gs500e '81 at deaths door? Ignition or fuel?

[jonan]

I bough this bike a few days ago, because the price was right and it ran well apart from some mild hesitation under 3000rpm. The bike has 83 000km on the clock, and as far as I can tell has no other modifications to the engine than a DYNO ignition.

Not more than about an hour after money had changed hands, it was a totally different bike.

Symptoms:

- backfires at idle and sometimes stalls because of this.
- when standing at lights for any perid of time, I find meself standing in a puddle of fuel coming from one or more of the carbs breather/drain? tubes
- the engine wont rev over 5-6k, serious backfiring and hesitation will commence. Except once it worked nicely for half an hour or so.
- sometimes need to get the revs up to 3k to be able to get the bike rolling
- sometimes idle revs stay at 3k for a few moments before falling to 800 where it idles nicely.
- general performance is at par with the 125 I bought a few months earlier as an introduction after a long break away from bikes.

I noticed the rubber grommets from air cleaner to carbs were not installed properly and were leaking air, so I fixed that. Plugs are new. Bike hasn't been standing, but probably not ridden a lot either.

The previous owner had adjusted the ignition to sligtly advanced, and local official Suzuki mechanic said I cant destroy the engine by too much advance, it'll refuse to start before pinging. I have no ignition lamp, and there is NO Clymer OR Haynes book for these old four cylinder GS500e Suzukis available. I'm using the bike for commuting, and can't afford taking it off the road for more than the weekends.

I'm thinking this bike is Europe version of the 550, but the mechanic told there are no roller bearing in the camshaft of this engine, which made me assume its a doubled up version of the gs450. Confused.

I will now go and buy some tools and will proceed to try to tune up this bike.

Overall, the engine sounds healthy and tight, so where should I be looking for the problem?

[mark]

and there is NO Clymer OR Haynes book for these old four cylinder GS500e Suzukis available.

I found a couple of manuals right away. By the way....welcome

http://www.repairmanual.com/motorcycles/1980/62/0/5524

You're right. You're going to have to do the basic maintenance and figure out where you're at. Compression test, valve adjustment. A carb rebuild with new O-rings etc. is probably the place to start. This is just routine on bike that old, there's a great thread on doing it on the homepage of this site.

Set your timing correctly. There's no need in your situation to advance the timing, someone probably did that to compensate for some other problem. You will need a continuity lamp to do so and its easy. Since you have a Dyna S, it won't be in the manual, so ask and I or someone else can help you there.

Its all probably going to have to be looked at from your petcock to your manifold O-rings to get things cleaned and sealed correctly.

Good luck and enjoy.

[focus frenzy]

standing in a puddle of gas indicates flaot/s not seating and it's time for a good carb overhaul.

the original GS500-4 is going to most likely be a Germany only bike as all the info I have ever seen on them was German.

possibly some sort of level in step licensing.

a manual for a GS550 (early 8 valve) should cover everything you would need to know except bore and stroke.

no GS multi (don't know about the 125 single) has roller bearings on the cam, they are all plain self bearing. (no inserts)

[Nessism]

Carb rebuild time and new o-rings for the intake pipes.

'81 GS550 has electronic ignition (at least in the USA it does). How do you know the ignition is advanced? If it truely is, put it back to stock asap and leave it there. The 550 pistons have a thin crown and detonation can punch a hole right through them.

[jonan]

Ahhaha! I meat the crankshaft, not camshaft. I'm starting to believe this bike is a GS550 with a different bore. It's hard to sift throught all the gs500e twin stuff on the internet.

I went for a bit longer ride and backfiring has all but dissapeared, but I have no power or appreciable acceleration. Top speed is 60mph. This can't be normal for a 500cc modernish japanese bike that weights 300 kgs wet with rider? Needle does not go over 6k (9k redline) but it runs smoothish now.

I bought myself a stethoscope and am going to sit and listen to the bike for a while, sort of get acquainted with it. I will check valve cleareances tomorrow morning after the bike has sat overnight unless someone knowledgeable says to skip it for now and just pull the carbs?

About the timing, there are homemade scratches in the case and the timing plate, and the previous ownes said he'd timed it to a bit earlier than stock. I've already taken it back a degree or two, just a safety thing.

As to the timing light, I have none, and wont likely get one since I have no breakers to adjust. Is it enough to do it the old fashioned way and to set timing to where it sounds healthiest/fastest and then retard it a bit? Used to do so with my beetle, but that's a different beast.

