big bore question

[bansheemorphine]

Last winter i had my 400ex built to a 440 with:
440 piston and sleeve
hot cam stage 2
sparks degree key
1mm oversize valves
and some porting

I rode this for about a week and it dropped a valve and blew on me, i was so dissapointed i actually decided not to race this season which i regret now.

The engine builder i used was a great guy he rebuilt my motor again for about 300 bucks and that was everything from the crank up. Now it is only a 1mm oversize piston the cam and the degree key and it sucks not near as much tourque as i had before.

This winter i was thinking about buying FST's 465 kit and using my existing head and valves but the other sleeve and piston, my question is will this last? or will it just blow on me again? or should i try a 440 again but with stock valves this time. Also can anyone give me a quote on what the machine costs would be to get the sleeve put in?

[F-16Guy]

What do you mean by "dropped a valve"? Did the valve break off of the valve stem, or did the whole valve drop down and hit? It may be that the keepers weren't seated correctly and caused the valve to drop. In that case it would probably be a mistake during assembly. If the valve broke, I'd be looking for a different brand of valve to use or looking for a reason for the breakage in the first place (valve to piston clearance, weak springs, etc.).
I think a properly built 440 is just as reliable as a 406/416/426, so I wouldn't let a little bad luck keep you from building what you want.

[drew416ex]

If you have a piston that is more than stock compression, you dont want to run the sparks key. It will make it run a little hotter than it should.

[maxfior]

Originally posted by drew416ex
If you have a piston that is more than stock compression, you dont want to run the sparks key. It will make it run a little hotter than it should.

x2.

Might also be time to find a reputable engine builder (not saying that this guy isn't good, but has he built more then a handful of 440's?).

Max

[bansheemorphine]

when i said dropped valve i mean it broke off the stem, i believe it was a kibblewhite valve, it was a manufacturer defect not an assembly problem. i'm not sure how many time my builder hasworked on 440s he built my 416 this time and it seems to be holding up great, i was thinking on sending in my cylinder to get rezleeved this time who is a good company to send it to?

[maxfior]

for a resleeve you might want to see if Duncan Racing can do it for you.

M.

[drew416ex]

If a valve broke, it hit something and the only thing that it could hit is the piston. Either it jumped timing, the valve to piston gap was too close, or the springs are weak and it "floated" causing it to hit the piston.

[bansheemorphine]

I wasn't asking why the valve broke, i wanted to know who resleeves cylinders and how much and if anyone has tryed FST's 465 big bore kit

[drew416ex]

Most of the performance shops can do it. FST, powerroll, ct racing, etc. If there is a local motorcycle machine shop they should beable to do it also. I think most charge around 100 for resleeving.

[bansheemorphine]

Thank you

[GOTFEAR]

I have seen this before the over size valves hits the piston you need to cut out the valve reliefs on top of the piston for more clearance