Installing a Dyna III on a Le Mans 3 - Timing question

[MikeLemon]

Morning everyone, I am installing a Dyna 3 on my lemon, and I've run into a problem with the timing.  The instructions tell you to set the right cylinder to the first timing line before the "D" TDC line, that being the 8 degree line.  Make sure the test light attached to the coil secondary comes on at that point, and then do the same for the left "S" side.  So far so good.

The instructions then go on to say " to be sure that full advance is being obtained, rotate the engine backwards and forwards again until the advance top mark aligns with the case index mark. Rotate the Dyna rotor clockwise against the advance spring. The light should come on just as the limit of travel is reached. If not, rotate the housing slightly counter-clockwise and recheck." 

The effect of getting alignment at full advance has retarded the normal spark point set earlier very nearly back to the TDC line, which is nowhere near the 8 degrees initially set.  The advance/retard unit seems to be working over a range of 34 degrees of crank rotation, rather than the 26 degrees I would expect. The bike won't start with the ignition this retarded.

I've checked the flywheel markings with a degree wheel, and they are spot on.  I've stripped, cleaned and lubed the a/r unit, and checked the springs, which are good.  The Dyna plate is in new condition, and is working.

In Guzziology the section on timing big twins states "the service manuals and owners handbooks all refer only to the full advance mark for dynamic timing. All too often the static mark has been erroneously assumed to be an idle speed mark."

 The distributor is the original Marelli type, and is in good condition.

My questions are whether I've misunderstood the process or whether I'm doing something wrong.  Should the a/r vary by 34 degrees between no advance/full advance?  I've also seen in differing sources variance between RPM at which full advance should occurr, from 3,500 to 6,200 depending on source, what should it be for a lemon 3?

My expectation before I started was that I would set to 8 degrees, then dynamically check it, adjusting it only a degree or so to acheive full advance above 3.5k.  This seems to be well outside that expectation, with the bike either not starting due to retarded ignition when using the full advance mark, or not making full advance at the right rpm if using the first static mark.

Help!

[Chuck in Indiana]

What happens when you set to the full advance mark at 4500 rpm using a timing light on the right cylinder? That is when the "hi performance" distributor is at full advance.

[MikeLemon]

What happens when you set to the full advance mark at 4500 rpm using a timing light on the right cylinder? That is when the "hi performance" distributor is at full advance.

I set the upper mark with the timing gun at 4.5k  That allows the bike to start fine and rev smoothly to 4.5k, hitting the mark on both cylinders. This has minimal effect on the static setting, which is steady at 8degrees at 1.2k rpm. Opening the throttle wider at 4.5k, however, is increasing the advance well past the mark at 5k, the timing light starts to jump erratically, and it starts misfiring.  I gave up at that point as it was getting a bit noisy! In other words, the advance/retard is not at full stretch at 4.5k, it still has some way to go.

I have made the assumption that the springs on the bike are original, correct and in good condition, based on observation.  I'm now thinking that may not be the case, although I'm still unclear as to why the amount of advance available on the a/r unit  itself appears to be greater than 26 degrees (34-8).  As I said earlier, when checked statically, setting maximum advance of the unit at the upper timing mark makes it well out at the lower.

[guzzisteve]

To start the install I take plugs out w/caps on them grounded to head, then use the starter to spin it. Then it's not hot stuff in case you touch something. I then set a hammer or whatever balanced on end with a level to the mark on the case hole, this way you are looking level strait in the hole every time. You just look across the top of handle and line up the case line to flywheel mark. I'm anal about having my eye in the exact place every time. Set your dizzy up for static 8* on each cyl. spinning it w/starter. Then I replace plugs, Start motor and check it at 6000rpm at the full max mark on ea cyl & adj sensors & air gap to get it dead nuts. You must be sure the screw on dizzy shaft has oil on it, under it and does not tighten up during the process.

[MikeLemon]

To start the install I take plugs out w/caps on them grounded to head, then use the starter to spin it. Then it's not hot stuff in case you touch something. I then set a hammer or whatever balanced on end with a level to the mark on the case hole, this way you are looking level strait in the hole every time. You just look across the top of handle and line up the case line to flywheel mark. I'm anal about having my eye in the exact place every time. Set your dizzy up for static 8* on each cyl. spinning it w/starter. Then I replace plugs, Start motor and check it at 6000rpm at the full max mark on ea cyl & adj sensors & air gap to get it dead nuts. You must be sure the screw on dizzy shaft has oil on it, under it and does not tighten up during the process.

The problem is that when set statically at 8 degrees, revving the engine to 4.5k aligns the full advance mark, and THEN throttling up further increases advance past the full advance mark, and into misfire territory.  It won't rev to 6k, as it has already  exceeded the permissible amount of advance at about 5k.  I can't set it statically to much less than 8 degrees, cos the engine won't start. Somethings wrong, but I'm not sure what. 

