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Frankenbike build thoughts 1983 RM + 1981 TT250 motor

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I've been contemplating this build for a while now. I've even gone so far as to buy both doner bikes.

The little Yamaha motor should be able to be built up to ~300cc +?(bore & larger sleeve) + cam, carb and a pipe. Maybe some BW 350 parts or 4wheeler motor parts. Stock tt250 claimed ~22hp so maybe a good build could yield 28-29hp?

The simplicity and reliability should be retained. The RM frame has held the XR200, and this motor is only slightly larger and only lbs heavier.. Rough measurements look very close.

I have a powrol XR218 and it just isn't quite enough for my 6ft 2, 210lb. I love that little bike but think this build could be a better replacement for it.

Anyone have experience building a TT250?

Edited by brother-gearhead

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There's a gentleman on here who goes by Fast Frank who has some knowledge building the TT250 engine. If I recall correctly, he built a TT or XT250 engine and married it to a YZ465 chassis.

 

 

Okay, it wasn't Fast Frank, it was Duggy T.

Here's the thread. http://www.thumpertalk.com/topic/614713-vintage-frankenbike-project-yzxt/?hl=%2Byz465+%2Bfrankenbike

Edited by zrxer

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subscribed. Been looking for a TT/XT250 build up thread to get some ideas for a project I've got in mind.

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I built the tt250 with pow roll doing the work on the motor they put the big wheel topend on it then stroked the crank so it basically came out as there 430 kit I had that originally in 88 cr125 broke that frame and then had C and J build a frame for me It is now in an avenger style chassis. Haven't done anything with it for a while, but just got a piston from mickey Dunlop been running an xt 350 piston new piston looks good, I pretty sure Mickey can get you anything you need for your build

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I built the tt250 with pow roll doing the work on the motor they put the big wheel topend on it then stroked the crank so it basically came out as there 430 kit I had that originally in 88 cr125 broke that frame and then had C and J build a frame for me It is now in an avenger style chassis. Haven't done anything with it for a while, but just got a piston from mickey Dunlop been running an xt 350 piston new piston looks good, I pretty sure Mickey can get you anything you need for your build

Hey Frank! Good to see you're still around!  I still have that carburetor. :)

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Have you tried it on any thing yet Mickey Dunlop recomended a trx 400 carb got one off eBay turns out its 38 mm cv will give it a try anyway. Good to see your still here too

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When you are out getting the insulation pick up one of these things:

 

http://www.homedepot.com/p/DuraHeat-23-000-BTU-Kerosene-Portable-Heater-DH2304/100045793

 

Not sure how big your garage is but mine is an oversized two car and this thing blew me away.  I go out there fire it up, go back in about a half hour - nice and toasty.  I normally have to shut it off or turn it down because it's too hot.   I even painted in the dead of the winter with no issues.

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Have you tried it on any thing yet Mickey Dunlop recomended a trx 400 carb got one off eBay turns out its 38 mm cv will give it a try anyway. Good to see your still here too

Not yet. Let us know how that TRX 400 carb works for you.

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Will do, mocked it up in the chassis to see if it would fit, seems to fit fine almost tempted to try it before put in the new piston,

By the way for everyone working on xr50, best carb I ever ran on mine was a 37 mm keihin similar to the pe. It actually came in the honda power up kit I would kill for one of those now. I know you can find an FCR for reasonable on eBay but I am pretty sure it would not fit as they are pretty bulky on top.

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Frank, really hope you meant XR500 not 50. A 37 carb on 50 would be a tad overkill. Ha Ha

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No proof reading skill. You mentioned an arias 600 kit for the XR 500 what size piston is that, And does it need to be sleeved,

Biggest I ever tried back in the day was 540 which didn't work out that good for me due to a faulty bore job, thx

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When I go back to portland this week I will look. Yes it requires sleeve and has one already installed and extra sleeve.

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