Author Topic: Trying to figure out why my lemans is fouling plugs  (Read 256 times)

Offline amamet

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Trying to figure out why my lemans is fouling plugs
« on: September 25, 2022, 07:31:31 PM »
77 lemans, rebuilt. Carbs have been ultrasonic cleaned and set at factory jetting, like it had been before the rebuild with lafranconi exhaust. Bike now has gilardoni 88 mm kit, megacycle p9 cam with heads rebuilt and a good balancing. Added a Zard exhaust and k&n filters.
Iím planning on doing a plug chop to see whatís happening and where, the plugs are getting slightly fouled after a few rides. Iím just surprised that itís that rich with the carbs being stock setting and the aftermarket exhaust. Iíd think I should be running lean not rich but the plugs are telling the opposite
Thx
Allen

Offline lucian

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Re: Trying to figure out why my lemans is fouling plugs
« Reply #1 on: September 25, 2022, 07:39:02 PM »
Are the enrichener plungers sealing tight? 

Online 1down5up

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Re: Trying to figure out why my lemans is fouling plugs
« Reply #2 on: September 25, 2022, 07:55:54 PM »
Choke Plungers would be my guess also.

I just had a similar issue with my lemans - https://wildguzzi.com/forum/index.php?topic=116412.0

Note, that I did the old trick of turning the rubber plugs over in the plunger to get a new "good" side, but the rubber was to old and hard to seal properly - solution was to buy some 6mm chord (or 6mm dia o-ring) and make some new ones and slot them in - instant improvement.

Offline Gusable

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Re: Trying to figure out why my lemans is fouling plugs
« Reply #3 on: September 25, 2022, 07:59:17 PM »
My bike ran ďokĒ when I got it and carbs were stock jetted ( phf36ís-50 pilot jets) I think it only ran ok because the choke plunger was ethier not sealing or itís o ring was torn ( Iím assuming it was sucking air and drawing fuel). I got the chokes sealing and running 60 pilots now.  Bike runs great now. I am on the rich side now and plugs are black-ish. Iím following your thread. Good luck
1994 California 1100

Wildgoose Chase Moto Guzzi

Re: Trying to figure out why my lemans is fouling plugs
« Reply #3 on: September 25, 2022, 07:59:17 PM »

Offline amamet

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Re: Trying to figure out why my lemans is fouling plugs
« Reply #4 on: September 25, 2022, 08:08:49 PM »
I have individual flip lever chokes I bought from mgcycle. Maybe Iíll rebuild my original cable operated one. Mine arenít  that old though so Iíd think the o rings are fine, maybe theyíre not

Offline Gusable

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Re: Trying to figure out why my lemans is fouling plugs
« Reply #5 on: September 25, 2022, 08:10:45 PM »
Maybe they arenít long enough?
1994 California 1100

Offline moto-uno

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Re: Trying to figure out why my lemans is fouling plugs
« Reply #6 on: September 26, 2022, 12:12:30 AM »
  Is there anything in the accelerator pump and jet assembly that is stuck or leaking ?  Peter

Offline Stevex

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Re: Trying to figure out why my lemans is fouling plugs
« Reply #7 on: September 26, 2022, 05:11:53 AM »
Have you set up your accelerator pumps?
When I refurb'd my LM2 carbs I put each in a vice and raised the throttle, then caught the fuel from the accelerator jet as it squirted out and measured it.
Did that to both carbs and adjusted until they were equal. Unfortunately I can't find the final measurement I set them at.
I remember one carbs pump NRV wasn't working; it has a small ball bearing in it which had stuck in the open position, might be worth checking them by removal and examination, although I doubt this is your problem; it just prevents the pumped fuel returning to the float chamber.
Finally, I'm sure fitting a K&N on stock (bell mouth settings) will affect fuel / air mix ratios. Try running the bike on the oem bell mouths and see how it goes.
As an aside, I run my LM2 on bell mouths and so did the PO; last time I did a compression check a year or so ago, both cylinders were returning 195-200 psi.
I'll take it for granted you've set your floats to the correct level.
« Last Edit: September 26, 2022, 05:21:44 AM by Stevex »

Steve
1980 Le Mans II
2009 Honda CB1300S
2005 Aprilia Tuono
Chief mechanic to wife's 696 Monster

If you think pushing 60 is bad, wait 'til you have to start dragging it.

Offline Chuck in Indiana

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Re: Trying to figure out why my lemans is fouling plugs
« Reply #8 on: September 26, 2022, 09:35:45 AM »
I'm very careful not to overuse the enricheners on cold startup, and get them off ASAP.
Chuck in (Elwood) Indiana/sometimes SoCal
 
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Offline guido guzzi

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Re: Trying to figure out why my lemans is fouling plugs
« Reply #9 on: September 26, 2022, 01:05:54 PM »
I'm very careful not to overuse the enricheners on cold startup, and get them off ASAP.

THIS^ I try to avoid the enricheners unless it's really cold.  :thumb:

Offline blackcat

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Re: Trying to figure out why my lemans is fouling plugs
« Reply #10 on: September 26, 2022, 05:25:40 PM »
I have the stock slides on my 76-LeMans and the following:

K5 needle on middle clip
AB 265 Needle Jet
60 Pilot Jet
140 Main Jet

I almost never use the chokes, just twist the grip a few times and it usually starts right up.

1968 Norton Fastback
1976 Lemans
1981 CX-100
1993 1000S
1997 Daytona RS
2007 Red Norge

Offline amamet

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Re: Trying to figure out why my lemans is fouling plugs
« Reply #11 on: September 26, 2022, 09:35:27 PM »
Iíll double check what I have in there, and rebuild the original choke cable. Iíll also measure the accelerator pumps to see what coming out

Online 1down5up

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Re: Trying to figure out why my lemans is fouling plugs
« Reply #12 on: Today at 01:59:09 AM »
I have the stock slides on my 76-LeMans and the following:

K5 needle on middle clip
AB 265 Needle Jet
60 Pilot Jet
140 Main Jet

I almost never use the chokes, just twist the grip a few times and it usually starts right up.

The issue isn't how much you use the chokes, it's weather the rubber in the bottom of the plunger is sealing off the choke jet sufficiently or if the cable is long enough/not getting hung up to be all the way down and not slightly hanging the choke/enricher circuit open


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