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maverickxp

non running 00 yz426f

23 posts in this topic

ok, so i just bought my first yz426 this weekend from a negligent, half retarded owner, im coming off of a long history of 2 stroke bikes, so its all a bit different to say the least.

so i bought the bike and it had a few issues and was not running at all. and hasnt been for at least 8 months to a year. i fixed everything and cleaned the carb but it still wont fire, i have run through several different "starting procedures" and none of them have worked. at best it will backfire once in a while

but first a few questions. when i kick the bike i notice air blowing out a hose that comes off the top of the valve cover. is this normal? i can actually hear it coming out of the hose. if not then where should this hose be routed.

secondi have my clutch cable at full adjustment at both ends and still cannot push the bike while in gear. is that normal?

3rd are there any tips for setting the carb for a fresh start, and is it possible that something is missing from the carb that would cause it not to start?

thanks for all the help.

ps i do plan on doing the 450 cam mod once im sure the motor runs ok

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but first a few questions. when i kick the bike i notice air blowing out a hose that comes off the top of the valve cover. is this normal? i can actually hear it coming out of the hose. if not then where should this hose be routed.

The air blowing out of the that hose is normal, it's the crankcase breather. The 'blowing air' is from the crankcase volume changing due to the piston moving up and down. Normally the hose is routed down the front-left side of the engine and is not hooked to anything at the bottom.

secondi have my clutch cable at full adjustment at both ends and still cannot push the bike while in gear. is that normal?

After sitting for a while, the clutch plates will "stick" together and will loosten up if you hold in the clutch lever in while rocking the bike forward and backward.

3rd are there any tips for setting the carb for a fresh start, and is it possible that something is missing from the carb that would cause it not to start?

Yes it is possible to have missing parts that will keep it from running. Do a search for proper starting procedure on the 426.

ps i do plan on doing the 450 cam mod once im sure the motor runs ok

There no mods that involve the 450 cams in the 426. 450 cams will not fit the 426.

You can get a Hot Cams aftermarket exhaust cam that incorporates the same type automatic compression release as the 450. This would be a wise investment on your bike and make it a lot easier to start.

Edited by 2grimjim

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There no mods that involve the 450 cams in the 426. 450 cams will not fit the 426.

Really? There will be several hundred satisfied users of YZ450 cams who will be surprised to hear that.

http://www.thumperta...078#post3706078

http://www.thumperta...040#post5378040

http://www.thumperta...ead.php?t=60381

They fit just fine, but the cam timing marks are not oriented to the 426 head, so they require an alternate timing method outlined in the instructions.

However, it does make less sense to use the OEM 450 cams for this change now than it once did, because for one thing the OEM cams aren't cheaper than the aftermarket ones anymore, and for another, the aftermarket units are made directly for the engine for which they are intended. Because of that, they are simpler to time, and the chain does fit a little better. The quality and functionality of the aftermarket auto decomp units has considerably improved as well.

The correct starting procedure is in the same place that info was, the Common Threads sticky.

http://www.yamaha-mo...troke_vid_a.mpg

http://www.yamaha-mo...troke_vid_b.mpg

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I have tried all starting methods but still no joy. I just fully cleaned the Carb and gas tank again and put another new plug in it. It still wont fire. Any thoughts

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my cousin bought a bike the other day that was doing the same thing... sheared flywheel key was his problem. maybe yours also??

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Have you even checked to see if you have fire? Have you checked the valves? Theres a million and one things it can be on a bike you know nothing about

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Yes. I do have spark and fuel. When I pulled the plug last night it was quite wet so I put in a new one and still nothing. I'm going to check the valves tonight and make sure they are not too tight. I'm.also going to check the compression release and make sure its not hanging up

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that will be part of tonights checks, but wouldnt i be bending valves if it was off??

If you are off one tooth it is possible to not bend valve but for the bike to not start. Some bikes will actually start (with some difficulty) and run very poorly with one cam off by one tooth.

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ok. so the timing is correct. i think its the float in the carb. so i hve a few more questions

1 im getting too much fuel and washing out the plug so do i need to lower or raise my float

2 i messed with the mixture screw but that didnt affect anythin, where is stock or correct position to start at

3. i have a 165 main jet im thinking i should drop it down to a 155? yes or no?

4 any tips on changing tires so i dont keep accidentally putting holes in the damn tubes

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I honestly don't know how to check the valves. If anyone has a how to please post. But the motor was rebuilt about 2 years ago so I'm guessing they are. It did run for a few seconds last night

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Are you sure it's the float level and not fuel bypassing the float valve due to an aged o-ring?

That was my problem, easily verified by hooking up the carb to the fuel supply with the float bowl removed, holding the float in the 'up' posiiton - does gas leak around the sides of the valve? I simply replaced the O-ring and was fine..

..a

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ok. so the timing is correct. i think its the float in the carb. so i hve a few more questions

1 im getting too much fuel and washing out the plug so do i need to lower or raise my float

2 i messed with the mixture screw but that didnt affect anythin, where is stock or correct position to start at

3. i have a 165 main jet im thinking i should drop it down to a 155? yes or no?

4 any tips on changing tires so i dont keep accidentally putting holes in the damn tubes

I honestly don't know how to check the valves. If anyone has a how to please post. But the motor was rebuilt about 2 years ago so I'm guessing they are. It did run for a few seconds last night

3) No. The main is not your problem

2) 1 3/4 turns out is a good starting point

On 1) and the valve adjust, download a manual here:

http://www.yamahaownershandbook.com.au/?r=0

...Then read this:

http://motoman393.thumpertalk.com/tech/valves.html

I recommend using a NEW spark plug. The 426 ignition is a bit weak at starting speeds, and it takes little or nothing to foul them.

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OK. So I adjusted the float level down a hair double checked the timing re-cleaned the Carb. Still nothing. I have spark. But is it possible my spark is too weak

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