GS850 will not run

[veedub]

Ive got a '79 GS 850 with the VM carbs. I have been trying to get this thing running all summer. I believe my problems to be in the carbs but I cant seem to get them to work no matter what I do. They are spotlessly clean (read: carb dip) I can see through the holes in all Jets I cant see anything wrong with any carb part. However the thing will not run. I have heard two different things about pilot settings on the VM rebuild PDF it says 1 turn out for the Fuel 1 1/4 for the Air screw. My manual and others have told me 5/8 Fuel 1 1/4 Air. regardless I have tried these settings and many others and cant get it to run. At best I have had it running on 1 and sometimes 2 cylinders (and to make it more confusing not always the same cylinders.) I have compression 125ish on all cylinders cold (cant get a proper reading warm it wont run). I replaced the stock points ignition with a Z1 electronic ignition kit the spark is bright and solid. With no carbs on the bike at all I can spray starting fluid into each cylinder individually and it will run for a quick second so the problem has got to be in the carbs. I got the bike to idle once where it wouldnt die but it was running only on one cylinder. Another time I had it running between 1/4 and 1/2 throttle for about 30 seconds but it was running on only 2 cylinders and not even the same one as the time I got it idling on the one. Correct me if I'm wrong but running at 1/4-1/2 throttle its completely past the pilot screws effecting anything so its beyond a setting issue. This is driving me crazy I cant drop any more money into this project I am ready to buy another one and keep this as a parts bike or just scrap it all together. Any one have any ideas I feel like I have checked everything twice.

 

[Big Rich]

How is your timing? You said the points got replaced and you have spark, but is it sparking at TDC?

And is the battery fully charged? Last one: are the plugs wet with gas or dry after you try to start it?

 

[Big T]

Is your petcock delivering fuel?

Is there fuel in the float bowls?

 

[veedub]

Timing is spot on (statically anyway). At least if I am understanding how to set it correctly. There are the lines looking something like this:

|T|F14|

The light should turn on just as the timing mark lines up with the Middle line next to the F correct?

The battery begins fully charged every time I attempt to give it another go. After a half hour or so of trying different things it might be a little less charged from running the starter so much. Have not pulled the plug after extended periods of trying to start to see if they are wet.

 

[veedub]

yes there is fuel in the bowls.

 

[BassCliff]

Hi,

Just a couple of thoughts...

Sometimes when you clean the carbs it will take two or three times in order to do it thoroughly. Check Mr. Nessism's new carb rebuild guide. There's a copy on my website.

Are you using OEM or aftermarket float bowl gaskets? Sometimes, with the generic aftermarket gaskets, there are punch-outs that need to be removed so that they match the original gasket. All four gaskets might not be exactly the same.

If I think of something else I'll let you know.

My uncle used to say, "If you try something and it doesn't work...try something else." He was a great man.

Have you been through the checklists HERE?


Thank you for your indulgence,

BassCliff

 

[SqDancerLynn1]

I would go back and first check and make sure you have 12 V on the coils. Them check each cylinder for spark

 

[Big T]

Timing is spot on (statically anyway). At least if I am understanding how to set it correctly. There are the lines looking something like this:

|T|F14|

The light should turn on just as the timing mark lines up with the Middle line next to the F correct?

The timing is good at the center mark, close enough to start

 

[Guest]

did you ever get all your valves set within specs? while you're in there checking your valve shims I would check and make sure your chain has not skipped, if it has it could easily be your problem.

 

[veedub]

basscliff: my gaskets do have that hole punched out however my carbs do not have a passageway there, they appear to be slightly different than your carbs I also do not have the passageway opposite the one you have highlighted behind the float pin uprights. Also the Bleeder(pilot Jet) is in a different location pehaps this pictures are a set of CV carbs not the VM I have? That new tutorial while awesome is also for the CV carbs. I have done just about everything on that checklist except:

azr: I never changed out valve shims I wanted to hear it run on 4 cylinders before I invested this money, some valves are tight but not to the point where I think it should stop it from running. It might run better with proper clearances but I still think it should run with them tight, no?

Also how would I tell if the chain skipped time?

SqDancerLynn1: checked the voltage at the coils I think I am doing this correctly just check from the hot wire to ground right? interesting thing here I get 10.2 volts while I have 12.3 at the battery. I do however have bright blue spark on every plug.

