Top End Rebuild - XJ650

Did you replace the chain?

 

No I didn't.

 

That may be why it keeps jumping time. The camchain tensioner can only go so far. Did you clean and reset the tensioner when you had the head off?

 

I did reset it..

Ok.. I noted this when putting cams in again... I can turn the engine clockwise just fine.. but I try to turn counterclockwise and the chain seems to bunch up.. and get sucked downwards until the crankshaft locks...

I had only one cam in when testing this.

 

Would an automatic cam chain tensioner bolt up in place of the manual one?

 

If you only had one cam in, there's no way that the chain could have stayed taut enough TO turn backward.

 

Yes.

 

Slow down. You're moving at a rabbit's pace but not accomplishing what's necessary. I've re-read this entire thread and imo most of the problems you're having are coupled with potential "pilot errors". A lot of the help you seek has been given. If all the components are within spec and are correctly assembled that engine will turn/run proper. Press the refresh button and follow the advice given. You can swap parts all day long but if the result doesn't change...well you know. We're all here to help and learn from each other.

Gary H.

 

Woh there, I just haven't told the full story. Has nothing to do with me asking a few different questions. Sometimes I have to wait for parts / tools to come in before I can accomplish the first bit of advice. While I'm waiting to I will continue to ask questions and play around with it.

I asked about the tensioner because the chain shouldn't be worn and stretched. It was working just fine a few weeks ago. It wouldn't wildy stretch in the span of 2 weeks and very little run time.
More likely it would be the tensioner that failed. I asked if an automatic tensioner would bolt up and work.. because I have one.

As for the leakdown tester, amazon refuses to send a drone to my house with one. I had to wait a few days. Now that I have the tester I can post results.

However, for the time being until I got a leakdown tester I tested the compression, and Hogfiddle noted that it won't tell me if I have a bent valve / not sealing. Anyhow, actuating the starter button I could watch the timing jump. I removed the cams and waited for the leakdown tester to arrive, no point of resetting timing one more time to check the shims to just double check one last time.

I did however play a tad with the chain to see if I could figure out what was happening. Hog noted that I the chain wouldn't stay taut to turn counterclockwise and thinking about it that made sense.

Since the cams were out, all the valves will be closed, and I can plug in a leakdown tester without having to move the engine to tdc of each cylinder.

Amazon package arrived and an otc leakdown tester was in it.

The results

1,4 were at about 2% leakage
2 was at 4-5% leakage
3 was the problem with well above 10% leakage on the intake valve.

There is my problem. This is what I need to fix. Head off, replace valve, head back on. Redo / check shims. since new valves in 3 will have been fitted.

 

Without more of the "full story" it appeared you were chasing a ghost. I've done this successfully a couple times and currently doing a case break (primary guide replacement) which will include rebuilding the top end. Just trying to help. Good luck with the build.

Gary H.

 

I don't think that's quite what I said.....

 

A compression test simply tells you your compression amounts.

A leak-down tester helps you determine if and where the compression loss is. By maintaining a constant supply of compressed air, you have the ability to listen for where the air is escaping . If you hear it at the carbs, you have an intake valve leak. If you hear it at the mufflers, you have an exhaust valve leak. If you hear it at the oil filler, you likely have either piston/rings leak, valve stem leak.

Neither will tell if a valve is bent or not .... They will only indicate whether valves are sealing or not ( if its determined that the leak is at a valve) then it's up to you to determine why

 

I'm sorry, it was K-moe who said that originally. One page ago.

Everyone has been a huge help.. I've just been getting you all mixed up.

 

Don't worry... We're not mixed up

 

Thought I would put in a good word. I am doing a similar rebuild here. I like this thread it has been reassuring. In my small shop I have a small utility drill press, one that can be bought on craigs often for 50 -75 dollars. It is very handy to drill out broken bolts and for simple drilling. But I bought it for another reason. With a small 3/8 ths extension mounted into the chuck, and with a wooden base to place the head on at the right angle, I found it works great as a light weight arbor press. And that means you can use it to disassemble and reassemble your valve train. I used an old socket that fits in the lifter bore and cut half of it off so I can get my fingers and a magnet to pull out and put in the valve keepers. I left half of the socket at the end for stability. The amount I cut off was about an inch. I also note that inserting the keepers it was made much easier if I coated the keepers in a grease to allow it to be pushed on, then rotated to the backside and then the second keeper pushed on and and stay before I release the spring. I am sure many of you have that same type of small drill press. The wooden "head holder" is made so that I have been able to do a maxim x head (20 valves) as well as a Suzuki a Honda and of course a Yamaha XJ.

 

I've considered buying a used Seca that has some problems and found this discussion while searching for clues as to how much work it will need.

I've read through the thread and I'm not sure it's conclusive regarding "Typical" cylinder head oil leakage on early Secas. It sounds like it could be a relatively minor or it might be a huge ($$$$) problem.

As I said earlier, I've been looking for a restorable UJM (Universal Japanese Motorcycle) from the late 70s to mid 80s and came across an 82 XJ650R that looked like it might have potential. The bike has been sitting for years and has several problems that are related to its non-use, I believe.

The bike has about 18k miles and looks to have been generally well cared for, but has just been sitting too long.

The fork seals are leaking. The cam chain is a little noisy. The engine does not smoke, or have other engine noises, though. There is oil contamination on the front calipers (may be the leaking forks OR a leaking caliper).

None of these things concern me too much and are typical of a bike that hasn't gotten much use, but there is one more problem that has me worried. The cylinder head gasket appears to be leaking oil on the left side. Reading this thread makes me leary of purchasing it, since it sounds like a top end rebuild or worse could be in this bike's future.

To those of you who've owned and repaired these bikes: Should I assume the worse (head rebuild and cam chain replacement -- along with machine work) or do these early)?

Thanks for your input.

 

@mrgem: We guesstimate a amount between $600-$800 to fully restore and make road worthy any one of the xj series bikes. This amount does not include missing or beyond repair damaged parts. It also does not include tools. At 18k miles the bike shouldn't have any major problems. A compression test will tell if the engine is in decent shape. The oil leak may not be the head gasket but the valve cover gasket and or the cam chain tensioner gasket. The brakes and forks will get rebuilt during the restoration process.

Gary H.

 

800 ain't bad...

 

+The knowledge of this forum...PRICELESS!

Gary H.

 

This is about how much I'll be into my Seca after purchase price. ~$1500 doesn't seem all that bad to me. /shrug