J-Madd

Well, it wasn't the pickup coil gap, so I tried a different stator and CDI.......still no good. I finally got it to start some how while the flywheel not torqued down, but when I tightened it, the engine wouldn't start and backfired. I found that the key was somehow moving the flywheel out of time, even though it was in the groove and tightened down. I took a flat screwdriver and scraped the flywheel keyway clean of metal deposits that the key had left, and it's fine now with +9 timing. No signs of metal flakes on plugs or detonation on either motor.

Well the 4 mil ran fine, but I didn't pull the plugs out and look yet..motor was too hot and never got around to it when it cooled. The stock stroke motor still backfires and won't start even at stock timing. The pick up coil gap should not have changed, but that has to be it. I'll have to check that Sunday. Thanks. :beer:

Now that I think of it, the domes did not come from the same people. The 4 mil domes came from Jeff and I think I got the stock stroke BB domes from Precision Powersports, but Jeff put the motor together when he welded my stock crank. I'm sure he checks the squish, I just don't know what it is. I'll try to check it and let everyone know. Also.........When I test out the 4 mil with +9, will I find out if that is too much timing before the motor grenades? Will there be enough warning signs? That is kind of scary , especially with a local race coming up that I happen to be in charge of.

It's normal for BOTH pipes to sometimes not smoke after the engine gets warm. If it's just one, your carbs are probably out of sync.

Thanks. That's what I kind of thought, but wanted to make sure before I tore something up.

I bumped up my timing from +5 to +9 on my 4 mil Cub and my stock stroke Cub. The 4 mil starts and idles fine, I haven't rode it yet (compression 180 psi, squish around 0.045). The stock stroker (160 psi, not sure about squish) won't start and it backfires. Running 108 octane in both. Of course I'm gonna back the timing down, but just wondering if the difference is due to the stroke, or if it is just an individual characteristic of my particular motor.... "every motor's different" as the saying goes.

I have one pipe that is louder than the other, but I cannot get the silencer apart to repack. The stinger seems to be riveted on, not screwed on with allen bolts.

I plan on having more races. We won't be bracket racing this first one for sure. I'm gonna have a suggestion box for future races to get rider input. As far as starting between the bleachers, the track is too short in either direction to start there. I've got to work on the track this week, and I can get exact measurements on track length, distance to the bleachers, etc. Buzz..we're a LONG way from KC. I'd be glad to have ya'll race, but I'm not sure this little race would be worth your drive.

A 4mill on gas would run in the open 2-stroke class. You could also run it in the pro-mod class as well. I may consider breaking that class up, though; as suggested. I know that I've got a lot of classes to deal with, but I don't really expect to have riders in every class. Not sure how to condense any of the classes, any help would be appreciated. This is the list of classes Jeff Ross ("THEBOM" on planetsand) gave me for places that he races. He did say that I would have to see what shows up, though; and that it's impossible to please everyone with class placement. Thanks. :beer:

Here's what I've come up with so far. Track will open 9:30 AM Saturday, July 28th. Registration at 11:30. Test and tune (3 passes only) from 12:00 to 1:00. Races begin around 1:30. Times are approximate. Here are the classes: Tentative Classes: - Youth Class o Ages 4

Make sure there is a little slack in your clutch cable and that the clutch arm on the case is lined up with the arrow. Did you soak the clutch fibers in oil before installation? Is it installed correctly? The first peice should be a clutch fiber plate, then alternating with steel plates. If there was a steel plate first, I suppose it could cause slipping. That would be an easy oversight. There is no reason for that clutch to slip, gearing doesn't matter.

Is it possible that the stator wires were routed in FRONT of the timing plate? The flywheel will rub the wire and eventually ground it. I had that happen once. Motor started and ran, then died and wouldn't start back. Have you checked anything that's been mentioned already?

Your jetting is probably way off. I have no experience with the single carb, so I'm not much help there. Have you checked the compression? Put in fresh plugs?

I have to disagree with that if the bearings are in very bad shape. I've ruined carriers trying to get the axle out when the bearings are toast. I've had some very bad luck changing the bearings. RED lock tight makes it very difficult to loosen the axle nut. Mine kept coming loose, so I covered it in the red. I had a hell of a time getting it loose. I'm not sure about the blue or green.

Stock boots should fit over the 28 mms. I had some 30's and the stock K&Ns would fit (barely). Other than a throttle cable and some jets, you should be good to go with the 28's.

As mentioned, the center nut probably came loose. BTW I have exactly the same motor/pipes/carbs(I think..or maybe 39mm)/domes, etc. as you, but I don't have any shifting problems. I have a F.A.S.T cluth w/easy pull lever and mod quad lockout. I doubt I have 107 hp either, though....and my timing is only at +5. Good to know that the potential is there for those hp numbers. What jets/temp/elevation are you running?

That's what I wanted to hear! Thanks.

I don't know if I have the 6-ply, but I've got a set of gnarlys and I HATE them for where I ride. I've had them on a Banshee and a YFZ. I could barely pull a wheelie on hard packed dirt on my YFZ with them...all they do is spin. On my Banshee, stock tires hook better. I'll sell mine any day of the week. There just setting in my shop.

So if my engine is due for a rebuild due to low compression, not cylinder wall damage, I have to get the cylinders replated everytime?

Not to hijack this thread, but I have a question to go along with this one. Can you actually hone nikasil, or do you just put in a new piston/rings when its time to rebuild. I've never seen a clear answer to this question. I'm assuming you locked your Cub up/damaged the cylinders some how? When that happened to me, I just sent my cylinders back to Jeff and he had them re-plated. The only down side to me was the few weeks of turn around time. I had actually considered boring through the nikasil and honing the cylinders, but I wasn't sure if it could be done.....and decided it wasn't worth f'in up a $800 or so set of cylinders just to get it put back together a few weeks sooner.

It looks like you've checked just about everything. Did you use a new head gasket after the rebuild? Could the head be warped? I've seen that problem with coolant leaking into one cylinder (as you mentioned). Water will be beaded up on the the spark plug in the affected cylinder. It doesn't take much water at all to stop the combustion. I doubt it is a crank seal b/c the right side would suck in tranny oil and should be noticeable on the spark plug, though I have no personal experience with any crank seal leak at all; only what I have read on this site.

I sealed mine with some silicone. You may also make sure it is torqued correctly; 20 ft-lbs I think.

My 4 mil Cub does the same thing, with 38 or 39 mm PWKs. I can run 300 ft fine, but when I get to about 450 ft, it cuts out. I'm gonna get some billet bowls for mine. I already have the dual pingel and gutted cap. Bigger bowls may help you as well, after you try the gutted cap, pingel, etc.

I have absolutely no problem shifting my 4mil Cub w/lockout. I did when I first put the motor together, but for some reason, it shifts fine now. However, every motor is different.....I know dajoger has said multiple times his wouldn't shift for shit.

We're gonna do this July 28th. I'll keep anyone interested updated as to the time and address of the location (not sure of the exact street address.) Are afternoon daytime races or evening/night races more popular? We have a well lit track, but mosquitoes can be a pest at night. I'll also be getting the information together regarding classes. Jeff Ross has given me a good idea how to to that. He'll be there, as well a some guys he knows from the St.Louis area, some of which have some R1 motors on atv frames.