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HELP! not sure on my problem here, it should run? GS550

  • Thread starter Thread starter 302Ford
  • Start date Start date
3

302Ford

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Hello, i recently bought a 1981 GS550 it had been made into a hardtail bobber, the guy messed up the wireing and skrewed the ignitor, i rewired the whole bike and put another ignitor on and now have fire on all four cylinders. i was sure the timeing was off with this different wireing and checked the order by hand with a friend, i found top dead on No. 1 and when the compression blew the finger off as i was turning it by hand, i then backed it up a little bit and found what spark plug was fireing when it passed the pickup coil, put that plug in as 1 and continued doing this until if found the order out for the bike. they all have fire when each piston is at top dead center and ready to fire. it only has two pickup coils so two plugs fire at once...... so the timing should be right. i put gas in each plug and tried to fire it up and it will SOMETIMES pop once. thats it. i have gas to the vacume actuated carbs, and they dont even get it to pop once, i tried starting fluid sprayed into each carb and i even put it in each plug, still nothing more than one pop..... i would think it should try to take off and run for a few seconds doing one of these things. i am lost and dont know what to do, i am 16 and walking into this with very little knollage about bikes other than what i have read in my repair manual. i know the wireing is right, it should be enough to make it run even if it wasnt running good, all four have blue blazes so i think they are actually pretty healthy sparks too. im not sure what else to try. i have fuel (just for a few seconds) in the thing when i put gas or starting fluid in it, shouldnt it take off for a few seconds? even if the carbs were junk and not working. looking for some tips here, i think my compression is okay too, i dont have a gauge but if it blows a thumb off it should still be enough to run right?.... Thanks for reading this all i know it was long. any ideas would be great and any way to test them would be even better Thank you so much,-- Tyler
 
Hi Tyler,

Your logical approach to investigating the problem is admirable. I agree that it's odd that you can't get more fire out of the bike. Not sure what to suggest other than to go through the bikes maintenance including a carb rebuild. Please check the Newbie Mistakes thread and carb rebuilt tutorial linked in my signature. Hopefully something will click and you will figure out the problem. If forced to guess I'd say the problem is related to the hack job the previous owner dumped on you. Bobber pilots are darwin award winners in training. Hope you make it through to the other side.
 
Sounds like you're doing some good work so far. Have you checked under valve cover to make sure no one has buggered up the cam timing?
 
Maybe the two plugs firing together is confusing things here. Since you got good spark, try something simple.....Switch the spark plug leads going to 1 and 4 to 2 and 3 etc. see if this interchange effects your starting fluid/gas in cylinder stuff.
In stock setup, the left ignition coil fires 1 and 4 ,while right does 2 and 3 (when wiring is correct!)

your wiring is similar to my 650, so go here click on,and get wiring diagram.

http://members.dslextreme.com/users/bikecliff/images/gs650wiring.html
 
It's common knollage that 550's start pretty hard without their rear shocks... lol kidding, sounds like you've got a great start so far and know quite a bit about the bike. My two suggestions (besides going to the website mentioned above) would be to make sure you check your valve clearances and take those carbs apart and clean them up really good. Get some new o-rings from this member and replace your old ones. If your valves are too tight, it will make the bike much harder to start. Are you running pods or the stock air box?

Oh, and post some pics!
 
I am new to this forum and will be following closely to this thread as that I have the same problem as you.

I have fire (spark) going to all cylinders and I also have gas and starting fluid going to each cylinder. But nothing but a pop out of each cylinder every couple turns.
It ran before I rebuilt the engine and the carbs. Also replaced the spark plugs and wiring. But cannot figure out why it won't start.
I have 2 1977 gs750's and I want to figure this out before I decide to rebuild the other engine as it is leaking oil from the base gasket and head gasket.
 
Hello, thank you for the many suggestions, i will look into the valve clearence. although i dont think it is, but its worth a shot. it was running before the chop, so i was pretty sure it was electrical, the engine turns over good under its own power and it has good fire on all four cylenders...... i honestly am lost, i already took the carbs off and all but one is squeeky clean inside them... looks like somebody cleaned them recently and just had a little water in one.... but even so it wont fire with ether in the cylender.... i mean is that enough to make it pop more than once? or not...... the vacume diaphrams look good in them also.... i will put up some pics soon, i have this one 1981 GS550L and i also have a 1981 GS650G
 
Where are you? :-k

There's a pretty good chance that one of us might be close enough to stop by and lend a hand.

.
 
Yes the one coil fires 1 and 4 and then other fires 2 and 3. While the coil is firing on cylinder 1 on the power stroke, for example, it is also firing in number 4 on the exhaust stroke. Its just a dead spark that does nothing during the exhaust stroke but theres still a spark. Otherwise there would have to be 4 coils or a distributor and rotor arrangement like a car.

You can have the coils 180 out so try switching them at the wiring harness and see if it hits. I have done this myself so thats what I would try first.
 
i had a very similar scenario with a 1983 Triumph T140 Bonneville;(masters of vibration); what we found eventually was that whilst we had set the cams according to the Haynes book(of lies) the cam timing marks had been changed by the factory and set-up as such there was no way she could run; when a genuine factory manual gave us the correct set-up detailing she fired up good as gold;
tappet (valve) clearances need to be accurate; too tight equates to lost compression and difficult starting; in the longer term valves and valve seats will burn out needlessly;
I believe the GSX four valve engines are more prone to this malady; the older GS's being hugely robust;
Robbie; Salisbury; England; it's dark and with a very hard frost
 
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