Hey xplorer What gas are you running ? What octane rating ? Also Is the gas you are using old farm gas out of the barrel ?

 

Xplor,

You may have already done this, but if not, it might be worth a try. You state that there were no problems before the porting, carb change, and flywheel mods. Since you have an extra 400 engine, I would try changing back to the stock flywheel first with the other mods left in place. If you have the same problem, stick the modded flywheel back on. Then, change back to the stock carb to see if the problem is there. If neither the carb or flywheel solve the problem, it must lie elsewhere. You've been through alot in trying to find the problem, and I'm sure that you can eventually find it. I would try one thing at a time though, so as to isolate the problem so you know exactly what is causing the trouble. Since you've had meltdowns in the past, aluminum/steel shavings most likely got into your crancase and possibly to the crankcase seals. Have you replaced the seals? That would be the next place I would look after trying the flywheel and carb. It wouldn't make sense that it would only run hot in the midrange and not on top if the seals were damaged, but you never know.

 

Dazed, I am running good quality 92 octane pump gas. I have even changed it three times to be sure.

Walexa, I am thinking maybe it is the flywheel. The carb is a bi!ch to change because it needs bigger jets and my airbox boots are cut to fit the bigger carb. Plus the carb got inspected and it seems OK by all standards. Crank seals, like you said, would effect all RPM ranges and the coolant problem would also. (I think) It wasn't the 12:1 Billet Head because she runs hotter all around without it. It is long and tedious but before parting her out I do not want to end up swearing and saying "Darn! It was only that and I sold all my mods"! Maybe I will try and "borrow" a used flywheel from a local used ATV dealer and if it works then just buy it from him... It could work?!?![img]i/expressions/face-icon-small-confused.gif[/img]

 

Xplor,

I don't think it's the flywheel. The purpose of the flywheel is to provide momentum to carry the crank and piston around to the next power stroke, through the intake. It has a sub function of providing a spark at a given time.

If you had problems with the magnets, it would probably run terrible, backfire, or just not run. If you think the magnets are on wrong, I would take a look at the timing first, as in essence that is the setting for the magnets/flywheel.

If you do go in there, check the crank seal very good.

Good luck,

Rainman

 

I just came from suffocating in the garage. That Klotz really gives me a headache! I just sprayed WD-40 "EVERYWHERE" with no apparent rises in RPM. All around the engine, tranny, crankcase etc...I doubt it is that...especially since last week when doing jetting tests with the EGT the WOT was rich thus a lower temperature than specs and the low end was right on with HPD's specs. Only the darn midrange is screwing up. [img]i/expressions/face-icon-small-cool.gif[/img]

Is timing easy for a dealer to spot if it is off? Can they test this in a short period of time? I don't want another 3 hour bill... If the timing is off, what do they change?

 

Xplor,

In theory, it could in fact be the crankcase seal(s). At low rpm's, the engine may not be pulling enough vacuum to pull air through a bad seal. If you have a mid-range pipe, maximum vacuum of the engine would be in the midrange, thus enough vacuum to pull air through wherever the leak could be. Just a thought. I would try the flywheel first, then replace the crankcase seals one at a time. I don't know how hard this is to do, but I would do it before throwing in the towel.

 

If you are going to try the flywheel, i would certainly see if the part numbers match on your other 400. Then you can see if the problem follows the flywheel.

Glad you used WD40. You may want to try it at the rpm you are having trouble with.

Good luck,

Rainman

 

Brian,

Even though you didn't find your problem, at least you got a good buzz off of all those funky fumes [img]i/expressions/face-icon-small-confused.gif[/img] .

Good luck.

-Josh