I acquired a 2002 bike with 8K miles that was sitting for 3.5 years, I replaced the fuel lines, cleaned the carbs and the bike started ok and i rode it for 30 minutes.
A week later it didn't start and I diagnosed it due to rust in the fuel tank clogging up the carbs. I replaced the tank, cleaned the carbs again, looked inside the manifolds and noticed gunk on the valve stems.
At this point I made a terrible judgment call that I really, really regret. I sprayed carb cleaner inside the manifest to dissolve the gunk. And in an attempt to do a better cleaning job, I turned the engine over by rotating the wheel while in gear.
After about 20 minutes I attempted to start the engine and after 10 minutes of cranking it began coughing out smoke out of exhaust and backfiring. I thought it was cleaning itself out so I continued cranking. Then a massive backfire explosion happened in the intake manifolds and smoke went thru the carbs and came out from below the seat.
After some more cranking I took off the air box so I had direct access to the carbs. I sprayed a bit of starter fluid into the left carb while cranking. To my immense disappointment white smoke came out not just from the exhaust but from the air port of the 2nd carb.
I suspect in the best case I have deposits on the intake valves but could the backfire have burnt them as well? I plan to order a compression tool to see how bad things are but i'm afraid an engine rebuild may be required which is way beyond my abilities and sounds like a really expensive job for a shop.
I would appreciate any suggestions, though I should have consulted you guys before i fked things up. Please don't be too harsh, i'm already really devastated over it.
An engine rebuild? Whoa ... calm down. I doubt very much that you could have done any kind of permanent damage to the engine with carb cleaner and/or starter fluid.
Just curious; how do your plugs look now?
Spark plugs were soaked and a blackened from being flooded but otherwise looked fine.
It's not just the carb cleaner that's in there but also the gunk that was previously on top of the valve stem got dissolved and flowed inside the cylinders. I tried to flush it out with seafoam by removing the spark plugs and running the starter but it didn't help.
how else to explain exhaust fumes coming out of the carb other than an intake valve seal issue?
The only connection between the 2 sides is the crossover in the exhaust (that I can think of). Am I wrong?
Quote from: sashkar2000 on July 22, 2013, 12:15:57 PMhow else to explain exhaust fumes coming out of the carb other than an intake valve seal issue?
One possibility would be a
timing issue, where the plug fires while the intake valve is still open. Or the cylinder is hot enough to fire the incoming fuel
without a spark. (Not that carb cleaner / starter fluid would cause either of those to happen, either. Well, maybe starter fluid ... since it's so volatile?)
hmm, would a massive backfire possibly screw up timing?
If there is something stuck to the intake valves, what are some options to get it off? I tried flushing it out by spraying seafoam and running with sparkplugs disconnected, and then with spark plugs removed so the liquid was coming out. It was bringing up some particules with it. maybe i didn't run that long enough.
Try push starting.....not particularly technical but often effective.
you sprayed carb cleaner into the carbs? :mad: :sad: there goes those Diaphrams :technical:
Quote from: Blueknyt on July 22, 2013, 08:07:10 PM
you sprayed carb cleaner into the carbs? :mad: :sad: there goes those Diaphrams :technical:
... wait... what? ... only for disassembled carbs? .. :icon_question:
... carb cleaner ... makes sense .. spray carbs!! ... not so much though?! .. i dont use the stuff so 'newbie surprise time!' .. learn something new everyday eh! :thumb:
i should say .. while i am jacking this topic .. i know my own limits and patience... for carb problems ive only ever gone to a carb guy ... may cost me more .. but if they frag it then they get to fix the frag! .. if i frag the job ... then i still have to pay them to fix it! :icon_neutral:
yeah, you don't want carb cleaner spray or dip on those diaphrams, they will distort and break down. ive learned that one the hard way. the use of starting fluid down the carb throats is not encouraged either.
Start simple. It may need a valve adjustment. Tight exhaust valves can cause backfiring through the carbs, as the exhaust isn't fully released. So, the new air/fuel mixture ends up pre-igniting.
I'd check the valve clearances, and while you're in there, you can check the top end for gunk and whatnot.
Chemicals can only do so much. Nothing beats a good hand job (hehe).
Looks like I'll be opening up the engine for the 1st time. I'll check valve clearance and timing but I also suspect the intake valve is not sealing properly so may have to take off the head.
Anyone know what all the tools are needed to get to the valves and how to check them?
OK I would really suggest you post where you're located and find a twinner near by who you would bribe with beer/pizza Wine/cheese $$ etc etc to come and help you.
Cool.
Buddha.
I'm in Staten Island. Any twinners here willing to lend a hand? Beer, dinner, and eternal gratitude is on me.
