01 426YZF Running Really Rough

I just bought a 01 YZF 426 and took it out today. It ran fine at first, but then as I would just barely give the throttle a twist it would run high, low, high etc. It ran fine when I would goose it, but other than that it was about as rough and random as they come. Any input for a guy with beginner mechanic skills?

How long were you riding before the problems started? Was it very dusty? When I ride in dry/dusty conditions, I can guarantee that after an hour or so, the air filter will be getting clogged up, causing sputtering. It could be a number of things though, I would check the most obvious things first (spark plug and air filter), then probably look at the carb' for any crap that's found it's way in there.

Sounds like a possible air leak. :)

Sounds like a possible air leak. :)

Good point. Check your manifold clamps between carb' and engine, also carb' to airbox rubber boot. I had a split manifold on my 426 some time ago. A simple way to check for an air leak is, with the engine idling, spray some engine start, or similar product at the manifold joints. If your idle speeds up, you are sucking air through that area. If your bike is sucking air, you can bet it's sucking in dust/dirt too.....

Thanks, I just cleaned the airfilter and I will check for any air leaks.

Also, after about half hour of riding I could not get the thing to kick over (the original owner showed me the trick with the compression lever) but I still was kicking it like a mule and had to start it will a downhill run. You think that might be something with the carb?

Check the float for debris. could have gotten some dirt in there and is clogging up the jets.

While you are at it put a Iridiumn spark plug in it.

Sounds good, but how exactly does a Iridium spark plug improve the performance? Does it conduct better?

Basic maintenance is needed. Clean the air filter, remove the carb and clean it with carb cleaner and blow out with compressed air, empty the gas tank and put in fresh gas, replace the spark plug.

Beyond that is is just fine tuning of the carb. While you have it apart check the float level, they are prone go out of adjustment. Also make sure the fuel screw is properly set.

Awesome, Thanks Satch0922, I just cleaned the carb, air filter, fresh gas and checked the spark plug. I'll check the floats and fuel screw. I dont think the guy I bought it from did hardly any maintenance, but it was a screaming deal.

How does it run after all that? I am looking to buy a 2002 yz426 (asking price is 2700).

what is a screaming deal??

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