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Discussion Starter · #1 ·
Hello!
My '03 Tdub started smoking this year (and it's not just overfilled with oil or something.) It's not too too bad yet but it's starting to smell and I don't like it.

The boys say it's "probably the valve stem seals", but unlike the base gasket replacement we already did (which was easy thanks to some threads here), I couldn't find a good walkthrough on what all is involved in that procedure or if there are practical concerns/tips and tricks, etc. Maybe it's so easy that the service manual should suffice?

They also recommended I replace the rings (check the piston ofc) and hone the cylinder while I'm at it, and might as well go up a piston size and bore out the cylinder if I'm going that far. They're saying to save it for winter but I want to be prepared if it gets worse.
It does have over 16k miles on it, and it was an MSF course bike for the first 6k miles until I got it, and I put 10k on it in three years, so it might be ready for a little extra attention.

Thought about picking up a spare cylinder to do big bore if I can get a good deal, since I think stock parts are always good to have as long as they're still in good nick, and I see some people just put a TTR225 cylinder, with either the 70 or (if bored) 71cc Wiseco piston. I know a lot of that is "get what you want" but I'm just wondering if it's a true bolt-on for the TW bottom half, if the base gasket needs to be a particular one for example, if the head is the same, or if there's something else I should be concerned about here if I went that route. I have never had to redo or adjust the timing chain on the TW so that's also intimidating.

I'm rebuilding some two-strokes right now but this is comparatively far more difficult to me on my TW and I just wanted to get some thoughts from others. Sorry if these are baby questions, but I'm still learning!
 

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2 strokes (air cooled) are SO easy!
4 strokes are not complicated, just be careful with timing chain.
The head, with valves, comes off as easy as a 2 stroke head...other than the timing chain.

If you have a compression tester, check compression (ground spark plug, fully open throttle)
If below spec, add some oil through the spark plug oil and retest.
If compression increases, rings are worn.

What weight oil are you using?
What geographic area (ambient temp)?
Condition of spark plug (getting oil fouled)?
 
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Ixel
Just my two cents..
If you have good compression and you are happy with the way it runs ...
Just leave it alone....
A little extra smoke is just a sign of a little extra lubrication....
Just watch your oil level .,
Plugs are cheap.....
There are too damn many mosquitoes on the trails anyway.....
And if the tree huggers are giving ya a hard time ,
There just giving someone else a break 😂
Now if you could just get it to smell like bean oil !
mike from NC
 
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I had a 2000 tw - purchased it used in 2012 -had only 1200 miles or so- got rid of it last year with over 13 k miles -it was starting to smoke a little during start up and WOT - went to 10-50 oil and problems went away -try going up in oil weight before tearing into- or sell and get another newer one that’s what I did
 

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Discussion Starter · #6 ·
2 strokes (air cooled) are SO easy!
4 strokes are not complicated, just be careful with timing chain.
The head, with valves, comes off as easy as a 2 stroke head...other than the timing chain.

If you have a compression tester, check compression (ground spark plug, fully open throttle)
If below spec, add some oil through the spark plug oil and retest.
If compression increases, rings are worn.

What weight oil are you using?
What geographic area (ambient temp)?
Condition of spark plug (getting oil fouled)?
10w40 oil as per stock
I'm in the Ohio River Valley, So this time of year it averages out to about 70-75F (and humid)
The spark plug looked as expected running unleaded, but not oily or black. I recently replaced it (to rule it out) when I had a dirty pilot jet keeping the bike from starting, so I'm keeping an eye on it and the oil level ofc.

I don't own a compression tester, but I am checking with some connections in town (who might also help with a valve job like this. Maybe we can just knock out the valve issue if we find it's not the rings while we're there.)


