Author Topic: Trying to figure out why my lemans is fouling plugs  (Read 831 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.
I’m planning on doing a plug chop to see what’s happening and where, the plugs are getting slightly fouled after a few rides. I’m just surprised that it’s that rich with the carbs being stock setting and the aftermarket exhaust. I’d think I should be running lean not rich but the plugs are telling the opposite
Thx
Allen

Online 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? 

Offline 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 “ok” when I got it and carbs were stock jetted ( phf36’s-50 pilot jets) I think it only ran ok because the choke plunger was ethier not sealing or it’s o ring was torn ( I’m 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. I’m following your thread. Good luck
1994 California 1100

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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 »

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 I’ll rebuild my original cable operated one. Mine aren’t  that old though so I’d think the o rings are fine, maybe they’re 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 aren’t long enough?
1994 California 1100

Online 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 »

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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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:

Online 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 »
I’ll double check what I have in there, and rebuild the original choke cable. I’ll also measure the accelerator pumps to see what coming out

Offline 1down5up

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Re: Trying to figure out why my lemans is fouling plugs
« Reply #12 on: September 27, 2022, 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

Online blackcat

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Re: Trying to figure out why my lemans is fouling plugs
« Reply #13 on: September 27, 2022, 06:09:52 AM »
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

Yes, I know that but he has new? flip chokes. I could see if one choke was bad, but both of them?

“I have individual flip lever chokes I bought from mgcycle. Maybe I’ll rebuild my original cable operated one. Mine aren’t  that old though so I’d think the o rings are fine, maybe they’re not.”
1968 Norton Fastback
1976 Lemans
1981 CX-100
1993 1000S
1997 Daytona RS
2007 Red Norge

Offline pressureangle

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Re: Trying to figure out why my lemans is fouling plugs
« Reply #14 on: September 27, 2022, 09:00:46 AM »
I'm on board with choke plungers being the most likely culprit, but I'll go the other way just to get ahead if it proves chokes are good.

Newly rebuilt; Gilardoni kit- what rings are used? What was used for lube during assembly? It's possible, even likely, that you will suffer some oiling of the combustion until the rings seat fully. The assembly lube has a lot to do with that, and if you have high quality synthetic oil at startup it will be a long time before the rings seat thoroughly.
I put new Sealed Power piston rings on the stock pistons and bores in my '85 LeMans. I asked them about break-in and they told me 'ride it like you stole it'. I did not, I rode it casually for 500 miles and easily for the next 500. I was rewarded with fouled plugs and combustion chambers. After I went out and thrashed it, everything cleaned up just fine.
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Offline Stratodisaster

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Re: Trying to figure out why my lemans is fouling plugs
« Reply #15 on: October 04, 2022, 06:47:27 PM »
When was rebuild?  Oil consumption????
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Offline John Croucher

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Re: Trying to figure out why my lemans is fouling plugs
« Reply #16 on: October 04, 2022, 07:27:33 PM »
When was rebuild?  Oil consumption????

Bad rings, bad valve guide, bad crankcase vent.  Look beyond the carbs.

 

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