850 le mans 111 ... Won't run above idle

[Pastaboy55]

Hi all ....

Hoping to pick your collective brain power and experience
 
Bought a 1982 Moto Guzzi 850 Le Mans 111 just over 18 months ago.
It had been parked up for 5 years at least prior to me buying it.

With some new fuel and battery it would start and idle, but run terribly on anything over 1/4 throttle misfiring, backfiring and no power.

To date I have replaced all of the following trying to resolve the running issue.

1.  The condensers,
2.  The Coils
3.  The wiring to the coils,
4.  The points,
5.  Spark plugs
6.  High tension leads
7.  Advance springs under the distributor
8.  Checked valve clearances
9.  Checked ignition timing
9.  Got an engine shop to fully recondition the heads (new guides seats valves)
10. Replaced carbs with a set of PHF36 lean burn off a bike that had only travelled 3000 km's
11. Ultrasonically cleaned the above carbs
12. Set float levels 18mm  and  re jetted with factory setting jets
13. new air filter.

It still strats and idles fine, and will start to pull just above idle, but with anything more than 1/4 throttle it misses and backfires and get all asmatic and just won't pull at all

Was about to try electronic ignition next But I'm just so damn tired of throughing money at this bike and still not resolving the running issue Please Please HELP
,
Could it I have a worn distributor drive gear ... Or a loose distribor drive gear ??? God I don't know I really thought I new Moto Guzzi's inside out ... But I'm starting to tear my hair out with this one.


(Pete Roper I hope you see this ...  you helped me lots with advice over 25 years ago when I had a mark 1 and mark 111 le mans )

Have owned this bike for over 18 months and still not ridden it .yet ..

Loved my original 850 Le Mans 111 25 years ago and only sold it to buy a 76 series 1 le mans ... Please don't let this bike put me off Moto Guzzi forever


Thanks all looking forward to any help you can offer.

Regards Marc

[Pastaboy55]

Hi all ....

Hoping to pick your collective brain power and experience ... Pete Roper I hope you see this ...  you helped me lots with advice over 25 years ago when I owned a couple of Le Mans'
 
Bought a 1982 Moto Guzzi 850 Le Mans 111 just over 18 months ago.
It had been parked up for 5 years at least prior to me buying it.

With some new fuel and battery it would start and idle, but run terribly on anything over 1/4 throttle misfiring, backfiring and no power.

To date I have replaced all of the following trying to resolve the running issue.

1.  The condensers,
2.  The Coils
3.  The wiring to the coils,
4.  The points,
5.  Spark plugs
6.  High tension leads
7.  Advance springs under the distributor
8.  Checked valve clearances
9.  Checked ignition timing
9.  Got an engine shop to fully recondition the heads (new guides seats valves)
10. Replaced carbs with a set of PHF36 lean burn off a bike that had only travelled 3000 km's
11. Ultrasonically cleaned the above carbs
12. Set float levels 18mm  and  re jetted with factory setting jets
13. new air filter.

It still strats and idles fine, and will start to pull just above idle, but with anything more than 1/4 throttle it misses and backfires and get all asmatic and just won't pull at all

Was about to try electronic ignition next But I'm just so damn tired of throughing money at this bike and still not resolving the running issue Please Please HELP
,
Could it I have a worn distributor drive gear ... Or a loose distribor drive gear ??? God I don't know I really thought I new Moto Guzzi's inside out ... But I'm starting to tear my hair out with this one.

Have owned this bike for over 18 months and still not ridden it .yet ..

Loved my original 850 Le Mans 111 25 years ago and only sold it to buy a 76 series 1 le mans ... Please don't let this bike put me off Moto Guzzi forever


Thanks all looking forward to any help you can offer.

Regards Marc

[fotoguzzi]

Could it be you got the wrong advance springs?

[nc43bsa]

Do you have access to different set of carbs you can use for diagnosis?

I chased an ignition problem on my Mille for a long time until I borrowed a set of carbs from Denis from his SP2;  problem went away.  Further examination revealed that my needle jets, though stamped with the correct numbers, were WAY too big, causing a very rich mixture above 1/4 throttle.

[DesertPilot]

Add my vote to, "I wonder about the spark advance."  Every time I've seen a problem like that, it's been the ignition -- usually dirt or gunk that stuck the spark advance in one position.

[kirby1923]

FWIW.
R1150 BMW.
Had a similar problem with the BMW that had been stored in a garage for a few months but when I tried to get it out of storage it would ldle but when the throttle was opened further it would stumble and not accelerate.

Checked every!! thing and found nothing out of tolerance, right to spec.

Long story short...the airbox was clean but I noticed while walking around the machine while idling there was hardly any exhaust out of the muffler. Got a light and found the can completely full of kibble and bits.

The resident rodent was preparing for winter and storing food and I got to say he/she was a real acrobat to carry out that job!

