Guys I've just spent hundreds and hundreds of dollars on my GSXR250 at the mechanics and it STILL isn't running right!!!

The carbs have been reconditioned....new gaskets, o-rings, jets etc etc. Valve clearances sorted....timing sorted.

Replaced the coils as one was poked.....

New plug caps and HT leads and spark plugs....

New battery....

ANYWAY...it's running terribly....starts cold without choke at all and dies when I give it choke. Greyish smoke comes out the exhaust when revved...smells like unburnt fuel.

It won't idle steadily and just feels slow to respond when throttle blipped. I thought it was only running on 3 but I pulled the HT leads off each plug individually to try and find the faulty cylinder and no luck. Pulled the plugs out and they are as black as the ace of spades.....covered in carbon.

Could this just be an air/fuel mixture setting issue?? I don't even know where the air/fuel adjuster screws are to be honest but I'll take a look in the morning.

These bikes are cursed. Why oh why do you guys love them so much??!!! Mine is a 250 which makes it even fiddlier and harder to work on if possible!

So..clean the air filter or get a new one...and then take it to a dyno for £30 and get an air/fuel graph.

Then you can change the jets as required..and there you go..sorted.

Hmmm....the parts are rarer than rocking horse poo....so 'getting an air filter' is not that easy I'm afraid....and besides...I've run the bike using a dummy tank and the air filter unit off completely and it still runs the same...so I think that negates the air filter being a part of the problem doesn't it???.....

Dont take offense but if its been to a mechanic thats worth his salt it should have been fixed or he should have given you a reason for returning it running ruff.

You list a number of replacement parts that have been fitted but did it actually need any of them seeing as its still not running right.

The 250 is super rare, very beautiful, but not alot about.
So.
You could download a service manual that would give carb settings and jet sizes etc.
Then you need to figure out why its so rich.
wrong jets, too much fuel, too much air, very weak electrics. etc.

To check its running on all cylinders you simply spit on your finger and dab each down pipe, it will be skin melting hot if running and cause the spit on your finger to pop.
Do not keep your finger on the pipe as it will cook it!!

Yeah thanks mate, you're spot on. I fair the mechanic wasn't worth his salt and I am now worrying that the 'new jets' are the wrong size, causing the over-fueling issue. Damn it.

Did the spit test and all 4 are running...so it's simply the over-fueling problem to conquer.

I'll have to pull the carbs off AGAIN and check the jets. Yay.

Thanks again for the advice. This website is worth it's weight in gold for me with my GSXR250RR and my CBR400RR!!

Bike sold. Thank god. Someone else's headache now.

Thanks again everyone for the advice.

Shame you could'nt sort it.
Beautiful and very rare bike.

You must have wished bad luck upon me.....the sale fell through, so I am stuck with it a bit longer now.

I had the same problem on my gk76a when I tried to balance the carbs, took the tank off and made longer pipes to reach the bike(3 pipe) 2 fuel and 1 vacuum pipe , started ok but after started to get very slow respond when throttle blipped and sound like running only 3 etc... We found out the vacuum pipe made the problem, as I made it longer the pipe made less vacuum, as we disconnected and started to suck provide more vacuum it behaved. Check your vacuum pipe maybe damaged or blocked.