[guzzisteve]

Leave your dizzy loosened up and move it while revving, you should find the spot where it goes.  Did the jetting in carbs do OK w/points?
 Be sure the dizzy cam rotor is in the correct place and snugged up tight plus doesn't touch the sensors. THIS could be the issue, maybe.

edit: The reason I do 6K rpm is that the supplement for LM3 is a continuation of the G5/SP manual and that ign graph shows advance levels off at 3K dizzy speed. I can't find any flyweight part #'s and that cut would be where they stop at.

[MikeLemon]

Regarding your edit, I had a look at the g5 manual, and interestingly the g5 advance starting at 2 degrees and going up to 33 degrees sounds very, very similar to what my dizzy would do if I statically set it to the high timing mark and maximum advance on the unit, then released the a/r back to minimum advance. This drops the spark point back to about 2 degrees above TDC. Is the lm3 dizzy the same as the g5, I wonder?  If so, how does it cope with the 8 to 34 degree sweep?

I'll play some more tomorrow and report back.


Edit: I notice that the g5 a/r springs are different to the lm3 springs according to gutsibits.

[guzzisteve]

Yes, dizzy is different part #, springs are also different. Springs would adjust the rate the weights open but not where they open to or begin at. That is set from the shape & cut of the weight itself. If you look at the weights you will notice a piece molded on to it on the inside (were it will stop at w/closed at static). I suspect there are different sizes. Carefull they will break off too, ask me how I know.

[rodekyll]

If it continues to advance past the max advance mark then it wasn't fully advanced at that point. If you can't get the full advance at your 37º or whatever the proper value is, it's because the weights won't throw out at that rpm.  That means there's too much drag on the weights, too much spring, something gluey on the shaft, too long a screw through the points plate causing contact below, etc, etc.  Find the bind and clear that out.  The top half of the distributor shaft should have a snappy, spring loaded relationship to the bottom half.  If you can't wind it up about 30º and release it like a watch spring, it's not right.  Any gummy or sticky feeling is wrong.  There should be two springs of uneven properties.  The bobweights should swing freely and the springs should act asymmetrically.


Once you can achieve absolute max advance at the rpm you want then worry about where the idle is.  I suspect it will be in the ballpark.  Remember -- "static" advance means the timing with the bobweights completely slack.  This is set with the engine not running or running very slowly, so as to not throw the weights.  You will almost always have a degree or two different than your idle advance.

The jumping around could be slop in the timing chain, worn dizzy drive gears, cam end float, gummy dizzy shaft halves, crap on the pickups, bad grounds, or any combination.  Unless it's extreme, it's not part of the problem.  One thing that would really help here is a timing light with an advance feature.  You can dial it in and watch the advance/rpm on the back of the timing light.  Your local auto parts store might have one for borrow or rent.  They are often in pawn shops for reasonable money, too.


That's all I've got in addition to the good advice already offered.

[g5guzzi]

to set the timing on my g5 i remove the screw in the centre of the dizzy
and replace it with a longer screw and a thick large diameter washer then
manually turn the advance and retard to full advance and tighten the screw
to hold it at full advance. set the timing to the full advance marks remove the screw
and then check with a strobe. i use a pair of pliers with 90 degree ends to turn
and hold the advance while tightening the screw
Malc

[MikeLemon]

I think that I'm getting it now. The speed of rotation should determine how quickly full advance on the unit is achieved, and I'm confusing that with a physical measurement. I've already stripped, cleaned and lubed the a/r unit, I'll replace the springs to see if that makes a difference as it still seems a bit stiff.  When i twist the rotor with my fingers, i can only advance half way, although it does twist all the way and spring back ok with a screwdriver in the slot.  Without the springs it moves very easily.

Sod's law being what it is, the heavens have opened today, so no riding anyway :(

What i really need is a fresh from the factory lm3 so i have something to compare my 40 year old mystery machine with. Thanks to everyone who has replied. I love this board!

[chuck peterson]

I wonder if you have the T-T3-G5-Vert springs instead of the hi performance LeMan IV-V springs?...Guzziology has a good section on this with dimensions to measure wire thickness and length to what you have and compare part numbers

[jacksonracingcomau]

imho it’s the miss you should be chasing , the 34 btdc figure is not an absolute but safe on reccomended fuel at time. some fuels can take more some will pink and need less,  but miss is something else.
possible just cleaning all will fix, then get 34 max even if it had t3 unit would still be 3 static, no worries to start at that.
if it actually has more throw than needed a thin tube will restrict initial therefore giving less throw. we do this for twin plugs.
but why fit ei and keep mech advance?
plenty of ei kits that give adjustable electronic advance
me i keep points, lube wick and adv unit, no worries

[jacksonracingcomau]

Morning everyone,

In Guzziology the section on timing big twins states "the service manuals and owners handbooks all refer only to the full advance mark for dynamic timing. All too often the static mark has been erroneously assumed to be an idle speed mark

Help!

very odd statement
my factory manual below
perhaps us got different?
if you run high idle turn it down for test

[MikeLemon]

The full quote from Guzziology

/I would like to reiterate an important point: on all Motoplat and point-ignition big twins except the V7 Sport, 750 S, 850-T, 1000S, big-valve California III, and LeMans I–V, the advance mechanism has already started to advance the timing at an engine speed below idle. For these bikes, and really all big twins, full advance is the most accurate timing reference.

