think the next step is to put each cylinder in firing position and see if the ignition lobe lines up with the timing sensor.
Sent from my shoe phone!
Absolutely. To the OP. There's nothing magical here. ;D You say you have compression, fuel, and spark at the right time. If so, it will run. It can't help it. ;) I know, it's easy to think, "I've done everything.." but *something* is amiss. *Probably* it's ignition timing on the cylinder that isn't running. It *could* be a lobe wiped off the cam. Check the lift at the pushrod, do what KR said, and get back to us.
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Not so, it might be possible to move the plate enough to get one cylinder to be spot on, the other of course would be miles out, Besides it's more likely than a cam worn away to a point it will not fire.
I think the next step is to put each cylinder in firing position and see if the ignition lobe lines up with the timing sensor.
Sent from my shoe phone!
Well , the OP never said the offending cylinder was not firing . From my experience it is hard to move any timing plate enough to compensate for 90 degrees of timing woogity . Maybe 20 degrees is possible . Once again , if I am missing something , apologies . Does anyone know for sure about this ignition system ?
Dusty
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Well , the OP never said the offending cylinder was not firing . From my experience it is hard to move any timing plate enough to compensate for 90 degrees of timing woogity . Maybe 20 degrees is possible . Once again , if I am missing something , apologies . Does anyone know for sure about this ignition system ?
Dusty
No, I think he said it was backfiring, this made me wonder if it was sparking with a valve open.
Remember it was bought as a non runner so who knows what the previous owner did to it.
I'm sure we will know soon.
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If it is a Motoplat, I'm clueless. I''m 99% sure that a Digiplex wouldn't do this.
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No, I think he said it was backfiring, this made me wonder if it was sparking with a valve open.
Remember it was bought as a non runner so who knows what the previous owner did to it.
I'm sure we will know soon.
Had that same thought . But he also stated it seemed as though the valve timing was a bit off . Yeah , hopefully we will get some baseline compression/leakdown readings , and some some idea of where the timing is .
Dusty
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If it is a Motoplat, I'm clueless. I''m 99% sure that a Digiplex wouldn't do this.
Does the digiplex use one trigger with two pick up points ?
Dusty
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Does the digiplex use one trigger with two pick up points ?
Dusty
It is the earliest of the computerized ignitions. Has a flywheel position sensor, and uses vacuum for advance.
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It is the earliest of the computerized ignitions. Has a flywheel position sensor, and uses vacuum for advance.
Thanks Chuckie .
Dusty
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I think we need the OP to give more details on the ignition system or at least some pictures until then we are grouping in the dark.
We know it's low milage, 19,000
The compression is good
It's backfiring through the carb
I tend to focus on electrickery as the cause of the problem because that's what I know best, I'm probably out to lunch but backfiring through the carb would occur if it sparked with the inlet valve still open, says the valves are ground in, could it be the tappets too tight?
Chuck, how does the flywheel sensor determine which coil to fire.
Would it be possile to put the flywheel in the wrong spot in relation to the crank thus throwing the sensor target out of position?
Simj26, please provide more details / pictures of the ignition system
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Hey KR , take me with you . To lunch that is ;D
Dusty
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Once again Chuck makes the most pertinent query for the most probable suspect. ;-T
92 V75. I'm guessing it is a faired Strada.
Do you have a couple of modules like this, probably under the seat?
(http://image.wikifoundry.com/image/1/0uN7KSvgXrh2phzZYpZt2A138824)
If so you have the motoplat system. Quite sensitive to poor earths. Clean and check ALL connections. If that doesn't work then swap over the modules and see what happens.
You're lucky. I normally don't help Triumph people. :P
Yeah, mines like that but the boxes are plain no ribs. Already tried swapping all of the ignition components over with no improvement (I have a good spark both sides already)
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simj --
We've asked for data and are getting none. We can't help you unless you also get involved.
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Thanks for all the replies chaps ;-T
Been away for a few days, but I'll try to have another look at it tomorrow and provide some more information then hopefully . :)
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Would it be possile to put the flywheel in the weong spot in relation to the crank thus throwing the sensor target out of position?
