GS500 1993 Will not start, was seized

[notelrat]

I have a 1993 GS500. The bike sat for over a year and water got in I believe the left cylinder (memory failing but that one has the worst compression). I removed the crank case cover a few months ago and using a large socket wrench I was able to get the bike un-seized.

The reason the bike sat so long is I took it apart to clean the carborators because the right cylinder was not firing at below 3500 rpm so it was having trouble idling and accelerating from a stop. During this time I installed fuel filters into the lines because there was rust in the tank. After putting the bike back together problems were even worse, the right cylinder still wasn't firing correctly and now it was no longer rid able with the power band totally out of wack, it would bog than accelerate than bog again, as if it were a fuel problem (yes the filters are installed in the right direction) or the something was still wrong with the carbs. After this it has sat for the last year and a half.

In the last 2 weeks I have returned to this project. I took the carburetors apart and somehow even though the bike has been inside most of this time, there was water in the gas lines, airbox and the carburetors. Also a large mouse nest in the air filter. It was a real mess in the carbs, and there must have still been rust in the lines. Upon cleaning the carburetors and putting it back together, the bike was able to fire up after pulling the plugs and squirting some gas in. It would fire up and run for maybe 15-20 seconds tops than die. It did this a few times than it refused to start up at all and than gas starting coming out of the airbox drain line, so one/both floats were not operating correctly.

I broke the carburetors down again, the right one still had some junk in there, cleaned them out again briefly and put it back together. No more fuel leakage, the floats are back to operational, it must have just been some sludge under the needle. Still though, I can not get the bike to fire up at all now, with starting fluid in the airbox, gas under the plugs. It won't fire up and run at all after firing up last week (but than it would die as if it were fuel starved..).

Compression in the left cylinder is at 75psi, the right cylinder is about 140psi. Squirting some oil in the left cylinder will get the compression up to 140, so there is definitely a problem in there, a broken ring, something, but I assumed that it would at least still fire up on the right cylinder, but than again this was the cylinder that was originally having problems at idle. With oil in the left cylinder (it gets 140psi compression with oil) and gas in the right, it will kick over and sound like its going to start the first second or two of starting but than it dies off again.

I have replaced the plugs, charged the battery and I am jumping it off of a car battery. I assume that the engine might be screwed and need to be broken down further but the fact that it won't start up at all anymore is perplexing. I didn't want to remove the exhaust in fear of ringing off a bolt, but that is the next step because I know there was some sort of nest in there as junk starting firing out after it started last week, still turning the bike over results in exhaust coming out so its not totally plugged.

Suggestions? Thank you

[moonzoomer]

Full top half strip, nothing less. Bores, pistons, rings, valves, valve guides, all seals etc etc etc, sounds like a nightmare to me and given the age of the bike hardly worth the effort but good luck.

[Fisty]

[notelrat]

Look I don't know exactly what i'm doing but I at least know that my 'powerband' didn't break and seize it. Water got in the cylinder and there is definitely some rust in there but I feel like it should still start.

[P.addy]

[davebike]

Unless you want a project not a running bike
Don't piss about
Get another engine if it has sized don't wast time and money £300 will get you a runner off ebay that will not get you more than a couple of sets of rings and a gasket set You bound to need more !!
Clean carbs and tank fit engine

Dave
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Dave
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[_Iain_]

I managed to get a GS500 engine for under £200 delivered. It's almost certainly the best option - mine was cheap as there wasn't a generator.
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Please be aware that the above post may be full of complete nonsense.
Riding: '07 KTM Duke II, Baotian BT49QT-20 Driving: '88 Volvo 340

[Islander]

As above, the minimum you're going to have to do is dismantle and check the top half of the engine. You're down on compression on one cylinder, that could be down to a ring stuck in the piston groove, a badly worn ring/cylinder or a broken ring which isn't going to do the cylinder walls any favours. I wouldn't be trying to start it if it were me.

Given the low price of second hand running engines and the cost of the spares you're likely to need, a second hand engine is probably the best bet.

[orac]

either rebuild or replace the motor.

the low compression is an issue and would sugget that there is a pisong ring issue

also gs500 once they have the carbs set correctly (not factory setting) dont really have a power band and deliver a fairly even power through the rev range with a flat spot around 5k.

i would suggest that you also return to the carbs, ensure they are getting fuel, and that everything is properly clean
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Current rides - 2016 Triumph Street Triple Rx, 1994 Suzuki Bandit 400 VM, TGB 204 Classic 125cc
"with nothing left to lose, there is everything to gain. It's not the size of the dog in the fight, it's the size of the fight in the dog"