Try swapping the spark plugs and see if the problem follows them. Then try swapping the coils. 

Well I didn't get that far I figured I would try a compression test since spark plugs were off I got 120psi on my left cylinder and 30psi out of my right cylinder I guess I have been riding my bike on one Cylinder all along 

30?! Wow. I'm hoping you forgot to have the throttle wide open before testing that......

Check your valve clearances - them being out of spec can give a low #. Good luck man!

Big rich is Right, also it wouldn't be a bad idea to borrow a bore camera, or buy one and inspect the cylinder walls


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Left the throttle all the way open but didn't screw the gauge all the way in re did the test and the number is 65 still not good but better... Poured some oil down there and re did the test and got 75 psi

I have the bike takin apart it's still hot so I took apart the carbs I pulled my air mixture screw out all the way and all I have is the screw and a spring isn't there suppose to be an oring somewhere?

There is. Find a parts diagram for the carbs - I think there's a tiny washer in there too. When I rebuilt mine the oring was so old it was stuck to the carb body - maybe yours is too?

Before you get into the engine, please check your valve clearances. That oil in the cylinder test points towards a problem with the valves....

Yes oring was stuck but there was no washer so ill order that and I noticed my carburator piston the plastic piece the diagram goes in is crack  any one know of a cheep place for them?

I'm going to take a look at the pistons for sure just need to pick up a small allen as all mine are to big to fit in the front 

Today is not my day

Quote from: Nocluejoe on June 20, 2014, 07:11:23 PM
Yes oring was stuck but there was no washer so ill order that and I noticed my carburator piston the plastic piece the diagram goes in is crack  any one know of a cheep place for them?

I'm going to take a look at the pistons for sure just need to pick up a small allen as all mine are to big to fit in the front 

Today is not my day

Your white slide guide is cracked ... WTF, that was definitely thanks to some clutz mechanic.
Yea you gonna need to get a good one, or you could remove it and clean it like a maniac and jb weld it and hope it holds together.
Buy a 04+ carb rack, I sure as hell done have them parts lying round. 89-00 I got some ... no guides tho.

Your lack of spark is a separate issue.
Your crank trigger or auxillary ground may be @ issue.

65 psi - you sure they checked the valves ... Sounds like its not sealing.

Cool.
Buddha.

Lack of spark was due to spark plug replaced it and its firing again for now about to get in the valves

Okay measured the valves here are my measurements

Right intake= .076mm

Right exhaust= would not fit .038mm     This was the only valve I couldn't not spin the shim or whatever it is that can spin like the others

Left intake= .051mm

Left exhaust= would not fit .038mm


Now I need to find the right shims

Was your 120 psi left and 65-75 psi right compression test done with a cold engine?  With a tight #2 exhaust valve bucket I'd do a hot compression test right now to confirm the tight valve is the cause of your compression results and it's not a bent or burnt valve.

I had a very tight exhaust bucket that eventually caused a broken exhaust valve when it stuck open and clashed one very cold morning.  But that tight bucket I originally left go for another 10k miles would free up and engine idle would smooth out within a minute after startup and bike would be OK for the day.

A bad plug is possible but rare and I still suspect the cause of your come and go idle problem might be electrical with a loose plug wire in the coil or something like that.  Two problems at one time can be very hard to diagnose and carb problems are the last thing I suspect.  I've done my 180k GS miles with untouched carbs.

I did it hot and cold when I got 30 psi it was a cold engine I have the whole bike takin apart so I can't run the bike right now how do I know if the valve is stuck open? What do I do if it is when I rotate the engine I see the valve get pushed down

If your basic engine is still all together with cams properly timed you can turn it over slowly clockwise with a 19mm wrench on the hex under the little round 3 bolt cover on the right end of the crank where the ignition pickup is and observe the valve action.  Most likely it will appear OK even with your tight bucket.  The valve springs have a spring rate as all springs do and their force is proportional to the amount they are compressed.  With a tight bucket the force will be reduced as the valve closes and spring lengthens and can become not enough to close the valve completely when cold.  When the engine warms after startup the aluminum head expands faster than the steel bucket and the bucket is freed to perform normally.  It would be a good idea to check the valve timing and cam chain tension at this time to verify they are OK:

http://img.photobucket.com/albums/v443/jcp8832/gs500signalgenerators_zps2134172a.jpg

Seems your compression on the #2 cyl increased as the engine warmed but may not have been warm enough to allow the valve to close completely?  Now that you have confirmed a tight bucket it would be good to get both a cold and a hot compression check before changing shims on that valve.  Even with my very tight bucket that held the valve open when cold I confirmed low or no compression when cold and good compression when hot before I let it go for a while when it would have been better to deal with the tight bucket when first discovered.

We still won't know if your low compression on #2 is due to the tight bucket, a too large shim, or if it is a bent/burnt valve causing the problem requiring pulling the head and repairing.  Good compression when normal operating temperature is reached would be good news right now.

Other opinions would be welcome.   

Joe, what size are your current exhaust shims? I might have a couple shims that would be the next size up I could sell you (if it's quicker than your local dealer).

IMO, I wouldn't look too far into other possibilities of low compression until you get your valve clearances correct. It would be a shame to pull the top end unnecessarily....

I agree with Rich.  Take that tight shim out and see if you can spin the bucket.  If the bucket doesn't budge, then you might have to pull the head and check the valve and get that bucket taken care of.

Okay I got the right intake shim out it is 265 I managed to wedge the screw driver under neath the valve and pulled them shim out with another.

My question is can I realease the screw driver with out a shim in the hole? I know I cant rotate the engine with no shim but will it be bad if I just realease the screw driver with no shim to remove the other 2 shims?


I didnt read the thread before I pulled the shim so im just going to get them to the correct sizes and then worry about compression after

No, you want a shim under there.

Speaking of which, a screwdriver isn't recommended either.

I wouldn't think it would be a problem to let the bucket up without the shim, but I might be wrong.  I know you definitely would not want to turn the engine over either by hand or ortherwise without a shim.

Well I've been using a screwdriver and an old Honda wedge tool for at least 20 shim changed for 15 GS500 years without a problem, works for me.  Two screwdrivers would also do the job.

http://img.photobucket.com/albums/v443/jcp8832/ValveShimTools.jpg

Rich, he'll need smaller rather than larger shims since his exhaust clearances are too tight. 

Joe, if you have that bucket depressed with a screwdriver and the shim out I don't see why you couldn't remove the screwdriver to release the bucket so you can maybe see if the bucket will turn, we don't know yet if it's a tight bucket or a too tight shim in there although I suspect its a tight bucket.  Don't turn the camshaft with the shim out, put a shim in before turning it.

Quote from: gsJack on June 21, 2014, 09:18:29 AM..........................We still won't know if your low compression on #2 is due to the tight bucket, a too large shim, or if it is a bent/burnt valve causing the problem requiring pulling the head and repairing........................

I see  bombsquad83 has just posted the same thing as I am saying.  Perhaps putting a 2 size smaller shim in both exhaust valves and then checking clearances would be a good start.  If adequate clearance is obtained on both then recheck compression.  Compression on #2 close to what you got on #1 would then indicate the problem was solved.  I was not suggesting you consider pulling the head at this time unless you find you have a bent/burnt valve.

Okay currently at work till late tonight but when I get home I will pull all the other 2 valves a local mechanic has the shims on hand so he said to come in and grab some and there 5-7 dollars a piece.

What is the required clearance for the valves? Exhast valves should be .10 correct? I remeber people run them bigger than normal and what is it for intake?

Thanks everyone so far for all the help I couldnt do all this with out everyone