77 GS1000 need help cylinder wont fire

[beno3gz]

iv got a 1977 GS1000. was running fine a month ago and then suddenly developed a miss. I just recently put Dynatec 3 ohm coils on it and it is producing great spark. Has dyna ignition and new plugs and wires. carbs are jetted. all exhaust tubes are hot except #2. i was wondering if anyone might have a suggestion on what the hell it might be. its really quite annoying. any help would be great. thx ben

[TheCafeKid]

I dont think they had a 1000 in 77. Likely a 78. At any rate have you adjusted the valves recently? When is the last the carbs have been cleaned? You say you have good spark, so we can assume that it isnt that. New plugs, and wires and caps, so it isnt that. First things first, if you've not adjusted, or at least checked the clearance on the valves in the last 3k miles, i would do so, to eliminate that from the equation, and if those are good, or you adjust them and it's still not right, move to a complete and thorough cleaning of the carbs, including the replacement of all interiour o-rings. You will also want to check your intake boots for cracking and dryness, if so, replace, and behind the boots are Viton orings that will likely need replaced, as air leaks will form around there. A compression test would be good as well, but only after you are sure the valves are in spec. If your compression numbers are low, especially in the cylinder at fault, it will be time to look at a ring and seal replacement i would think.

[Suzuki_Don]

Recheck spark plug on #2. It might have sparked initially but might not be sparking so good now. I had a faulty plug straight out of the box. Also the plug can glaze over with a film if using unleaded fuel and then does not spark so well. Check if you have fuel to the #2 carb. Best way is to undo fuel bowl drain plug and observe fuel flow on prime position.

[beno3gz]

sorry it is a 78. carbs were rebuilt about 6months ago and larger jets were installed to help compensate for the highly modified header. the valves i have not checked in a while so i will get on that. the cylinder is firing but it just is not right. would these issues cause it to have a slight miss? thx for your all your help!

[TheCafeKid]

Indeed. Valves out of spec would certainly cause that problem. If the valve is still open when the plug sparks, the cylinder is going to misfire because the air to fuel ratio within the cylinder is wrong. Check your valves, adjust as necessary. Chances are this may fix your problem, and if it doenst completely fix it, its going to help you identify where the problem is AFTER that. If that doesnt correct it, you've removed that from the equation, and then can move on to timing and carburation, provided you're certain that spark is consistant. Also, once you have fixed your valve adjustment, airleaks can also be a culprit, and are a common problem on these old girls. A good way to test is, with the motor running, spray some carb cleaner around where the rubber intake boot meets the head on all the cylinders. If the idle changes ( some say their bike revs higher, mine bogged on idle when i did it) you have a leak on that intake boot. Its likely the rubber oring gasket between the rubber boot and the aluminum head, and they can be purchased at www.cycleorings.com (Sold by a fellow member, high quality, and certainly cheap. Also i would suggest picking up his allen head bolt replacements for the boots while you're there. I think all total cost me 15 bucks shipped) The rings over time, become brittle and crack, dry out and no longer seal. Air leaks would also cause idle and firing problems. If you've still the stock airbox, check it for a good seal everywhere too.

you say you've rejetted, so if the valve adjustment isnt the fix, you may have issues there yet to tackle, but, again, to beat a dead horse, you wont know untill the valves are in spec. Let us know! :-D

[beno3gz]

hey guys thx for all the helpful info. i adjusted the valves (which were in great need) and changed plugs in it and so far it is as smooth as silk. no more misfire issues which is great because we just had a break in the weather here in kentucky and got the 1st ride in of the season. cafekid you are in ohio? just traded an old scool vw to a guy in dayton. lookin for some more people here in ky or ohio(daytons not too far) to ride with and that are in to the old stuff if you know anyone. again fellas just want to thank you all for the advice and if i have anymore problems i know where to come. ben :-D

[TheCafeKid]

Well sir, actually, i have a good friend down KY way who is also a member (mriddle) Very good guy. And a bunch of us GS guys are doing a weekend rally in Red River Gorge July 18-20th. I am not positive but there may still be room in Cabin #2 if youre interested! I do plan on getting down there a couple times this spring and summer to visit if at all possible otherwise, and you're always more than welcome up here to come ride. I am always up for riding lol. All the guys on here are good people, and there are a couple of rallys and get togethers planned with in the tri state area this year. Check the GS Meetingplace for those.

[beno3gz]

right on i ride with a bunch a guys on modern crotch rockets but it just not as fu n as ridn with some dudes on hand built machines. i cant believe i didnt find this forum until just recently. oh yeah i posted a reply on your seat cowl you made totally sweet by the way. i would assume you already have it finished but if your looking to relocate electronics and battery just let me know it really is not that difficult.

[TheCafeKid]

Thanks again for the compliments on that cowl. My first time with glass, but i think it turned out pretty ok. There are always things i would do differently or better in hindsight, and it will definately NOT be the last cowl i make. I also didnt do it completely alone, as i had a good bud helping me out, learning as we went. Always good times to have a fellow wrencher to BS with while you're doing it. I replyed to you as well, i would love to see those pics. I have a whole slew of stuff i planned on doing, but succumed to the pressure of having it rideable by spring. I WILL be breaking it down again to do the things i wanted to sometime this year, so your help and input there would definately come in handy

[beno3gz]

yeah i agree with the cowl i made it was the first and definitely an expiriment and will do somethings differently next time. but cant wait until i have another bike to make one for. suprisingly enough i think it turned out alright after inhaling resin fumes for too many hours and killing a 12pk of suds in a weekend.

[TheCafeKid]

Yeah i dont have a garage so i did mine in the basement. Fumed the whole house out, but it was in the name of PROGRESS damnit! LOL Ive actually built that whole bike in the basement. Couple of things to wire up and clean up, pick up a chain for it, and haul her out of the basement to get the motor put in, and send the tanks and body pieces off to the GSR member who is painting it for me. She "should" be up and running by late april i would think. I have to do a lil carb tuning yet, as she was definately NOT set up for the pods and pipe that were on her when i bought her, so ive changed the jetting set up based on some suggestions from guys here, and we'll see. The big "fingers crossed" is the motor. I picked up a spare on fleabay, MUCH cleaner and nicer looking than the one that was in it (IT runs fine, but looks like hell. Broken fins and some serious patina going on) The "new" motor ive never heard run, as the bike was in pieces by the time i bought the motor, but i changed out the shims so the valves are all in spec. and done a visual inspection of everything short of crackin open the cases. She seems to have compression, tho wont know numbers till i get it running, and is in otherwise great condition, with VERY little journal wear on the cams, and no scoring that i can see. We shall see..lol

[beno3gz]

damn the basement how the hell you plan to get it out? either your not married or you have one kickass girlfriend/wife because that sht put out enough fumes to get all of jamaica high!

[TheCafeKid]

Well its a straight shot up my basement stairs out the back door. I took the motor out outside, then the tank off, and down she went easy peasy. Im a pretty big guy so muscling up the stairs wont be much harder, and again the motor will go back in outside..lol Im not suicidal, and while i do have pretty good insurance, i dont think the idea of a hernia is too appeasing..lol Imagine the riding time i would lose!

And you arent kidding. That stuff is NASTY! I dunno if its because the fumes tended to float upstairs, but it seemed worse up here than down there. Course it may just have seemed that way cause i was high as a kite, but i dunno..lol