Many questions

[trbig]

Hello.

I am having troubles with my XJ. When I first got the bike it had sit-itis. ('82 model... 5,000 miles) When I finally got it running with some good gas, it was hard starting first time of the day, then good after that. The only real problem, was that after it warmed up good, when you came to a stop, the motor wanted to rev way up to about 4 grand with the clutch in. It didn't do this while it was cold. I was told it was probably the slides in the carbs a little bit gummy, and if I ran some MMO in the gas for a bit (4 oz per 5 gallon), it would clear it up. I ran it several hundred miles, never did clear the rev-up problem, but now it has gotten dang near impossible to start.
I adjusted the cam chain tensioner, and it is almost ALL the way into the motor. I am surpised the retaining bolt got any of it to hold. I got curious and checked the compression on it and it SUCKS!! 55, 65, 85, 80 pounds, 1,2,3,4 respectively. When I went to check the valve adjustment, the #1 cyl wouldn't even let the .04mm feeler in! The other 3 were less than .10mm. All the exhaust were between .10-.15mm, so they are way too tight also. I realize I need to shim these, but where do you start on the #1 when it is obviously riding the cam the whole time? I have the chart in my manual, and it tells what to use, but is there a way to measure something and get precise if it IS touching?
Do you think that by running MMO in it, I have carboned up the valves? I have since been told that my rev-up problem is maybe ther starter jet on the carbs? I took the carbs off a while back and tried to clean up the slides in the carbs with some emory cloth, even though they looked fine, but I didn't feel comfortable messing with the jets or anything. I just took the main jet out and looked to see that they were clear. I have installed some inline filters, but the carbs really looked fine. (No trash and such).
So.... do I attempt to tackle the possible carbon problem, or just shim it up and check it again later. (With no MMO) The shimming seems easiest, but seems I will be doing it again if I get the carbon burned off. I am taking the carbs out again for a complete cleaning, so that will rule out Starting jets. What about my cam adjuster?? Stretched cam chain already? Bad cam chain guides? The top one between the cams seems ok.
So many questions, so little time! I don't care if it's in the low 30's I WANNA RIDE!!! Anyone help me get back going?
Thanks to everyone on here, this site is great!!

Tod
P.S. I have purchased a mostly complete motor and trans, but no nothing about it really, other than the guy said it "Checks out good". Should I abandon this 1st motor for a bit and try the other I know nothing about, or try to fix the one I know was running???

[prometheus578]

Tight #1 clearance

Only thing to do is pull the #1's shim, read the number(or measure it with a micrometer), and but in the next thinner shim. spin the motor a few times and check the clearance again. If need be.. pull the shim and go one number thinner. Check/reset all your valve clearances and then recheck the compression again. The compression should come up a bit, if it doesn't do a leakdown test to see where the compression is going.
And this tip for people that take out the schrader(sp?)valve from their compression checker's hose to do a leakdown test. This is a special valve... (weaker spring) You cannot replace it with the same looking valve from a tire valve stem. You will get lousey compression readings. (85 pounds, where as if you had the correct valve in the hose, you'd be getting a true 142 Lbs) Don't ask me how I know this. Ok, if you must know... One day, while I was sta.........
As for swapping engines. There's nothing wrong with the engine that you have... until you make adjustments, check it out properly and prove to yourself (and me),that there's something wrong. (geez, what an ego I have!)ahahhahah

[trbig]

Do you think it was carbon build-up in the combustion chamber that made these shims get so tight? Ever heard of Marvel Mystery Oil in the fuel doing this?
As for removal of the valve in the gauge... nadda. It's a quality tester right out of the package.
What about the cam tensioner??

Thank you for your quick reply.

Tod

Why can't they make a 50,000 mile BIKE tire??

[TopCatGr58]

Hey there TRBig,

Welcome and congrats on your find! Okay, it's been stated by other knowledgable mechanics that it's a tendency for the valve seats to get further seated in the head, which can reduce the clearances. If there was significant carbon buildup on the valves and seats/burned valves, it should have reduced your compression due to particles separating the valve from the seat, and with MMO possibly cleaning the valves, it might have actually improved the compression thru better sealing of the valves!?

First question: How did you do the comp test? Did you have the throttle Wide Open? Also, was it done cold, or had you driven the bike first? Supposed to be done with a warmed up engine!

For cleaning and keeping the carbs clean,use of SeaFoam or Techroline is recommended in the gas more so that MMO. Your runaway idle could be carbs out of synch, could also be a vacuum leak leaning things out, or just a simple matter of adjusting the main idle screw back a bit. The engine leans out as it warms up and can cause it to run up the idle. When Starting the bike, there's a choke(actually fuel enrichening) lever and cable on the left handlebar that can facilitate starting the bike, and with it the idle should slowly increase, that lets you know the bike is warming up, and you can then reduce the enrichener after a few minutes.

Are you sure it's only 5kmiles, not 105kmiles? Really hard to believe the cam chain or any of the other components would be worn that much with only 5kMiles? You stated that you already put several hundred miles on it. Putting a little MMO in the OIL and running the engine WITHOUT any stress load on it for a few minutes at warmed up temps can help remove varnish and gumm from the oil/engine/clutches and can also help to unstick rings that might be partially stuck, which could also contribute to low compression levels. Then Change Oil/filter with fresh!

Did you actually take the cam chain tensioner apart? Sometimes, a notch can get worn into the adjusting rod, and it can stick and not fully extend, catching on the worn spot? Some emory cloth can deburr it? Okay, I'll shut up for now!

[trbig]

Ugh!!!

Just wrote this really long reply and lost it... said I wasn't signed in and couldn't go back and get it!!

Anyway.. Hi TC. For the shorter version,

The guy I bought the bike from has had it since almost new. He says he doesn't ever remember riding it more than about 50 miles a year... what a waste!
The tensioner does not have a burr I dont think, otherwise it wouldn't be nearly inside the engine. I used a punch and measured how far the pin is up into the hole, and then measured next to the set screw, and it is BARELY catching it. I didn't know if there was a part on the tensioner that could fail. I have a friend that has an XS 1100 and he says he has never seen one so far up before.
When I did the comp check, it was warm, and I did it both without the throttle open and with it wide open... no difference. I then squirted a little oil into the cyl and re-tested with no change, so assumed it was top end.
I had read somewhere on here before about carbon build up causing to lose compression. That's why I was wondering about the MMO. I guess it cleans, like you say.. but seems kind of reverse since you are burning oil?? Anyway.. thank you. I will take the tensioner apart tomorrow and see if anything looks "Funky" Will I be able to see any more chain guides with this off??

Tod

[John]

Cam chain guide

There are cam chain guides on both sides of the chain. It is actually one part. The guide on the back side is not movable, but the guide on the front side, where the tensioner makes contact will pivot on it's mount. .
Here is a pic. It is item #9

[prometheus578]

Carbon build up on the vavle faces would account for the lower compression as they are holding the valves open a little. But anything holding the valves open a little would then give you more valve clearance at the camshaft, not the tight readings that you have. Leakdown test will tell you where the pressure is escaping to.

[trbig]

I don't have an air compressor, so leakdown testing is tough.. lol. I do see that as tight as my clearances are on the valves, when the bike gets warm especially, that my valves would be kept partly open.... hope I didn't burn any. Still puzzled by the adjuster though. What usually goes bad?? The chain or the guides? Both??
I am just wondering if this guy was just going out and starting it occasionally, not letting it warm up.. just start, rev a few times.. kill it. Starved the chain of oil and it stretched??

Tod