TZR250 1KT Running on 1 cylinder

[Demon666]

Hi all. My 1KT has been runign on 1 cylindiner.  I have replaced the coil, cleaned the carbs and installed complete new jets, etc.  Full carb refurb.
Fired up first kick, but only runing on one cylinder. Right pipe is cold and no/little smoke on right side.  Any ideas?
Don't want to strip the whole engine unless it's totally necessary, but will do if that's the answer!
Cheers.

[yanw]

Have you tried fresh plugs? I had a similar fault on my 3XV after I swapped some old plugs back in after a plug chop. I put the new/chopped plugs back in and the cold cylinder ran just fine. You may have tried then already but if not it's a cheap test.

[Demon666]

I've checked the spark on both HT leads, and that's OK (using an old plug).  It has new plugs, which I didn't take out, but will check that tomorrow, as it's a simple thing.
Will do a compression test also, in case its a crank seal.

[LCRacer]

Is the non running cylinder plug showing fuel on it? If it's bone dry you have a carb problem, if it's soaking wet it's more than likely an ignition problem. Check to see if that side is sparking with a plug resting on the head and kick it over.

Even if the crank seal is shot you normally get some signs of life from the affected cylinder

[Demon666]

It smoked a little from the right pipe on start, but then stopped running on the right (you could hear it sounded different).
I tried revving it a bit and it revved wildly at one point.  I killed the ignition and it was dieseling (running with no spark/ignition).
I think this is symptomatic of crank seals (either air or oil getting in), but hope someone with more experience can advise.
I will check the reed valves also before stripping the engine.

[rubberfingers]

Hi

Have you swapped the plug leads left to right? The coil is a wasted spark so see if the problem moves to the other cylinder?

Have you checked the piston through the exhaust port?

How about a leak down test?

Andy

[Demon666]

It had not been run properly in years.  I'm just preparing to take the engin out and rebuild it with new seals, gaskets etc.
These older 2 strokes are notorious for crank seals going if they've been left standing for a long time.

[Mick]

Hi

Have you swapped the plug leads left to right? The coil is a wasted spark so see if the problem moves to the other cylinder?

Andy

If he is using the stock Coil remember one HT lead is shorter than the other so it wont reach the other cylinder.

[Jashough]

I know this is an old post but did you solve the issue? I have a similar problem and tried everything listed. I also switched the carbs over so they are running on the opposite sides of the engine and the fault moved with the carb, which suggests it's a carb issue but the have both been rebuilt and rechecked. Any thoughts would be much appreciated. Cheers

[Cexley]

Stuck float or float needle, or the tiny fuel filter 'sock' that sits in the carb fuel inlet pipe is blocked up with crud.  These are often overlooked and block up.

[Kev]

Almost certainly the brass pipe that supplies fuel when on cold start cycle. It’s the one that in the carb body and points down into the carb bowl. Fine wire poked down to the bottom will clear it,

[Jashough]

Cheers for the replies, much appreciated. I have checked the sock and  it's clean. Had the carbs ultrasonic cleaned, but will check the brass pipe. Forgot to add that it starts to tip fuel out if the rear overflow after a while. Would this point to a stuck float? When it does start it has run on both but only for a few seconds before it drops down to one

Thanks again

[Kev]

Go to dtpedia.de in chrome so you can translate. select motor then vergaser, it will help a lot.