Resurrecting an old thread to try and find what proper PowerJet tube length for a 144 (2014 CR, if it matters). My carb was a MotorSportz build (from August 2014) and has never behaved right in the mid to high transition. I went back to stock carb for a couple of years, then gave it another try. After finding this thread, I measured my PowerJet tube and found it is the standard length (0.800"). Earlier in this thread a shorter tube is recommended, and is supposed to ship with MotoSportz builds. But the suggested length varies in thread. First 0.4" , and then 0.5-0.55". Does anyone know what length is supposed to arrive with a MotoSportz build? I'll call Lectron in the morning as needed, but was hoping to finish prepping tonight (including cutting tube) for ride tomorrow afternoon.
Thanks! I'll see what happens with .6" I got an interesting reply from Lectron: The old Motosportz build (2014 and earlier) called for a .600” length power jet tube. We now build with a standard long tube and a 3-2M metering rod for your bike.
Things did not go to plan. I made a jig, and cut: Aimed for 0.6" but was being cautious (hard to make it longer). Ended at .62" and decided close enough. Given the radical change in PJ setting people reported. I decided to (almost) start over on tuning. Set PJ to 1.5 turns out, played richer and leaner with needle and found 1/4 turn richer than before was right. Started playing with more throttle in the woods and found a flat spot around 3/4 throttle. Tried 1/2 turn richer on PJ and massive burble/bog when I opened throttle. Went 1/2 turn leaner on PJ (from baseline) and seemed better. Finished a few woods sections, came out to dirt road and opened it up. Nothing felt odd but within a few seconds it locked. Would turn over but would not start. I haven't pulled cylinder but it looks like a mild seizure: And the plug (looks lighter in person, but not white): Not blaming the shorter PJ tube. At time of seizure I was at 1 turn out and had been at 2 1/8 with long tube. Didn't think anything of the change due to wide variation in settings for people and the fact I was richer on needle. So it finally happened. After 46 year of riding dirt bikes (including racing air cooled bikes) I have had my first seizure.
Ok, maybe not so mild. Stuck at front, back and both sides of piston. And the ring was stuck on the exhaust side, explaining why it wouldn't start. The 144 top end has 35-40 hours, so was holding up great apart from this.
Sorry man that sucks. My first go around with the "Smart" carb ended worse than that. Finally got it running OK on the bottom/mid, opened it up on the road to check top end and bang.
