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Homewrecker

2000 YZ426 will not run properly

12 posts in this topic

A friend of mine has a '00 426F. He took it to the shop a few weeks ago because the gas left in it over the winter was not preserved and thus ended up varnishing the carb.

The shop cleaned it and everything was fine at the time. When he brought the bike home from the shop he rode it around the block and it ran nicely.

About a week later we go out to ride and he finds now that the bike will not run unless the choke is on. We even turned the idle screw to maximum with no success. It seems to be running rich - popping and sputtering at idle.

Could it be a fouled plug? Keep in mind that the last time it was ridden it ran fine (arond the block).

Any suggestions would be appreciated.

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Of course it would run rich with the choke on. I would suspect a clogged main even though it just got cleaned. Did they change the fuel or just clean the carb? Will it run long on choke or just start and die? Can you rev it at all while the choke is out and it is running?

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Of course it would run rich with the choke on. I would suspect a clogged main even though it just got cleaned. Did they change the fuel or just clean the carb? Will it run long on choke or just start and die? Can you rev it at all while the choke is out and it is running?

I'm not sure about the fuel being changed. With the choke on the bike will run - once you can get the bloody thing started. He rode around with the choke on for about a minute. It can also be revved with the choke on. But once you take the choke off the engine wants to die.

He's changing the plug now so we'll see how that goes.

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the bike will not run unless the choke is on. We even turned the idle screw to maximum with no success. It seems to be running rich - popping and sputtering at idle.

It sounds more like it's running too lean. If you need the choke on for it to run, something is still clogged, or it's getting too much air through somewhere, on the engine side of the carby or the carby itself. Does the fuel screw still have the o-ring on it? Are the hose clamps tight between the carby and engine?

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Check for clogged jets (obviously already discussed), but I would check fittings and what not as well if they had pulled the carb off to clean it. Like ben said, they could have misplaced the o-ring from the fuel screw or something like that.

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Had very similar probs. Make sure to get ALL old gas out of tank/ carb. Sounds like you could have a clog in your carb too. I would pull it apart yourself. Get the Clymer or Yami manual, and follow instructions/ pics. Make sure all jets etc are clear, spraying everything with carb cleaner as you go. Check your float valve and float itself for proper operation (all explained in the manual, and not difficult if you are at all mechanically inclined) also, check that your choke valves are working properly. I actually had someone put mine on backwards, and thus the hot start was the reg choke, and vice versa. Run down the checklist of the fuel system, and you should find your problem. Good luck!

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while race prepping the bike I found a cut wire from the cdi box....may have been my problem...will see tomorrow..I hope ...

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I figured I would update this thread.

We pulled the spark plug and checked for spark. It looked like a good strong spark - blue in colour.

I then removed the float bowl and cleaned out the crap that was still left in there. The Pilot Jet looked partially clogged. I proceeded to clean both the main and pilot jets and the bottom half of the carb assembly. We also purged the gas tank and filled it with fresh fuel.

Once I put everything back together the bloody thing still wouldn't start. There was a small backfire once but that was it. It doesn't even sound like it's trying to start. With every kick now there is a puff of white smoke/vapour coming out of the exhaust.

Could this signify the need for a top end? We're scratching our heads at this point. There seems to be compression - can't kick it over without using the decomp lever.

Any ideas?? :crazy::ride:

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Well you eliminated all the other problems I could think of except the fuel screw. Try messing around with that for a while just turning it in 1/4 turn increments both ways and see what happens then. Also possibly the choke try it with it on and off. It might pay off now to try a few simple things than tear apart the whole thing to find out that there is no problem with the top end

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update on my bike...I was preppng it for a race and had found a wire that was cut coming from the CDI box...resoldered it back in...and the bike runs like a champ...it even idles now....I have learned to not discount the electrical in this equation..so just look around...carefully..it took me soem time to find this wire..mind you the bike started without this wire but just ran bad...

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