83 250r carb rebuilt. Now fouls plugs.

[Yamaha Tri-Moto]

So my 83 250r was running too rich so I bought a new carb rebuild kit. The Jets are the correct size.

Everything went together well but now it won't stay running for more than a couple mins without fouling a plug. And then won't start again without putting in a new one.

The main issue I'm having is setting the float height. (The manual says 20mm) I'm honestly not sure how to follow the instructions in the manual. It's not much help the way it describes it.

If I bend the tab to far back it pours gas out the overflow, I have it set just past the point where that happens.

Do you think the problem is my float height? Would that set incorrectly foul plugs? Or could it be something else.

[350for350]

What do you mean by fouling plugs? Are they fouling by being too rich or burning out from being too lean? Did you change jet sizes? If you did not, did you visually compare the two sets of jets to check their sizes? I mean by holding them up side by side and looking at the holes in them? Sometimes, the rebuild kits have jets that are different sizes even though they are stamped with the correct number.

[Yamaha Tri-Moto]

The plugs are very wet and black. I will visually inspect the jets to be sure, but they are stamped as the sizes listed in the manual.

I did the blow test on the carb to set the float and the air flow shuts off before the floats are parallel with the body. (The tab is pretty much bent down as far as it will go)

You want the air flow to shut off when the floats are parallel correct?

The trike will run for a few minutes but then stalls out. I'm pretty sure its do to getting too much fuel but maybe its not getting enough?

[ATC King]

How certain are you it's not ignition issues? If it's low on ignition power, it will foul plugs because it's not getting a complete burn.

I'm no Air Fooler expert, but I've had some air cool two strokes, and liquid cooled. You've stated there were problems to start with, so maybe it's ignition.

Sadly, testing resistance on ignition components won't tell you much unless something is dead. You can use an adjustable spark gap gauge. Those cheap things that have a ground clamp and a threaded electrode. You're able to guestimate spark energy by the gap it'll jump. Drum up some support from the air cooled 250R crowd and see if they have a joule estimate.

Also, on any older two cycle, a engine leakdown test should be at the top of the list when problems arise.

[shortline10]

I rebuild a lot of 2 strokes and the most common problem with fouling a spark plug is low compression .

[Yamaha Tri-Moto]

So now I know the issue is definitely the carburetor, I put the carb from my 84R onto my 83 and it ran perfectly.

I opened up the working carb and made my 83 carb identical with measurements, but the machine still does not run properly with it installed.

Can I use this new carburetor (it is 30mm, same as stock) and just replace the jets in it with my rebuild kit?

I would hate to buy it and find out it won't work.

https://www.bikebandit.com/aftermark...p/16986?m=1907

[yaegerb]

So now I know the issue is definitely the carburetor, I put the carb from my 84R onto my 83 and it ran perfectly.

I opened up the working carb and made my 83 carb identical with measurements, but the machine still does not run properly with it installed.

Can I use this new carburetor (it is 30mm, same as stock) and just replace the jets in it with my rebuild kit?

I would hate to buy it and find out it won't work.

https://www.bikebandit.com/aftermark...p/16986?m=1907

Why not have your carb rebuilt?

[ATC King]

New non stock carb, new can of worms.

Do you have a jet drill kit and can you solder jets to resize them? It get's very expensive buying handfuls of jets trying to sort a carb out and then you're left with a handful of jets you can't use.

At this point, I'd disassemble the carb again, to make certain it was clean and none of the air passages were clogged.

[Yamaha Tri-Moto]

Why not have your carb rebuilt?

I did, but it's still not working, so I just bought a new one. hopefully it works.

[yaegerb]

I did, but it's still not working, so I just bought a new one. hopefully it works.

Too bad you’re in Canada. I could rebuild it to like new. If interested, PM me.

[Yamaha Tri-Moto]

New non stock carb, new can of worms.

Do you have a jet drill kit and can you solder jets to resize them? It get's very expensive buying handfuls of jets trying to sort a carb out and then you're left with a handful of jets you can't use.

At this point, I'd disassemble the carb again, to make certain it was clean and none of the air passages were clogged.

I did notice that a little stopper tab on the float was broken off. ( Stopped the float from dropping all the way down) I was able to put a tiny bolt in it and worked pretty good.
I looked on eBay for a replacement float but had no luck.
Other than that it was identical to my working 84 carb.

I'll try out this new carb when it arrives and hope for the best.

I swapped the carbs on my 110 and Tri-Moto 175 with aftermarket ones and had great results.

Thanks for the help.