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Discussion Starter #1 (Edited)
Will only start/run on full choke when cold, say <60 degree. With full choke the rpm are to high to shift or idle in gear stoped. If I screw in the idle I can turn off the choke. Any ideas? Does the idel jet need to change, curently at factory size?
 

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I bet you have an intake air leak.
 

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You asked for ideas with very little info, so assuming there is no air leaking in.....
You don't have enough gas going in for the amount of air without choke.
The factory jets use to work, so I would look for gas blockage next.
 

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2000 Yamaha Kodiak 411 4x4 Ultramatic
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If there isn't an intake air leak as previously mentioned, you could possibly have a clogged low speed jet or passage in the carb. The low speed jet usually controls the fuel air mixture from idle to part throttle, before the mid range (if it has one) and main jet circuit starts to work. Did the problem start after you replaced the intake boot? Maybe the pilot air screw adjustment was set to compensate for the intake leak, and with the new part installed and air leak eliminated, the pilot air screw needs to be adjusted back to the stock setting? I have a 2000 Kodiak, the carb is pretty simple to remove, disassemble, and clean.
 

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Discussion Starter #6
2 new carbs with the same result. Compression is 150 psi cold so it shouldn't be a cylinder/valve issue. If the carb had a restriction or air leak it would have a restriction at all tempretures, correct?
 

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if you have no intake leak, I bet you have a timing problem.
I my opinion, its not what is happening, but when.
 

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:)
I know you haven't, that's why I mentioned the when.
Proper valve lash is critical to how these low output, low compression engines perform.....CRITICAL!
To properly set the lash the top end timing to the crank has to be dead on, I use the straw down the plug hole trick to confirm t.d.c. of the piston, then confirm the timing chain is in spec, that the cam is in proper time so the lash can be set to open then close the valves EXACTLY when needed.
If the cam is out of time, determine why. You can have good compression at the wrong time, and the engine will not operate properly, like you have going on now. This is just a guess through a computer screen, but it makes sense to me :)
 

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Discussion Starter #10 (Edited)
Looks like the timeing is not adjustable, so if it is off do I just replace the CDI? Or am I just checking the timeing chain and not that the timing light fires at the correct spot?
 

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You are asking a lot of question that to be answered correctly the one doing the work would need to be there.
To know I suggest you check and adjust the valve lash, to learn if the top end can be timed to the bottom end. Use the straw down the plug hole trick to confirm t.d.c. then inspect other areas from there while setting the lash.
And....your plug looks like its as old as the bike, i would replace that too as these are low compression, low output engines and everything needs to be right for top performance.
 

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Looks dirtier than what I replace each year and I have my engine under water many times a year.
Its the right color just built up with a lot of residue.
You can see where gas has got around the crush washer, your bike must not have a sealed plug boot to the head when installed properly like mine.
 
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