Top end rebuild - advice needed

[DSmoke]

I have an 81 XS650 that I picked up last fall. The previous owner made it look good, but mechanically needed a lot of work. I have most of it done and got it running. The bike came with a different motor in it, the original number matching motor was pulled with the top end off of it. The motor in the bike right now is blowing a ton of smoke and both plugs are oil fouled and wet. I am trying to get this bike running right for my wife to use while I finish up my XS500 cafe project before moving on to this future project.

I have decided it is time tor rebuild the top end. This would be the first time for me. I am not intimidated by it, I know I can do it. I will probably be back with a question or two, and I also have 2 different manuals that came with the bike. At the moment I have 2 questions.

1. What do you the experts here recommend for the top end rebuild? I am planning on new gaskets, rings, and cam chain. There are a few lights scratches on the cylinder so I plan on honing them. I would appreciate if you could advise of the must do parts for this. I want to order the parts ASAP so I can get going on this. I am trying to avoid the learning curve of getting halfway done to realize I need another part.

2. I have pictures below. The PO said this "I took the valves out of the heads and I had them sandblasted. then I painted the head with Rust-oleum high heat flat aluminum good for up to 2000 f Item no. 248904. I got it at Wal mart. I seat the valves then I put them back in the same valve chamber I took them out. I also put new valve seals in them." You can see in the pictures that the valves are painted and the underside of the head where the rocker arms are is painted with black paint. I am concerned that this might come off and get in the motor. Please let me know if I need to correct this before proceeding. I am planning to pull the valves to check their condition, and read about lapping them so that might happen to.

I really appreciate any and all your feedback. I am hoping this rookie can get this done right the first time!

 

[deadchef]

the inside of the head cover on my 81 was painted black the same as yours. although my 83 wasn't painted. haven't heard a definitive on what years got the paint and which ones didn't. as far as painting the valves, yeah that sounds whack.

just noticed your cam chain guide is toast. add that to the list...

 

[5twins]

I would test the valves for leaks. If leaking, then they need to come apart and be lapped. If not, they can stay together. I would strip the paint off the valve heads, combustion chamber and head gasket surface. People do some strange things to machinery, don't they? On the one hand, the P.O. went through all the trouble of cleaning and painting. On the other, he left a totally FUBAR'd front cam chain guide in there, lol.

 

[DSmoke]

5twins, thanks for noticing the front cam chain guide, I will add Part #05-0006 from Mikes to the list. With everything painted I can't tell what's worn and not worn. After reading about the part it sounds like there should be plastic on it. I will probably get the cam chain tensioner too, seems like that is recommended in other posts here.

Should I use water to test the valves? I am afraid anything else could strip some paint that is in there. Or, maybe I just pull them and strip it, clean it, refit and test.

 

[5twins]

I suppose you could use water. The best way to test for valve leaks is with compressed air. Fit some old spark plugs in the head, set it upside down and level on the bench, fill each combustion chamber with liquid so the valve faces are covered, and blow compressed air in the intake and exhaust ports. Watch for streams of bubbles emanating from around the valve outer edges where they meet the head.

If you look at your 1st pic, it appears the rubber strip from the front guide is sitting there in the top box of parts. Your rear tensioner blade looks OK. Most of us don't replace them. That front guide is nearly always a problem though.

 

[DSmoke]

That's a good eye you have there, yes the strip was in the box. I thought from reading around here it was the tensioner that was the problem. Now, I see that deadchef picked that up too. I will probably leave the tensioner, thanks for saving me some money.

I will be doing some reading up on rebuilding the top end and want to be as thorough as possible, like I said, I only want to do this once on this motor. I do have 2 others that I will need to get to next. Thanks for the advice thus far.

 

[TwoManyXS1Bs]

Paint not designed for air-cooled engines acts like a 'blanket', and tends to hold heat in.
If you've never done one of these before, 'avoid the learning curve' will be a challenge.
Working on a known engine is much different from a 'basket case'.
Assume everything is worn out-of-tolerance, and measure/mic all parts referencing a good overhaul manual.
Visually identifying suspect parts is an experience skill, take your time, be scrupulous...
The guys on this post are very good at eyeball scanning parts if you post crisp/clear pictures.

 

[DSmoke]

Thanks for the info about the paint, I was debating having it blasted again, now I am seriously debating it. I am sure my powder coater can do it for a good price. Based on the condition of the rest of the bike, I don't really trust anything the PO did. I plan to read both the manuals tonight to get a good parts list and to-do list. Then I will go through each item and parts that needs put back together, trying to visually build it, inspecting each part. I then plan to read more on here about each item I question before really getting into it.

 

[deadchef]

if you are just stripping paint i would suggest the heavy duty aircraft stripper from napa or make a quick soda blaster setup. i would check those valve seats too. if the po had everything sandblasted i doubt you can just lap the valves back in. i could be wrong but such heavy abrasive on a seat might need to be cut.

 

[TwoManyXS1Bs]

Please excuse this waltz thru ancient-land...

In 1972, our charge for a top-end overhaul on a single cylinder H*nda 100 was $45 labor plus parts.

On a several occasions, an owner/customer would appear with an empty frame, crate with engine bottom end, boxes of grungy top-end parts. "I want a top-end overhaul, and I want a discount because I've already done half the work!"

"Yessir. That's $90 plus parts..."

Study those manuals, download the parts diagrams, you've got your work cut out for you.

 

[DSmoke]

After that waltz, which I enjoyed, I might go a different direction. There is a motor in the bike now, complete and runs. I think what I might do is pull and rebuild the motor that is in it. This would have a few benefits for me and give me the experience to build the number matching motor the way I want for the final version of this bike.

 

[member3480]

For what you did so far is cleanup and you will have to lap the valves if they were sand blasted. If you take the valves out it would be good to upgrade the springs and retainers. Bore for better compression and change both guides. BUT if it was my motor you are half way there do the complete rebuild and do the seals on the bottom end. I have seen so many top ends done and leak there ass off because of bottom end seals.
You are dealing with 25 plus year motor and if it sat with no oil seals are dry now. If you have any questions you can email me direct at DADDYGCYCLES@YAHOO.COM and I will try and walk you threw. My garage is in South New Jersey and doors are always open if you want hands on experience.. Everyone here gave you great advice and if its broke down do it right the first time. Its great when new guys want to do this themselves.
KEEP CHOPPIN
DADDYG