cr250/250r cylinder interchangeability?????

[reknelb]

I thought I saw a cr250 cylinder on ebay set up for a 250r. Whats the deal, do they fit? Can you swap a whole engine?

[RideRed250R]

i have heard of people using the cr250 heads and cylinders the heads bolt up and the cylinder requires machining so the power valve will work
adam

[reknelb]

What if i wanted to put a 250r cylinder on my cr250, and just get rid of the power valves all together? The reason I ask is, I would like to go with a big bore,300cc, but the biggest they go on the cr250 is 265cc (I'm pretty sure it's because the power valves limit how big it can be bored)

BTW, the cylinder I saw on ebay had all the power valve stuff off and blocked. Said the cr250 ports were better than the 250r????

[PWK39]

I beilive duncan racing used to make a kit to do this.I think they used an 88-89 Cr250 cylinder.It was in some of their old catalogs

[Red Rider]

I'm running a 1990 CR 250 cylinder on my ATC engine. It's just a stock cylinder, but FTZ racing offers quite a few modified CR 250 cylinders for ATC/TRX use. They say the port design is more modern & advanced than the ATC/TRX's, which makes sense since the last TRX cylinder was an '89, and they're still making CR's in '04. http://www.ftzracing.com/ATVpg.html

[Mr. Sandman]

Hey Red, I haven't seen you on the board in while. So are you saying your gonna do the FTZ setup? Just wondering what you might have in store for me for this dune season.

[NICKG]

they used to use the earlier (i wanna say 84) cr 250 cylinders without powervalves, you guys all think that the cr or kx's always had powervalves. the non powervalved cr clyinder was a bolt on deal, just like with a tecate, you need to use the cr piston. worked very well

[Red Rider]

Sandy, I didn't say I was switching to an FTZ cylinder. Did you say I was switching to an FTZ cylinder? Who said I was switching? No one saw me switch. You can't prove a thing!

[reknelb]

So, If I'm reading it right, I could pretty much just bolt on a trx/atc 250r cylinder to my '87 cr250 bottom end, and just dissable or get rid of all the power valve actuating levers and such? This would allow me to go with a 295cc kit or bigger.

Actually, I wouldnt be able to use the trx250r cylinder, right? It's longer or somethuing like that?

[John mendolera]

The 1982-83 cr250 cylinder is the one honda used on they 1985-86 250r's.Just like kxt used 1983 kx cylinder but with little differance in port design.A 1984-86 cr 250 cylinder does bolt on but the atac need's to be modified and you would need major mod to pipe.

[John mendolera]

I like what you did with your R .It look's like a "88"250r. I bought a 1984 cr250r cylinder with atac and it bolt's on my 85 atc motor but the governor hook up,I was going to run a cable like the clutch on throttle side.So when I want the power just pull the lever.It would look a bit cluttered and with the brake on same side a bit of a problem.Do you have any picture's of work you did on side case,I may go the same way.Is there a major differance in power and topend,would it woop a 86-87 t3.

[Red Rider]

Thanks John, I do have a pic of the side case work on my website. As for whoopin' Tecates, I don't know. I haven't raced a Tecate now that the powervalves are fully automatic. Back in 87-89, my buddy had an 87 Tecate, and we'd race all the time, but my powervalves were cable-operated via the throttle. On top end, the bikes were pretty much even, but from a stand still, he'd walk away from me 3-4 bike lengths. With the centrifugal governor-controlled powervalves, my bike is pulling harder than it ever has before, enough to beat a Tecate though? I don't know. I'll have to find one to race.

[EAT_A_450]

So what do you have to do for the 84' & 85' cr atac cylinders to work?

[dansvan]

Work as in run without the power valve or work as in run with the power valve? Without = make a custom exhaust flange or an adapter. with= lots and lots of custom machine work and welding. I am working on an ATAC cylinder on mine. Just got it. Will be making an adapter plate for the stock exhaust flange. I'll have a full write up when all it is all said and done.

[EAT_A_450]

Work as in run without the power valve or work as in run with the power valve? Without = make a custom exhaust flange or an adapter. with= lots and lots of custom machine work and welding. I am working on an ATAC cylinder on mine. Just got it. Will be making an adapter plate for the stock exhaust flange. I'll have a full write up when all it is all said and done.


I don't know- I guess without. Will it have more bottom through top end? which way are you gonna run it? Can't you run a dome head with the 250r piston? My cr head is an 84' I know the atac is diff on the 2 years but I don't know if there will be any diff on the bypass of it.