want to boost the compression ratio on 88 250r

[88terex]

hey guys this year i am heading to the drags with my 88 trx250r I have three cylinders that i can play with. two of them are stock and the one is a paul turner big bore but just doesn't seem to cut it. I want to machine my own custom two peice head two play with the compression a bit. as well as advance the port timing. so my main objective is go with the biggest bore, highiest compression ratio and maxx flow, anysuggestions guys?

[Flattrack]

this is a hard question to answer... What is the displacement of the PT BB ? . What cyl do you want to build on stock or PT ? If you build on the Paul Turner what is the Port timming on it? What pipe are you planning to run? Just a few Questions I would ask a customer if they brought me a motor and wanted it to build..along with DO you really want to run race fule or pump gas? Is it going to be drag race only or do you want to pleasure ride it also? THese are the things that you need to answer befor you build a motor. Then we can get in to the other 20 questions...

[flotek]

why would you want to bother machining your own 2 peice head to "play"with static compression? just save yourself alot of mental anguish and buy a damn prodesign billet coolhead and have some custom domes cut of various cc's so you can interchange them for play or drags or whatever.ive got 3 words for you :stroker ,stroker ,stroker

[88terex]

the pro design sounds good, thats not a bad idea it is just that i work in a tool and die shop and isn't really that hard for me to do the machining. just getting the appropropraite domes. also doing some port work to the jug. I am looking to drag this bike as well as keep it off the pavement aswell. what is this spacer you can get to advance the port timing? is their any other mods like decking the top of the jug? I have a paul turner jug aswell as two other stock cylinders but the main objective of this deal is I am trying is just simply an experiment but any suggestions would be a good help and would be much appreciated.

[370banshee]

you can deck the jug if you want... but why bother... just do your milling on the head... i'd say just do up a stock head and forget the damn cool head crap.... the squish is wrong on em.. the easiest way is to take that stock cyl... have somebody drag port it.. toss in a stroker long rod crank.. get a nice ESR pipe and 40mm carb.... then you'll be getting somewhere...

[Flattrack]

I think the Idea of making his own cool head is great this is how new designs come about.. If the oppertunity is there then do it...The R dose not benefit from useing a spacer plate as much as one might think. All the spacer will do is not a damn thing buy move your power band up just a little towards the top. Save your time and money and have the whole Jug ported the way it should be..

[flotek]

the prodesign domes are same angled and recess squiash band as stock ,custom cut
fancy ones are available if you plan to have the luxary of changeing out domes for various performance conditions,if your sure of how you and what cc volume you desire simply machine the stock head down ,but your squash will still be the same but youll gain performance and can easily get +20psi without rechambering

[Flattrack]

I still haven't found a After market head I really like and dose not need rechamberd for my style of porting..I ordered Blanks for the R Just so I can machine my own to my spec. There just isn't enough control on the after parts I have CC domes on the pro design and have seen as much as 1 1/2 cc difference on the same 22 cc Banshee domes LOL ain't that some shit.... Its not like every part is checked when manufacturerd..I know that todays CNC equipment is accurate but then again the people that come in to the Equation aren't ...

[hallz123]

go with a thinner base gastket i will get more clyinder fill

[flotek]

this thread is ancient history