[Nessism]

Ahhaha! I meat the crankshaft, not camshaft. I'm starting to believe this bike is a GS550 with a different bore. It's hard to sift throught all the gs500e twin stuff on the internet.

I went for a bit longer ride and backfiring has all but dissapeared, but I have no power or appreciable acceleration. Top speed is 60mph. This can't be normal for a 500cc modernish japanese bike that weights 300 kgs wet with rider? Needle does not go over 6k (9k redline) but it runs smoothish now.

I bought myself a stethoscope and am going to sit and listen to the bike for a while, sort of get acquainted with it. I will check valve cleareances tomorrow morning after the bike has sat overnight unless someone knowledgeable says to skip it for now and just pull the carbs?

About the timing, there are homemade scratches in the case and the timing plate, and the previous ownes said he'd timed it to a bit earlier than stock. I've already taken it back a degree or two, just a safety thing.

As to the timing light, I have none, and wont likely get one since I have no breakers to adjust. Is it enough to do it the old fashioned way and to set timing to where it sounds healthiest/fastest and then retard it a bit? Used to do so with my beetle, but that's a different beast.

Your carbs need to be cleaned and you need new intake pipe o-rings. Problem with pulling the carbs now is you need the parts thus you may have to do the job twice - once to keep the bike on the road and a second time later to do the job right (after the parts come).

According to my factory manual the GS500 bore is 3mm smaller than the 550. Otherwise the bike is same, including the roller bearing crank.

[jonan]

I have the carbs on the kitchen table, and will begin cleaning them now. I wonder how many hours it'll take me. Gotta get the bike back together before 6am, 10 hours to go....

I checked the valve clearances and I got 0.05 - 0.10 - 0.15 on all but 1st cylinder exhaust valve which was 0.15 - 0.20, and 2nd cylinder which was less than 0.05. Could even be on spec, if 0.03 is minimum clearance. The lack of accuracy is because of my tool, which didn't have less than 0.05 and went up in 0.05 increments. This was my first ever clearance check and can't quite say if the numbers are still OK, or if I am in trouble.

Is that Suzuki shimthingie a must, or is there a way to pop those things in and out without it?.

All the rubber seems supple and flexible, nothing between the airbox and the heads looks 25 years old. Carb to head rubberthingies look brand new with stainless bolts to boot. But, someone's left the airbox connection to the airfilter box unfastened from the bottom, so the airbox isn't all that snug against the filter. Fixable with two screws if I got them.

I have two questions I cannot answer myself without a manual.

1st, the airbox has two inlets for tubes for it. One at the top which takes the breather tube from the cylinder head, that's ok, but there's another underneath the airbox, which didn't have anything attached to it.

But then again, my carbs had -in addition to the four chamber tubes - two tubes just dangling around free...

There's one at the top left side of the bore of the 2nd carb, and there's another at the same place in the fourth carb. I have the fuel intake and the vacuum tube between the second and the third (unless I already got them ,mixed up), but where should these two other tubes go? One to the airbox? And the other?

Thank you in advance.

[Nessism]

Those two tubes are vent tubes, route them up on top of the airbox hanging free. The tube under the airbox is a drain tube - open to the air.

[jonan]

Hello helpful people.

Update.

I've been cleaning and examining the carbs for four evenings and counting. Things are slowed down a bit by the potency of my spray-on carb cleaner and my girlfriends violent reaction to any chemical stronger than dish-washing liquid. That, and my immense respect for those little fiddly bits that seem to be dropping off every nook and cranny.

These things have come apart quite a few times, it seems. All the screw-ends are worn round. Dremel and a grinding wheel came to rescue a few times in reslotting those screws.

My main jets are 82.5, as opposed to the 80 Haynes tells me they should be, but I just noticed (doh) that my bike has a Motad 4-1 pipe and a new generic non-stock air filter. This is ok?

Two of the pilot fuel screws were tightened fast, and the other two were more than 2 turns open. Springs missing from nearly all adjustable jets and float height was several mm off of required on all carbs. I'm happy I found something wrong here. No gunk anywhere though.

In taking the carbs off, I've managed to disturb the apparently fragile hacked state of my bikes electrics, and now everything earths straight from the fuses even with ignition off! Luckily I have a retired electrician in the family who just loves to diagnose some cruddy old bike in some slummy backyard.