IIRC, it's just Allen wrenches to get the heads off. You'll need a socket wrench to pull the right side cover and spin the engine to check the clearances. And a feeler gauge that can measure .03-.08 mm. You can pick one up for $5-10 at an auto store. You may want to consider replacing the head gasket, too, if it looks worn out.
Here's the page from the wiki: http://wiki.gstwins.com/index.php?n=Maintenance.CheckValves
It's not too difficult if you're mechanically inclined, but it would probably be better to have someone there who's done it before if for no other reason than the peace of mind that no harm is being done.
how did we go from "......bike started ok and i rode it for 30 minutes." to opening the engine? :nono: THink carefully :cookoo: start simple....check carbs again after a new set of properly gapped NEW sparkplugs. kinda rare for something to change that drasticly inside the engine. even valve clearences dont change that quickly unless something is very wrong and you would have noticed it in that 30min of riding.
Performed a compression test today. Both cylinders registered under 10psi. Just to double check I tried the finger instead of spark plug test and i could definitely overpower the pressure from pushing my finger out.
I think it's the massive backfire due to the gunk i put into the cylinders which caused valves to burn. or it could be something else, i won't know till i open her up.
i've ordered most of the tools. still need a valve spring compressor. anyone know of a cheap one online?
Quote from: sashkar2000 on July 23, 2013, 10:52:02 PM
Performed a compression test today. Both cylinders registered under 10psi. Just to double check I tried the finger instead of spark plug test and i could definitely overpower the pressure from pushing my finger out.
I think it's the massive backfire due to the gunk i put into the cylinders which caused valves to burn. or it could be something else, i won't know till i open her up.
i've ordered most of the tools. still need a valve spring compressor. anyone know of a cheap one online?
You hold the throttle open during compression test ?
Cool.
Buddha.
I had the carbs out during the compression test.
Whoa sashkar, I'm in Staten Island too. I wish I could offer my help but I am not very knowledgeable when it comes to these sorts of things. I just do a lot of googling and ask the friendly people on this board.
However, I recently (and still) have an exhaust valve issue when my bike overheated which required me to attempt to take off the cylinder head on my own. I never actually got the head off but maybe if you read through that thread a bit, you can learn from my mistakes which mainly included stripping/rounding every dang bolt on the bike.
PS. I had the carbs out when I did a compression test. Should make no difference.
perhaps I am missing something here, or im just really slow on this thread but "bike started ok and i rode it for 30 minutes...........A week later it didn't start "
um, not starting could be a couple things, but complete loss of compression from a 30 min ride that was running ok and then sat for a week?????
Don't think ive ever heard of a back fire bending valves or knocking cam timing off :dunno_black: sticking valves could do it
do this, pull the cam box cover and check valve clearences if you have bent valves you will have HUGE gap in valve lash, if cam chain jumped you will see the allignment of the cam notches will be off and number of pins in the chain (18 i believe) between gear marks will be off. all this you can see before worring about pulling the head.
Blueknyt, i will follow your advice because AlexT's saga removing the exhaust pipes scared me off a bit.
uh to be clear. with the rotor mark R-T centered on the left pickup coil. (signal generator behind right hand engine cover) the notches on the end of the cams should both point inward towards each other and be even with the gasket surface of the head. there should be an arrow with a #2 on the exhaust cam gear (front of engine near exhaust pipes) that should be pointed nearly straight up, that arrow is pin 1, counting towards the intake cam (back of engine near carbs) should count 18 pins in the cam chain to a arrow on the intake cam gear next to a #3 that arrow should be pin 18.
Did you by any chance spin the engine backwards using a wrench or the rear wheel with it in gear? while rare, that COULD, cause the cam chain to slacken enough to POSSIBLY :cry: jump a tooth messing up cam timing.
Thanks for the details Blueknyt. I'll check it out tomorrow. If those things check out and i manage to remove the head, what are the indications of a bad head gasket, does it look any different?
to comp test out to 10psi in both cyl, it wont be a head gasket issue, even if chunks of the gasket are missing. its going to be bent/broken valves or if really lucky cams will be off time. aside from HOLES in both pistons, even rings worn out you would still see 40-50 psi. it has been many years ago that i was constantly elbow deep into the GS, (just cuz i loved it) i vaguely remember something about it being very bad to spin the engine backwards beyond a few degrees. i will be resorecting my GS very soon. any how. check those things first then on to next step. dont be affraid of breaking bolts, they can be dealt with.
Intake valve has .5 gap, so I proceeded to remove the head. Exhaust bolts were easy but the 8 nuts holding the head are really tough. Will get a long torque wrench tomorrow and a deep socket.
