First Bike - GS650G - Rusty Crusty

[Nessism]

VM's are fine. Easier to tune, if you change intake or exhaust (although I recommend against it!) The intake ports are smaller on the VM engines also, so not that easy to swap out anyway.

[Eric4]

I've got the engine nearly freed up, but it seems like something is holding up the 550 in the rotation. I'm using a wrench on the crank, and can cycle the bolt ~720* in both directions before hitting something firm. Anyone have an idea of what could be holding this up? Hopefully I don't need to dig into the engine, but it sure doesn't feel right.

[rphillips]

Batteries on GS's are no different than on anything else. I have a couple of bikes that's a pain in the arss to get to the battery, ie Suzuki GS1100 and Honda CB1100F, those will always get a sealed batt. If batt. is reasonable to get to for fluid check and fill, it really don't matter. GS's are no different, do what suits "you"... Not sure what ~720* means but hitting something firm don't sound good. Possibly remove cam cover and check for a stuck valve someplace.

[Eric4]

Batteries on GS's are no different than on anything else. I have a couple of bikes that's a pain in the arss to get to the battery, ie Suzuki GS1100 and Honda CB1100F, those will always get a sealed batt. If batt. is reasonable to get to for fluid check and fill, it really don't matter. GS's are no different, do what suits "you"... Not sure what ~720* means but hitting something firm don't sound good. Possibly remove cam cover and check for a stuck valve someplace.

Yeah a stuck valve definitely came to mind... The pistons seem to go through a full rotation cycle, so I don't think something is stuck in the combustion chamber

[rphillips]

OOhhh, I'd got to tinker with that kick start, it ain't right. Bike on center stand and in gear, see if eng will go farther than your ~720* when turning it with kickstart, just to see...Don't force it.

[Eric4]

OOhhh, I'd got to tinker with that kick start, it ain't right. Bike on center stand and in gear, see if eng will go farther than your ~720* when turning it with kickstart, just to see...Don't force it.

I was mistaken about the engine rolling fully when in gear. It stops rotating regardless of being in Neutral or in gear... The kick starter does rotate the engine now, but still not a full rotation.

I'll start on removing the valve cover. Not a great start, seeing one valve cover bolt already fully stripped out of it's threads

[Eric4]

Valve cover was removed, and it looks like we've got a stuck valve. What's the best remedy for this? A marvel mystery oil soak?

Unfortunately some of the head threads have been stripped out by the valve cover bolts as well. Some can probably be retapped/cleaned up, but one set of threads is totally toast.

Here's a picture of the sleeved head threads.

[rphillips]

Don't think that sleeve is a thread repair, 2 of those bolt holes, on diagonal sides of the head, should have a sleeve that looks like what you have pictured that is there to work as a dowell, just to get the cover aligned properly when installing. It should pull right out with a pair of needle nose.

[Eric4]

Don't think that sleeve is a thread repair, 2 of those bolt holes, on diagonal sides of the head, should have a sleeve that looks like what you have pictured that is there to work as a dowell, just to get the cover aligned properly when installing. It should pull right out with a pair of needle nose.

Ah, yes you're right. I see in other ebay listings for 550 heads, that they also have this sleeve. Hopefully that can be easily sourced, as the threads are totally gone inside.

Know of any reliable methods on fixing a stuck valve? Seems like in my case, the valve is stuck up, as the cam lobe is unable to push it down. I'll work on measuring the clearance...

Edit: The intake clearance on the stuck valve is 0.6mm, so significantly slack, compared to my other valves which are within spec. Maybe its got the gap because it's stuck halfway? A bit stumped on how to proceed...

[salty_monk]

Can’t you remove a plug and use a mirror or an endoscope to see what’s going on? Maybe the valve is already bent.
… good luck

[Eric4]

I couldn't get a great view of the valve, but it did have a fair amount of soot on it. When using the borescope, I noticed the cylinder wall having some odd markings that sure don't look good. It's either an oil/soot line, or a crack...


Photo_2025-08-13 12_41_43_467.jpg

[Eric4]

Photo_2025-08-13 12_41_31_175.jpg Here's another view

[Rob S.]

Look like a gouge to anyone?

[salty_monk]

Looks like oil/gunk that's gone solid around the top of the piston when it was left without moving for years.... I would try to run it before I opened it up personally. That lump could be what's holding up the piston.

[Eric4]

Looks like oil/gunk that's gone solid around the top of the piston when it was left without moving for years.... I would try to run it before I opened it up personally. That lump could be what's holding up the piston.

I hope you're right! However this 'stuck valve' is still keeping the motor from cranking fully around... The valve isn't lifting fully, or seating fully when the cam lobe interacts. Gave it a good soak in PB blaster, and Marvel Mystery Oil to no avail.

I'm a bit inexperienced on things like a stuck or bent valve. Any thoughts on methods to test this, before I start working on removing the engine from the bike?

To confirm it's not a gouge in the cylinder, I'll try to give that apparent edge a poke with a wire, to see if it hangs up on the dark spot.