J-Madd

Are the cylinders from a 1997 CR250 Nikasil'd? If so, do they have to be replated, or can you bore/hone through the nikasil and leave them unplated? Finally, where would be the cheapest place to get them replated? Thanks

I would think so.......wouldn't the OD of the sleeve be the determining factor there? The cylinder casting should be the same (I think). Maybe someone else could say for sure if it will work.

I've got them, but don't have a scanner, and the file won't post here. For those that have a dyna, know that the "stock" curve on the dyna is NOT the stock CDI curve.

You should be able to run it as is, but it will be softer unless you get it revalved. Sorry, I forget who does that.

Could be a bad ground. Do you still have a kill switch and key? Make sure those are good, or bypassed correctly.

I always tie it into the orange coil wire, and haven't had a problem. (as long as its a normally open circuit kill switch), and ground the other wire.

Here is the timing curve of the stock CDI. As you can see, the timing is never at zero (TDC), like we think, ....at least I used to think that.

Ok, gotcha.

I might add, if the cylinder wasn't damaged, it has to be deto. Bearings/foreign material would damage the cylinder wall, piston and head.

EXACTLY..you need to diagnose what caused this, not just replace the dome. Looks like deto, or metal (i.e. pieces of a bearing) in the cylinder.

YOu need to do a leak down test. And yes, you probably have a leaky crank seal.

This is the minimun safe clearance; maybe not optimal for your setup, though.

I like around 175 - 185 psi on alky, and that seems to be to concensus of some others that I race with. I'm about to bump up the compression in my 392 cub...going from 20 cc (160 psi) to 19 cc domes (?? psi). I'll let you know if it helped or not.

TABLE 2.1 Minimum squish clearances Cylinder size (cc) Clearance (mm) 50-80 0.6-0.8 100-125 0.7-0.9 175-250 1.0-1.4 300-500 1.1-1.5 If this is correct, it should be 0.040'' - 0.055''. Squish on most of my engines is 0.045'' The0.035 that I stated before may be a little tight.

You can't tell without checking it. Depends on how the domes are cut and base gasket thickness. Not sure cc has anything to do with the squish. Most run 0.035'' - 0.045''.

That would be my guess.

OK. :thumbsup: I have no experience with racing with a CVT, but I agree 100% on everything else. Hard to pick up on the exaggeration in a post sometimes. :biggrin:

My times are on a stock chassis, I assumed yours were as well. I think you can get more out of it than 4.20s on a ridgid. Ran my best ever time on my 421 (stock chassis) a week ago [email protected] mph, 1.45 60 ft. Its all about gearing and tires. I finally found the sweet spot with this motor, I think.

There were some 421 Cub cylinders, pistons, and head/domes on planet sand for $600 the other day...just add crank. Great buy if its still there,

QUOTE (ChippewaTSI94 @ Oct 12 2008, 04:30 PM) In a straight up drag race there isn't any "driver skill" besides the launch, and then keeping it straight down the track. If you want to see driver skill, go do MX or watch a rally cross event. That's pretty harsh. I have to disagree with that, Now......does mx or tt, etc take more skill?....Of course, And does drag racing take more money than skill.......yes. But to say that drag racing takes no skill is ignorant.

Just noticed you have the 358 cub. My reply was referring to my 392 Cub, just for clarification.

RDZ has them. He actually has them built by metaltech, I think. I like mine..I may buy another set,

Mine has some port work and has run 4.21 at its best. I'm trying to decide if I want to get more port work done to it as well. 190 lb rider, lightened stock chassis. 4.23 is a good time for that motor, imo.

I got a PE billett basket (srp metals/magic racing). No problems at all..4 yrs and hundreds of passes down the track. Not a sign of wear, other than when the idler gear clip came off and banged around on it.

RDZ has them, I'm pretty sure.