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Kodiak ATV won't start

5336 Views 11 Replies 7 Participants Last post by  Fish0rDie
I have a 2000 Yamaha Kodiak 400 that I have had since 2002. I have ridden lots of miles and done (I am sorry to say) virtually no maintenance to it. Late last fall (nearly 2 years ago), I was using it around the farm and it was running fine. After shutting it off for a few minutes, I went to start it and it backfired, blowing the boot off the carburetor (between the engine and carburetor). Try as I might, I could not get it to start after that.

Fast forward (past a shoulder surgery, and many months) and I have been trying to get it going again. I have replaced the carburetor (with a cheap ebay carb) and the spark plug. I have replaced the gas with brand new, super unleaded (non-ethanol). I changed the oil and took off the valve covers and they appeared to be working.

It turns over fine and the spark plug sparks when grounded to the frame or engine.

When I put my finger over the spark plug hole, it is pushing air out when I turn it over and it is pulling air through the carburetor. The carburetor is taking fuel, and (assumedly) injecting it into the engine. There is air (and gas smell) coming out the exhaust.

When I remove the plug, it is not very wet, and only faintly smells of gas (sometimes) and other times smells more like vanilla (yes, like a candle and I have had a friend verify this).

The connections between the carb and engine have been checked for leaks, cracks, holes and are tight.

I have tried pouring gas into the spark plug hole. I have tried spraying starting fluid into the plug hole and into the carburetor. I have tried the starter, for minutes at a time, with the choke on, or the choke off.

Nothing that I have done makes any difference at all.

The only exception to that is when I have sprayed a LOT of starting fluid either into the carburetor, or directly into the head (with the carb removed), after a couple minutes of turning over, it will finally ignite the starting fluid on top of the engine, or in the air cleaner box (depending on which way I did it). The engine never, pops or lets out exhaust smoke, not at all.

A google search suggested the following things:

Incorrect valve clearance "as the engine gets some hours on it, the valves may seat deeper in the valve seats and need adjusting".

The timing is off/the flywheel timing key is sheared. (I'm not even sure that it has one of these.)

So, any thoughts/suggestions?

Thank you so much!
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Step 1. Do a Leak Down check on it
Step 2. Check the valve clearances
Step 3 Take the jets out of the stock carb and put them in the Chinese one. They are rarely
jetted properly.
Step 4 check for a strong spark

Oofah. A lot of information to cover. Look on YouTube for videos of checking the valve clearances. It's not that hard.
Basically you remove the spark plug and set the engine up to Top Dead Center on the compression stroke, take the valve covers off and check with a feeler gauge. If you have screw adjusters it's easy to set them.
A leakdown test can tell you a lot about the health of your engine. First you need an air adapter that screws into
your spark plug hole. I found the house from the Harbour Freight compression tester works fine. Again set the motor
up on TDC but this time you'll need to remove the stator cover so you can have an assistant hold the crankshaft
from turning. Then introduce air into the spark plug hole. Not too much. About 40 psi should do.
Open the throttle. If you feel or hear air coming out of your air box it means your intake valve is either too tight
or hanging open. If you hear air coming out of the exhaust pipe it means exhaust valve too tight or possibly burned.
Remove the house that goes from the crankcase to the air box. If you hear air there it means your rings are not
sealing very well.
As for spark, when cranking, the spark at the spark plug electrode should be bright white or a bit blue. If
it's a dull orange it's weak. Clean all your ground connections and check your batteries health.

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