Continue with top-end tear down?

[staf0s]

Found lots of fuel and a little bit of grit in the oil as well as globs of what looked like melted plastic. Turns out it was pieces of the rubber bushings that are on the head studs. Figured I would replace the chain guide..yada yada. When I got the guide out, I noticed that it was perfectly fine and looks brand new. The bike is an 81 with a little over 13k miles. After inspecting everything, it all looks really clean. There was a little but of carbon and slight corrosion on the tops of the pistons but it cleaned up nicely.

I have not removed the cylinder bore yet.

So after doing a little more looking around I noticed that there is a gouge on the cam and and some markings on the bearing that’s closest to it. Does this warrant a reason to replace the cam and bearing? Or leave it?

Leave the factory chain guide or replace? The factory one is to the right of the MikesXS guide shown in the pictures

I’m still at the point where I can replace gaskets and put everything back together and call it a day.

Is it worth pulling the barrels and getting them honed and replacing piston rings? The only reason why I can justify doing so is because I originally planned on getting the casings and the top end cleaned up and refinished/coated. I also have a chipped fin which irks me. Now would be the time while everything is apart

I’m including pictures. What do you think? Put everything back or continue along?

 

[staf0s]

I’m also wondering if that little bit of grit that was in the oil could have been shavings from the cam/bearing. I just don’t see it getting turned into fine grit like how it was

 

[jpdevol]

Does this warrant a reason to replace the cam and bearing? Or leave it?

I think that chip may be just a casting flaw; I'd run it. Hard to tell from the pic, but if the bearings have spots etc. on them, I'd replace them. And...replace the guide with Hoos Racing guide. The guides fall apart just from age. I'd likely ring it too. All opinions......

 

[staf0s]

I think that chip may be just a casting flaw; I'd run it. Hard to tell from the pic, but if the bearings have spots etc. on them, I'd replace them. And...replace the guide with Hoos Racing guide. The guides fall apart just from age. I'd likely ring it too. All opinions......

There does seem to be marring and some marks on the outside of the cage with a little bit of surface rust on the inside. I was wrong, it’s actually the outer bearing and not the one closest to the cam. Probably a good idea to replace it.

As far as the chain guide from Hoos, can you confirm that it’s any different than the MikesXS one? They look identical. Thanks for the input btw.

 

[jpdevol]

I think I've heard of issues with the Mike's guide (??) I've used several Hoos guides and think they're OEM or equivalent.

The cyl. can be a little stuck on the dowels; a few wraps with a soft mallet and should wiggle free - doesn't matter where pistons are

 

[Jan_P]

What was the reason for tear down ?
13 k miles is not much and I cannot se anything strange
Personally I would replace that bearing because I have had problems with them ..for a higher mileage
Unless something can be seen in inspections
Pouring gas in the top see if there is leak and so

Maybe the ring gap can be seen and checked

Hitting is not good ..Is it stuck ?? ---Oil and patience .
I would consider not to separate Cylinder and Pistons unless reason for it.
Risk causing problems .. depending on tools and experience available

 

[Jim]

Agree with JP... the cam is fine. Just a casting flaw.
There's a guy on Ebay that sells OEM cam bearings..... cheap. I'd replace all 4
The Hoos guide is light years better'n Mikes.
You've come this far... seems kinda silly not to ring it too.... in my opinion anyway.

 

[jpdevol]

Couple threads RE Mike's guides:
https://www.xs650.com/threads/new-front-guide-stopper.56531/page-2#post-689926
https://www.xs650.com/threads/check-new-cam-chain-guide.59799/#post-696222

I hoped I wasn't imagining hearing "things"

 

[staf0s]

Reason for tear down was because I initially thought the chain guide was chewed up and I wanted to see if there was some noticeable reason as to why there was so much gasoline in the oil. I’ve had the carbs off the motor since I stripped the bike down years ago. The PO could have had the bike on its side at some point I don’t know. I also read that failed rings can cause this?

So I actually just got the cylinder off. I haven’t touched the rings at all. This is how they were when I pulled the cylinder off. I was under the impression that the ring gaps needed to be opposite sides from eachother (I don’t remember the exact layout of the rings)

Can you confirm?


Well, there is no going back now. I will most likely find a used cylinder that doesn’t have a broken fin, get that honed professionally, and get it coated or polished as well as the head and the jug. With this process, I’ll need new piston rings and gaskets. Moving up to the head, from what I’ve read the valves will need to be lapped and I probably have that done professionally as well. Other than a new guide, am I missing anything? Seeing as this bike has 13k miles and none of this needed to be done, I think I can get away with keeping the factory timing chain and not having to split the cases, correct?

 

[Jim]

No... no need to split the cases.
As far as the chain goes, I have this rule of thumb I try to stick to....

If you have to tear the engine apart to replace it.... replace it while the engine's tore apart.

 

[jpdevol]

The pic of the pistons suggest there may be some scuffing that warrants having the piston skirts measured (micrometer). If you're gonna replace the cyl. the clearances should be checked anyway. So, I'd hold off ordering rings until all that is determined.

Yes, ring gaps should be staggered at assembly, but that doesn't mean they stay there

 

[Jan_P]

Cylinders and Pistons are matched There is Numbers on top of the piston and the base of the cylinder.
So getting a replacement cylinder with the corresponding dimension can be difficult.

As JP says Above.

 

[staf0s]

Cylinders and Pistons are matched There is Numbers on top of the piston and the base of the cylinder.

Got it. That’s actually a little annoying considering my cylinder was just fine before I started messing with it and breaking a fin. MikesXS sells a complete kit but it’s not an OEM cylinder and I’m trying to stay away from Mikes as much as possible

 

[Jan_P]

Got it. That’s actually a little annoying considering my cylinder was just fine before I started messing with it and breaking a fin. MikesXS sells a complete kit but it’s not an OEM cylinder and I’m trying to stay away from Mikes as much as possible

No experience myself but seen it in Motorcycle magazines that sometimes fins can be weld repaired.

 

[Jim]

No experience myself but seen it in Motorcycle magazines that sometimes fins can be weld repaired.

Yeah... find a small welding shop that does TIG. I'd bet it would be cheaper than replacing the jugs.

 

[staf0s]

You guys are right. Thinking about it, that’s a wild waste of money just because of a little fin. I could probably easily get someone to repair this.

 

[toglhot]

Absolutely, that's why engines have all those nuts and bolts holding everything together, so you can remove them and pull the engine apart. If engines weren't meant to be pulled apart, they would have made them sealed units. That goes for everything BTW, not just engines.

Can you think of a more enjoyable thing to do with your time, aside from the obvious?

 

[Paul Sutton]

A common cause of fin damage is hitting the cylinders to remove them. Even a rubber mallet can break them. I have seen small breaks on fins repaired by TIG. They just build the fin up to were it used to be and then file/grind it to shape. If you follow the TIG route then warn the welder that when the cylinder warms up the liner could drop out when picked up hot. Not a problem if the liner drops out, they are easily put back in with gentle oven heating.

Have fun relaxing over an XS650...