Project FZR250 project

G'day, thought I'd start a project thread rather than endlessly bombard the Yamaha 250 forum with posts about whatever is going wrong.
The old owner seemed to give the bike a lot of love, but didn't really know what he was doing I think. Already found about 3 kill switches hidden under the fairings and a bunch of new ground terminals. Exhaust seems to have a spot for EXUP, but nothing connected to it? Guy I got it off bought it as a project and never got round to it, he rekons the motor has been swapped at some point.

So first question on getting it going, is carbies. I pulled them off and thought they would be solid with old fuel. First bowl to come off looks really clean though. Is this some deception or are the carbs actually okay? And what motor is this?

 

Hmm, guess I'll have to temper my expectations a bit. I've got a mate with assess to an ultrasonic cleaner so ill give it a good clean this week while I order some stuff.

Seems the bike is a bit of a Frankenstein too. Frame number pins it as a 2KR, motor number makes it's a 3HX1, and the carb slides look like 3LN 6/7. Exhaust has EXUP, but there's no valve in it or a servo. If I added a servo and vale and whatnot, would it work as an EXUP bike?

 

Nice that sounds doable

 

Could you elaborate? I'm not sure what you mean...

 

Sorry I meant the carbs are different from original, based on what I can tell from the slides

 

Bit of an update on the carbies. I'm still dissecting them, but they are damn clean. Bit of crap from fuel sitting but I gotta say, can't fault them apart from that. I think they've been done recently because all the brass is brand new. Float valve and seat are new I think. Screw that holds the valve seat in I'm %95 sure was a Phillips not a JIS. Is it still worth rebuilding them with new stuff, or is it worth cleaning them and seeing how they go first? My money's worth a lot more than my time...

 

Sounds good haha. Any recommendations on good JIS screwdrivers online?
Are there any writeups on dissasembly on the 3LN6/7 carbs, I could only find the earlier ones

 

Success! Carbs cleaned, wouldnt fit in the ultrasonic so i did it the old fashioned way. New battery, fresh fuel, bit of cranking, and boom. Started. Smokes like nothing youve ever seen before though, but I'm optimistic. Might post a video in a while

 

Bike goes well and starts quickly. Few fuel issues though, im sure none of you are suprised.

Backfires on deceleration with no or little throttle.
Idle is patchy.
Sucks fuel like theres a hole in the tank.

To top it all off, bike died while taking it for a test run, at about 80ks started to lose power. I pulled the clutch in, motor dies. Pull over and the tank is empty. But after filling it up again, no start. Theres fuel coming from under the bike somewhere and it smells of petrol when I crank it.
So yeah. Any ideas?

 

How could this happen suddenly though? It's done multiple cold starts and no problems

 

Checking now

 

Fuel pump doing what its meant to as far as i can tell. No petrol smell from the oil but plug 4 was quite wet. Gave it another crank and it sounds like it wants to start, maybe not firing in all cylinders?
If its the float level, would that cause the backfiring?