I would think so. It's one of the reasons I asked what kind of ignition it uses. I'm totally clueless (my normal condition) ;D about the Motoplat, though.I don't even know how it's triggered. I'll look in Guzziology for some clues. I'd still like to see some compression figures, along with assurance that it is sparking at the *right* time. Just some basic things.
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I would think so. It's one of the reasons I asked what kind of ignition it uses. I'm totally clueless (my normal condition) ;D about the Motoplat, though.I don't even know how it's triggered. I'll look in Guzziology for some clues. I'd still like to see some compression figures, along with assurance that it is sparking at the *right* time. Just some basic things.
Chuck, the 'plat runs from pick ups in the normal small block location on the front of the camshaft. Timing is set in the normal manner. All the one's I've worked on are so but being a 'Police' model they sometimes had special requirements. I need one of your shrug smilies.
The flywheel can be put on incorrectly but both sides would be affected and due to the number of crankshaft bolts it would be way too far out for both sides for it to function or fire on one side if the sensor was located there. The PO should be able to see if the timing marks and good side ignition line up.
If his modules are a later version then I'm not sure if the pick ups are set independently or are set 'teamed.'
I'll go back to my original suggestion about connections and earth points. They need to be immaculately clean. Might not be the problem but it needs to be eliminated.
The 'plat often gets a bum rap. Its not my favourite system but will often run faultlessly for years. I've been told the pick ups are analogue rather than digital senders. The modules are known to fail but like twin engined aircraft that is only logical. 2 engines means twice the probability of a failure. The good things about this system is that you can limp yourself home on one side and the advance system is incredibly smooth, unlike the mechanical system.
Rod
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We didn't get the Motoplat small block over here as far as I know. Guzziology just has a small paragraph about it. Dave mentions lining up a line on the pickup plate with a mark on the engine case at about 11 o'clock. He says the left line is for 350s and the right for 650s and 750s. Then, he says the later versons of the pickup plate won't have any marks at all. ;D In that case, just line up the pickups at about 1:00 and 7:00 to get it started, and time it with a timing light.
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Has anyone mentioned that this might be a leaky *Thrunge grommet* , or a bad *dust excluder* , OK , yeah , you're right , going to my corner now :-[
OK , so this is an Eyetalian model , what kind of ignition system does it have ? If both sides are sparking , is it even possible that only one side is in time ? OP swapped components side to side , no change , which still leads me to believe this is a valve lift or timing issue .
Dusty
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Has anyone mentioned that this might be a leaky *Thrunge grommet* , or a bad *dust excluder* , OK , yeah , you're right , going to my corner now :-[
OK , so this is an Eyetalian model , what kind of ignition system does it have ? If both sides are sparking , is it even possible that only one side is in time ? OP swapped components side to side , no change , which still leads me to believe this is a valve lift or timing issue .
Dusty
I think you've hit the grunge grommet on the head there Dusty. ;-T I stand aside to your lateral solutions! :D
Chuck, I'd bet my bottom dollar you've got some of them over there. Early carb Nevadas would be the first place I'd look. I just can't see Luigi not sending you some or changing just for the USA. small blocks after all were a big hit in Europe so the US was a small market for them on these.
There were 2 different static timings for the older small blocks. 5 and 8 degrees off the top of my head witht eh smaller ones being the lesser. Can't be bothered to look it up and I've marked my flywheels to suit.
Its a Kettering system still so any disruption to the current to the coil will generate a spark but not when you want it. This can be on the +ve or -ve side. As the power to the coils is usually in parallel and one side is working fine then this is unlikely but a dodgy connector/ion to the coil can still cause this. This does remind me to ask: Does this model have an electronic or mechanical tacho? If electronic does it wave around when misfiring? May be a case of the tail wagging the dog.
The modules control the advance on a 'plat. They do this by controlling the earth circuit from the coils which is why good connections to earth are essential.
All this aside I'm starting to run with the thrunge grommet theory. :D
I need answers to my questions as do others. I'll bow out now until we get some material feedback.
