the smoking could also be a bad head gasket but if your going to take the valves out you have to change the head gasket anyway so i would change the seals and the head gasket; hopefully i could help and if you ever have any question just ask away and i will definitly try to answer them.
1998 Fourtrax 300 Engine Work
New to the group. I am rebuilding a Fourtrax I bought for $1000. This thing was in pretty rough shape, but it's starting to come together. I have rebuilt the carb, new exhaust, replaced all bearings, the rear brake plate and hub, the rear diff case and rebuild (pinion side - broke while removing pinion bearing), and the list goes on. It is running great, but it is now smoking at startup. The smoke appears blue, and I am certain it is burning oil. I read that smoke at startup means bad seals. I haven't checked compression yet, because the bike is on stands in my garage, and I don't want to run it to warm up. My question is, should I replace just the valves and valve seals if compression is good, or rebuild the top end as well while I have it apart?
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Yeah, the rebuild kit includes valves and gaskets, including the head. I'm going to comp test after I finish the front ball joints and can turn around in the garage. Thanks for the response.
yep no problem thats the only reason im here.
I had a similar situation. I bought a well used '95 Fourtrax 300 a few years ago for $1500. It started and ran well however it also had blue smoke at start up and also it had no engine braking which I figured was a worn out clutch or two way bearing. I decided I could tear it down and do a valve guide job and replace the two way clutch bearing. I had a few problems in doing all that but basically when I got it running again the engine braking was good however it still smoked at start up. After it was warmed up no more smoke. It does take a little oil and I check it quite often. It has good power and pulls well when I give it the gas. I now suspect I have worn piston rings which is a really big job at least for me. So I will just live with the smoke at start up. That's my experience.New to the group. I am rebuilding a Fourtrax I bought for $1000. This thing was in pretty rough shape, but it's starting to come together. I have rebuilt the carb, new exhaust, replaced all bearings, the rear brake plate and hub, the rear diff case and rebuild (pinion side - broke while removing pinion bearing), and the list goes on. It is running great, but it is now smoking at startup. The smoke appears blue, and I am certain it is burning oil. I read that smoke at startup means bad seals. I haven't checked compression yet, because the bike is on stands in my garage, and I don't want to run it to warm up. My question is, should I replace just the valves and valve seals if compression is good, or rebuild the top end as well while I have it apart?
Thanks for the info. I bought the valve seal kit which includes valves, springs, and seals. My rear end rebuild will be completed this weekend. I'll probably ride for a couple weeks before I do the valve seals. If it still smokes after valves, I'll probably wait a month or so and do the top end. My four wheeler has good power and pull. I have good tires on the rear end and can break traction easily. I'll let you guys know how it turns out.
Yeah, the rebuild kit includes valves and gaskets, including the head. I'm going to comp test after I finish the front ball joints and can turn around in the garage. Thanks for the response.
[/QUOTE
If you are handy replace the timing chain and guides as well it will save you in the end
Yeah, I'd bet valve seals.
So, I finished the rear end build and have been riding for a few days. My wheel was bent from a wreck by the previous owner. Ended up on some rough trails and that bent wheel caused my front wheel hub to fracture and disintegrate, which in turn caused my brakes to intermittently seize (due to debris jamming behind the pads), which in turn caused my tie rod to snap off. Had to get trailered home. Lol. Good times. Got the front end rebuilt and finally decided to do the compression test. Well, I got 100 psi warm. Did the wet test and got 110 psi. I think I should be getting 170 psi per the service manual. I haven't done the valves and seals yet, but I do have the kit. Could it be just the valves?
Finished the valve install last night and will be cranking today. Cylinder looked great. Valves were a tight which may have contributed to the low compression. Will update today.
It all went down perfectly. Had to adjust the valve lash, but not a big deal. Unfortunately, the compression did not increase. Did the wet test again, this time with more oil, and ended up getting 190 psi after a few tests. Fell back to 110 psi after about 5 tests. Cry, cry, cry. I need a top end. Lol. Seems stronger somehow. Oh well. It'll be a while on the TE replacement. Good night and good luck.
I never even did a compression test on my 300 before or after doing the valve seals. It pulled so strong that I never even thought it would have low compression. It still pulls real strong and starts and runs well. Just smokes like crazy until the engine warms up.It all went down perfectly. Had to adjust the valve lash, but not a big deal. Unfortunately, the compression did not increase. Did the wet test again, this time with more oil, and ended up getting 190 psi after a few tests. Fell back to 110 psi after about 5 tests. Cry, cry, cry. I need a top end. Lol. Seems stronger somehow. Oh well. It'll be a while on the TE replacement. Good night and good luck.
Dude, this thing is solid. It does seem more responsive, despite the same result from the compression test. Doesn't smoke much at all. I'm going to ride it for a while before I even consider any more work, hell, I might not even worry about it. I just need to replace the left front wheel (and probably the starter), which is happening tomorrow, and I'm golden. Got two wheels and two stock tires for $40 (don't need the tires). The dude had them lying around.I never even did a compression test on my 300 before or after doing the valve seals. It pulled so strong that I never even thought it would have low compression. It still pulls real strong and starts and runs well. Just smokes like crazy until the engine warms up.
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