Cleaned (quite a job) the can and all was well..so check the air box if you have on and the exhaust for obstruction.

BTW the engine sounded normal while at idle even though full of dog food.

:-)

[nc43bsa]

Together with the "stored for 5 years" situation, this makes more sense than ignition or carburetors.

[Pastaboy55]

I have replaced both the Carbs (with the right lean burn PHF36 Carbs) and the distributor's advance springs (carefully and lighty greasing them) ... Plus the list of things that I have tried in the start of this thread.
I am getting super frustrated as I've poured way too much money into this bike after paying way too much for it (buying it sight unseen) have owned in for 20 months and not been able to ride it once.

Thanks Marc

[Pastaboy55]

Oh I hadn't thought about having been possibly sent the wrong advance springs.
Although they came from a very reputibleparts supplier here in NZ
Have had the airbox out and apart when i installed the new airfilter and had exhausts off to have one of them repaired, so know neither were blocked. I love the ideas though please keep them coming.
Someone will nail it and find the cause of poor running above 1/4 throttle.

Is Pete Roper still on this site. He can be the source of all knowledge on things Guzzi. Helped me lots with little problems with a previous LM 111 and my 76 series 1 LM

Cheers Marc 

[bacongrease]

 I started my 71 CB750 and blew out a family of  mice and their groceries. 

[bacongrease]

 My experience has been fuel starvation.

[Pastaboy55]

Yes I too thought it was fuel starvation so put new fuel taps in the tank and new factory fuel hoses wih the cross over and new filters in the banjo's on the sides of the carbs, with no success.

Could it be that I have a worn or loose distributor drive gear ... Or a worn camchain affecting timing ... Might be clutching at straws here but running out of things to try

[SED]

Does opening the choke lever change where it starts to stumble?

have you confirmed that both slides are lifting when you open the throttle?  It's a pita to pull the airfilter elbows but might reveal that one of the bell crank cables is not connected or...?

This does not sound the same as yours but on my LMIII there used to have a stumble off idle, not nearly as bad as yours, but a dead spot between 0 and 1/4 throttle.  I found you can start the bike and let it idle and screw in the idle stop screw on one side.  The engine should increase rpm without stumbling until the screw is all the way in.  If it stumbles go up 1 idle jet size and see if it is better.  Then repeat on the other side.

BTW I've found the stock idle jets are too lean even with the stock airbox.  I'm running a 55 right and 60 left.

Another weird stumble.  Had just cleaned the float bowls on the carbs on my Monza and started and ran great, but as soon as I tried to ride it it acted like yours - stumbling and puttering on 1 cylinder.  Pulled the bowls again and on one side there was a small piece of the red sealing gasket sitting right under the main jet.  The piece got sucked up to the jet every time the main started to flow.

Shining an inductive automotive timing light at the timing marks and accelerating the engine might tell you if it is the ignition breaking up rather than a carb problem.

Not sure any of these is what you have, but might give some inspiration.

[wirespokes]

I'm leaning towards the idea it's something else entirely - something you haven't yet touched.

Leave the cap off the gas tank - perhaps it's not venting and creating a vacuum.

What about the breather? Try leaving the dipstick loose and see what happens.

Maybe the flywheel was changed and the marks aren't correct. Check to ensure TDC is actually that. Then count the number of teeth to static and full advance, to see if the marks are correct.

If you think there's something wrong with the timing, you can always leave the clamp loose and twiddle the distributor while running to see if that makes a difference. Have you put a timing light on it?

Have you watched each valve move through a full cycle? I had a Volvo with the same problem - wouldn't run past 35 or 40. Adjusted the valves twice, just to make sure - but the third time I used the procedure where you watch for a particular valve to open, and then adjust the one I was on. Took a few times to realize I hadn't missed the one opening - it just wasn't opening. It was a camshaft with three bad lobes. I'd spent four or five full days coming to that point and it was driving me crazy.

Are the jets stock? My LM3 had some jets changed by a PO and got horrible mileage and didn't run that great either. Stock jetting fixed it.

That's all I can think of for now, but remember - all that's required is air/fuel, spark and compression. After that it's quantity and timing.

[Kiwi_Roy]

You changed the condensers, thats a red flag for me, modern condensers from a certain country are absolute crap, you would be much better with the old ones the bike left the factory with. If the condenser is not working the spark will be so weak when you open the throttle the higher pressure makes it impossible to jump the gap.

It could also be a blocked jet of course, does it run better if you open the enricher lever?
Another possibility would be the coils but I doubt you would have 2 bad coils.
Measure the resistance from each plug cap to chassis, it should be the same on both sides, around 8k if the plug caps, leads and coils are intact.

