XT600E Smoking/Low Compression/Oil Consumption

I'd like to get some troubleshooting advice on my 99 XT600E, last fall it started smoking like crazy on start up, white smoke, started up about the same as usual which is to say not immediately but always reliably, except of course in spring when it takes a bit more coaxing, power seems to be the same as when I bought it 3 years ago, it's got 60.000 + km on the odo. at about the same time as the smoking appeared it started using oil like gasoline, would use a whole litre in 2 to 3 hours. I've done a compression check it's got 55lbs :-(

So I'm wondering, is it time for a top end or could the lack of compression be caused by tight valves ? can that also lead to oil consumption ?

I could also use some help with general specs, since my bike is a 99 and XT600's were not imported to north america after 95 I don't have access to the usual manuals. I'm looking for valve adjustment procedure and specs, top end torque values, stuff not to forget relating to gaskets/O rings/seals etc, and any tips or advice would be greatly appreciated.

Thanks guys.

I'm amazed that it runs with only 55 pounds compression .

It sounds like a top end job is in store . The valve seals most likely have seen better days .

Yes . Tight valve clearances can cause low compression . Not to mention burnt valves . Plan on at least having to lap the valves ( for a better seal ) while you have the head off to replace the stem seals .

And , I would at least check the ring end gap while the top is off .

I found an Owner's Manual , but not a Service Manual .

I took the following from that OM :

Adjusting the valve clearance

The valve clearance changes withuse, resulting in improper air-fuel mix-ture and/or engine noise. To prevent this from occurring, the valve clearance must be adjusted by a Yamaha dealer at the intervals specified in the periodic maintenance and lubrication chart

Maybe they think 'we' aren't smart enough to figure that procedure out ...

As far as torque specs , you could use bolt size to determine torque . IINM , most factory service manuals will have a torque chart in the general information section .

I don't know which type of valve adjustment your bike uses , so I can't suggest anything on that front .

Smoke on start up is almost always valve seals. I'd say it is tme for a top end job, probably piston/rebore as well.

Thanks everyone, I have an online pdf manual for an 03 or 04 TT600RE I hope it's good for my 99 XT. it turns out the intake valves were tight so I adjusted those and the exhaust valves to the specs from the TT manual, 0.05 ~ 0.10 mm intake and 0.12 ~ 0.17 mm exhaust. I've gained a bunch of compression but not enough to get the bike running. I was hoping for one more season out of the beast but I guess it's time to pull it apart and dig out the micrometers.

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I've pulled the top end and thought I would let everyone take a look, is it just me or should these parts look much worse than this considering the excessive smoke/oil consumption and the low compression ? I know the tight intake valves were part of the cause for low compression, but I was expecting to see something much worse than this, or will I find the answers when I start taking measurments ? any suggestions ?

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One of the exhaust ports.

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Probably just gummed up rings and bad valve seals, stuck rings. If it cleans up and the cylinder wall to piston clearance is ok, maybe just a new wrist pin, clips and rings, plus the valve seals and a re-lap. If the valves aren't step worn where they touch the seats, then reuse them. If they are, replace them. You can gently relap them and see what they look like. Whatever is in spec, reuse. If there is a step (ring ridge) on the cylinder, it is probably time for a rebore. I see something in the photo, but you can feel it with your fingernail and if a step, rebore. Assuming these don't have nikasil or ceramic cylinder coatings. ( you can tell: no oversize pistons available from Yamaha)

Don't put fresh rings into an engine with a ring ridge, the new rings will hit the step and batter the poo out of the piston until a ring land breaks off or the rings get killed. The cam and valve stuff look great. No scoring, nice and smooth. Don't rearrange any of that, it is broke in perfect.

Most four strokes look about like this when torn down. Unless they sat in the rain for ten years after being run without an air filter, then they look really bad.

Thanks Yamaguy55 thats what I was hoping for too, thanks for all the tips, it's looking not too bad for now, I took some close up detail shots of the rockerarm/cam followers, they look good to an untrained eye. The rings were gummed up pretty bad, the 2nd ring had no movement at all but was fairly easy to remove, I fit the piston back into the cylinder and it seemed a bit loose, I'll have to buy a 4" micrometer to get more accurate measurments, as you can see in the photos the piston has lots of holes for the oil to get through, not sure if the Wiseco has more or less than the oem Yamaha part. checked the side clearance of the conrod big end/crank, slipped a 0.59mm in there but couldn't get an 0.61mm to go, the specs show 0.35 ~ 0.65mm. the specs I have are from a pdf file for a 2004 TT600RE manual, I still gotta check if this thing has a nikasil cylinder cause the manual is saying to replace the cylinder liner if it's out of tolerance. oh yeah and there's no ridge at all at the top of the cylinder :-)

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Piston to wall clearance is the measurement you need. If in spec, put new rings in if the gap is at the loose end or out of spec. If everything is in spec and still meets spec, but it back together ungummed. You can tell the cylinder has a liner: it has a flange on top to hold it in, the head clamps it in place. Plus, there is a very obvious groove where the liner meets the head gasket surface. The shot a few below the exhaust port makes this obvious. I'd certainly change the wrist pin and clips no matter what.

The general rule is one crankshaft rebuild for each worn out cylinder: rebore the cylinder until you run out of rebores, then you need a new rod/main bearings, etc. That has proven to be pretty accurate over the years.

The flats on the rocker arms show they are getting closet to needing replacement. I'd do it now, unless you can't feel that with your thumbnail. I'd bet you can. The XT/TT/SR500s would do this too with lots of miles.

Thanks for you reply Yamaguy55.

I should point out the shots of the rockers were taken in Macro and it makes any lines or grooves look really huge, in fact you can't feel a thing on your finger nail it's as smooth as glass.

