Take a peek at these plugs

[cmyoch]

I've noticed that I'm smoking on the left side on deceleration plus a plume when I twist the throttle pretty hard. I pulled my plugs tonight to notice that my left plug is pretty black and crusty. I assume that this is burning oil from an issue with rings? I cannot think of anything else that could cause the issue. I'm gathering that I am looking down the barrel of a top end overhaul?

 

[mrkil]

Could be valve seals as well. Both will cause oil to leak into the jugs.
Have you done a compression check on it yet?

 

[retiredgentleman]

Looks like a passing head gasket allowing oil to be sucked into the cylinder from the camchain tunnel.

Top end overhaul...................yes, I'd say that's the solution. What's the history of the engine? If it has not had top end work for 15 or 20 years, then its due for an over haul anyway. A neglected engine is just crying out for some attention

 

[mouser]

smoking on deceleration generally means a valve issue, worn valve stems, guides, and or seals. Check your compression. If it is low give it a shot of oil in the spark plug hole and repeat the test. If it goes up you prob have a ring issue. If not valves are usually at fault.

 

[cmyoch]

It's a 63,xxx mile bike. I put 2,000 miles on it since I got her running last year. I know nothing about the history of the bike but based on what I've had to do to it this past year, I'd venture to guess that she's wore out. It still has a lot of power. The last compression test was 150 on both sides. This test was done earlier this year. I am leaking oil around the block so most likely it's leaking internally as well. I've priced parts and with with a gasket set, 1st over rings and pistons, cam chain, and guide, I'm looking at about $280 before honing and a valve job.

I'll have to start poking around the metro east St. Louis area to see who is reprutable to do the machining and not break the bank.

Once this is done, I think I pretty well have a brand new bike again!

 

[retiredgentleman]

With that many miles and unknown history, its a no brainer. There's no reason to speculate whether its rings or valve seals or gaskets, because the top end has to come apart anyway.

Once you take the top end apart, you measure the components and compare them to the specs in the Yamaha service manual. That will tell you what needs replacing.

 

[cmyoch]

Maybe I should start a new thread for this next question. What has been the typical turnaround time for a "Do It Yourselfer" to do an overhaul? I understand the largest variable is going to be the machine work if necessary. I'm debating riding it out the rest of the season then do this as a winter project.

 

[retiredgentleman]

Why not keep riding and enjoy the bike for the fall season. Once the weather turns nasty, you can take your time to work on the bike.

If you are a professional mechanic, then doing engine work quickly is OK. Most of us are not mechanics, so its best to take your time, measure carefully, double check everything and you will get good results.

I also see that many lads want to order all the parts, before they take the engine apart. That's not a good idea, because you are just guessing. Once the engine is opened up, and measured to the specs, you will know what to order.

 

[cmyoch]

Thanks for the advice RG. You have helped me out quite a bit with advice this past year. Yes I was in the process of getting my parts list together until I read your post. I'll just wait and see what I all need once I have the heads off. At least for now I have a pretty good idea what I'll have spent in parts. The main deal now is finding a good machinist to do the honing. I have time to look.

I got a lead yesterday on another XS that's been sitting in a barn under a tarp for the past 15 years. Apparently the owner has oiled the cylinders every once in a while but I have no idea of the condition. The price is $300 and I figure if it's in decent enough shape, I may swap motors so I can take my time on my current one. The big problem is talking my bride into letting me bring another bike home!

 

[650Skull]

Just tell her you will be saving money by not having to do up your present motor and the other parts you can sell and get your money back to buy her that loverly dress she is after

 

[cmyoch]

Well the barn find was a dud. I was told that it sat for 10 years or so and the owner oiled the cylinders every now and then. Well, the bike sat on a dirt floor for over 20 years. If the cylinders were oiled, it had to have been in year number one only. I kicked it to see if it was free. I got the motor to turn a little bit then froze. Not a good sign. The gas tank had 20 year old gas in it and it appeared to be about 1/8 of rust scale covering the entire inside of the tank, including the gas cap. This thing is way too far gone for $300. I'm not sure I even want to make an offer on the thing and just focus on the one I got. $300 can get me the parts I need for an overhaul. A little more for machine work and I have a new bike that I know everything about.

 

[DirtyErnie]

If nobody's said it yet, and your bike has the vacuum petcocks, check them over real good. It makes a difference if the smoke is blue (oil) or black (gas).
but if your gaskets are leaking anyways... probably time for a change. But have you checked the torque on the 8 big head nuts? Supposed to be something like 25-28 ft/lb, I think a lot of the guys here go as far as 32-34 ft/lb to seal some leaks. Have to pull the tank and upper engine mount to get at all of them. Not really a big deal.
E