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GS1000G with engine noise

JTGS850GL

JTGS850GL

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Past Site Supporter
I have a 1980 1000G engine that I was planning on doing a top end rebuild on.

The engine has a solid 140psi compression cold across the board and the valves were almost all in spec with only a couple that needed to go down one size. I've been able to start the engine on choke but will not take and throttle input and wont idle off of choke. Carbs were rebuilt once but I'll be doing them again just to make sure. Complete dip, sonic clean, boil, poke and spray again.

When it does run on choke I hear what sounds like a marble in a can clanking sound near the top end. Kind of sounds like a loose screw bouncing around but nothing I can see under the valve cover indicates it. The two bolt timing chain tensioner was mounted backwards (spring side facing left of engine toward starter motor), but I turned it around and reset it. I did check timing and the two cam gear marks pointed straight up with the timing mark set. 20 link pins between each timing mark. Nothing loose that I can see with the valve cover off.

My plan was to use the engine as a spare after a complete top end rebuild but really was hoping to get a good health assessment before I pulled it out of the frame. The reason I was going to do the rebuild was just to freshen up the engine for another 30 years.

Any ideas on what may be causing the noise and what to look out for?

Should I just forget about getting it running first and pull the motor for rebuild?
 
Uh, I'd say you need to get it running through all rpm first, or post a video where the noise can be heard clearly. There is a phenomena in high-mileage 8-valve GS engines called cam end-walk that only occurs at low rpm. It's quite harmless, and goes away at speeds much above idle. Getting rid of it requires good machining skills. Several of us know this noise first hand and might confirm it if we heard a recording.

Having the tensioner mounted upside-down shouldn't have affected anything.

Or, if you're committed to the rebuild, just tear it down. The symptoms presented with choke and throttle aren't related to anything that can make a noise. Have you been running it in a bike with a complete airbox? Sometimes people leave that off and it really screws up the various flows and pressures the CV carbs need to work correctly. 850s with stock jetting usually won't start at all without an airbox. I'm not sure about a 1000.
 
Yes, I've heard of cam walk issues but haven't heard it first hand. Sounds a little more then that though.

Replaced the pods with an air box that is missing the rear snorkel but otherwise complete and sealed with stock air filter. I also returned all the jetting to stock. Like I said, I'll be going back through all the carb rebuild just to make sure I didn't miss anything. Any way to confirm cam walk mechanically? I hear the sound when it's running at higher RPMs with the choke on and it's not subtle. Can't get the engine to idle currently.

Any trained ears in the Grayson, GA area that would like to have a listen?:-\\\
 
Hmmm. If you can get it up over about 2000 rpm with choke, and the noise is still there, then it won't be cam end-walk. When I've heard it, it was really only noticeable at or just off idle at about 1000 rpm.

You can confirm cam walk by taking off the cam cover and checking clearance in the cam's thrust bearings areas. I have no idea what the clearance spec is, but I imagine it's in the service manual somewhere. If you get it at even slightly elevated revs, that not it anyway.

The only thing I can think of that might make random bouncing around kind of noises in the top end is maybe a broken valve spring. I don't hear of that happening, though. I'm told the starter clutch can sound like that, but it's not near the top end.

That's not much help, but your thread at least gets a bump.
 
JTGS850GL said:
I did check timing and the two cam gear marks pointed straight up with the timing mark set. 20 link pins between each timing mark.
Click to expand...

You DO mean that there are 20 link pins including each timing mark, right?
 
GSX1000E said:
You DO mean that there are 20 link pins including each timing mark, right?
Click to expand...

Correct. Timing mark lined up, cams in correct locations and 20 pins from arrow to arrow.

It's the Frankenstein bike engine that I'm working on now. Like I said, the compression is good across the board so I don't think it's a valve timing issue. I have the carbs back together and will play with them this week. I figure I can always swap them with the ones on my good running 1000G and make sure the carbs are sorted. That way I can rule fuel out as an issue. May keep them on that bike anyways since the carbs have the 1982 choke linkage and I have a 1982 left side control to match. I like that choke assembly much more then the center pull type on the older bikes.
 
Dogma said:
Hmmm. If you can get it up over about 2000 rpm with choke, and the noise is still there, then it won't be cam end-walk. When I've heard it, it was really only noticeable at or just off idle at about 1000 rpm.

You can confirm cam walk by taking off the cam cover and checking clearance in the cam's thrust bearings areas. I have no idea what the clearance spec is, but I imagine it's in the service manual somewhere. If you get it at even slightly elevated revs, that not it anyway.

The only thing I can think of that might make random bouncing around kind of noises in the top end is maybe a broken valve spring. I don't hear of that happening, though. I'm told the starter clutch can sound like that, but it's not near the top end.

That's not much help, but your thread at least gets a bump.
Click to expand...

Thanks for the input though. The sound is hard to localize. It sounds like a ringing through the engine. Kind of like the sound when you hit one of the fins. It has that tinny ringing sound. I'm hoping it's just pre-ignition from an ultra lean condition. Worst case I'll just pull the engine and inspect it as I tear it down for the rebuild.
 
Why not fix the carbs, and get it running first? I hope its a starter clutch. They make an awful racket from the left side of the crank, but its hard to pinpoint exactly where a noise is coming from sometimes.
 
Fixing the carbs is what I just completed. Haven't installed them yet but will some time this week. They were rebuilt once but I decided to go through them again just in case they were the source of the running problems. Complete redip, sonic clean, boil in water, poke all orifices and spray carb cleaner through everything. Admittedly the bike has no history. The PO said that he could never get it to run and the "shop" said it had a blown engine. I purchased it more for parts then anything else. It had a decent stock exhaust, a nice new rear tire and some nice new chrome valve cover end caps that I used on my other bikes. The tank is decent and the recovered seat has no rips. Brakes all worked with no leaks, nice rear fender and brake light assembly, a unique handle bar set, good instruments and all electronics working. Once I get the engine sorted out I'll remove it and then part out everything else. Already have the frame sold since it had a title. It's mostly a 1980 GS1000GL with some 78,79 brake parts up front.
 
It sounds like a ringing through the engine. Kind of like the sound when you hit one of the fins.
Click to expand...

It could be the fins ringing, then.

Does that engine have the rubber fin dampeners installed? Can you make some for test purposes?
 
Looked over the engine and found none of the rubber spacers on any of the fins on the topside of the head. Not a single one.
 
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