[njfish]

Hi All, I have a 2007 TRX420 that's blowing a little smoke and I think I need to replace the valve stem seals. I'm mechanically inclined as I have 2 antique cars, so I'm not afraid to dig in. What I need help with is a list of ALL parts I'll need up front so I don't get midway and realize I'm short anytrhing. Besides the seals, are there any gaskets I need? Also, since I'm doing this, should I do anything else in there while it's apart? Here's S/N if this helps determine parts: 1HFTE359074004324

thanks in advance.

 

[Jeepwm69]

You'll need a new head gasket and valve cover gasket, and the seals.

Do you have valve spring compressors? You can make some, but cheap Chinese versions are available and work fine for ATV's.

Is your Honda smoking all the time or just on start-up?

 

[misterclean59]

You'll need a new head gasket and valve cover gasket, and the seals.

Do you have valve spring compressors? You can make some, but cheap Chinese versions are available and work fine for ATV's.

Is your Honda smoking all the time or just on start-up?

Another option is to hook your air compressor hose up to the spark plug hole. The pressure holds the valves up so you can remove the springs without removing the head. I've never done this with a four wheeler but I've done this many times on small air cooled engines. In fact on small air cooled engines that are overhead valve, compressed air isn't even necessary. I put the piston at Top Dead Center on the compression stroke and the valve can't push into the cylinder because it hits the piston first. I do my work then pull the valve stem up with needle nosed pliers and install the springs. Experiment first before pulling the head. Worst case scenario would be to pull the head to install the valve......you were going to do this anyway! LOL I think it's worth a try. Hope this helps.

 

[njfish]

Thank you both, I have access to the spring compressor. It smokes at start up and running but sometimes not so much and other times more smoke. I just thought this would be first step before rings.

 

[Carolynskii]

What's the history of the bike has it been sitting up for a long time or has this bike been mud riding? Any mods? Been in water?
I'd question the inconsistency of the smoke before assuming just valves sounds like piston rings and cylinder to me. What color is the smoke? What does the wear on the spark plug say?

 

[njfish]

What's the history of the bike has it been sitting up for a long time or has this bike been mud riding? Any mods? Been in water?
I'd question the inconsistency of the smoke before assuming just valves sounds like piston rings and cylinder to me. What color is the smoke? What does the wear on the spark plug say?

History: No mods, no mud riding, never been in water. During winter I plow 5-10 times, rest of year maybe used 10-20 hours total at weekend "country" house for slow trail riding/grass riding/simple yard work, no or very little garden cart towing. In other words, not worked hard at all. Might sit for 1 month at a time average all year.

Spark plugs looked normal. Smokes at idle and more at acceleration. Not billowing, but enough to be noticeable. White/gray smoke.

 

[shadetree]

11 year old atv ?, i'd say it's time for a top end. new rings, new oil seals through out, cam chain. don't skimp on just valve guide seals, do it once, do it right !.

 

[fishfiles]

I would also do a top end job if I where taking the head off ----do a compression test and see what you got before taking it apart ---- go to G+H ATV and they have a good deal on a upper rebuild kit , I just purchased a kit for my 300's , it included a new jug , piston , rings , wrist pin with c-clips , all gaskets , valve stem seals , oil filter , spark plug and shipping for $249 ---- you can't beat that

 

[Jeepwm69]

I would also do a top end job if I where taking the head off ----do a compression test and see what you got before taking it apart ---- go to G+H ATV and they have a good deal on a upper rebuild kit , I just purchased a kit for my 300's , it included a new jug , piston , rings , wrist pin with c-clips , all gaskets , valve stem seals , oil filter , spark plug and shipping for $249 ---- you can't beat that

Let us know who makes that 300 kit and how it works.

If it's good quality stuff then that's a pretty good deal.