smoking and burning oil

[bikewarrior350]

so about 6months ago i rebuilt the topend of my 98 warrior and went through the head and replaced the valve seals and lapped the valves as well. Not 2 rides into the new motor and it started smoking on startup but would go away as soon as the motor was up to temp. today it got really bad again. like really bad. my yard had a huge smoke screen across it after it ran for like 5 min. best part is i keep having to add oil like every other ride which is getting really annoying. ive put valve seals in this bike 3 times in the yr since i bought it and every time the smoking goes away for a short time and then comes back. any ideas whats going on here cause im at my wits end?

 

[tcombs0064]

Sounds like Rings, did you put a new piston and rings in it? or maybe your cylinders a lil scratched up.

 

[87warrior917]

Hmm seems like warriors have a problem with them smoking and then clearing up. I had the same problem with my 87 when i had it. Ever since i rebuilt the top end with new piston, seals, and guides it would smoke on startup and clear up after it was warmed up. Got really annoying, when everyone would just look at me at the trails, made me feel like it was a beater quad or something. Before i sold it i replaced the valve seals AGIAN and still it smoked, and still does cause i know the kid who i sold it to and ride with him sometimes. I havent figured it out, but so far, (FINGERS CROSSED) my 366 motor does not smoke at all.

 

[duneracerweston]

Sounds like ur valves anr bad were the seals ride and it wears them out really quick

 

[87warrior917]

But how would it still smoke if everything in the head was completely replaced? Valves, guides, seals, cam, springs, keepers, rockers....

 

[MotoArts]

If it still smokes when hot, lean towards rings. Valve guide wear/leakage usually shows when cold and (kinda) goes away when hot. Valve seals will usually (key word usually) leak when the guides wear out, causing the stem to wobble/side load on the rubber wiper surface. They don't wear fast if the guides and stems are ok.

My warrior had a shitload of compression, started instantly and ran fine but smoked like a locomotive. Oil would drip out of the pipe.
Pulled the standard bore, scratch free jug off to find the bottom oil rings had lost all of their tension. They were flush with the piston; top rings looked new.

Don't forget to hone a shiny bore before installing new rings. Also measure "taper" of the bore if just reringing. Fresh round rings won't seal well in an oval hole...

 

[bikewarrior350]

i know the rings are good because the jug was bored to a .5mm over wiseco piston and honed(professionally done) and the rings were gapped to spec. i also know that the cylinder is in good condition as i had the whole topend off two weeks ago when i swapped out the bottom end to get a new transmission. theres even crosshatching left on the cylinder so theres no way its rings.

the valve guides have been in the back of my mind for a while but ive never messed with them. how would u tell if there bad? if the valve guides are bad how hard is it to replace them? and im assuming i would i need to buy new valves too?

 

[MotoArts]

It's possible to break a ring when reinstalling the cylinder, but it probably would have started smoking immediately. If its a oil ring, it unfortunately won't show up in a compression or leakdown check.

Have you tried retorquing the head?
Missing or pinched oil galley O-ring in the jug (right rear cyl. bolt)?

Valve guides can only be checked with the head off and valve springs removed. Gotta lift the valve off its seat a little bit and check for play in the guide.
Valves are cheap. If there is ANY wear on the stems or seats (aside from the typical shiny surface), replace them. I bought these on ebay:
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=140518454253
They appear to be stock OE Yamaha valves, with the same markings on both valve heads. Maybe Shindy makes them for Yamaha?? Dunno.

Guides need to be pressed out and in. Some experience recommended for that job...
I would imagine, after having mine apart, that the stock guides should last a very long time. I don't see anything crazy, like weird rocker arm geometry or excessive valve lift, that would make 'em wear out fast. Mine were snug, almost like new (and mine's a '93).

Good luck.

 

[bikewarrior350]

i had the head apart prob 2 months ago and i dont really remember there being much play if any. and it has a new head gasket and the bolts were properly torqued so there shouldnt be leaks there. when you pull the exhaust off its pretty obvious that the exhaust valve is leaking oil though

 

[bikewarrior350]

well i pulled the head last night and discovered that im missing a the valve seats on both valves. Almost didnt even see it was missing cause its always been that way on this bike and ive never had two motors apart at the same time to compair them. im thinking that because the valve springs arent sitting in the correct position mabey thats causing the seals to go bad? im just hoping that the seat being missing didnt dammage anything.

 

[MotoArts]

Valve seats, or valve spring seats? I'm assuming spring seats?
Why/how aren't the valves sitting "right"? There's only one way they'll go in.

Either way, still won't account for oil usage, unless the head is cracked.

Any pics?

 

[bikewarrior350]

http://www.bikebandit.com/houseofmotorcycles/1998-yamaha-warrior-yfm350xk/o/m8049#sch102927

its number 3. im guessing the previous owner decided that they didnt need parts that yamaha put in there cause i never took them out so that would mean there werent ever any in there.

what im thinking is that the inner spring is either able to move around or there isnt enough tension on the spring which would allow the valve to move around more than it should which i would think could wear out the seals.

i have another head from the spare motor i bought but its an 88 and has the decompression lever style rocker arms and is missing the valve covers so id have to swap out the rockers. anyone have any suggestions on trying to pull them suckers out cause i know that the rocker shafts are in there really good

 

[elwood]

your supposed to use a slide hammer to pull the rocker pins out according to the manual. I didn't know the rockers were different I thought you could just change vavle covers, but I see they have different #s

 

[MotoArts]

That's the valve spring seat.
It keeps the springs centered (concentric), along with providing a wear surface (aside from the aluminum) and to maintain valve spring installed height. In a nutshell, manufacturers use this installed height to basically measure the tension the spring can exert, both in the open and closed position of the valve. Too heavy of spring wears out the rest of the valvetrain. Too light will let the valve float at high RPM.

I'm more surprised that you didn't float a valve and poke the piston, since the spring effectively "gained" that 1/4"-ish of height from the missing seat(s).

Anyways, unless the head is cracked, still no reason that I can see for it causing to burn oil unless it totally side loaded the guides and broke one/both. The seals won't wear that fast or bad unless the guide is toast. I don't think by missing the seats that the springs would cock at all since both top/bottom spring faces are ground flat anyways.

I'd keep looking for another clue.

I pulled my rocker shafts cause the cam and rocker faces were destroyed. I used a piece of 6mm all thread and a new header nut (yes, one of the tall ones that holds the pipe to the jug) and an aluminum bar with a 6mm hole in it. I used a new one since the shafts are in there VERY tight and wanted new, sharp threads spread over a lot of surface area. Lay the bar over the cam opening and run the allthread into the shafts. After pulling 4 of them (2 heads worth) both the all thread and the nut were junk, so I recommend only doing one head per nut/allthread.

I think it would be worth your time to strip both heads and at least inspect the guides since you're down this far already (especially if you can get away with NOT pulling the shafts .