I got my 3 kids 4 wheeler for Christmas so i had to go get one so i could ride with & keep an eye on them. It's a 1997 Honda TRX 300 EX.

It had a little bit of oil smoke on initial start up but the price was right so i went with it. A couple weeks ago it was a little low on oil so i topped it off with 10w30 & probably put less than 1 hour ride time on it before i got around to doing the oil change i had planned. I changed the oil & filter with the Honda recommended oil & filter from the local dealer.

The smoke has been getting noticeably worse. Fairly heavy smoke when idling after initial start up, very heavy when reved up in neutral. But will eventually lighten up to where it is only noticeable when under heavy acceleration or if it idles for a few minutes.

There's the history, now the question:
Can someone give me a brief run down on where i should start looking, what to look for & how to diagnose the problem. I'm ordering the shop manual monday so i don't need alot of detail (although details are appreciated) but i would like to start looking in the most likely spot & eliminate possible problems in the order of most likely to least likely.

I'm pretty mechanically inclined and have all the tools. I just need to be pointed in the right direction. Thanks............................................ .........DF1

 

It's going to be the rings or the guides. This is the bottom line for me. Others may dissagree with me. If it's the guides and seals the head will have to come off. If it's the rings, the head and barrel will have to come off. Either way, your done.
Do you really want to take the head off to fix the guides and seals and NOT give it a fresh set of rings? Or if it's the rings do you really want to fix them and NOT freshen up the guides and seals?

If it were mine I would do everything at once and be done with it. Once done correctly, you have many many trouble free years of riding ahead of you.

 

I'm betting its your rings if its smoking while your reving it up.It is light colored smoke and not black smoke isn't it?I agree with Doctorturbo,spend a little extra and not worry about it.

 

I would ride it for a while with the Honda oil in it, see if it stops smoking.
Many times quad owners will use oils other than Honda oil and when Honda oil is put in, the unit will smoke as you described. The Honda oil is high in detergents and will clean the scum of other oils left behind, from internal engine components causing the smoke. I have seen time and time again where the unit is rode for a while with the Honda oil in and they will quit smoking once the scum is burnt out of the inside of the engine

----- Gimpster -----

 

I agree with doctorturbo, however I'd bet that you can get away with just rings and valve guide seals and skip replacing the valve guides. Most top end gasket kits come with the valve seals included and chances are your motor has never been opened up so you could just take your chances by ordering stock replacement rings and measure the cylinder once it's off. You'll need to buy a cylinder hone to to the job correctly, and you can rent a valve spring compressor for free from Advance auto (the one by me has that program at least).

 

Update: The kids were out of school monday so i just had to go riding monday smoke or not. It started out early in the day as a heavy white smoke, constant when idling & heavy when accelerating. But as the day went on the smoke slowly started to go away. It is now down to just a little puffing smoke after first start up and a small amount of smoke under acceleration about like it was when i first bought it. Very minor & not enough to be annoying.

It looks like gimpster was right about about the smoke & honda oil. It also sounds like everyone else is in agreement about the rings & seals so it looks like i'll be picking them up before to much longer to get rid of the last little bit of smoke.

Thanks for the advive guys.............................................D F1