New Member with a problem

[Alex03 1]

Looking for a possible answer to a 350 Fourtrax problem when I came upon this site. 
Approx 2000 Fourtrax which runs perfectly fine for a while and then for no apparent reason billows of white/grey smike comes from the exhaust. Switch off and leave it a few minutes and will then start with no smoke. During the smokey period there is no missfire of lack of power.
It had a new piston/rings fitted maybe two years ago but that did not resolve the issue. 
Any suggestions would be appreciated.

[_Wilson_™ 6,567]

Was it ever sunk being it's had some new top end work done ? Oil level ever drop between oil changes ? 

 

Welcome to ATVH Alex. 

[Alex03 1]

This bike is normally only used during the shooting season so can sit about doing very little and as such I have just let it go. It has had this issue for a long time and two years ago I had a new piston, rings and gaskets fitted but this did not cure the issue. I now have the need to use it more often and a couple of weeks back serviced the bike. I have used it a few times over the last week or so with no problem but although there is no smoke there is an oily smell from the exhaust. Last night I ran it for about an hour with no smoke but just as I got back to the yard white/grey smoke began billowing from the exhaust.  When I serviced the bike the oil was at the second marker but on checking after the smoke incident I note that it is now just about the first marker, so is using oil.
I would have thought that if the bore was worn, even with the new piston/rings, there could be buring oil but would be more consistant with the smoke. THis appears to be more of a flood of oil getting into the bore but has no effect on running or power. I am thinking possibly valve seals or guides. The strange thing is if you switch it off, leave it sitting for a few minutes and restart, no smoke. It starts first touch on the button.      

[Fishfiles 20,145]

Hi Alex , Welcome to the forum --- I would start off with doing  a compression test , dry then wet ----  there should be a copy of the manual here on the site 

I also would ask , did you ever sink it in water and maybe bend the rod  or a valve 

[Alex03 1]

To my knowledge it has never been sunk in water. I have owned this quad for about 7 years. I will get a compression test done and see where I am with that. It starts very easily so I would imagine that the compression cannot be too bad.  
I will have a look for a manual on the site. Thanks

[Fishfiles 20,145]

Here the manual link 

 

https://drive.google.com/drive/folders/1VocUaF1K4_fDh_SVCaq3Rkc747M58ZQd

[Alex03 1]

Thanks for the link

[Alex03 1]

Now had the compression tested and is 63psi. Going by the manual this is low but with a worn bore I would expect some smoke constantly and not just randon bellows. Today I used this quad for about two hours and at no time was any smoake coming from the exhaust.

[Alex03 1]

Just as an update I have now solved the issue with this bike. I stripped the engine and found that the bore and piston/rings were fine. Removed the valves and found that the exhaust valve guide was loose. I have replaced the guide and as a temporary measure until I get a new head have put some chemical weld on it. Rebuilt and the bike is running sweetly with no smoke or oily smell. Hopefully success.

[Mark from Northern Iowa 12]

Just a little late to the party. 😁

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I read your thread from the beginning, and the mech in me was thinking something on the exhaust side.

Not knowing that your engine had guides that could possibly move or come loose. haha

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Being on the exhaust side would make sense though.

It would not effect how it was running, because any oil is being pushed out the exhaust as smoke.

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If it would have been the intake side, it would pull it into the engine, burn some of it, and eventually start fowling the plugs.

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Glad you found the problem and posted back.

Now maybe it will help someone else.

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Have a good day

Edited June 25, 2023 by Mark from Northern Iowa