Some before and after pics, this really shows just how much grunge collects after 60.000km. the huge globs on the exhaust ports must be from the last days of it's life when it was using lots of oil.

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More to follow.

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More to follow.

Nice before and after. The valve seats should probably be touched up with a cutter to move the contact patch to the middle of the valve face. It is ok to have it towards the outsides, but much much better to have it about 2mm wide, centered in the valve face. Any decent auto machine shop can cut these for you. They used to grind them with special stones, but now they use a pilot and a cutter, makes it glass smooth. The valves are hard faced, so if you go through that too much, they tend to wear quickly. I see the usual pits in the faces. You can just do a quickie redo now, and when the piston needs replacing, replace the valves then. It should be OK for another 20K like that. But by then, you will need a new piston. Depends on how you feel about the bike. If it is a long term keeper, then do the head correctly now.

I notice the intake valves show a definite step, I was going to try my hand at lapping the valves in and using bluing to see where the contact is, if I can get them to seal I'll probably run them for as long as they'll last. in the dirty condition I filled the intake/exhaust ports with solvent and all four valves leaked. before I lap them I think I'll throw them back together and do another solvent seal test just to see what happens when their cleaned up.

I measured the ring end gap in the cylinder and was surprised to see the measurment is twice over what the specs are ! I had to use two feeler guages just to get the 1.07mm. I'm wondering if the specs of 0.30mm ~ 0.45mm are correct for my 99 XT600E since they came from a pdi manual for an 03/04 TT600RE. so much for re-using the old piston.

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It is probably the correct spec. The engines were similar throughout their life. That much ring gap could just be worn out rings. Here's what I was saying earlier: what matters is piston to wall clearance, and ring gap. If the piston is in spec, and the rings are not, re-ring, if both are out, rebore. If you're going to rebore, you should probably redo the head properly while you're there, to prevent another trip. I think you'll find that the wrist pin has enough wear to warrant replacement. Be sure to use new clips.

If you replace the piston, and go with a Wiseco, be advised that forged pistons have a different expansion amount than the stock cast, and they also have higher compression, which would suggest rejetting.

I'd use Yamaha gaskets as well, some of the aftermarket stuff isn't quite so good. There should be an O'ring at the base of the cylinder, replace it too.

I have no idea what level of experience you have, and don't want to insult your intelligence; but:

- Don't forget the assembly lube all over everything.

- Change the oil and filter, and after 300-600 miles, change it again. Don't use car oil. use JASO-MA petroleum oil during break in, switch to synthetic after about 600-1K on new rings and piston, etc.

No problem Yamaguy55 I appreciate every bit of advice I can get, you can never have too much good information, it's time to box up the parts now and have a machine shop advise me as to what the options are. I'll be moving onto the carb next so I'll start a seperate thread, one more question before this thread sits idle while the machinists go to work.

I'm still concerned about the oil consumption issue, a guy from another site mentioned that maby the oil consumption was related to a crankcase ventilation problem, how do I check this ? I noticed one hose leading from the cases right in front of the starter and entering the airbox, that hose was clear with no obstructions, is there anything else to check or do you think the stuck rings and hardened valve seals were cause for the high oil consumption ?

Thanks for your tip on the Wiseco pistons I might research all the options and see what's involved but I'm more interested in simple reliability verses mods, if it needs a piston I'll probably stick with Yamaha, I didn't realize rings could wear so much more than pistons, maby I'll luck out and only have to replace the rings.

The hose to the airbox is the vent, and if unobstructed, should be ok. Be sure your airfilter is intact and properly oiled, and sealing around the edges. Wear often comes from whatever gets past the airfilter. If the airfilter is all foam, with no rubber part where it seals against the airbox, then grease this section so it makes a really good seal. I use an old tub of white lithium grease that is long past wheat I'd use for lubrication to coat the sealing portion on my WRR. If it has a K&N, don't clean it until you can't see the pleats: the existing dirt helps filter the new dirt. You just remove them and re-oil from the inside once in a while. I have one on my truck that I remove once a year, relube from the inside, and reinstall. The truck will be scrapped before I need to clean it.

Some people have had problems with Wiseco, but I never have. I've used them in two and four strokes, they're fine by me. They used to offer them in stock compression, and then a few steps above as well. I believe that somewhere around 10:1 is probably ideal and would still give long term reliability. A compression boost gives better throttle response and better low and mid range. I realize single 600s have plenty, but you can never have too much. ( sort of like too beautiful women and too much ready cash, too good health, etc etc..)

You can drill the stock jets to get a little better fuel mixture. I did this with my XT350, it worked out really well. Look through all of the years of the XT600s, and TT600s, and find what jets are available and start there. Yamaha parts lists are right on line. Although they just redid them, and I don't think the new version is better.

Good luck. let us know how it turns out. Nice photoessay.

My air filter looks to be the stock paper type, bonded to a nylon base which slips into a slot in the airbox and is snugged up when you screw the sidecover on, the foam gasket that seals it to the airbox appears to have never seen grease, I'm not sure if the manual says to grease it. I noticed one of the two intake tracts was dirtier than the other, I think it may be sucking dirt in from one of the intake manifolds, the rubber is losing it's bond to the aluminum manifold.

While looking for a part number I found this hairline crack on the piston skirt, I don't feel so bad now she didn't fire up this spring.

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I noticed one of the intake tracts was noticably dirtier than the other.

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This could be one of the reasons, the rubber is losing it's bond on the flat part of the aluminum intake manifold, I could also feel movement on the round section which leads into the cylinder.

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Time for new spigots. I'd replace the air filter with a foam or K&N. I didn't know they were paper.

I wouldn't mind a foam filter I was used to those on all my two smoker motocross bikes, but I doubt they make one for it. I might try sealing the manifolds with something or maby buy new ones.

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