Hi Folks.
I have a 850 lemans fitted with 940 barrels, high comp pistons, B10 camshaft, lafranconi competition exhaust and velocity bellmouths on 36mm carbs. Carbs are jetted 145 main and 60 pilot.
I cannot get the bike to idle smoothly and it will cut out without constant blipping throttle. It’s perfect once any throttle is applied up through the full range.
I have wound in the throttle slide stop fully and I have the slow running screwed at least 4 turns out and the mix still seems weak. Carbs have been stripped twice and cleaned.
I was thinking of increasing slow running jet size and was hoping someone might have a similar set up and could advise.
With throttle stop screws wound right in yer bike should be revvin its thingys off !
Top of me head, airscrews 2- 2.5 turns out, will check later tho they do vary. Check for air leaks and make sure your tappets aint tight. Tdc on compression stroke and not on the base circle of the cam.
We have 4 lemons between us, curmudgeonly old things, they all differ !
Assuming they are actually raising the slides and not just making big 'oles in them? I dunno this sounds like a tune-up kit, and it may be that that by itself burns your bridges in the good idling department, but what do I know Otherwise I would have said yes try bigger idle jets. Or check that the jets hole sizes are actually correct, and not partially blocked (guess how I know about that one!)
 Assuming they are actually raising the slides and not just making big 'oles in them? I dunno this sounds like a tune-up kit, and it may be that that by itself burns your bridges in the good idling department, but what do I know  Otherwise I would have said yes try bigger idle jets. Or check that the jets hole sizes are actually correct, and not partially blocked (guess how I know about that one!)   [/QUOTE]
Nothing like screwing the tips of the idle slides iinto the slides. guzzi-t52013-07-30 18:02:24
Thanks guys for all your ideas.
No holes in slides, no obvious air leaks. Just checked valve clearances, all spot on. Jets have been cleaned and are full bore.
Ian Dumore’s suggestion of exhaust gasket is worth a try, have a couple of new ones so will do at weekend. Thanks for all replies.
4 turns out sounds too many, 1/2 to 2 1/2 is the range, starting at about 1 1/2. As you have size 60 pilot jets, I would say they should be quite adequate to deliver enough fuel.
The early slides can wear where the throttle slide contacts the slide tickover adjuster resulting in ultimately no (upward) adjustment. Does the bike “idle” if you put a fraction of throttle on? If so check to see if the throttle stops are actually doing anything…look down the venturi and see.
Make sure the timing is timed correctly at full advance, no air leaks and that the float heights are correct.
There is an article on this site as to how to tune Dellortos.
All of the above but also give eurocarbs a call for their reccomended jet sizes heck on a V1000 with 30mm carbs and K&N’s they run 140 jets so maybe you do need bigger jetting as well as the other checks BUT no way an I any sort of authority on jets took me years to even alter mine guzzibear2013-07-31 11:40:51
make sure you start with valve clearence , exchaust check, manifold rubber check (if you have them) , timing/points, the move on to the fuelingMay also be worth dropping the fuel taps out and the carb filters to check all is nice and clean before you start on the carbs
Yep an air leak between the carb and head really screws up all attempts to get it to idle, you may not think you have a leak but can you be absolutely sure. EDIT: having said that though it tends to make it race, not cut-out. “the mix still seems weak” as I know from current experience, modern petrol if left in carbs to dry out can clag up the jets like nobody’s business; you may have constricted jets, sure there’s holes through 'em but are they actually the correct diameter?
Mike H2013-08-01 12:51:02
Check your float heights are correct as the first job. If they are wrong no amount of adjustment of anything else will correct the situation.
All the best,
David.