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TygerTung
16th March 2005, 01:08
Got my CG back together, and she runs sweet, I have a 125cc barallel, 20 thou oversized, XL125S high compression piston, mild port and polish head, but she seems to have a miss at higher rpm? What could cause this? Maybe it's not getting enough fuel, as I'm using the 110 carb? Would I need to re-jet it? Or could it be ignition related? It shouldn't be though, just replaced the points on satuday!
Sniper
16th March 2005, 16:28
Nope, same thing I had, need to get a bigger jet or find out a way to increase fuel into the motor, that will have you sorted

Sniper
TwoSeven
16th March 2005, 17:21
The re-jet will fix everything solution often doesnt work.

Try holding the throttle open in 1/8 or 1/4 intervals for 20 seconds at each stop. When the missing spark occurs that'l give you the throttle setting that you can then map on to the carb setting. As soon as you hear the 2nd or 3rd miss, hit the kill switch, wait a bit, then shut the throttle. CHeck the plug to see if its black or white as to what you need to do to the carb. Might be you are running fuel lean a little.


Also, have another go at cleaning it first :)
gav
16th March 2005, 18:23
I think you need to fit a turbo, hell, with the right gearing, you'd be able to do 215mph!!!
http://home.comcast.net/~dan0421/edna_lg.gif
Motu
16th March 2005, 21:01
You may have moved into valve bounce territory with your improvements
TygerTung
17th March 2005, 00:20
Nah it certainly isn't valve bounce, it's just a miss, perhaps it is insufficient fuel....
Oscar
17th March 2005, 07:41
Could be an air leak.
I had a high rev miss on a XL175 and it turned out to be a leaking manifold.
TygerTung
17th March 2005, 12:03
I checked the plug, it's a light brown/ tan colour which I think is normal.... I might reseal the intake manifold for air leaks?

It seems to have got a lot worse, maybe the jet has gotten blocked up, because I don't have a fuel filter?
TygerTung
17th March 2005, 12:32
Ok, I checked it with my exhaust gas analyser, and it seems to be running extremly rich, like richer than 10 to 1 (my analyser only goes up to this), maybe this is causing the problem....

So I'll have to get a smaller jet? I'll have a look in the haynes manuel, and see if it sez anything about this.
Sniper
17th March 2005, 12:57
Told you so, (No I didnt()