Need help guys all info here..........

[Wrenchhead]

Model: GS750
Year: 1980
Mileage: 19k

Work perfomed recently: New Battery, Cleaned and Inspected Carbs, Put Fresh Fuel In.

Things noticed: Left coil is powering Cyls 1&2, Right is powering Cyl 3&4. I thought left coil did 1&4 and right did 2&3. Tried switching and bike didnt fire that way. No airfilter just airbox(I understand they have issues without them on but this doesnt seem soley caused by this alone). Bike smokes not terrible but like its really ritch. Sometimes does a little backfire out of the right muffler.

Story:
I bought a week ago for 850$, Guy cut rear end and made into a "Cafe Racer". The bike ran but had a weak battery when I got it, I bought new one and put in nike will only start with the choke out. Barely runs and idles when fully in. MY main issue is that when I try and rev it I get almost nothing I get a bogging sound and smoke from the rear. It seems like its gaining a small amount or rev no matter the throttle positon. The carbs are clean, bench sync'ed, and checked all slide diaphrams. I have watched them the come up about 1/4 the way when I attempt to rev it. All slides move up and down as they should by hand. If I really get on and off it for awhile it will eventually work its way up and rev out and sound great. But then dies right back down. As for trying to drive it, it dies really bad when I try to start out in 1st gear. I need some help this is going to be my only vehicle for the season.

I will be keeping a strong eye on this thread in hope of getting some help I know there are alot of smart guys here. I am a parts guy too so I will be getting parts and installing the quickly. I really appreciate it guys. New GS member here so lets see how good this forum is!!!! Thanks

 

[rustybronco]

first post? I suggest you use your low beams... it hurts the eyes.

 

[Larry D]

Welcome !!
Nice looking cafe. Not my thing, but, I like that one. The bars look kinda scary, but, whatever......

Do you know any other history of the bike ? The carbs have to be sparkling clean. If they just been sprayed with some cleaner, that's not good enough.
http://www.thegsresources.com/gs_carbrebuild.htm

I'm wondering what the previous owner (PO) did with the carbs. If they've been rejetted, you'll have issues. I would recommend getting as close to stock as you can, as far as the airbox, filter, jetting, etc. These bike are particular as to the air/fuel mixture. But, when they're right....hold on !!!

Best to clean the carbs with new o-rings, as described above. At the same time, check the float heights. Complete a valve adjustment. Alot of info can be found at BassCliff 's "little site"
http://members.dslextreme.com/users/bikecliff/

Good Luck !!

 

[Steve]

First of all,

BassCliff should be along shortly with his full Welcome Wagon bit.

I think what RustyBronco was referring to was ... please don't use bold letters. It is hard on the eyes.


Now to your bike problems.
Normally, the left coil DOES fire 1&4, but you have to trace the wires from the ignition triggers, through the ignitor, to the coils. Someone might have switched positions so that the left coil might power 2&3, instead. Either way, one coil does the outer cylinders, the other coil does the inner cylinders.

I think that your starting problems are entirely related to the coil issues. It is normal for the bike to start (when cold) by using the choke. When properly tuned, you won't need the choke for more than a minute. When you get the coils properly sorted, you should be happy with the bike. It looks real nice.

.

 

[yaddy]

seen this bike before

seen this bike before

Bike was "cafe'd" by a member of this forum wasn't it? I remember seeing this pic before, was it "cafe bike in 1 hour" or something?

 

[bonanzadave]

Put Fresh Fuel In.

Thats square #1. Now make sure that clean fuel is getting to the carbs. Square #2 - Check the petcock, fuel hose & vac hose.

 

[earlfor]

The left crankshaft trigger goes to the left coil which fires cylinders 1 and 4. I would chase down the wiring and make sure its connected correctly.

Earl

 

[rustybronco]

I think what RustyBronco was referring to was ... please don't use bold letters. It is hard on the eyes.

Forgive my rudeness... I does hurt this old parts guys eyes.

Steve is correct, 2 & 3 for one coil and 1 & 4 for the other.

straighten them out and you are on your way to being golden.

 

[yaddy]

Yup, originally posted in the appearance section under the title:

"my 1 hour cafe racer, nothing fancy......"

I haven't read it all but it may give an insight into what was done with the bike before you bought it?

Coils are deffo wrong if connected as you say. Should be: one coil for outer cylinders, one for inner. Left coil is usually outer cyliniders but that depends on the wiring configuration now.

 

[Wrenchhead]

Does anyone have any schmatic info on the primary voltage wires for this bike? I had my buddy try switching them and the bike didn't start at all. I was also heard these use a wasted spark set-up. Is this true? Anyone have any other input?

 

[Wrenchhead]

Yea, and I'm not sure exactly how "well" he had this bike running, he told me it started and ran good. Run good means it can drive itself down the street without issues but it doesnt do that.

 

[Wrenchhead]

The fuel petcock would cause this? Who thinks so or better question how common is this?

 

[Dave8338]

Greetings as well. Have you pulled the p;lugs to ensure that it is in fact, running rich? If so, they'll be black.

I tend to think that it is running lean. You stated that the filter was not in the bike. You mention that the bike bogs when giving it a twist. This is almost always lean.

I agree with what steps the others have mentioned but a filter (of some kind) will be needed in order to even get that thing to breath right...

 

[rustybronco]

Does anyone have any schmatic info on the primary voltage wires for this bike? I had my buddy try switching them and the bike didn't start at all.

Baammmm... http://members.dslextreme.com/users/bikecliff/ example... GS750ET "T=1980". "x=1979" "z=1982"... 8 valve, 16 valve?

I was also heard these use a wasted spark set-up. Is this true?

yes, a wasted spark system.

Anyone have any other input?

fix one problem at a time, then go on to the next one if it "rears it's ugly head".

 

[Guest]

+1 on lean.
Put a clean air filter on first.

Check intake boots. Spray carb cleaner between boot and cylinder, if revs go up, they're sucking air and will need replacement.

 

[Wrenchhead]

Ok, so heres a theory. Seems lean is the scenerio we are favoring, possible lean conditon caused by poor fuel flow???

 

[Guest]

Ok, so heres a theory. Seems lean is the scenerio we are favoring, possible lean conditon caused by poor fuel flow???

Did you try it with petcock on prime?

 

[Wrenchhead]

Is there a prime/on setting on it? It looked like a vacuum petcock.

 

[Larry D]

Ok, so heres a theory. Seems lean is the scenerio we are favoring, possible lean conditon caused by poor fuel flow???

Get your coils straightened out first. Putting a new air filter in will help with the leaness. Then go from there. Without the coils right, you'll chase your tail.

 

[Wrenchhead]

Does that sound right with the coils though? I believe it is not fully burning the mixture because the spark timing is off which an incomplete burn would result in a "rich" spark plug reading and or symptom. But up to when it actually gets there the spark timing increases.