I've been working on my gs for around 2 months now. It's at 43,134 miles on odometer. Initially I thought my problem was carbs, so I took them apart and cleaned them, the pilot jets were blocked so I soaked them in carb cleaner and unblocked them with an air compressor. It didn't make much difference so I checked valve clearances and I couldn't get the 0.38mm feeler gauge under any of the valves so I changed the shims.
Exhaust valve clearances are both 0.64mm and intakes are 0.51mm. Valve timing is in spec. I put the valve cover back on and used rtv on the half moons of the gasket. I started the bike up from cold and once it got warm oil started pouring out of the PAIR system on the front of the engine. So I installed block off plates with high temp rtv sealant and took the PAIR system off and it still leaks oil. It still won't idle and I will sync carbs once the oil leak is fixed. I appreciate any help at all
damn, sounds like my bmw, after one small problem is fixed it starts to leak oil from somewhere. Sounds like it wont get enough fuel, hows float level? If carbs are way off sync it affects idle pretty dramatically
The float level is good, I bench synced the carbs so the butterfly valves are opening at the same time (roughly). The air/fuel mixture screws are at 2.5 turns out (I took the brass stoppers out), I don't think that it is running rich because of this but it could be a possibility after taking the PAIR system out
Check the compression before you spend any more time or money on it. IMHO.
Quote from: mr72 on April 01, 2020, 06:55:16 AM
Check the compression before you spend any more time or money on it. IMHO.
maybe that, but on my engine fault cases it have idled fine but as soon as i put load on engine it stalled
When my bike was dying with low compression it would only idle when cold and once warmed up would only run at high rpms. Most of the time I tried to fix it with carbs I was consistently told failure to idle was caused by carbs. I wish I had done a compression test before I brought the bike home.
Don't waste time with a poorly running bike if you have not checked the compression. Lots of things will be not working if it has <100psi compression and no amount of carb tuning will fix it.
Quote from: GSscott on March 31, 2020, 03:45:12 PM
I've been working on my gs for around 2 months now. It's at 43,134 miles on odometer. Initially I thought my problem was carbs, so I took them apart and cleaned them, the pilot jets were blocked so I soaked them in carb cleaner and unblocked them with an air compressor. It didn't make much difference so I checked valve clearances and I couldn't get the 0.38mm feeler gauge under any of the valves so I changed the shims.
Exhaust valve clearances are both 0.64mm and intakes are 0.51mm. Valve timing is in spec. I put the valve cover back on and used rtv on the half moons of the gasket. I started the bike up from cold and once it got warm oil started pouring out of the PAIR system on the front of the engine. So I installed block off plates with high temp rtv sealant and took the PAIR system off and it still leaks oil. It still won't idle and I will sync carbs once the oil leak is fixed. I appreciate any help at all
What is that ? The front of your engine has the PAIR system ? I've never seen or heard of that - is it a US spec bike ?
Bikes with low compression - but nothing else broken and carbs, valves properly adjusted etc tend to be down on power, especially mid range and they make a little less rpm up top.
PS: The worn motors also use a crap ton of oil, but not by sending it out anywhere where you can see it - it will essentially spray out liquid droplets - and it may burn some oil, but typically this bike can use oil without burning it and in copious quantities. Running only when cold, and high rpm when hot - likely a valve burnt or not sealing there, Typically you can wear the valves to where you cant get a shim thin enough, you can wear the cyl/piston to where it loses a ton of compression and maybe eventually it would lose enough there to not burn at all. In other words no compression = no suction = no filling of the cyl hence no burning. You may have wear, but that should not be why it wont run properly. Maybe if the guides were leaking like crazy so much oil will get in the chamber that it chokes out the flame - remote possibility for you. You're likely dealing with a lot of compression blow by because I think your PAIR is the Crank vent - but if it runs at all - we can see why its spraying it out - maybe that metal scrubber that's in the vent isn't there or something.
And you have .51mm of valve clearance ? You know there are feeler gauges that are available in much much thinner than the .38 mm however loose valves make a crap ton of noise and not affect it running. Its an Item you can fix once you get it running right.
Cool.
Buddha.
Quote from: mr72 on April 01, 2020, 07:09:33 AM
When my bike was dying with low compression it would only idle when cold and once warmed up would only run at high rpms. Most of the time I tried to fix it with carbs I was consistently told failure to idle was caused by carbs. I wish I had done a compression test before I brought the bike home.
