XJ engine noise

[gwh57]

Hello out there, I just got my 82 xj1100 with 7461mi. on the clock. I got the bike running and the performance is impressive. This bike starts , idles and pulls strong all the way to the red line. In neutral the engine revs fast with no knock but I seem to get a slight engine knock from the left side between 2500 and 3500 rpm in gear at normal running temp and just enough throttle to hold speed. The noise goes away under load and deceleration. No knock when cold. Is this normal ?

[jimboreeno]

Well First..
Welcome to the forum and congrats on the bike. We love pictures around here so check out the posts on how to, and put a few up.
I may not be the person to answer this question, though I will throw in my bid on valve clearance adjustment, but several will give you the answer!
You will never have a question about your XJ that the gurus here can't answer!
(OK...pressure's on gurus!)

[DiverRay]

Number one question, how long was the bike sitting BEFORE you got it running? I would look at the oil you are using, and pull the left side cover. The advance unit hides behind there, ( I think, as I have older models) and if it's sticking, it could cause noises. Give the mechanism a squirt of lube, and see if it helps.
If it's still around after that, you will need to do more investigating.

[dale_1]

noises

Also.... check for exhaust cracks and loose motor mounts. They sound almost exactly like rod knocks or piston slap. Even a small crack in the exhaust makes one really noisy engine. If you see a small amount of gray powdery (sometimes greasy) substance close to the engine mounts but the bolts seem tight.... they aren't.

Let us know what you find ...........

[TopCatGr58]

Hey GW,

Welcome and congrats on a great low mileage find!!

Hey Ray...your age(of your bikes) is showing!

The XJ does NOT have any advance mechanism under the left engine cover, just the pickup coils and plate. The advance curves are ALL handled by the XJ's TCI both cent. and vacuum, hence the vacuum sensor under the gastank, not connected to the timing plate!

GW, what grade of gas are you running? You say you got it running, what is the history of your work on it? Did you rebuild the carbs? If so, did you vacuum synchronize them, and did you know about the YICS tool required to do this? Did you check the coils, measuring their secondary high tension resistance values? Have you checked the spark plug caps and their resistance?

More info will assist us in assisting you!
T.C.

[trbig]

GW,

I get the exact same noise under the exact same conditions on my XJ. I won't say that it's normal, because it didn't used to do it, but I have changed the crank and rod bearings recently and it still does it. It's not loud... but is sometimes concerning. I will tell you that I tried pretty hard to blow the thing up this last weekend. I rode it pretty hard at top speed and many, many times close to red-line. I put nearly 900 miles on it since Thursday under some pretty tough conditions, and the knock is still the same... no worse.. but no better.
So... I'd still like to know what the noise is... but it isn't worrying me as much now. I'll post if I figure it out.


Tod

[gwh57]

Hi, You asked what I did to get it running. The bike sat in a heated garage for about 10yrs it took me and the second owner 20min to clear the junk off of it to get it out. The second owner drained the tank, lines and carbs. I overhauled the Front and rear brakes, both petcocks and carbs, replaced both tires, battery, spark plugs, oil filter, changed oils in engine, middle gear and rear end, Adjusted cam chain and valves. I'm sure I forgot some things I did. By the way I use Castrol 20w50 oil and premium fuel. I will check for loose engine mount bolts and exhaust leaks that others here have suggested. I did not sync the carbs yet I have to make the YICS block off tool. Thanks for the info