[Pastaboy55]

Thanks team loving all the suggestions might try re-installing the original condensers in case I got a faulty replacement

I have near new carbs on the bike with stock jetting (ultrasonically cleaned them put new factory jets in and carefully set float levels at 18mm)
Near cable set when new carbs were installed carefully adjusted all the lash out of the cables just 2mm free play. Slides are lifting are closing together perfectly

LOVE the idea of checking that the fuel cap vent is not blocked ... That could be it .... Thanks will check that tomorrow. THIS COULD BE AN EASY CHEAP FIX
LOVE the idea to check crank case breather another suggestion i hadn't thougfht of ... Thanks


Hope it's not worn cam lobes aftyer all I've spent on this bike to date.

Keep suggestion coming really appreciate the input  Marc

[SED]

Could it be that I have a worn or loose distributor drive gear ... Or a worn camchain affecting timing ... Might be clutching at straws here but running out of things to try

Don't know about distributor drive gear, but wouldn't think wear could be so bad that it wouldn't run.  The stock cam chain tensioner is a rubber block and the solution is to fit a "Valtek" blade type.  The stock tensioner was very worn on mine so replaced it with the blade type, but didn't notice much difference.  Ran OK with both.

Wirespokes might be onto something with the timing marks.  There are 3 marks for each cylinder and if the timing was very far off it might start but not run well.

[Tony F]

Fuel supply issue? Remove the fuel taps and check the filters that are mounted on the taps and fit in the bottom of the tank for blockages. Also check taps themselves for blockages and the the filters at the carbs and any other in line filters if they have been fitted.

[Frenchfrog]

Could be the tank venting hole...somewhere near the filler cap, possibly under the rubber flap there should be a small hole for air to enter the tank.If it blocked it soon forms a vacuum in the tank and petrol no longer flows.Try running it with the filler cap open...

[Frenchfrog]

Wirespokes could well be getting a cigar...easy enough to check.

[blackcat]

“Maybe the flywheel was changed and the marks aren't correct“

The timing marks on my 81-CX were wrong from the factory.

[Huzo]

When it’s playing up, is it on one cylinder or both ?
Suffice to say, is one pipe getting hotter than the other ?

[czakky82]

Lots of advice here. I like Kiwi-Roy’s idea as it’s easy to diagnose too.
Pull the distributor cover off and start it up. Are there an abundance of sparks off the contacts? New condensers suck!

[Huzo]

Put a timing light on it and see if it leaps around like a cheap sex toy left running on the table..
You’ll know after that if it’s spark, timing or fuel.
That’ll immediately reduce to buggery, the possible causes.

[chuck peterson]

Backwards carb slides?

 

[Frenchfrog]

Don't think that is possible on the PHF's unless the sides are reversed. Worth a check though !

[Dukedesmo]

Check the carbs again?


My LM2 was running fine after I'd gone over everything and then after a year or so it started spluttering at high RPM. There was a small collection of dirt (looked like sand) in the bottom of the carb, not much and only enough be sucking up and blocking the main jet at high speed when the fuel was flowing faster.


Cleaned it out and it was fine but it gathered again shortly afterwards, I assume it is dirt/rust etc. dislodging from the inside of the tank as the bike had been standing for several years before I got it  but, it took a while for it to wash through.

[Stevex]

I found my distributor gear rivet head in my sump, apparently they do shear.
Is it possible yours has gone and then tightened up, altering your timing, I doubt it but if you're pulling your hair out, it's not hard to pull the dizzy and check.
I checked mine and found the rivet had been replaced with a roll pin.
These engines will run with the cam chain flapping all over the place, My oem 'tensioner' was toast and I put a Valtek in there, but even so it ran ok with the worn oem unit.
From everything you've done so far and found nothing, I'd get a strobe on it and check whats happening with the timing, after checking tdc with a piston stop and timing disc, then timing marks from there.

[lucian]

Fuel supply issue? Remove the fuel taps and check the filters that are mounted on the taps and fit in the bottom of the tank for blockages. Also check taps themselves for blockages and the the filters at the carbs and any other in line filters if they have been fitted.

^^^^^  this  rust in the tank?

Oops I just noticed the same thread further down the page. seems you have already ruled out fuel starvation other than the  tank vent. Definitely rule that out. Sounds like you'll just need to start from square one and rule out proper set up starting with static timing. East enough to check advance function with a light provided it will rev up a few thousand rpms. You can manually advance the dizzy if needed while attempting to rev to see if it helps. How do your spark plugs look after running? Wet / dry , oily or sooty ?  Check spark with plugs grounded to heads.. Both should be bright blue spark equally. And firing at TDC . Also check for any intake air leaks on manifolds, a little wd40 sprayed around while idling will let you know as the idle will rise when the wd gets sucked in . I have a 84 LMIII that is my favorite guzzi to date. Hope you get out on it soon.

[twowings]

Starving for fuel?