Don't waste time with a poorly running bike if you have not checked the compression. Lots of things will be not working if it has <100psi compression and no amount of carb tuning will fix it.
What was it on yours ? A valve being tight could cause a similar issue. More like starts perfectly and seconds later wants to die, and when revved revved revved till it will run, It runs good at high rpm, but stalls at low rpm. If a valve was even tighter and/or burnt then it wont start easily and wont run cold or hot unless you're revving it to 4-5k.
A poor compression bike would have worse compression and suction when cold than when hot. So that symptom would be the opposite - or more like super hard to start, barely runs till it gets warm, and then only gets slightly better. And uses a crap ton of oil. Smoky exhaust (optional).
You could have over a 50psi difference between cold compression and hot compression. Ofcourse you may still have too poor compression to run even when hot, in which case it will be impossible to start, impossible to keep running - pretty obvious.
Cool.
Buddha.
It was bent exhaust valves on mine. Without pulling the head, the only way to tell if you might have bent valves is to test compression... they will show as having the correct valve clearance but the valve doesn't seat. Same thing for worn valve seats, burnt valve, etc., all of which cause low compression.
I suppose if the head was in good shape but the rings were shot then "low compression" may not cause the same symptoms, I don't know.
BTW on mine it would run just fine for about 15 minutes but once it got warm it would not run below 7000 rpm. It ran fine above 7k rpm if you could find a way to ride it above 7k rpm all the time. Then once it died it wouldn't start until you let the engine cool.
Sorry Budda I put the wrong valve clearances, exhausts are 0.064mm and intakes are 0.051mm. The PAIR system is an emissions control set up because the bike was imported from Spain and I live in New Zealand so I don't need it. Basically it squirts extra air into the cylinder to burn hydrocarbons before coming out of the exhaust. It does have loss of power because I took it down the road and in 5th gear it starts to bog down and I had to pull over because it died. I had to wait a while then start it so I could have the same problem as you mr72. However mine has to be reved at at least 3-4k or it will die, occasionally it will idle fine for a little while and then it'll die. I can't do a compression test yet, but would a leaking head gasket cause loss of power and poor idle?
Leaking head gasket will basically squirt the crap out onto your pants etc etc. If its not too bad, it will sorta sneeze out the head once in a while, usually when cold. This bike is air cooled - you will see it, usually even get sprayed by oil.
Compression test yes, then leak down test, to be sure.
However the bent valve like mr72 describes would almost the only condition that shows that behavior. Because its the only symptom that gets worse with heat. All seals usually get better with heat, warpage or bent stuff get worse.
Anyway you're getting oil from where air is supposed to get into the exhaust. Is there some hose that's connected up wrong ? Is the air filter housing full of oil ? Does crankcase vent go into the airbox ? Blowby will get oil into that.
Let me read your posts again.
Cool.
Buddha.
Is the bike still leaking out of the PAIR system? That seems really odd to me. Never heard of a leak there. When you put on the blockoff plates did you install new gaskets?
I have the blockoff plates on my bike. All 2004+ GS500s in the US come with the PAIR system.
OK so I've checked again and it's not leaking out of the PAIR system, when I put the block off plates on and ran the bike for a bit, oil started pouring from the front of the engine and was dripping off the PAIR plates, so instantly I thought that was where it was coming from. Its leaking just above at the gasket where the head meets the block so I will replace the gasket. Does anyone know where I could buy one from or does anyone sell them on here? Also I forgot to mention the left exhaust shim bucket was super tight and I could barely rotate it. Is this a sign that the valve could be bent as the bucket doesn't fit nicely into the valve guides?
the bucket doesn't fit at all into the valve guides. The valve stem fits into the valve guide.
If you are talking about the cam cover gasket, then you can get that pretty much anywhere. Mine leaks and I need to replace it myself, will likely do it this weekend.
If you actually mean the HEAD GASKET (and the cylinder head really is a lot taller than most people think), then that is a way bigger job. And if you are going to do THAT job you might as well do a full on top end rebuild while you are at it. Rings, hone the bores, valve seats, valve surfacing, valve stem seals, etc. because 90% of the work is pulling the head.
I am thinking you mean the cam cover gasket. That's the gasket that you reused when you checked the valve clearances.
Only external sign you'll have of a (slightly) bent valve is poor compression. If it's badly bent then you'll have a loud knock and a hole in the piston, an engine that will barely run.
