Top end rebuild questions

[efilnicafesin]

I hope this isn't a mee to post, but I've got a few questions about an engine I'm about to rebuild....

87 250x---

I'm changing the head, piston and boring .50 over... I picked up a Wiseco 12:1 piston, which I don't know if I really wanted :o...... Anyway, I'm hopefully ripping into the quad next week to do the work....

Lemme say that the majority of my riding is gonna be backyard with the kids or trail riding balls to the wall.. I don't get a whole lot of time to ride, but when I get the time, I don't want to be fixing the thing everytime I go out...

Is the 12:1 gonna be ok for my use?

What fuel do I need to run? I was told either avaiation fuel or octane boost 104....

Spark Plug? Do I need to run a hotter plug?

I've got a FMF Megamax II full exhaust system that I want to run with a quiet core.... Will it work?

What would the recommended jetting be? I've got a K&N with a few holes drilled in the airbox.....

How much of a increase in HP should I expect?

Is there anything I missed?

[nakomis0]

12:1 is to high. You said you don't want to be fixing well a 12:1 could/will lead to alot of issues.

I imagine you could get thinker base and head gaskets to get the compression to 11:1 or under. With that you could run pump gas and wouldn't have as much heat and blown head gasket issues.

If you do go 12:1 you need to run race gas and definately not octane boost.

Same plug is fine, anything you wanna do to the exhaust is fine too.

Beats me on the jetting and I would guess about a 3hp gain.

[87 250x]

i have a 87 250x running 12.5 to 1 and i don't have any trouble except kick start it when it's hot but my compression
release does not work. my is bored .080 over with hot cams in
it
i run 92 octane in my amoco gold

[efilnicafesin]

Originally posted by nakomis0
12:1 is to high. You said you don't want to be fixing well a 12:1 could/will lead to alot of issues.

I imagine you could get thinker base and head gaskets to get the compression to 11:1 or under. With that you could run pump gas and wouldn't have as much heat and blown head gasket issues.

If you do go 12:1 you need to run race gas and definately not octane boost.

Same plug is fine, anything you wanna do to the exhaust is fine too.

Beats me on the jetting and I would guess about a 3hp gain.

What gaskets would you recommend that are thicker? I like that idea as I have noticed posts with problems regarding head gaskets blowing out...


87 250x
Kick starting is an issue for me as my right knee is a bit f'ed up (ok more than a bit f'ed up :eek2: ) ... I do have the decompression hooked up still, so hopefully I'll be alright. With your setup though, I would expect a higher octane gas to make a big difference... Mine is gonna have the stock cam, with Kibblewhite valve springs and intake valves....


OK now that I know what I'll be up against, what should I watch out for/ what assembly tricks should I know before digging into this... I've done many auto engines, but never a bike engine... I've read some posts, and I have the Clymers manual on it... I've got lots of tools, but all automotive stuff... is there anything bike specific?

[efilnicafesin]

It was also mentioned to me that I may want to put on an oil cooler... whatdoyathink?

[nakomis0]

I don't know enought about thicker base or head gaskets to tell ya what to get. If it was me I would call C&D (our sponsor) tell em what you wanna do, they should be able to help you out and get you what you need.

With the manual you shouldn't have any problems. All I would say is don't over tighten and use a torque wrench.

You could do an oil cooler .. it would keep the motor a bit cooler, probably help it last longer. If you did you should go with the FST cooler.. or a homemade 'RamChargers' version. Either way your gonna spend $150, and about 3+ hours and you would need to tap your cylinder head. Its a good idea.

Or your could take that <$150 and get a cam... cam and higher compression go hand in hand.

[87 250x]

i used Cometic gasket from dennis kirk

come with head gasket , base gasket and i think one other gasket . price is around about 20.00 dollars here is the part number

Top End Gasket Kit #261204

im auto mechanic and was the first quad motor
i have ever done it cake

just make sure your timing is set right
and the top rocker cover seals good

and make sure you mark where the bolts go because that can be a pain in the ***
it not that bad at all . on my i had to replace cam chain
both chain guides and lower timing gear plus piston

follow the manual and you will be fine