new guy with a stock head squish question

[t_shee]

should also mention i would like to stick to pump gas if possible

[Langbolt]

Question: Do you have a really thick base gasket ???

That would raise the Cylinder and cause the excessive squish....I've seen some quads where the owner cut their own gaskets but used waaaay too thick gasket material.

Also an Incorrect spacer plate (if you're running an '86 Piston with the '87-89 long rod) would do this aswell.

You could try a CR250 head gasket they're only 0.020" thick.

[t_shee]

I didn't think to measure the base gasket but I'm pretty sure it is .020 thick. There is no spacer plate but that's about all I know. I can get the number off of the piston if it helps. I remember it is a wiseco and 68mm. So go with a .020 head gasket? How much if any should I have head milled?

[acecarlos]

Base gaskets, OEM's measure .5MM or .020". The CR250R head gasket measures .25MM or .010". Normal squish clearance for an OEM cylinder will vary from 1MM to 2MM or .040" to .060"...you really need to check your squish clearance and perform a full UCCR...check under the BDT Motorsports section in this forum for a full explanation on how to check your UCCR & Squish.

Carlos.

[t_shee]

I thought I did that already. Its all in this post on first page. Let Me know if u need more info

[acecarlos]

Yup you did, I missed the post. Knowing your current UCCR and Squish, calculate what your UCCR would be if you had a .020" Thick Head gasket, a .010", ect...and see if you get the UCCR numbers you need for the fule you will be running like Pump Gas.

Carlos.

[t_shee]

how would i do that? about what uccr should i be looking for? sorry to be such a pain just wanna get it right.

[acecarlos]

Here are the links listed in the http://www.trx250r.net/forum/bdt-motorsports/10657-uccr.html write up, follow the directions for checking the UCCR by calculation, substitute the gasket thicknes (HGV) for each thickness of gasket, .010", .020", ect...

http://www.sacoriver.net/~red/uccr.html

http://www.torqsoft.net/squish-velocity.html (this one comes from Polonda)

If you still need assistance I will post an example...

Carlos.

[Gauthier-250]

Question: Do you have a really thick base gasket ???

That would raise the Cylinder and cause the excessive squish....I've seen some quads where the owner cut their own gaskets but used waaaay too thick gasket material.

Also an Incorrect spacer plate (if you're running an '86 Piston with the '87-89 long rod) would do this aswell.

You could try a CR250 head gasket they're only 0.020" thick.

It almost sounds like you're running an '87 piston with an '86 crank. What's your negative deck height measurement ((distance between top of jug to piston (edge) at TDC))? Check the numbers on the top of your piston. That's the only way that I can see you'll have those squish numbers... unless you're running extra base gaskets or have squish band clearance machined out of the head.

[acecarlos]

Take the head off the cylinder, look at the piston edges whith the piston at BDC...are the edges flush with the bottom of the Port windows...? I they are, then the piston is the correct series for the crank you have in place (85/86 Piston with a 85/86 crank). If the piston edges at BDC are flush or within .5MM (.020"), then the squsih clearance you measured at TDC is correct, however; way too high. For pump gas, a good UCCR is 12/1...a resonable squish clearance is .060"-.070". I would not go to .040" with Pump Gas as you will end up with a UCCR above 13/1...

Doesn't sound like you need to cut the head if you have a .070" squish clearance with NO head gasket. Use the OEM thin metal head gasket at .25Mm or .010" or take one of the thin outer pieces out of the TRX250R 3 piece metal head gasket...they measure .010" (.25MM) as well...

Carlos.