It is definitely the head gasket so I probably will do a top end rebuild. I'm just waiting for a compression tester to arrive in the mail so when I've done readings on the bike I'll let you know.
well if you are doing a top end rebuild then might as well budget for valves. you might have a bent one, but one way or the other you can rule out compression issues.
Quote from: GSscott on April 02, 2020, 07:38:08 PM
It is definitely the head gasket so I probably will do a top end rebuild. I'm just waiting for a compression tester to arrive in the mail so when I've done readings on the bike I'll let you know.
Try torqueing the head bolts first. I don't think a head gasket leak on this bike will leave you with just a drip, it will sneeze out the leak. A base gasket leak may just leak oil. I'm pretty sure head gasket will create some funny noises.
I also think a head gasket leak will be worst when its coldest.
Secondly, a tight valve could be burning because its hanging open in the combustion chamber and never cool down cos it never sits back in the seat. A bent valve is more likely to be loose, but then again if it was already worn to the thinnest, and then the valve was bent I can see how it would measure out within range while still being essentially broken.
Here is a cool experiment you can do without a compression tester. seeing as yours is probably on the corona boat from china.
Take off the exhaust and carb and spark plugs (IIRC you already have set the valves to spec). On a dark night (no this aint some bad horror movie) put each chamber at TDC and shine a light in each hole (no its not that kind of movie either) looking for light from the other 2. If you see any light anywhere in the other holes that means the valves aren't sealing.
Like for example put flash light in the intake and look in spark plug hole. If you see light - Intake isn't sealing, if you see it in the exhaust - both aren't sealing. You may likely be burning them, but most likely its bent because your valves have been adjusted to spec.
Compression test etc etc is all great - but this motor was made before the previous ice age. How in the world did we fix it back then ?
BTW a head gasket leak is likely to get better as it warms up. A valve cover gasket leak will get worse and I am beginning to think its the valve cover gasket. So next experiment.
Put the pipe and carbs back on. Or heck, its running now, do this first - before anything else.
Clean the motor and dry it. Put Desenex foot powder everywhere in the cyl/valve cover area.
Start it. See where the thing gets wet first. That's where its leaking from.
Cool.
Buddha.
Quote from: The Buddha on April 03, 2020, 02:20:23 AM
Try torqueing the head bolts first. I don't think a head gasket leak on this bike will leave you with just a drip, it will sneeze out the leak. A base gasket leak may just leak oil. I'm pretty sure head gasket will create some funny noises.
Yes, try torquing the head bolts first. Suzuki recommends doing this every 4,000 miles anyways (every time you check the valve clearance).
Slack them off in the correct order and then re-torque to spec in the specified order.
OK my compression tester arrived, I did a test at cold with throttle wide open, the left cylinder is at 50psi and the right cylinder is at 75psi. I will replace the head gasket but I plan on pulling the head first before I order any parts to check the valves properly and rings.
Do you guys think it is worth doing a whole top end rebuild or just replacing parts that need replacing?
Thanks Budda the powder test worked good but I just used baby powder.
Absolutely whole top end rebuild. Why do 90% of the work for 30% of the benefit?
Compression that low and only running at high revs may indicate bent valves. You can't resurface that. So you might start looking for replacements, at least exhaust which are the most likely to be bent. If it was me I'd just replace them all. And make sure you have a good machine shop to do the valve seats and other machine work.
You're in New Zealand - I dunno you have a place like Kibblewhite etc who sells high quality valves ?
I don't know what these things cost over there. But I would be pretty happy just swapping the head gasket if that's the only issue - you have 43K - its due for cyl/rings/head, but how easily can you get these over there. That would determine it IMHO.
In NC/SC area US, I am surrounded by Nascar mechanics. I have easy access to the best parts and mechanics on the freaking planet all in a matter of miles from my door. I'd do the whole thing, but well, if nothing was easily available, I'd be reluctant to put in that much $$$ into a bike I haven't ridden to know what its actual issues are all there.
Cool.
Buddha.
Thanks for the replies, I would like to do full top end rebuild but honestly I don't think it's worth it if I don't need it. Mainly because you can't by any new parts for gs500 over here and I have to import everything including head gasket. Secondly, I want to break even on what the bike owes me. We have no stores like kibblewhite but I did see that brand of valve on ebay, so if I have to I'll buy those.