Has anyone fitted a TRX 250r engine into a TRX400ex frame? If so,any major problems?

 

What would be the point, 250r frames are all over the place. In addition to having to rig mounts for the radiator, engine and numberous misfitting parts, when you are done you have a 250r with round tubing. Not worth the trouble.

 

I disagree, when you are done, you have a 250r with round tubing and a brand new frame instead of a 15 year old one thats been through who knows how much abuse. It would take some work to get the motor to fit, but not that much. Look for posts by a guy named Sickman on here, he has done the conversion with both a 330r motor and a YZ426, his bike has removable motor mounts so that he can switch the engines back and forth depending on what he wants to run at the time.

 

I wish 250r frames were all over the place. They are extrememly hard to find around my area and they always command top dollar.

 

There are three on ebay right now for around $350 and you could pick up a brand new one from service honda for $830 any year. It's going to b a lot cheaper in the long run to just buy a new one than to have to try to rid everything on, also the red frames I'm my opinion look better than the silver 400ex frames.

Also, I think I read somewhere that the square tubing is stronger.

 

Actually round tubing is much stronger against cracking. I can't explain myself but I am sure somebody can.

 

round tubing is much stonger in crush tests becuase with square tubing the force is only spread along 2 supporting surfaces, with round tubing the force is spread through out the entire surface of the tube when pressure is applied at one point. A round tube frame is also usually slightly lighter as less material needs to be used to get the same strength as square tube.

 

I wouldn't waste my time! 400EX frames are known for being week from the start...they crack and break alot...just get a 250R frame and gusset it and it will be good an strong.

 

The whole point is this.Honda Australia only brought two TRX250r's into Australia back in 1987.The few others that are here were mostly imported by me when the Australian dollar was worth something.Now its worth approx.half of yours(the $850 frame just became $1700 excluding freight and taxes)so importing a complete 250r is not on.On the other hand,there are 400ex,s available from dealers and as I imported over 100 ATC250's,engines are not a real problem.

 

Honda destroyed the jigs for the stock 250R frames, and all that are left are '86 and maybe '87 year frames. We had a guy try buying a stock '89 frame back in '96 or '97 and they were no longer available then. As far as gusseting a 250R frame, it will still break. Mine was broke after every ride, because metal has a way of losing its tensile strength as its flexed over and over. Plus a stock frame is only meant to last a few years when raced anyway. So when it was time for a new frame for my R I went ahead and used a 400EX chassis, because the parts are cheap, it handles better than an R (It does for those who don't believe it), and its new. That way I know when I am racing I can get a new frame every couple of years and and have a new quad again at a low cost verses aftermarket.

I have pipes built and am looking at making aluminum mounts for either the 250R or YZF engine in the EX frame. If interested, e-mail me at Sickman80@hotmail.net.