LCGB Forums

Hi all,
Recently fitted a mugello 198 and a new GP crank with lightened flywheels to my mates Li125.
It all went together well and I made sure the piston was the correct way, ring gaps and squish were spot on etc.
Carb is a nearly new 26phbh with small type ram air,
53 pilot
AV266
X2 needle

Started off with a 115 main and she fired well after a few kicks, strobed timing to 18 degrees.
She revved nice and clean but bogged down at high revs like a blocked main jet.
As hes running in hes gone steady for 30 miles so far so tonight I dropped main to a 110, but still bogged down at high revs.
Changed carb and cleaned jets to my good spare 26phbh, still same!
Took filter off...same.
Checked fuel flow which is fine.
Changed plug, same.
Changed cap & lead..same
Changed cdi...same....pulled cut off wire out..same.

I tried it up the road and it goes like a stabbed rat with throttle opened up until revs get high then its like its hit a rev limiter.Im thinking pick up on stator now? Its surely all thats left?

You seem to be contradicting yourself here as bogging down, imo, indicates too much fuel whereas a blocked main jet indicates fuel starvation. Both may give similar symptoms though. Have you tried dropping the needle by one notch? I know this only really affects the mid-range but I found that it does have some effect on the main jet too.

Rich'

Not bogging down as such but wont rev out like it should.On the road with throttle cracked open it accelerates clean until the revs get high then seems to missfire.Needles in the 2nd down slot and carbs set up the same as my mugello 198 was which ran perfect.Even open mouthed its the same which makes me think its electrical

my money is on the pickup being the cause, try changing the stator to a known good one. I had one a few years ago that wouldn't rev over 6k rpm

Doing that tomorrow Eden, he bought the stator last year but think its a cheapo one.Hopefully it will cure it.Dont you just hate it when you spend ages building someones engine to the best of your abilities yet the gremlins still keep rearing their ugly heads!
Loving your vids btw, I hope the GT kits running well!

not disputing the possibility of stator/pick up problem but change the x2 needle to a x7?

Umm what exhaust and what gearing please??

not disputing the possibility of stator/pick up problem but change the x2 needle to a x7?

Doh! must have had a blonde moment last night! sorry,the needle is an X7

Umm what exhaust and what gearing please??

Running an Li125 box with 17x46 and an Ancillotti

i had problems coming home from isle white 1 year had to toddle along at low revs my problem was down to the indian cdi on way out changed cdi and it ran fine again

It does sound electrical. I had a similar problem which turned out to be the plug. Wouldn't rev out in 4th and juddered a bit as though fuel but after stripping and changing the carb' I eventually changed the plug and worked fine.

hmmmmmm certainly starting to sound electrical I have to admit. Id think swapping out the plug / cdi and then possibly the stator for known good ones are gonna be the way forward. Check the rivets on the stator too.

did you open up the transfers in the casing?

Miss match between pick up and flywheel triggers. MB sell a kytronic thing that is supposed to eliminate the problem.

This has happened to me and it was a faulty CD unit.

Changed the plug,cap,lead and Cdi for good spares and still no joy.Hes coming round soon and im gonna try changing the pick up for a new one as i dont have a spare stator.

What type of flywheel is it?

I was working on a mates scooter today which was suffering from limited revs, it got to around 6k and would rev no more. I strobed the timing and at the point that it wouldn't rev any higher the arrow was jumping to 180 degrees from where it was when running under 6k rpm. Changed the pickup and it was fine, it revved all the way out.
This is another example of the problem I had myself a few years ago!

^... what type of stator was it and what type of pickup did you use to cure it?

was on an SIL stator, the stator I replaced it with is also an SIL stator but with piaggio pickup.

Ta