Not sure what to look for once the head is out but hopefully will see the damage tomorrow.
Quote from: sashkar2000 on July 27, 2013, 09:24:59 PMIntake valve has .5 gap, so I proceeded to remove the head.
Why do you insist on opening the engine? A tight valve just needs a new shim.
A 5mm shim? Neh something must be wrong with those valves.
Blueknyt called it spot on, both intake valves are bent. Which parts should I replace and should I put in new exhaust valves as well to be on the safe side? I guess head gasket should go but what about block gasket, the block did move a bit while lifting the head.
The rest of the engine seems ok but really dirty from all the gunk and sprays. What's the best way to clean it up?
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should i be concerned about rings or anything else since the valves actually bent from the backfire explosion?
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let me guess, when you pulled the head, you found the intakes wernt sitting flat in the ports even with the cams removed right? now you need a set of valves, you need to check that the valve guides are not hurt, pistons are tougher then valves when it comes to turning the engine by hand so those wont be hurt. invest in another set of valves (i think the gs1100 uses the same valve size but i could be wrong) http://www.ferrea.com/Motorcycle-Valves/c8220 (http://www.ferrea.com/Motorcycle-Valves/c8220) have a machine shop redo the head for you. Get a gasketset it will have a base gasket in it as well as fresh O-ring that go between head and jugs. other thing you can do is locate another head from a running bike and relap the valves and replace the valve stem seals.... but a gasket set would still be a good idea to put it all back together with. while its apart you could invest in a set of rings and re-hone the jugs rounding out a top end rebuild. its up to you and how far you want to take it, either way, inspect the timing chain guides and tensioner parts for wear an tear and replace what you must.
did you notice if the cams were miss-aligned?
Yep, the intakes had about a 2mm gap against the ports. And the valve stems are visibly bent (not immediately noticeable but it's there on close inspection). The timing chain was in the right place and the cams looked fine.
You think getting a used head may be better than getting the valves separately or are you suggesting i throw out the head? The bike has only 8K miles on it so i just want to replace what i may have damaged with the backfire.
So you think the backfire explosion happened with the intake valves open which forced them up and bent them? Are the valve stems the weakest parts to take on that force or do you think the cams took on that as well? and should i be concerned about the exhaust valves? it was a bit tough to remove the buckets, and i didn't see any shims on any buckets, though i haven't seen buckets before so maybe the shims are there but really stuck hard.
thanks a lot for all the advice!
the back fire from intake is the result of fuel in the cyl and the spark plug lighting it off, having bent valves left an easy out for the explosion. I discribed the valve bending process in your parts cleaning thread. as to replace the head or rebuild the head, that is your choice. you could cheap it the best you can and replace just the bent valves and bolt it back together with new gaskets. the old head , the valve guides need to be inspected to see that they didnt shift or get hurt in anyway. chances are nothing is wrong but still should be inspected. new valves, whats the cost? how much for a shop to dress the seats up and lap in the new valves (or good used ones for that matter) finding another head and do a complete valve job with new stem seals... regaurdless of the choice you will have to adjust the valve lash again (shims) seen a couple used heads on ebay for just under 200$, you could lap the valves in yourself install new stem seals, slap some new gaskets on it and adjust the lash. just keep in mind. you dont want to do this again in 6 months to a year or less. so make sure what ever you do, go through it and check it all out.
I decided to buy new intake valves and leave the exhausts. Got head and base gaskets and 4 o rings, $130 total but would have needed the gaskets for a replacement head as well.
I wonder what a typical cost of a lapping job is and would a machinist be able to inspect valve guides to spec?
Just read your 2 threads, had a sticking exhaust bucket on my 02 and one very cold morning it broke an exhaust valve off when it stuck wide open during cranking and intake valve and/or piston collided with it.
Got new valve, bucket, head/base gaskets, cleaned carbon and fixed it. That was with 20k miles on it and now have 99k without further incident. The valve guide for the broken valve had it's tip broken off in the port area and I let it go and also didn't change valve seals. I lapped both the intake and new exhaust valve for that cylinder to insure good seal. Since you have it all apart suggest you lap in all four valves to make sure you have good seal, only cost you an inexpensive tube of lapping compound from auto parts store. No tool needed I just turned valve back and forth with my thumb while lapping.
Looking at pic of your valves it's hard to believe your 02 GS has only 8k miles on it, here's a pic of my broken exhaust valve with 20k miles on it. Never know for sure buying a used bike, maybe your valve seals are worn?