My manual is vague about this, so I'll ask here. Is Your GS550E airbox right hand side cover bolted full of electronics? It doesnt look too OEM to my eye, but I could be wrong. When it says remove airbox, in my case it would mean dismantling just about every electric lump associated with the bike. This is as it is supposed to be?

A week into owning a bike and I'm already talking shop, thanks to this site.

[jonan]

I'll keep on documenting my lack of progress on this very thread.

My bike is a Finnish '81 GS500, which I gather is equivalent of about and around an US '79 GS550.

Plugs are too hot (#6), and plugs 1, 2 and 4 are sooty black.
Plug 3 is sooty black and a bit moist.
Header #3 is golden, although I can't remember if it was so from PO.
Dyna S ignition, and some japanese 3ohm coils.
4-2-1 Motad pipe
A bit bent #1 jet needle
82.5 main jets
maybe a bit weak spark on #1 and #4, can't be sure.
petcock works
battery is new
carb O-rings seem ok
Airbox's gotta leak a bit from bottom, but is has an aftermarket brandless (thin) dryish, clean, foam filter.

I've managed to successfully clean, adjust and re-install the carbs and fix about half a dozen electrical issues.

All the rubber boots seem very supple, and intake side boots have shiny SS hex bolts (PO's replaced O-rings then, I hope). I bench synched the carbs and set the fuel pilot jets 1 1/2 turns plus to factory notch. The "not to be found in any manual" mystery air mixture jet-thingies were all turned exacto 1 turn out.

After a promising start, running nicely on all four cylinders (after replacing a dead #4 plug) I took it for a spin. Worked beautifully under 3000 rpm, with solid tickover, but after warming the machine up and driving outside downtown, the old symptoms were all over the bike. Ridiculous amounts of backfire after 4000 rpm and revs limited to about 5000. Top speed about 40mph. Grrr!

The #4 cylinder died somewhere around 20 miles, and I guess at least one other cylinder is having issues at staying alive. Lots of black smoke from the pipe, but thats because all the cylinders are running rich at idleish, and I'm not capable of revving the engine at all. No backfiring at idle (900rpm, stalls at times), the carbs have stopped leaking fuel, and it seems the revs come down nice and fast to idle even when hot, which it didn't previously. No backfire when letting go of the throttle. Only when trying to push it even at quarter throttle.

Lots of rain kept me from touching the bike for weeks, but I managed to pull a compression test just the other day. The bike was cold and throttle was closed, but since I was only interested in consistency between the cylinders that was ok. Results were 107-109 psi on cylinders 1,2 and 4, but only a pathetic 59 psi on cylinder #3. Wet results for #3 were off the charts, but that's because I was being a silly yob and added nearly two table spoons of oil in to the cylinder; cranking the engine resulted in a loud pop and my compression meter flying across the yard with about half of my plug threads following... I'm just happy I think I didn't hydrolock the cylinder.

Electrics are dodgy, but I don't really know which wiring diagram to follow.
Reg/rect case/cooling fins are live, and earth to the battery case, and should the battery case touch the frame, the main fuse blows (which it did when the case was breathed on hard). PO had solved the issue by swiching the main fuse to a slow 30 amp one, the git.

I'm to adjust valve clearances, change to correct temp plugs, and fix that plug thread next, but it just rains here all the time. I'm also going to take the cams off to adjust the valves clearances, since I can't get a hold of that adjustment tool.

Some questions:

How much of a job it is tho check the cylinder/piston condition while the (pretty clean) engine is still attached to the bike, and how necessary You think it is? I really want to finish the season, even if it means limping.

Am I off the mark in thinking valve adjustement without SpecialTool(tm) is going to be only done with the cams off?

My Dyno S ignition unit has some black plastic bit where the big nut for turning the crank should be. I only have the 12 mm nut visible. How safe I'm to turn the engine from that when all the plugs are off?

Should I record a very tiny weird sound from the bike throught a stethoscope and post it here, would someone be able to diagnose it?

Sorry for the long post, hope you can make any sense out of it.

[SAN]

gs 500,1981

hello, rare bike you have. my 81 550T airbox is same, as are most all gs's of those years. For info on your bike, besides the help you'll find on GSR, www.gs-classic.de/index1e.htm follow inst for lang pref. some of 500 had diff cams to reduce hp to 27,instead off 40-43hp. good luck. sn.

[jonan]

Registration papers say 37 kW. You had me worried there for a a second.

What a site you've got there! Spent the whole evening reading it through Babelfish.