Hello guys,
I rebuilt a 250 CR from 2001 last year.
Motor was completely rebuilt (piston, nickasil, reeds, gaskets, crank, bearings, etc.).
The bike has litterally no power at low RPM and starts to pull from mid to high RPM. I have a Mikuni TMX on this bike, jetting is completely stock. I owned other 2 strokes in the past, they were way more crisp at low RPM. My bike is pissing black oil from silencer/pipe connection also.
Do you guys have any recommandation regarding jetting on this bike ?
I've read that owners sometimes switch to Keihin PWK Air Striker. I am considering also this option.
Any jetting recommandation with this carb ?
I live and ride at 300meters/1000ft altitude and weather is 20°C / 70°F at the moment in my region of France.
Thank you
I think the 2000 model ran a keihin carb, might wanna start there...
Did you make sure the powervalve linkage between the cylinder and the cases was properly aligned when installing the cylinder? This is a common mistake when rebuilding the top end. You can check powervalve function by removing the check plug on the left hand side of the cylinder. It has markings that show “L” and “H” for power valve position through out the rev range. Take that plug out and verify the powervalve is moving correctly.
A piston installed backwards will also do some word stuff. It’s rare, but it happens.
Powervalve seems to be OK.
I've been advised to install a S7 nozzle, it's supposed to make Mikuni TMX work way better.
I'll try that and then swap with a Keihin PWK Airstriker if needed.
Here are the current jetting :
Main jet :400
Slow jet 30
Air mixture : 1 3/4
Needle 6BEH1 74 (leaner) at 3rd clip
Standard jetting is :
Main jet :420
Slow jet 35
Air mixture : 1 3/4
Needle 6BEH1 73 at 3rd clip
It means my bike was already very lean when I purchased it.
I will put back everything stock and start fine tuning from the OEM jetting.
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