(http://www.gs500.net/gallery/data/500/valve1.jpg)
thanks for suggestion gsJack. What exaclty are valve seals? I thought the valve closed metal to metal against the port, by replacing valve seals do you mean have a machine shop grind them?
I think i caused the valves to look that way during my 30 minutes of opering the bike. I got it from a friend who abandoned it in the garage for 4 years w/o fuel. so tank rusted and fuel lines were gunked up and i was eager to get it to start so introduced crap into the engine.
Unfortunatley I don't fully understand how the valves got bent (Blueknyt is convinced i turned the engine backwards and caused valve to hit piston, but i don't think i did that). And due to my cleaning efforts i caused 2 huge explosions in the engine which somehow resulted in bent intake valves and 0 compression. So i'm not sure what needs to be replaced. Exhaust valves are kind of expensive so will try to measure them for straightness and try to reuse. Do valve buckets go bad? was the damage visible in your case?
i saw a nice youtube video on lapping valves. doesn't look too hard but i think i want a machine shop to inspect and measure other aspects, like the valve guides, since this is my 1st time ever looking inside an engine.
"At this point I made a terrible judgment call that I really, really regret. I sprayed carb cleaner inside the manifest to dissolve the gunk. And in an attempt to do a better cleaning job, I turned the engine over by rotating the wheel while in gear."
It happens, it does not take much muscle to do it either. just rocking the wheel back and forth can do it as the engine spins more revolutions then the wheel does. motorcycle valve stems are very thin (unless your talking harley) they are easy to bend.
Scary how thin those valves are. How often should the shims be checked?
Thx,
Sean
<<<What exaclty are valve seals? I thought the valve closed metal to metal against the port, by replacing valve seals do you mean have a machine shop grind them?>>>
The good metal to metal fit between valves and seats is commonly referred to as valve seal. Valve seals are an entirely different thing, they are rubber seals on the valve stems that keep the pockets of oil on top of the head around the valves from leaking down between the valves and guides into the combustion chamber causing higher oil consumption and smoking from the exhaust. That little "s" makes for a big confusion if your not yet familiar with engines. :icon_lol: Bargain older bikes with very low mileage can have dried out seals from just sitting too long. Doubt you need valve seals if they really only have 8k miles use on them. Hard to determine on non running engine.
<<<Unfortunatley I don't fully understand how the valves got bent (Blueknyt is convinced i turned the engine backwards and caused valve to hit piston, but i don't think i did that). And due to my cleaning efforts i caused 2 huge explosions in the engine which somehow resulted in bent intake valves and 0 compression.>>>
We might never know, I find it highly unlikely the explosions bent the intake valves and a small amount of turning the engine backwards is unlikely to bend valves unless the cams and crank got out of time somehow. A loose cam chain could cause it if you removed the chain tensioner and then later turned the engine backwards.
<<<So i'm not sure what needs to be replaced. Exhaust valves are kind of expensive so will try to measure them for straightness and try to reuse. Do valve buckets go bad? was the damage visible in your case?>>>
Lap the valves and find out, it's best way to check for bent valves. If you work a valve back and forth and around and around with lapping compound on seat and valve face you will get a continuous gray circle the width of the seat on the face of the valve if it's straight showing it's touching all around Lapping will also improve the seal.
My valve bucket didn't go bad it was just too big for the hole and thus too tight in the head. Misfit at the factory, there have been quite a few of them reported by members here.
Quote from: musicmarley on July 30, 2013, 07:01:46 PM
Scary how thin those valves are. How often should the shims be checked?
Thx,
Sean
Manual calls for every 3-4k miles I think. I checked twice a year on my 97 GS for about 80k miles, that was about every 8k miles or so. On the 02 my annual mileage was less and I've done it once a year every 10k miles or so. Half way thru the 02 I started setting the exhaust valve clearance wider to .003-.005" and they went another 40k miles without a shim change. Last valve check at 86k miles, now at 99k miles, and doubt I'll ever check them again. Exhaust valves now holding like intakes which have never required a shim change on my GSs.
http://www.gs500.net/gallery/data/500/GSvalvelogs.jpg
the cam chain tensioner takes up slack on one side of the engine. its setup so that minimal effort is needed to keep that slack taken up. when you turn the engine in the opposite direction you are pulling that slack out and putting it in the other side. it doesnt take much slack when it comes to cam timing and piston interference especialy when spun in a direction it was not designed to operate. most of all, ONLY the intake valves were bent..
