[lbxr]

that makes sense. Ive had it approach the 400 mark a few times on WOT steep hills in first. I have yet to find a hill long enough at low speed to be an issue. Ive had a couple times where it would ping when lugging when It was hot but it subsided quickly. Ive never had to shut it down from heat. I always run premium fuel as well. Im hoping dropping the CR to 9.5:1 will help curb the heat a little and keep it from pinging. I am building the 250 as a complete and if it proves to be less reliable the 225 will go back in. I realize im pushing the limit further, but after a few conversations with frank and his kit thats 11.5:1 that he gets almost 30hp out of I think im well in the safe limit. he swears he runs just premium pump gas. I remember talking with you in moab a couple years ago and comparing notes. seems like out engines were close twins.....

I remember that as well, I should have turned around and joined you guys....I think a 9.5 to 1 CR would be a better choice, especially when lugging the motor when it is hot.

 

[Spawner]

what the hell did I get a friday afternoon case or what!?



You use the 200 fly wheel and the 200 stator and pickups stay with the tw left case. you will have no ttr electrics at all.

that makes a lot more sense. thank you

 

[joeband]

My 2000 TTR225 engine case was already machined to accept the kickstarter shaft assembly .

mine too. it has the place and what looked like a plug that even says "kickstarter" but it needed to be machined, not just popped out.

 

[ben2go]

I'm glad I read this. I thought I read somewhere that the TW250 was a TTR225 bottom end with an ATV 250 cylinder and piston with head, and the TW200/225 output shaft machined to fit the TTR transmission and case with the TW200/225 side cover.

 

[Spawner]

Question of the day, as I continue to amass parts... Will a cylinder head from a yfb250 work for a 250 conversion? yamaha part number 4BD-11101-03-00. My research says yes, but I figured better to double check than be sorry at assembly time. Thank you. Bottom end will be an 03 TTR 225, with a moto4 225 cylinder.

 

[Trail Woman]

If a 250cc would over heat at low speed high RPMs, would an oil cooler compensate adequately?

I'd love to hear more on this. I've learned enough about these engines now that it's starting to make sense.

 

[ben2go]

If a 250cc would over heat at low speed high RPMs, would an oil cooler compensate adequately?

I'd love to hear more on this. I've learned enough about these engines now that it's starting to make sense.

If you're not moving fast, there's no airflow over the oil cooler to cool it. Having the extra capacity will always help.

 

[JerseyJeeper]

For real hot runs I put a little muffin fan on the cooler. For the winter I put a piece of canvas over the cooler that has elastic sewn in.

 

[Grundieg]

I have on my TW (125 originally) an 250cc engine. But it is XT250 engine...

 

[TW-Brian]

I have on my TW (125 originally) an 250cc engine. But it is XT250 engine...

Interesting. . . . . . Is this an actual XT250 engine or an XT225 engine modified to be 250cc's?

 

[Juno]

Curious, doing the straight 225 6 speed conversion will give you what? The new gear range adds what at the top and bottom end of the rpm range? How much HP? 2-3? What is the new comfortable cruising speed? Which sprocket choices are preferred with the 6 speed?

 

[ben2go]

Curious, doing the straight 225 6 speed conversion will give you what? The new gear range adds what at the top and bottom end of the rpm range? How much HP? 2-3? What is the new comfortable cruising speed? Which sprocket choices are preferred with the 6 speed?

If I'm not mistaken there are two different six-speed options, one close ratio and one wide ratio. You can gear for low-end grunt while reducing cruise rpms on the highway. You can also run multiple sprockets on the engine and on the wheel hub to get a similar effect but it requires moving the chain between sprocket sets. Stepping up to the 225 from the 200 will gain a few HP and torque points. Depending on the 225 set up and the use of an aftermarket cam and piston, the torque/HP range can change. There's a lot of varibles to consider. On the TW any HP or torque gain can be felt.

 

[Juno]

Thanks @ben2go I may order one of Fred's production run of extensions just in case I go that route in the future.

 

[ronnydog]

My observation is that it’s a lot of fun! I rode with a friend in the AZ mountains last week at 6000 ft. He has a 2015 XT250 with the smog crap removed and he was slightly faster than me. If we swapped rear tires “26x9x14” he would loose in a race. The build is TW250 SIX SPEED.

ronnydog

 

[Derrick Adams]

Please excuse me for my lack of knowledge. I would like to bump up my TTR230 to a 250 as well. I understand there was some availability of (custom) 11.5:1 pistons for this set-up. This is what I am looking for. "Franks kit" was mentioned in this thread. Who is Frank?