250R no top end power

[Iliketogofast]

I just got it running again after the woodruff key sheared in two.

Now it runs good, has good midrange but when you get into the top end it falls flat on it's face. It revs up high and sounds healthy but there is just no power.

When I pulled the plug the outside was black while the inside white part was tan, with one small black area. The ground strap was also tan.

Could it still be jetting? What else could it be?

I'm pretty confused once again, with no idea what could be wrong.

[GPracer2500]

What kind of pipe and porting?

[Iliketogofast]

FMF Fatty, mid-top port.

It can't be that, before I rebuilt it and got the new bottom end it was fine. It has to be some type of problem.

[GPracer2500]

Have you played with the jetting? Reeds ok?

[Iliketogofast]

Reeds looked good when I put them in, haven't screwed with jetting at all because it seems good. 39MM PWK at reccomended settings from ESR, outsides black but the inside white part is tan with a small black area. Ground strap is tan.

Could it be that the header is leaking? I looked in there and there was a little bit of black residue on the front of the cases.

However it had this before and it ran fine, there's just a bit more now.

[Iliketogofast]

I took it out today and it was still running bad so I started playing with the air/fuel screw and all of a sudden it was getting harder to start, then it wouldn't start at all. Took it apart and it had sheared another woodruff key after only about 15 minutes of riding.

Would having my flywheel lightened help this at all? It's pretty heavy, about 2 pounds or so. I'm thinking that if it was easier to turn there wouldn't be so much of a load on the key and it wouldn't fail. Also could that be my power problem as well, that the flywheel has been weighted or something?

[deathman53]

your flywheel keys tend to break from not torquing then enough or your main bearings going bad. I haven't had one break. There is a reason they are breaking. When I tighten the flywheel nut, get everything set, turn it with a 1/2 socket till it turn over the motor. Put the bike is gear, have a friend stand on the rear brake and tighten it more with a breaker bar or impact wrench. I think honda specs that nut to be tightened at something like 80 ft/lbs. Its basically tight enough that you can almost pull your back out.

[Iliketogofast]

Can't be bearings going bad - there is only about 30 minutes on a brand new top and bottom end.

Is it safe to tighten it with an impact wrench?

[deathman53]

most impact wrenches(not talking about automotive shops heavy duty ones) only tigthen to ~80-90 lbs, so I would say its safe.

[Iliketogofast]

So could the problem all along have been that I just didn't have the flywheel tightened down enough or what?

[biff rider#19]

first of all you have to check your compression it should have well over 120 lbs, 2nd your stator could have moved when your flywheel let go.its not uncommon. i have a way to tighten fly wheel it sounds dangours but it wont hurt anything pull plug out get piston allmost to tdc use a piece of 1/2 thick rope, put into plug hole, about 4 or 5 inches turn motor over in direction of tightning nut till it stops then tighten nut you only need yourself to do it

Originally posted by deathman53
most impact wrenches(not talking about automotive shops heavy duty ones) only tigthen to ~80-90 lbs, so I would say its safe.

yeah be careful with impact wrenches on flywheels and such. I know for the 400ex the flywheel bolt is 94ft/lbs might be the same for the 250r, not sure

[Iliketogofast]

I got it tightened, but still no top end.

It has a small amount of top end pull, but not much. It still gains speed, just not nearly as quickly as it should.

Any ideas?

[gandgracing]

What main jet are you running?

[86 Quad R]

i'd suggest you do a WOT plug chop to see what the plug color is.