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Angry, and about to light a GS on fire...

  • Thread starter Thread starter TheCafeKid
  • Start date Start date
T

TheCafeKid

Guest
Ok, I am at a point where i have run out of ideas. I am helping a fellow GSR work on his 79 750L. We re-cleaned his carbs, dipped, new rings, all the norms. I have followed everything to the book. Valves are done, this is one of MY motors in the bike, it ran in the cafe last summer, i know it runs. Factory airbox, resealed, new boot rings, no leaks around either. Carbs are stock. Jetting is stock. Followed the manual for float levels, screw adjustment, etc etc.

The bike fires on one and two, and apparently four sometimes. Three is stone cold. Spark on all four plugs. Swapped wires with corosponding cylinders, problem doesnt follow the wires. Stays with three and four. The bike has a Dyna S in it, and i suggested that maybe the timing was off, but that doesnt make sense because its one and two that fire. The plugs on three and four are wet with gas, they seemingly just wont fire. Fuel screws on the VM26SS carbs are 1 out, air 1.5 out.

Im out of ideas boys. this bike is fuggin cursed, and its not mine and *I* want to smash it with a hammer. Anyone have anything i may have missed or not thought of?


TCK
 
Try new plugs. New ones can be faulty. Screw air screws out a bit more. Maybe a total of 3 turns out. Run the bike in the shed at night and see if there are any sparks leaking anywhere.
 
Well you need air, fuel and spark (and compression!). Since you're getting fuel and spark, there must be a mixture issue on those cylinders. I think you need to pull the carbs off and double check the work on those carbs and all the intake rubber. Go slow. It's so easy to make assumptions when you're double checking your work. Just check everything in order. Good luck!

Josh
 
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Well we have gone over the carbs more time then I can count an we have measured and triple checked every thing that we could.

We have had all 4 cylinders firing we just can't seem to get them to all fire at the same time.
 
TheCafeKid said:
Ok, I am at a point where i have run out of ideas. I am helping a fellow GSR work on his 79 750L. We re-cleaned his carbs, dipped, new rings, all the norms. I have followed everything to the book. Valves are done, this is one of MY motors in the bike, it ran in the cafe last summer, i know it runs. Factory airbox, resealed, new boot rings, no leaks around either. Carbs are stock. Jetting is stock. Followed the manual for float levels, screw adjustment, etc etc.

The bike fires on one and two, and apparently four sometimes. Three is stone cold. Spark on all four plugs. Swapped wires with corosponding cylinders, problem doesnt follow the wires. Stays with three and four. The bike has a Dyna S in it, and i suggested that maybe the timing was off, but that doesnt make sense because its one and two that fire. The plugs on three and four are wet with gas, they seemingly just wont fire. Fuel screws on the VM26SS carbs are 1 out, air 1.5 out.

Im out of ideas boys. this bike is fuggin cursed, and its not mine and *I* want to smash it with a hammer. Anyone have anything i may have missed or not thought of?


TCK
Click to expand...
Ohhh i forgot to add. The bike runs on the two cylinders ON CHOKE. It will not run off, or accept throttle at all.
 
Pull the valve cover off and check the cam timing.
After that check the ignition timing. Do you have a timing light? Put it on the #1 plug wire and see where it hitting.
I know jack about VM carbs but it sounds like you've done the dance. Move to ignition.
 
Well I too thought timing, but its got a Dyna in it. and its one and two that fire. So wouldnt it NOT fire at all on two or one if the timing was off? They arent paired, but i dunno if that would matter or not. At this point im out of ideas beyond that. Cam timing SHOULD be right, because this motor ran last year and hasnt been changed other than that.
 
Get a timing light and check the timing on all the wires.
Are the plug caps and wires good?
 
chef1366 said:
Get a timing light and check the timing on all the wires.
Are the plug caps and wires good?
Click to expand...
Well i assume so, and i know that is assuming and what it leads too, but we swapped threes wire to two, and one to four, and the problem didnt follow the wires. Stayed on the offending cylinders
 
You think you have it bad the 450 I got those signals for has a big bees nest of melted wires in the headlight bucket. Had to buy a new harness and I'll have to get busy with that.
Some jackass bypassed the main fuse and did some Mickey Mouse wiring on the turn signals and melted the ignition switch plug to all the other wires. :?
 
chef1366 said:
You think you have it bad the 450 I got those signals for has a big bees nest of melted wires in the headlight bucket. Had to buy a new harness and I'll have to get busy with that.
Some jackass bypassed the main fuse and did some Mickey Mouse wiring on the turn signals and melted the ignition switch plug to all the other wires. :?
Click to expand...
Yeah at that point i would rip it out and either do one of your own, or find a replacement. I have thought it would be cool to do your own harness.
 
a warmish test revealed 120-125 across the four. On the low side of spec, but i attribute that to the temp as well. This motor RAN last summer.
 
Did it run with the Dyna S? These can be faulty. Try some stock parts and see if it runs.
 
nope, ran on points and condensor. we may have to try the stock ignition and see if there is a difference.
 
I agree with Chef. The plugs are wet, so you have fuel. The plug fires out of the engine, so you have spark. The fuel enters the cylinders via venturis, so you have air. Has to be something to do with the timing. You've got enough experience with carbs to get them somewhere in the ball park, enough to fire anyway. And do a final check to be sure that everything is routed correctly - fuel and vacuum hoses, and all wires. And going back to stock ignition sounds like a good idea for now.
 
TheCafeKid said:
nope, ran on points and condensor. we may have to try the stock ignition and see if there is a difference.
Click to expand...

Boy, I wouldn't hesitate on that one. I'm from the old camp, & can set the timing on a points bike using a VOM (although a strobe / timing light is also handy to watch the advance working). Eliminate one variable right away.

Ya got compression. Ya got fuel gettin' in there. All ya need now is spark to make it go 'voom!'. I'd be tempted to feed it a sniff or two of ether and see if it responds.

Good luck.
 
robertbarr said:
Boy, I wouldn't hesitate on that one. I'm from the old camp, & can set the timing on a points bike using a VOM (although a strobe / timing light is also handy to watch the advance working). Eliminate one variable right away.

Ya got compression. Ya got fuel gettin' in there. All ya need now is spark to make it go 'voom!'. I'd be tempted to feed it a sniff or two of ether and see if it responds.

Good luck.
Click to expand...
Well, I havent ever really messed with the P&C adjustment, I have my manual tho, and a multitester, so hopefully i can get it right with that. If you have any tips Robert id be appreciative. Also, when i say this motor ran on the P&C, it was in a different bike at the time, with different carbs, but that shouldnt make a difference. I know that my carb cleaning job is good. Nother question, if its running on the two, why is taking it off choke or feeding throttle killing it? Just not hot enough to sustain a faster combustion?
 
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Checking timing using the Dyna S is easy, stick your test light in the white or black bullet socket and and turn over the engine. Light should illuminate when the F mark comes up on the appropriate mark on the advancer. Also, make sure the mechanical advance moves - the spacer was too thick on my bike so the advance was binding.

Hope this helps.
 
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