XJ650RJ Engine - Rebuild or not?

I picked up an XJ650RJ in quite a few pieces. I need another project like I need another hole in my head, but whattaya gonna do?

Anyway, the top of the engine is in pieces. I have no idea why. Attached are some pictures, and I am hoping maybe somebody else can see anything wrong.

The question is this: Should I attempt to put this back together and make it run again? Or is it a basket case?

So far, I don't see anything that makes me think it is a basket case. There are 20,xxx miles on the odometer - I can't say for sure whether that's actual or not, but to me the engine looks consistent with that.

My current thinking is to invest in the bits and pieces and gaskets needed, lap the valves, lightly hone the cylinders, and put it back together and hope for the best. Just want to make sure that I'm not being too foolish.

Theory #1: From talking to the seller, the bike was taken apart by a friend of his, and maybe he just liked taking things apart, so he figured he'd just give the top end a refresh even though it didn't really need it.

Theory #2: As seen in the picture below, it looks like the cam chain hit the valve cover a little bit. Maybe that was enough to convince somebody that the top end needed to be torn down.

Valve cover inside:


Here's a look at #2 and #3 pistons. #1 and #4 are similar. Doesn't look like anything alarming to me. Maybe a little bit of skirt slap. Is this consistent with 20,000 miles?


Here I tried to get a shot of a couple cylinder walls:


Cam journals:


Here I tried to get a shot from underneath to see primary chain and guide. Appears to be intact:


And finally, the gunk in the sump. Doesn't seem bad. No chunks of chain guide! I've seen worse:


Thanks for looking.

What do you think?

 

From my point of view....
I have a (very) cheaply purchased, titled 650RJ that had sat indoors but near the ocean for about 25 years and the engine was stuck. I have it out and apart and would really like to put it back together someday. In the mean time I am putting in an almost equally cheaply purchased XJ750 engine from a no title parts bike. My 650 was not in as good condition as yours appears to be.
What does the rest of your bike look like? Good condition? Think of the fun and satisfaction you will have making it whole again. And Yamaha isn't making these awesome bikes anymore, save one from oblivion. I would really like to see it get saved. But you are going to spend way more money saving it than you expect, but less than the price of a new bike.
By the way, I have 4 bikes in the rehabilitation process right now, 2 XJ's, a Honda Nighthawk 450 and a Honda Nighthawk 750 so my opinion might be a little biased!

 

Put it back together quick.

 

You're going to need some shims and some patients.

 

Get a set of new rings ,hone the cylinder , remove all the valves from the head and clean the valves , lap them in the seats . Put new valve seals in and you will be in business.

 

Ok. Thanks everyone.

I’ve started to work on it.

I’ll admit I’m pushing my boundaries as a mechanic.

How the heck are you supposed to get the valve stem oil seals out??

 

Did you get the valves out yet? Once out you can just grab and pull.

Do you have lapping tools/compound? If not PM me, I lent my stuff out before and they sent it all back plus some so I need to pay it forward.

 

Thanks @jayrodoh

Yes, I’ve got the valves out. It seems like you would be able to grab them by the exterior and pull, but I don’t want to damage the guides.

also thanks for the offer for lapping supplies but I’m good there

 

They’ve been in there for 40 years, not gonna fall in your hand but I’ve never had one fight me. Common sense and some 0W15 elbow grease you should be fine.

The “real” gaskets to put that motor back together are pricey so take your time on the small stuff and double check that head for flatness. Specs are in the FSM, PM me if you don’t have that.

 

Ok. With a little less fear and a bigger pliers I was able to get those little buggers out.

 

I think the engine internals look good. Are you planning on replacing the cam chain? Just asking since it marked the cover. But if the 20 odd thousand miles is correct it should not be worn. If you sit the head on the block with four pistons mid cylinder and sit the cams in their bearings and fit the cam chain you can check how extended the cam chain tensioner will be. Just to get an approximate idea of how much wear the chain has.

 

I'm thinking I will need to assess the cam chain situation during re-assembly. This was originally equipped with the manual cam chain tensioner - so most likely it was just never adjusted and eventually tickled the cover. I plan to replace the manual tensioner with a newer automatic version.

 

The original ones from the factory had a split link. You can always fit a split one if you are not splitting the cases if necessary. Chacal might have the split ones. Actually you are better waiting until you assemble it makes more sense doing it that way.

 

Valve lapping in progress. Left side (#1) has been lapped, right side (#2) has not in this photo. Left looks nice to me, where right is pitted and shiny. This looks good to me - tell me if I’m incorrect:

 

Yep, that looks good. A nice even ring all the way around. Good job.

 

Thanks @Fuller56

I also got all of the top end parts cleaned up today:

 

Looks good but make sure to do a leak test. I have been testing with water covering the valves, with an old plug in the plug hole from the head side, and blowing compressed air into the intakes and exhaust.

 

I would check the end gap on your rings also. Looks good Dan..

 

Got a little painting done today

 

Looking good. What paint did you use? Rattle can?