Folks, im not saying this to accuse someone of screwing up, nor to sound as a mechanical guru. I did this same thing on a bench when i had to fix the counter balance shaft bearings in one of my GS engines, turning the crank one handed with a wrench,it was not hard to do. turning backwards, the intake valve can not get out of the way of the piston fast enough before each piston is TDC and shifting the slack worsens this issue. the smaller faced exhaust valve doesn't open as far and is setup to be open at nearly TDC for the exhaust stroke to finish. the intake is not meant to open until after the piston starts its travel down and is clear within a few degrees of crank travel.
it sounds plausible to my thinking also Blue ... not a mechanical guru either .. but a little chain slack can make a big difference when tolerances are close! .. and valves/cylinders are usually awfully close! .. :icon_eek:
Is it possible that an uncontrolled backfire explosion in both cylinders reversed spin direction to cause the bent intakes?
.. plausible? i think?... how likely .. dunno ..
again ... to my 'bush mechanic/hillbilly fix it' thinking ...you had a butt load of carb stuff in there... sustained firing/flame/bang 'might' result in enough force to 'stop' and reverse cylinder direction of motion/rotation ?! ... and if as Blue says the intakes can clash with the pistons in reverse because of chain slack then it could be the thing that did it.. ?
.. you watch top fuel dragsters when they go bang ... flames out of blower hats, holes and flames out of engine blocks and heads , head separated from block ... seized motors and or bent heads/crushed valves/broken rods/cracked pistons ... ..... OK thats huge power and a massive fuel load ... but its in a big engine too!! ...
we have a little engine ....
regardless of size an explosion is by its nature 'uncontrolled energy release' .. sure they have 'controlled explosions' but thats kinda the amount or direction of force .. an unplanned explosion goes everywhere! ..
anyway .. probably just talking out my butt again.... it just makes sense to my 'order of things' in my head. :thumb:
:dunno_black: I dunno and don't need to know, if the valves got bent they need to be replaced. Only one word I'd change in my post above, change we might never know to we will never know. :icon_lol: Your comments on valve timing are interesting but I just don't see that much difference between the intake and exhaust timing relative to tdc. The exhaust is normally closing as the piston goes over the top and is closed at 37* past tdc. Run it in reverse and the intake is closing as the piston goes over the top and is closed at 34* past tdc.
(http://www.gs500.net/gallery/data/500/VALVE-TIMING.jpg)
I agree that if the chain tensioner collapses or is removed and the engine is then turned backwards the valve damage could occur as the slack changed side. But the tensioner clicks out notch by notch as the chain wears and even at top rpm the centrifugal force of the chain doesn't over ride the tensioner. :dunno_black:
jack, when the engine is spun opposite direction, the cam timeing is changed. its not the same on paper as the came chain tension does not remain a constant in the reverse direction. something looks funny with your diagram, intakes begin to open almost imdiately after exhaust close. the exhaust valve has the clearence to be open at TDC, the exhaust closes and the piston is just completeing its travel up. as the piston starts down intake starts to open. the cam chain tensioner on the GS is a sleved screw system with a spring, its not a rachet jaw system and the chain guides take up and redirect most the centrifical forces hence their length all the way down to crank level. the tensioner is prone to being pushed back in, it doesnt take much movement.
Well I don't believe that the sashkar induced explosion directly bent the 2 intake valves, it took metal to metal contact to do that, and I don't think it's likely to have been caused by slowly turning the engine backwards; sashkar believes he only turned it forward by hand.
From first post: "I thought it was cleaning itself out so I continued cranking. Then a massive backfire explosion happened in the intake manifolds and smoke went thru the carbs and came out from below the seat." The bent intake valves were evident after the explosion.
My theory, and it's only speculation, is that the engine was in a position with a piston a little before tdc where the big explosion could have driven the piston downward spinning the engine backwards at least 180*, probably more, to bend both intakes, collapsing the tensioner at the same time, and all evidenced by the smoke coming out from under the seat.
We'll never really know for sure but it's broken now and needs fixed.
Thanks For the explanation gsJack, That's what I suspect happened as well. Now why is it so hard to get parts quickly? Looks like no one stocks them on the east coast so it takes over a week to deliver...
Quote from: sashkar2000 on July 22, 2013, 04:13:15 PM
hmm, would a massive backfire possibly screw up timing?
If there is something stuck to the intake valves, what are some options to get it off? I tried flushing it out by spraying seafoam and running with sparkplugs disconnected, and then with spark plugs removed so the liquid was coming out. It was bringing up some particules with it. maybe i didn't run that long enough.
If you have filled the cylinder with liquid then turned the engine over you have hydraulically locked the engine hence the bent valves.
I ended up opening up the engine and replacing the 2 bent valves. It was quite an adventure doing this for the 1st time and overall this has been a success story and i'm grateful for the guidance i got on this site. thank you guys!