I decided to rescue a DT250B that I had purchased as a parts bike for my original unrestored bike. The parts bike ran well before I scavenged the ignition switch, coil, stator and flywheel. So I purchased replacements for those items and went to work on it. Being retired allows me to make pretty good progress spending weekdays in the garage. I am still waiting on a few parts before I fire it up. It does have spark and it has very good compression. I’m waiting on a new petcock and UNI air filter. I may have to replace one of the floats because it seems to occasionally get hung up on the guide post if you hold the bowl in your hands and roll it upside down. I’ll update this post once she’s up and running.

imgur.com/a/6R8Hxqg
 

I’m happy to report that the 2fitty fired up on the third kick. It leaks fuel from the bowl gasket which I tried to reuse even though it was hard and cracked….   

It’s just too soft and muddy to take it for a ride. But the herd has now grown to 16 vintage Yamahas and they ALL RUN. This is the only place I can say that where people will understand what it takes to keep that many 50+ year old 2-stroke bikes running.





 

Sounds good!  

You mentioned float bowl gasket was cracked...  obviously that's a problem if it's broken all the way through.  But the original gasket, even if rock hard, should seal just fine after it gets wet with gas again.  They are amazing like that.

Clutch lever seal is leaking.

Nope. Just checked. Those wet spots on driveway were from the leaking float bowl. New gasket is on its way.

That's a sweet front porch to sit out on and think about fixing gaskets on your very lovely 250. Nice!

Brand new Yamaha gasket installed and the bowl STILL LEAKS……
The bowl screws are pretty chewed up so maybe I’m not getting them tight enough. I have four socket head cap screws being delivered tomorrow which should be easier to snug up as needed.

It clearly seeps out of the joint between bowl and carb. The edges of the joint surface are badly dinged up by the previous owner who was tying to deal with the sticking float that I had mentioned earlier in this post. He had obviously been rapping the side to free up the float.

I believe I cured the sticky floating by inserting the tapered tip of a mechanical pencil into the brass tube that fits over the guide pin and gently flaring the edge. I believe it had a burr around the edge of the tube.

But if it is leaking around the joint of the bowl to the carb then the float valve must not be shutting of the fuel supply. Oddly enough there is no fuel coming out of the overflow……… Very frustrating.

Edit:
The carb has been cleaned multiple times in the ultrasonic cleaner and all passages have been probed and blown clear.

Edit #2:
I just searched “leaking float bowl” and wow do I have a bunch of things to try…

Well I seemed to have stopped the leak around the float bowl. There were a few issues to address so I don’t know if it was simply one or all of them.

It appears someone had tried using YamaBond or something similar in the past so I had to carefully remove that from the joint surface with some 600 emery paper.

As I had mentioned earlier, someone beat the hell out of the sides of the carb trying to deal with a sticking float. They dinged up the perimeter edges of the main body and actually cracked the raised lip around the perimeter. That cracked portion was bent inward ever so slightly and may have had an effect on the bowl properly seating against the gasket.

My float valve/needle had substantial wear. To the point where the needle has a pair of grooves in its tapered surface. I installed a different valve/needle that was in better condition although it still has witness marks but no actual grooves. I water tested the valve and it shuts off properly.

As I mentioned earlier, one of the two floats seemed to get hung up while the other float worked fine. I water tested the floats and if I pushed that float to the bottom it would stay there….. I found out it was due to the guide tube being slightly off center which made that float favor one side of the bowl to the point where it would wedge itself against the inside radius of the bowl. You could see a witness mark where the float comes up against the radius. The other float did not have this issue. If you swapped them from side to side the sticky float would again wedge against the other inside radius. So I releaved that area of the inside radius using a tiny ball cutter in my dremel. Basically made that inside radius a little larger. No more sticky float!

I also bought a pair of what was supposed to be genuine Yamaha bowl gaskets off eBay where the seller had the Yamaha label in the photo. I don’t think they are OEM gaskets. They are pretty thin and wimpy, so I actually installed both gaskets!

My final thing was replacing the bowl screws that were destroyed by the previous owner. I used socket head cap screws which allow me to use an Allen wrench and tighten the screws with the carb installed on the intake!

imgur.com/a/wo6FL7a

Sorry I didn’t take any photos of my bowl after the dremel work, but you get the idea.

Good work, Schu.