Guzzi Lemans Plug Fouling

[Voltaire]

My Guzzi Lemans 2 has been WIP for a year.
LH plug fouls after about 30 KMS.
I've checked the ignition, valve clearances, stripped and cleans the carbs ( multiple times)
Tonight I printed off the specs and stripped and wrote down all the jets and needle numbers, all as per spec.
Then I thought i'd swap the carbs over and see if the problem was the engine or the carb.
Ran ok for about 20 kms then started to bog down.
The problem had moved to the other side so its the carb.
I've played with Dellortos on my BMW and this is first time I've stuck this.
Wise words welcome :niceone:

[AllanB]

Stock air filters or pods? If the later is one a dirty bitch and the other a clean nun?

[Voltaire]

Stock air filters or pods? If the later is one a dirty bitch and the other a clean nun?

It came with cone shaped K and N pods. I have just cleaned and oiled them.

[jim.cox]

Worn needle and/or seat

[Grumph]

Standard PHF36's ?

Possibilities are:
blocked air correction jets/passages
Worn needle/needle jet combo
Crack in the carb body - below fuel level on the central tower carrying the jets.
If the problem only shows up hot, this could be it...
Do the floats carry the same numbers ?
Float needle jet fitted correctly into the body ? Any crack around that ?

[Voltaire]

Standard PHF36's ?

Possibilities are:
blocked air correction jets/passages
Worn needle/needle jet combo
Crack in the carb body - below fuel level on the central tower carrying the jets.
If the problem only shows up hot, this could be it...
Do the floats carry the same numbers ?
Float needle jet fitted correctly into the body ? Any crack around that ?

List for tonights investigation.
floats are both the same, 10 grams
next on list is checking for worn parts and cracks.
This is why we love old bikes...isn't it....keeps the brain active....

[Kickaha]

Check the accelerator pumps as well

[Grumph]

Check the accelerator pumps as well

Thought about that - Dellorto take the fuel up and over the top to the nozzles in the bore. I don't see how there can be a bleed of fuel through the system while running. I'd check the pump ramps in the slides in case one side is a very long ramp...
Mikunis, Yes, with their system there can be a fuel bleed if something sticks. Bloody Dellorto pumps are hard enough to get to work in the first place...

[Paul in NZ]

Also check the choke mechanism - they are VERY prone to sticking....

[Voltaire]

So got home and stripped the LH carb again.....
Checked out the main suspects, needle, needle jet and idle jet.
Found in my BMW racer bits box another PHF 36 and it looked less munted.
As they are not the same mounting took out the bits needed and compared them.
Visually no real difference.
Found a drill bit that was a sliding fit into the needle jet and it was a bit sloppier on the old one.
What the hell I thought fit them and go for a ride.
I did the same 30 kms as last night, bit of mean streets of Onehunga and Mangere plus a few strops up and down the motorway.
Initial impression was smoother, no popping from exhaust, seemed to pull better and happier to run a higher gear at lower revs.
Pulled out plug on the actual spot I did it last night and not sooty.
Rode back thru urban area and it would feather along at 60 KMPH/2000 rpm without issue in 5th ( try that on your Ducati )

Conclusion: when you buy an old bike fit new jets.
Gong to order all new ones.
Thanks for all your advice and tips, always appreciated :yes:

Photo from a while back.
Its a lardy thing compared to the R90s but its got lots of ommph and old blokes come up and talk to you...:msn-wink:
328011

[Grumph]

Guy who lives around the corner from me has a Laverda 3C. Carbs needed a refresh.
He got someone else to supply and fit the new brass and slides - not cheap..
He came round to me with them in his hand asking why they wouldn't synchronise - and what the hole in one new slide was.
They wouldn't sync because it had the short cables in the gantry of 2 different lengths...
The hole in the slide was at the bottom of the ramp and is supposed to have a plug in it with a spring to stop the needle fluttering.

He found cables of the same length and fitted them. I made up a brass plug for the slide and pressed it in. Never heard of that missing in a new slide...

The guy who did the job apparently lives in Rolleston and i'm told is a truck mechanic. He knows how to charge....

[Hobbyhorse]

A good result John.

Do you think that new jets would sort the Vespa front end?

[AllanB]

Rode back thru urban area and it would feather along at 60 KMPH/2000 rpm without issue in 5th ( try that on your Ducati )



Not a chance in hell - it would buck me off - I've recently gone from a 15 to 14 tooth front sprocket - it would still pack a paddy. At last I can run all 6 gears at sub walk home speed on the open road (but still get a ticket speed...).


Carbs. I have one somewhere in the garage. Oh my Lawnmower still has one.

[OddDuck]

Rode back thru urban area and it would feather along at 60 KMPH/2000 rpm without issue in 5th ( try that on your Ducati )
328011

Since fitting the Keihin FCR41's I can tootle around at 2,500 - 3000 RPMs quite happily. Simply wouldn't have happened with the stock Mikuni's. Not sure about 5th gear at 60 though... massive driveline backlash, high gearing and all...

Nice looking Guzzi btw, love the classic styles.

[OddDuck]

Carbs. I have one somewhere in the garage. Oh my Lawnmower still has one.

Carbs. Had new slow jets arrive today, looking forward to doing some more tuning. Sometimes crude and stinky is good :2thumbsup

[Voltaire]

Not a chance in hell - it would buck me off - I've recently gone from a 15 to 14 tooth front sprocket - it would still pack a paddy. At last I can run all 6 gears at sub walk home speed on the open road (but still get a ticket speed...).


Carbs. I have one somewhere in the garage. Oh my Lawnmower still has one.


Since fitting the Keihin FCR41's I can tootle around at 2,500 - 3000 RPMs quite happily. Simply wouldn't have happened with the stock Mikuni's. Not sure about 5th gear at 60 though... massive driveline backlash, high gearing and all...

Nice looking Guzzi btw, love the classic styles.

I had two SS's and they did not like the city traffic, last one I had the Mikunis had been rejetted and ran nicely around the 2500- 3000 region. My SL has 39mm FCR's which I'm over due to the lack of choke and listening to the sprag clutch complaining as I try several times to get it running.
Guzzi can do it as the flywheel is massive, shame its got such a stupid clutch arrangement.

[Kickaha]

Rode back thru urban area and it would feather along at 60 KMPH/2000 rpm without issue in 5th ( try that on your Ducati )
Used to be a minimum 100kmh on the MHR before even thinking about top and that was after I lowered the gearing

[Voltaire]

replaced the main jet,needle, emulsion tube, slow running jet and gasket kit.
All stock sizes. Main Needle in middle.
Went for ride to Silverdale and back down 16.
Stopped at Dairy flat to fill up and check plugs.
Noticed slight pinking in top gear up hills.
Plugs had brown electrode but whiter than I would expect.

I wonder if you jet the same for modern fuel?

Thinking go up from the 138.

R90/S runs a 155 for road.

Race BMW runs from memory 145's.

Next budget test drop needle down on notch.

The Guzzi is nice enough to ride but not a patch on the R80ST on a twisty road.

[F5 Dave]

A mate used to have a mk1. Also featured in this (subscription so could be a month away at least) classic mc mechanics mag.

Mainjet size of any other bike is of no interest.

K&Ns always require richer jetting. Don'tgo crazy, small steps on main but a clip change worth trying as well and gauge. Always think throttle position on slide carbs, rev range is symptomatic.
Pinking up a hill for example you probably are still on needle.