Help with head/piston/cpmpression ?'s

[Handyman]

Correct me if i'm wrong with what I'm about to say..... If I'm reading this right. I can get a NOSS MACHINE head with 21cc domes for my 99 banshee with stock bore size Wiseco pro lite pistons will raise the compression a little from stock compression?? If i am wrong please correct me. The reason I ask is because I my bike is past due for a top end kit. I have been looking around and found what I would like to do as far as pistons, head, etc....I dont have the money to have the thing bored out and get bigger pistons etc. So i was planning to get the head from NOSS MACHINE so when I do in fact plane to bore it out and raise the compression some more all I would have to do would be to change out the domes.

[racer]

if you are trying to use a high comp head to compensate for your compression loses through wear, then you are on the wrong path. that is simlpy a band aid, one that is more expensive than the topend kit itself. even if you do take this route you risk complete piston failure. that scenario will send aluminum debris flying around your crankcase, cylinders, and domes. should that happen, you will be out a large sum of money.

[Handyman]

if you are trying to use a high comp head to compensate for your compression loses through wear, then you are on the wrong path.  that is simlpy a band aid, one that is more expensive than the topend kit itself.  even if you do take this route you risk complete piston failure.  that scenario will send aluminum debris flying around your crankcase, cylinders, and domes.  should that happen, you will be out a large sum of money.

393568[/snapback]

I see what you're saying but no I wasn't going that route. I'm going to put in a complete new top end kit. i think i will just stick with Wiseco pro lite pistons with stock specs. If that doesn't fix anything I'll be at a complete loss as to why the comp was 110 and then dropped to 100psi or below after it warmed up. Now I just have to figure how to tell whether or not my jugs need to be honed.

[Shee-Male]

Your compression loss is due to the expansion of the matirials when the engine is warm.

If your gonna go with new pistons (which I think you should) then go oversize if you go with the smallest oversize you won't have to bore it just have them honed.

I'd take it to a local shop to have the jugs checked out properly with a dial bore guage, this will tell you how far you need to go with the honing.

If your running forged pistons stick with around .003-.004" worth of clearence.

[dlnoss]

Handyman,

 

Where are you located? What is your elevation?

[Handyman]

Handyman,

 

Where are you located?  What is your elevation?

393650[/snapback]

 

Central california at about 400-500ft above sea level

[racer]

I see what you're saying but no I wasn't going that route

393626[/snapback]

whew, good.

 

these fellas got you on the right track.

[dlnoss]

Yea, your compression is a little low for that elevation. Make sure the compression checker threads down into the head the same amount as the spark plug does. I wouldn't worry a lot about the drop when it's warm. You might squirt some oil into the cylinder and see if the compression goes up much which would indicate that the rings are, indeed, leaking.

[Handyman]

Yea, your compression is a little low for that elevation.  Make sure the compression checker threads down into the head the same amount as the spark plug does.  I wouldn't worry a lot about the drop when it's warm.  You might squirt some oil into the cylinder and see if the compression goes up much which would indicate that the rings are, indeed, leaking.

394111[/snapback]

The left jug is off and the right one is coming off tonight fter work. I'll take it down to the shop to see if they need honed or bored and to look at the pistons. there is a wierd wear mark on top of both pistons at about the 7 o'clock position.