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Discussion Starter #1
Hello.
putting this into my own thread so I can hopefully sort this out!

This kodiak of mine sounded like it had a flock of birds in it when I got it. Managed to get it out for a few hours which seemed to clear up much of them. There’s still a bit of a high pitched noise in the top of the cylinder.

On the original carb it was sweating fuel. It had very little power under throttle or up a hill. On the flats it maxed out around 45kmh and wouldn’t get to the higher revs.

since that ride I’ve done the valves, swapped the plug for a new one and replaced the carb with an imitation model. I’ve also tried the three different needle settings on the new carb. I also found a weak wire next to the main fuse. I’ve fixed that with a new fuse line.

None of this has changed its behaviour.

The biggest development in my troubleshooting is that the engine is blowing back through the carb. Had I not been test riding without the plastic on I wouldn’t have felt it. As it’s bogging through the revs it’s blowing back. Eventually it overcomes this and will find the higher ones but it takes a long time.
I’ve ordered a new ignition coil to see if that helps.

it seems like a timing issue to me. I’ve checked the TDC to the cam shaft mark and it looks fine.

hoping one of you fine folks can give me a hand with this!
 

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I use the straw down the plug hole to feel the piston at t.d.c., then I look at the marks to see if the chain is tight. Then I rock the crank slightly back and forth to watch the cam move with the crank. Any chain slack and the crank can move but not the cam, thus a timing problem. And if the chain is slack the valve lash timing can vary.
 

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Discussion Starter #3
Thanks Jim!
Now if this method works... let’s say there’s chain slack... what to do about it?

is there a way to still valve lash it using your method to get it right?
 

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Discussion Starter #5
I’ll try the straw method tomorrow and let you know.

now would it matter that it does not have this issue at idle, only under throttle or load?

it made me believe it was the main jet but it clearly seems to be timing.

I’ve had the chain tensioner off and it seems to tension as tensioners do. Anything beyond that I think I’m into removing the cylinder head and side of the engine.
 

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You need the engine timed properly before starting, to get the fuel mixture right.
The deal is, there might be a small amount of chain slack that causes a greater problem at higher r.p.m. than low.
If your tensioner is good, there will be no slack seen or felt when you rock the crank right, then left. I watch the rocker arm when rocking the crank, to look of movement at exactly the same time the crank moves. Rocking back and forth several times.
I use a wrench on the crank for less wiggle to be felt than with a ratchet, and eventually I touch the rocker arm to feel at the same time.
This will make more sense as you do this the first time.
Also, if there is play in the wrist pin, you can feel the crank move before the piston through the straw.
 

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In addition to inspection of the timing, inspect the carburetor adapter boot for cracks and tears.
 

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Discussion Starter #8
I replaced that one early on as the original had a break and I was confident it would help. Still no joy.

I did the straw down the hole trick and TDC is accurately marked.

I haven’t gotten into the camshaft tolerance yet but will get around to that later today.
 

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OK, did you approach t.d.c turning the crank both ways?
You said you are getting blow back through the carb, that is generally from the intake valves not being fully close when she fires, or that has been my experience. you said you only felt this with the lid off, so it is very weak pressure.
Another aspect of this valve adjusting is the feeler gauge. I learned to use an angled blade, not a straight blade. A straight blade does not lay flat, 90 degrees to the opening, for exact fit. My first time adjusting the lash I used a straight blade and thought it was flat, but it wasn't and the adjusting work didn't turn out right.
I heated the blade (its hardened steel) to bend, then re-checked my work to learn the lash was way out. Not to tight, but too loose. Just throwing that out there......
If you're absolutely sure the chain is good, not a problem, and at t.d.c. there is wiggle in the rocker arm(s) so the valves are fully close, the puff of air back through the carb indicates a valve not sealing fully.
It may be time to do a compression test and leak down test with the engine properly timed.
 

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Discussion Starter #10
The chain seems good! Zero play from the crank.

I redid the valves. I put the exhaust to the higher end of spec and looser than before. Now I have a little bit of valve noise but less of a loss of power.

I have always had a bit of a high pitched noise from the right side of the top of the engine. Not sure if it’s related to the entire issue or not.

I don’t think I should adjust the exhaust any further out.

it’s still not quite where I want it to be, but it’s progress.
 

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I suggest adjusting all valves the wide side of the lash range for full valve closure, but didn't say that here earlier....ops :)
With proper lash there is a slight ticking sound, like from an injector.
 

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Discussion Starter #12
So the valves are redone. I think it’s better, but not completely. I’ve still got a bit of a bog at full throttle.

the blow back is definitely improved and bogging is less.

I set the valves at a fairly lax 0.20 and 0.10mm. I could go a little more open?

the last thing I’m going to recheck is the petcock. Any more intel or is this all strictly valve, given the improvements?
 

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:)
Weeeellllllllll...........
I don't know the factory lash specs. I wouldn't go greater than the max for the factory range. That's as good as its going to get with valve adjusting. If you play with opening more, your in territory I haven't traveled.
Now, with the low compression from the slightly opened valves you probably have a slightly fouled plug, I would look to see if its got any residue on it, and replace.
I would set the a/f screw out 2 turns, and make sure there's no crap in the gas. If you find crap in the tank, you can bet its in the bowl too.
 

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Discussion Starter #14
So it seems just okay revving at neutral but still giving me trouble under load.

I redid the compression test. 100psi.

there’s still some blow back at the intake when it’s bogging.

I cleaned up the plug, ran it, revved it, came out very very black and sooty.
 

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If you have the lash adjusted and there is still intake blow back, and you have an incomplete burn as the sooty plug shows, Its sounding like you have internal engine wear, probably a burn/scored valve, maybe more than one.
I think your compression test shows to the lowest side of OK, and this is probably from a valve leak back through the intake.
With the engine at t.d.c. and the valves closed, can you do a leak down test? You should not hear air escaping the intake valves. If you do, that might confirm top end parts are needed now.
 

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Discussion Starter #16
So I’ve replaced the coil and plug.

I also put the fuel filter on. At first I thought it was doing better for a few minutes. Then pretty terrible again.

Still at a loss here. Plug was blackity black carbon soot. Incomplete burn?

can feel the backfires our the airbox and the intake still.
CDI?
 

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Now look for bad parts.
 
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