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Well actually it's our old Honda 350 quad bike (single cylinder 4 stroke). It is 20 years old, just trying to decide whether to sell as spares or worth repairing (which might be too costly to justify). Poor running and not starting seems to be down to the plug oiling up frequently. Put a new or cleaned plug in and it's fine for a bit and then same happens. Suspect valve stem seals or piston ring shot. Any other ideas or similar experience or recommend anyone down south who is good with this sort of thing etc?
cheers
Does it smoke whilst running? Could you do a compression test? Valve guide seals should be reasonably cheap to do depending on a few things. Surprised if it is running ok it would get that much oil to stop it running without lots of smile being obvious? Have you tried cleaning the carb and making sure all breathers are clean and clear?
It'll be the ring. If you popped in a new piston and ring, got the valves shimmed up you'd be spot on again for another 20 years....in fact that old might even be on rockers so easily adjustable.
Any MX place should be able to sort that out and will know more about that type of engine than a dealer/motorbike place
Suspect valve stem seals or piston ring shot
Think you could be right .
Is it a hard job to whip the head off for a look?
I used to have an XL250 and can't remember it being a big deal to strip down,just had to get camchain sprockets lined up on TDC ,and Robert was your mum's brother . 🙂
This might help if you don't have it:
[url= http://www.mediafire.com/download/yq2442xyt62wfkj/1986-1989+Fourtrax-Foreman+350.pdf ]Fourtrax and Foreman TRX350 Service Manual[/url]
catsplums got most of it. An easy way to check to see if it's valve guide seals is to get someone to follow you and and see if you get smoke when engine-braking. Though i'd reckon you'd have to have no guide seals to foul a plug.
When doing a compression test do a wet & dry test. If the compression is low when the cylinder is dry squirt a few drops of oil in the cylinder to wet the rings. If the compression comes up you've got worn rings (lots of oil through the breather is a symptom of this due to excessive blowby). If the compression is still low you're looking at knackered valve seats.
If you're mildy mechanical and aren't to worried about minor mishaps you should think about fixing it yourself. The 1-cyl, jap, sohc thumpers are relatively easy to do top-end work on although access may be a bit difficult on a quad. You will need a 1/4" torque wrench (5-30ish Nm).
Thanks for the advice and manual link. I'll check the breathers and clean carb first, I don't think it particularly smoked much on start up or decelerating but it has been laid up for a while now because of the problem. I'll see if I can get it going and check this. I've not done a top end engine strip before so a bit wary, just do usual servicing stuff. Down to time and money really, if it looks like a load of hassle I may not bother and just ebay or p/ex it (need another for work) but if we can find someone local to have a look, diagnose and quote reasonably we may hang on to it.
Though i'd reckon you'd have to have no guide seals to foul a plug
I meant to say "load up a plug" which is different and sounds like what you've got. More of 2t thing.
If I was local I'd say I'd give it a go foc. Currently rebuilding a 1984 CR250 including full engine rebuild, shock rebuild, new exhaust etc. Really good fun and wishing I could find a way to make a business out of it...
Just been chatting to colleague, I think actually it's at an age and served us well we'll get shot of it now. Bought off the RNLI near us when it was a couple of years old, we've added another 18 years use so not bad really. Time to look for another newish one I think