Engine rebuild nightmare!

Remove flywheel and inspect woodruff key. It might be sheared.

Do you have decompression mechanism timed correctly? It might be 180 degrees out.

Hi there,
Thanks for the reply - i do fear that flywheel key but the chain was still on the top cog it had just come off the bottom one, might it still have sheered the key. What is the decompression thing? Is it just timed along with the head / valves or is it a different procedure?
Cheers

It does seem to be a bit down on compression actualy from what i remember.. i timed it by along the t on the flyweel and the mark on the case and alined the line on the cam gear with the line on the head - when it didnt start i took the chain off and rotated the crank 360 degrees incase it was 180 out and repeated the above but still tye same?

Timing the decompression is done with the cam sprocket.
As I have never done the decompression timing on a 400/450 engine, it's in your best interest to download a service manual for it. All answers will be in it, including the proper timing sequence to follow. They are less than $20 from tradebit.com

I do have the manual for it and i followed the timing steps for the cam gear from there so ill assume the decompression thing will be operating correctly. What are the likely culpris now - the flywheel key seems likely i suppose, i did take the side cover off before i realised the chain came off , thinking there was an issue with the starter clutch i didnt see any issues but then again i wasnt lookin. Could anything else result in similar simptoms?

I reread all your posts above to get my head around this.
These are interference fit engines. If the timing chain came off a sprocket, the piston could have possibly hit a valve, bending it.
I also still would not rule put a sheared woodruff key on the flywheel. Only way to check this is to pull the flywheel.

Thats not good news i had hiped they were not interfernce engines. There was no vissible signes at all on the piston or valves of contact ( i re-pulled the head to check) is it possible they could still have hit?

02kodiak400 said:

Thats not good news i had hiped they were not interfernce engines. There was no vissible signes at all on the piston or valves of contact ( i re-pulled the head to check) is it possible they could still have hit?

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You would know if they hit...lol. Thats good news for you.

Ok well thats a relief, as you can tell this is my 1st attempt rebuilding anything. What may cause the lowish commpression? Being as it was all good before - i didnt remove the piston or barrel. Could the flywheel key mess up the timing and cause it in some way? Or would the flywheel only effect ignition timing?

I have never done a Kodiak 400 engine. But have experience with lots of Yamaha's.
On the cam sprocket there should be mechanism to operate the decompression. This needs to be timed correctly or the bike will not start. It is very easily timed 180 degrees out. I have done this myself before, and I even know about it....lol.

I am not sure if the Kodiak 400 has this on the cam sprocket. But if it does, it's needs to be timed right. There is a timing mark that will need to be lined up.

I would start there first before assuming flywheel woodruff key is sheared at this point.
FYI, a sheared key will effect all timing.....mechanical and electrical. But you won't know it until you pull the flywheel. All the timing marks will still line up. It's the piston that will not be in the correct position to everything else.

I do not believe the 400 has any decompression mechanism.

My 06 does not.

Hi,
Thanks for all the reponses.
Upon further inspection it appears i have almost NO compression i can put my finger over the plug hole and its like a small breeze but no more. Intake valve is still in spec exhast is wayyy lose (i gaped them both before i put the head on 1st time round) what on earths going on?? Ive taken the valve covers of and the cam shafts still spinning and both valves appear to be opening ..

joey90210 said:

I do not believe the 400 has any decompression mechanism.

My 06 does not.

Click to expand...

I never realized or even thought about this. Good point.

02kodiak400 said:

Hi,
Thanks for all the reponses.
Upon further inspection it appears i have almost NO compression i can put my finger over the plug hole and its like a small breeze but no more. Intake valve is still in spec exhast is wayyy lose (i gaped them both before i put the head on 1st time round) what on earths going on?? Ive taken the valve covers of and the cam shafts still spinning and both valves appear to be opening ..

Click to expand...

I wish I was there to help you out. But when you set the valve clearances, you might have been in the correct position for the exhaust valves. I see this quite a bit.

What could actualy cause the lack of compression? Would timing cause it? Could an exhaust valve have got bent when the chain came of yet caused not niticable damage? I reused the head gasket 2nd time round but surely even if this caused an issue it couldnt make it have almost no compression? Is it possible the large amont of slack could somehow cause the issue? Many thanks

Many things could cause low or no compression. Everything you listed could cause it.
And you never reuse a head gasket. They are crush type gaskets and are a 1 time use. I am sure you already know this though.

Are you 100% sure a valve is not bent? Did you do a valve leak test? Put a liquid (solvent or gas works great) behind it and see it if leaks past the valve seat?

Any updates on this one.

Hi there, i did a crude leakdown twst by pouring fuel over the valves didnt see any leakage, iv driven about 10 miles and it has used oil from the full mark to almost the minium. The smoke gets far better when it gets towards the minimum mark which i find a bit odd. It only had one replacement valve(the exhaust) could there be exessive wear on the intake valve? Its definatly burning oil on harder acceleration when before the rebuild it was only on after run. Could i have increased compression causing this to show? Iv had about 6 of these and it doesnt feel to down on power. Whats my next step? Disassemble and do rings? Ive got a lot into this quad so i want it sorted out. Cherrs

Sounds like you need piston and rings.
I bought a used '02 Grizz. Seemed fine at the sellers house.
Did a warm up ride at home and changed the oil. It started smoking immediately. Needed valve job and piston and rings. Not sure what the PO used in it to keep it from smoking at his place...Good luck........jkm