Rod
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I should have said we didn't get the the Motoplat 750 small blocks. Probably Guzziology wouldn't have said anything about them at all if we didn't get *any*. My bad. Again.. ;D
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Its a Kettering system still so any disruption to the current to the coil will generate a spark but not when you want it. This can be on the +ve or -ve side. As the power to the coils is usually in parallel and one side is working fine then this is unlikely but a dodgy connector/ion to the coil can still cause this. This does remind me to ask: Does this model have an electronic or mechanical tacho? If electronic does it wave around when misfiring? May be a case of the tail wagging the dog.
The modules control the advance on a 'plat. They do this by controlling the earth circuit from the coils which is why good connections to earth are essential.
I like this explanation, it would explain the bike going from a runner into a farting spitting machine without human input ???
I think a timing light would be useful at this stage.
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Hello again. Took me a while to sort out how to work instagram....but this is a pic of the EI pickup
http://instagram.com/simonj6160/
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Oh yeah...it's an electronic taco working off the right coil, seems steady, no flapping about,but will check that again when I've put it all back together....tried disconnecting it...made no difference.
Checked the valve lift and there's no discernible difference between left and right cylinder.
So of the two marks on the timing plate the upper one should line with the mark on the casings for the 750? I'll go back through the contacts and earths and check them again. ;-T
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Hello again. Took me a while to sort out how to work instagram....but this is a pic of the EI pickup
http://instagram.com/simonj6160/
It appears to me as though the two round pegs correspond to the spark for left and right cylinders, I suspect they are magnetic.
I assume the rotor is fixed to a mechanical spark advance, is it possible to turn the rotor against a spring in the CW direction?
It should spring back.
The two wires we can see will be connected to a coil around each peg, they should be identical in resistance to ground. It's also possible there is some electronics in each of the blue plastic lumps in which case you might not be able to measure the resistance, try swapping the meter leads.
Put each cylinder in firing position (TDC with the valves closed) and I suspect you will find the ignition rotor lines up with one or other of the pegs.
Take a photo of the rotor with left then right at TDC
I note the zero mark is slightly off the pointer on casing.
Is it possible to unbolt the rotor and move it to a different position, if so how many different positions will it fit?
Please photograph the other ignition components and if possible a sketch of how they are interconnected.
I suspect an ignition strobe would illuminate the rotor adjacent to one or the other peg, it shouldn't show firing at any other point.
Please note:
I have never seen one of these systems, I'm applying simple logic based on past experience.
I haven't entirely given up on my crossed wiring out of position rotor theory :beat_horse
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Does it have a mechanical burrito ? **C
Dusty
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Don't give up on us now ;D
P.M. sent
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Only just got back to this (bike at the back of the shed while I get on with some other stuff)
The rotor has no movement, so not a mechanical advance and there's also no vacuum advance. My understanding is that the advance is controlled by the two ignition boxes.
The thing that has struck me though is that the pick up plate and screws look an awful lot newer than the surrounding area......Recently fitted perhaps?
I'll have another bash at it as soon as I can lay my hands on a strobe......should give me an idea what's happening (or not happening ???)
Thanks for the constant input chaps :bow
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Only just got back to this (bike at the back of the shed while I get on with some other stuff)
The rotor has no movement, so not a mechanical advance and there's also no vacuum advance. My understanding is that the advance is controlled by the two ignition boxes.
The thing that has struck me though is that the pick up plate and screws look an awful lot newer than the surrounding area......Recently fitted perhaps?
I'll have another bash at it as soon as I can lay my hands on a strobe......should give me an idea what's happening (or not happening ???)
Thanks for the constant input chaps :bow
Recently fitted wrong perhaps ???
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Recently fitted wrong perhaps ???
Yeah, it's sounding like a timing issue..
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If there is no mechanical advance would the ignition pegs be located at fully advanced position and delayed at idle
or
located near TDC and advanced somehow electronically
Enquiring minds need to know ???
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The modules control the advance. I have no idea how it is done but it is as smooth as silk from idle to full advance.
I've written it before, the poor old 'plat gets a bum wrap.
May have a reputation for module failure but as there are 2 it is only logical you are twice as likely to have one fail. ;)
I'd take a 'plat over a dyna these days. Dyna 3 should be renamed 'dying in 3 days' IMO. Old ones seem to go fine, try fitting a new one. ::)
Rod