 The service manuals and owner’s handbooks all refer to only the full-advance mark for dynamic timing. All too often the static mark has been erroneously assumed to be an idle-speed mark. /

I guess it's meant to refer to the engines statically timed to 2 degrees, not the 8 degree engines

[MikeLemon]

imho it’s the miss you should be chasing , the 34 btdc figure is not an absolute but safe on reccomended fuel at time. some fuels can take more some will pink and need less,  but miss is something else.
possible just cleaning all will fix, then get 34 max even if it had t3 unit would still be 3 static, no worries to start at that.
if it actually has more throw than needed a thin tube will restrict initial therefore giving less throw. we do this for twin plugs.
but why fit ei and keep mech advance?
plenty of ei kits that give adjustable electronic advance
me i keep points, lube wick and adv unit, no worries

I think the misfire was because it was advancing about 6 degrees past the top timing mark, so it was quite a way out.  I've spent the day measuring and photographing the reluctor to establish the actual throw, and it seems to be operating over an angle of 16-17 degrees from nothing to full advance on the rotor, which makes it about 33 degrees crank.  The throw is supposed to be only 13 degrees rotor and  26 degrees on the crank.

I can't see any obvious wear on the unit, and in theory the engine has only done about 18k miles so I'm still a bit confused.  I really need to restrict the throw back to 26 so that no advance starts at 8 degrees and climbs to full at 34 degrees. 

I'm using a dyna 3, which relies on the existing advance/retard, if I knew then what I know now, I'd probably have gone for one of the alternator based ignitions.

[jacksonracingcomau]

take complete unit off motor, hold drive gear in vice soft jaws degree wheel or protractor to measure throw , takes out backlash
as above throw can be limited with thin tube

but just maybe pin holding drive gear is about to break , does happen, replace with roll pin
1/8” from memory.

[MikeLemon]

My replacement springs arrived today. They are the black ones on the right. Everything suddenly makes sense..... 😀


(Good call, Chuck!)

[guzzisteve]

Looks like you may have found the problem, maybe. Good luck w/it.
I have a set of brand new springs in a bag. The same as what's in my LM3. They were for the Cali2, but it runs so good w/o them pulling the sidecar. I decided not to swap them, instead I put on 32mm carbs and a V700 flywheel.

[MikeLemon]

Just to round this off, I took her out for a long ride this morning before the rain, and everything was just as it should be.  No more misfires or farty pops, and  nice strong acceleration throughout the range. 

I've been unable to identify where the springs come from, as they aren't any of the ones listed in Guzziology.  I have no clue as to when or why they were fitted, and, as the previous owner is long dead, not much chance of ever finding out.

The useful lesson I take from this is that just because something looks right, and seems to be working, doesn't mean squat!

[chuck peterson]

Dinging dinging dinging! Like a broken clock I'm right twice a day...same thing happened to me in the opposite direction....w hi perf springs in a low perf bike

Same distributor and weights, both timed to full advance, but springs are the only difference

Ordering by model name may not get you the right ones. The specs Guzziology has and a measure will tell you which you have...

New bike, eh?............

[MikeLemon]

Dinging dinging dinging! Like a broken clock I'm right twice a day...same thing happened to me in the opposite direction....w hi perf springs in a low perf bike

Ordering by model name may not get you the right ones. The specs Guzziology has and a measure will tell you which you have...

New bike, eh?

Problem is that they don't match the specs of any of the Guzziology table, either in number of coils, or in length.  They are more like the lo perf, but the one with the long eye is a way off anything listed. 

I've had the bike a while, and over time I've chased this problem through the carbs,  the coils, the points and lastly the Dyna 3.  Please God, let it be over!  

[guzzisteve]

Could have been like that from factory. What do they do when the box of parts is empty and there aren't any more, wait? No, they grab something else.

[jacksonracingcomau]

Yes, dizzy is different part #, springs are also different. Springs would adjust the rate the weights open but not where they open to or begin at. That is set from the shape & cut of the weight itself. If you look at the weights you will notice a piece molded on to it on the inside (were it will stop at w/closed at static). I suspect there are different sizes. Carefull they will break off too, ask me how I know.