I feel like this bike is bad juju...

So this bike likes no jetting whatsoever nor does it like any needle, or any needle position. Its a big bore rm250 to a 265cc. Has fresh crank seals bearings crank top end reeds etc.  Is hard as heck to start by kicking, will only kick with throttle wide open and spits fuel out the overflow hose when doing so.  Adjusted the float every way possible, no difference.  Fouls plugs like crazy.  Went as lean as possible on the carb, made no difference.  Spooges like no other.  Wont rev clean into the mid/top powerband.  Smokes like crazy when at idle and low rev range.  Does anyone have any clue?  Powervalve was clean and opens/closes freely.  It will bump start fine and start first kick when warm/hot.

i would pressure test to make sure it is sealed up to start. 

What year is the bike? what carb?

If you have the fuel on and just sitting dies the fuel come out of the overflow?

4 hours ago, tom125 said:

i would pressure test to make sure it is sealed up to start. 

What year is the bike? what carb?

At the shop, all the possible tests were done with the engine in the frame. We're pulling the engine out and stripping it down to see what we find internally. But stock Keihin 38mm carb pwk. 2002 rm250

4 hours ago, Wcm250 said:

If you have the fuel on and just sitting dies the fuel come out of the overflow?

No. Fuel only spits out when kicking and when throttle is wide open. Doesn't spit when idle or low rev's. 

I am asking when the bike is not running.

6 minutes ago, Wcm250 said:

I am asking when the bike is not running.

Sorry.  No it doesn't. 

 

 

What should I look out for when splitting the cases?  First time splitting a case with the help of a friend whom has split a case twice. 

I'm not sure that I would split the cases yet without an idea on root cause. Basically just make sure the case gasket is good so the crank is sealed off from trans.

 

Also make sure flywheel key is good. Check that the stator plate marks are lined up. Check clutch side crank seal.

 

Sent from my SM-G930V using ThumperTalk mobile app

 

 

 

 

 

 

But this bike acts like it has a vacuum leak is why I was wanting to split it.  I think that seal between the two cases got crinkled upon previous owner re assembly and got sucked in. I was wanting to split it and replace every single seal in the entire motor with fresh ones.

Sounds like you are on the right track.

Sent from my SM-G930V using ThumperTalk mobile app

Would going to a 265 big bore be okay for longetivity though? Or should I just get a stock bore cylinder and bring it back to a 250 while its apart?

Interested in how you like the 265

3 hours ago, Wcm250 said:

Interested in how you like the 265

Well when I first got it it ran decent. Was hard to start still but I was able to rev into the top end powerband then after I put an hours worth of riding is when problems arised. But I am a 240lb man and on this bike, when I cracked the throttle about half way, the front wheel pointed to the sky in any gear, without having to pull on the bars or compress the forks then yank. Just pure torque. And the back wheel loved to slip and slide, never could get traction anywhere, but it loved to just shoot up big rocks like a rocket. Definitely more of a monster than a stock 250, in which a stock 250 felt more stallable and not ballsy with me on it and kinda bogged. I rode a stock yz250 a handful of times. 

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