Also for the most part I'm with y'all saying to just leave it hah! I have a little 80cc 2T that leaks a little oil at the base and head and runs a little rich and I'm just leaving it that way for now because it's better to know all of it is getting enough oil. I've been chasing down leaks on the TW since I got it because it's just getting to that point in its life (I had the classic base gasket leak for like a year before it got bad enough to do anything about) but it just smells way worse with the cooking or burning oil than with a two-stroke imo lol.
 

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It's not too hard to pull the head and install replacement valve seals. The Service Manual is very good at showing how to disassemble and reassemble. A few tips:
1. Once you remove the cam cover, you need to loosen the cam gear bolt. Shove a rag down the hole where the chain goes first, because once you take that bolt off, you'll pull the gear and the gear is indexed on a little pin/dowel that can fall out of the cam. It's a bitch to get it back out of the motor once it falls all the way down.
2. You'll also need to take the side cover off and shove a rag down the hole there too. Just in case.
3. Keep the chain tensioned so it doesn't fall off the lower sprocket. It's hard to put it back on, but if it does come off, use a pick tool to hook it and slip it back while standing the bike more upright. I used a short bungee from the chain to the handlebars to hold the chain up. The stretch of the bungee allows you to thread it through the cam chain cover hole in the head and not lose tension on the lower gear.
4. Do not forget to torque the cam gear bolt. I did that. Ran fine for about 5 minutes before it came loose, the metal dowel fell into the crankcase and the cam was destroyed.
5. It is possible to remove the valves without removing the rocker arms. You only need to remove the cam.
6. To pull the bushing that the cam rides on, I reinstalled the bolt a few threads, then used a claw hammer to pry it out. Some people use a puller, but it's not in that tight.
7. Consider replacing the cam bushing with a 6005 bearing.
8. Be absolutely sure the cam gear and the rotor timing marks are perfectly aligned with their respective timing marks. One tooth off will make a big difference.
9. I bought a set of gaskets that included the seals off eBay for the same price seals cost from Yamaha.
10. You do not need to pull the cylinder off the crank cases. In fact, DON'T. It will mess up the way the rings are aligned to the barrel and how it was broke in. Leave the two bolts over by the clutch bracket attached to keep the barrel and gasket preserved.
11. You need to clean the head from all that oil blowing by the valve seals and coking up the piston head and the valve head. Use brake cleaner and a green scrubby.
12. Lap the valves to the head to ensure a good seal before reassembly.
13. After reassembly, check the valve to head seal using brake cleaner spray. Fill up the cavity in the head on the other side of the valve and look to see if any leaks past the valve onto the combustion head surface. After 5 minutes of no wet leak, it's good. If it does leak, turn the cam to lift the valve off the head, wipe the surface, rotate the valve 1/4 turn and try again. Sometimes there's a little valve lapping paste in there that is keeping the valve from sealing right.
14. You do not need to remove the automatic chain tensioner. You do need to remove the cover bolt, and turn it all the way until you feel it lock into the full open position to relieve the pressure on the chain.
15. Don't forget to turn the chain tensioner to unlock. It will spring back into position to keep tension on the chain. Check timing marks only after you have the chain tensioner back in service.
 

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You will need a valve spring compressor. Admiral made one from a C-clamp. Copy that. Way cheaper than buying one.

Lap that valves while its apart. That will insure its a good seal.

Before replacing the base gasket first try loosening the head bolts and re-torquing them. Often that is all it takes to stop the leaking. Easy to do and free.

If you buy a spare cylinder take your time and find a dirty / rusty one for real cheap. Boring will freshen the cylinder walls and elbow grease will clean everything else.

Stock cylinder can be bored to 70mm. Cheap Chy-knees pistons work well but I like Wiseco for its higher compression.

Good luck. Tony
 

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Not discouraging a top end rebuild, but if you want to prolong use now, 20W50 might reduce oil consumption.
 
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Eventually leaking valve stems can/could cause a buildup of burnt oil reducing power and causing a type of pre ignition knock but unless it does that, or uses and spues oil oil maybe you can live with it as is. … but eventually you’ll have to deal with it.
 
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