Hi Everyone. This is my first post. I bought a 2000 Honda Rancher TRX350 knowing it needed a little work but gambling a bit. So far, I've been able to do all the brakes, replace cables, remove and clean gas tank, rebuild the carb and it is running well "on the jack stands". I wasn't able to test it much due to it having no brakes when bought and it kept dying (dirty carb and dead battery).

Long story short, I just got my compression tester and it reads 80psi (yes, i held throttle while turning over). I know it should be 97 ideally. Is this "really bad" or do you think I can get by for a while? Do ATVs have valve adjustments that could improve the compression like my old VWs did, lol? I'm new to ATVs. I'm not the best mechanically but do pretty well and think I could rebuild the top end if I had to but really don't want to and am trying to stay within a budget. Thank you!

Sylvia

 

Yes, you can re-set the valves 0.006" for both. It has a steel rocker cover gasket, so that should be renewed. 350 valve clearances usually get bigger though, so wouldn't affect compression. Problems with excessive piston "blow by" on the 350 is usually burning oil, causing plug fouling. We have a 350 that we bought in, which makes more smoke than a chain saw. The plug was quite badly fouled, this eventually stops the engine, but a new plug and you are away again, so keep a spare plug and socket in the toolkit.

 

Merryman... thanks for the reply. I don't have much smoke. My main question is if that compression is okay and do i likely have some time before having to do the top end or is this something more immediate with 80 psi compression. Thoughts?

 

As long as it doesn't burn much oil, no problem leaving it as is. However the 350 only holds 2 litres of oil. I must have had to re-bore at least 30 350s due to owners letting them get short of oil. I have a spare cylinder and piston now so I can just pop it on when we get a seized 350 in, rather than strip, check if it has been re-bored before, order piston etc, get it bored to suit new piston, all of which takes time.

 

Run it until it hard to start or no power yes rebuild would help but if dont abuse should last for a little while but just keep eye on oil levels.

 

thank you so much!

 

I thought it was nessary to leave the tester on for a few hours for the real slow leaks.
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"I thought it was nessary to leave the tester on for a few hours for the real slow leaks"

That is a leak down test. Compression tests just take a few seconds, and as a compression tester only shows maximum compression, would not alter it's reading anyway.

 

What is the correct compression for the 350 motor? I don't see it in my manual where is should be.

 

Anything above 90psi is OK. There is a de-compressor built into the camshaft which cuts out as revs rise, so you can't be certain of a correct reading at starter motor speeds. A 350 in good order seems to show circa 110psi when spun on the starter.