Valve shimming and tuning (GS450E)

[ChickenStorm]

Hello! My bike has long suffered from a sputter out of the carburetor when coming down from revs, and after some rejetting I decided to look into the valve clearances. Turns out the valves are all a little tight. I couldn't get my 0.05mm feeler gauge under any of them but the shims are able to rotate freely underneath so they aren't that far off spec I imagine. Now here's the issue, I'd like to reshim every valve a little looser now that I'm at it but I don't own the special tool required, but since I'm doing all the valves at once it'd make sense to remove the camshafts for easy shimming. What is the procedure for such a task? I tried turning the knob on the automatic chain tensioner but it wouldn't budge, to be fair I didn't look into it very thoroughly at the time and thought it better to ask first. The timing wouldn't be affected if I just carefully lifted the camshaft assembly with the chain just enough that the shims could be removed? How does one loosen the chain enough to do this?

The sputtering out of the carb wasn't an issue until it just straight up popped one of the carbs right out of the boot , I switched the pilot jets for smaller ones and it runs a lot better now but as stated it sputters out the carbs and backfires loudly when revving so there's still some work to do on that end. With the previous jet (47,5) it would only run idle without running away with the idle screw turned all the way shut.

Thanks!

[Nessism]

https://gsarchive.bwringer.com/bikecliff/images/valve_tool_zip_tie.pdf

[Bobbys 94]

https://gsarchive.bwringer.com/bikec...ol_zip_tie.pdf

Great info Ed, Thx

[Bobbys 94]

"it'd make sense to remove the camshafts for easy shimming"

"IMHO" it would make zero sense to remove or lift the cams to shim.

The chain tensioner knob is not suppose to turn while installed and set.

[Rich82GS750TZ]

If you tried to turn the knob on the on the cam chain tensioner and it wouldn’t budge, you need to rebuild it. There is a tutorial on BikeCliffs Website for that. Yours may be slightly different and the gasket against the cylinders may be different from yours but the rebuild, reset and install should be the same. Take your time with this and do it right.

https://www.bwringer.com/gs/camchaintens.html

[grcamna2]

Following your thread.

[ChickenStorm]

Awesome info guys thanks! I'll try the zip-tie trick in a moment so I can order some shims for the end of the week hopefully. Last night in bed I was thinking about the backfiring issue I'm having and came to the conclusion that my slide needle is propably now set way too lean since I adjusted it to compensate for the very rich pilot. I'm a bit impatient so I'll propably just put the shims back and tune the carbs untill the new shims arrive

[Rich82GS750TZ]

Tuning carbs before setting your new shims would be a waste of time.

[ChickenStorm]

IF someone were to drop a shim down the timing chain into the engine where would one start to look for it? Should I check the oil pan or just start crying right away?

[Rich82GS750TZ]

I'd try poking around with a telescoping magnet thingy. (you can pick one of these up at any auto parts store or hardware store here in the states. Not sure what you got in Finland. You could get lucky and pick it up. I did when I dropped a razor blade. I'd take the chance of magnetizing a shim if it meant not having to remove the oil pan. If not, it's oil pan off (and probably the exhaust before that)

[rphillips]

I'm always trying to be uplifting and optimistic... Let's not even think of dropping a shim down there, just poke rags or towels all around in the openings before you get started and we won't need to have such a negative conversation.

[ChickenStorm]

The worst has come to pass, the shim wasn't in the oil pan. Now what?

Could it still be behind the large screen visible when looking into the engine from below or is there somewhere else I could look for it? I'm not very familiar with the internals of this engine so I didn't know what to expect when removing the oilpan. Good thing I did though since there was a considerable ammount of fuel in the oil, which does explain why it's been hard getting into neutral lately .

The shim I managed to get out without incident was 2.58mm so it would be reasonable to switch it out for the next thinner one and so forth for the rest of them? They were uniformly tight so if another one is the same size I'd propably order four 2.55mm ones?

The shim fell down the timing chain channel and fishing for it with a magnet didn't yield any results . I honestly didn't even think about this being an issue but here we are

[Rich82GS750TZ]

You're not going anywhere til you find that shim. You can't be sure what to order until you measure that one and know what the clearance was before you removed it.

[ChickenStorm]

Thankfully I measured the clearances of all of them before removal, all were under 0.05mm which was my smallest feeler gauge. But you're right finding that shim is top priority, I just hope it doesn't come to splitting the cases

[Rich82GS750TZ]

If probing for it didn’t find it, I’d probably try laying the bike over all the way to one side, see if the shim moves to somewhere you can get it with the magnet. If no luck, stand bike up and over to the other side. Spare rugs and an extra strong back/pair of hands would be nice. You could get lucky and it just falls out the bottom. It’s in there somewhere.

You could alto try advancing the cam chain manually, gently. If you meet resistance, stop, and back it up, slightly. And see if the shim reveals itself.