i removed the head.from my 250r name paul turner and there are numbers carved on it

[honda4h]

i need to rebuild the motor. i have no idea how many hrs are on it so i'm not taking a risk. i'm just wondering can any 250r gasket kit work or dose this head need a different size.162966162967162968 markings carved on the head are 1.516 and 22.5cc

[RIDE-RED 250r]

22.5 cc doesn't seem like a high compression setup. But admittedly I don't know off the top of my head what an unmolested head has for capacity...

[honda4h]

neither do i. i had a old dirt bike before and someone shaved the head or something? but a stock gasket would not work. i had to get a thicker one ordered in.i do not want to hurt my motor. super hard to get parts for it around here where i live.

[MTS]

Ill take a bit of a stab in the dark here, i dont know 250r motors much at all. but if i would have to guess the 1.516 is the ext port height a bit low..i would think, but with a 22.5cc head would make for one heck of a high compression bottom end pulling motor somewhere in the 9:1 CCR range without doing the math, whats the rest of it look like?

[RIDE-RED 250r]

MTS, I did a little searching around at a couple of 250r mod shops. I was looking at their cool heads for OEM top ends and the high side of chamber capacity was 22-23cc for pump fuel and the low side was 18cc for race fuel. But that might not be 100% accurate for a stock atc or trx head as those heads were chambered to cr250 profile. But I would think it would be similar.

I'm inclined to say that head is very lightly modified if its modified at all.

[MTS]

Guess i should have said that a bit different, my mistake, it probably was modified little,,numbers to keep track of what is what. the Volume of the head (said 22.5cc) is going to change your compression ratio varying on porting from motor to motor, 22.5 on one motor may make it signifigantly higher compression and require high octane fuel, but stick it on one that has a 2mm taller exaust and your compression will drop down compared to the first one with a shorter port height, and thats where the Stock head gasket or differnt things will come into play...a Bit depending on sqish clearence and thicknesses of gaskets to hit that magic number and keep it in one piece on pump gas. did i make any sense? :lol::lol::crazy: i guess i kind of muddled all of the OP's questions into one hairball of an answer sorry! :lol:

[RIDE-RED 250r]

LOL! No, I get ya. Porting does play a role for sure.

[RubberSalt]

I just tossed the 1.516 number into my software reguarding the exhaust duration. If the number was related to timing. It could mean a 190.3 degree exhaust port. Good reving top end machine there I'd guess.

[RubberSalt]

LOL - White stripes ?:)

Measure down the jug to the top of the exhaust, if it's 1.516, then it's related to your exhaust port. If you get some other magical number - I'm goin ta-.. wait, I'm there. :-p

[honda4h]

pics of a stock 1986 250r head and the paul turner head. 163193163194163195163196

[RIDE-RED 250r]

OK, so it has been shaved a fair bit. But from what I gather, 22-23cc is almost certainly a lower compression, likely pump fuel setup. I bet the head was rechambered to a different (possibly more like a cr250) profile and had to be shaved overall after re-chambering to bring compression back up to what it should be....

[MTS]

Yup..set up for top end!! i forgot the honda runs more stroke,,i was wrong about the port height being low, sounds about right by what rubbersalt posted, pt narrowed the sqish area and changed the angle alot!!..looks more like a YZ!!

[RubberSalt]

The exhaust port timing shows 9725 RPM for optimal flow, but thats only half the info. Compression is the other half. What PSI should this motor be?