 

[veedub]

WHOAH hold on a second I just was reading over my manual on static ignition timing and double checked with this link as well http://members.dslextreme.com/users/storagecliff/images/electrical_odd-n-ends.html#A18

If I am understanding correctly if I rotate the engine clockwise my static timing light should just go OFF as I come to the |F1 line. I have it set so it just goes ON as I get to this point clockwise. Which would mean my timing is drastically off. I have only ever set points timing on my VWs where you are aiming to get the light to just come ON as your marks line up not sure why it would be opposite but someone please tell me if Im reading the Suzuki stuff right and this light should be turning OFF as the lines line up?

 

[Big T]

Also how would I tell if the chain skipped time?

SqDancerLynn1: checked the voltage at the coils I think I am doing this correctly just check from the hot wire to ground right? interesting thing here I get 10.2 volts while I have 12.3 at the battery. I do however have bright blue spark on every plug.

Chain - check the service manual for the correct alignment of the marks at TDC

Voltage - 10.2 is static voltage, right? What does it drop to when you press the starter button?

 

[Indysteve]

veedub, these may seem obvious but lets get them out of the way anyway

Did you bench sync the carbs before re-installing?

If so, are the throttle shaft bolts all tightened?

Have you verified the airbox is sealed when you installed it?

How were the intake boots, hard? soft?

You may want to consider dropping your bowls to verify that you have fuel in them.

Are the vacuum lines all hooked up?

 

[Indysteve]

I think you read that right. I went a read the whole thing twice and I got what you got from it, the light should go OUT at the mark.

 

[Big T]

I think you read that right. I went a read the whole thing twice and I got what you got from it, the light should go OUT at the mark.

Nope, comes on due to lack of current flow thru the points

 

[Steve]

Nope, comes on due to lack of current flow thru the points

Evidently you missed part of the original post. :-k

... I replaced the stock points ignition with a Z1 electronic ignition kit the spark is bright and solid. ...

I don't know how the electricity will flow with the new kit, but yes, something should change at the timing light. Whether the light comes on or goes off will depend on the unit. Contact Z1 or the manufacturer of the kit for details.



One other comment caught my eye:

azr: I never changed out valve shims I wanted to hear it run on 4 cylinders before I invested this money, some valves are tight but not to the point where I think it should stop it from running. It might run better with proper clearances but I still think it should run with them tight, no?

Tight valves WILL prevent proper running.
We keep telling you guys and telling you guys, ... THERE ARE NO SHORTCUTS.

CLEAN the carbs.

ADJUST the valves.

CLEAN the electrical connections, especially the charging circuit.

THEN, you can fire it up to see if it's worth putting any more money into the bike.

Not sure what you thought you might have to "invest" in a valve adjustment, but a new valve cover gasket is $10.25 and valve shims have apparently just gone up to $5.64. In the worst-possible case, where you would need all eight shims (highly unlikely), you would spend $45.12 for shims and you will need the valve cover gasket anyway, for a total of 55.37. Usually you don't need to get but a few shims and move a couple of others, but you can also check into the shim club for details on how that works.

.

 

[cowboyup3371]

When you were looking at Basscliff's site for the carb rebuild guide, did you click on the one below the CV article that says VM carb Rebuild Guide? http://members.dslextreme.com/users/bikecliff/images/vm_carb_rebuild.pdf

You will burn up things on those tight valves if you don't adjust them. Get that done ASAP like everyone has tried to tell you.

 

[veedub]

When you were looking at Basscliff's site for the carb rebuild guide, did you click on the one below the CV article that says VM carb Rebuild Guide? http://members.dslextreme.com/users/...rb_rebuild.pdf

Yes I used the proper guide for my carbs.

I am well aware tight valves will cause an engine to run poorly and that prolonged running of an engine with tight valves is going to burn valves and eventually eat valve seats etc, On my VWs I usually check and reset valves about every 1500 miles, then again I can do those valves in about 10 minutes and they are all adjustable without any swapping of parts. Anyway, I think they would need to be very very tight to not be able to hold an idle when cold.

I never said I wasn't going to get the valves properly set before riding the bike, I just wanted to hear her run on all 4 cylinders for 30 seconds before I spend yet another $50.

I just checked the timing dynamically and its spot on perfect so that appears to not be the issue.

I did replace the airbox boots and the intake O-rings, the intakes are still soft and pliable on the carb side. However I was just looking at the airbox a little closer and it seems like I am missing something. The air cleaner itself is in a chrome metal box that slides into the airbox slides and attaches with one screw to keep it from sliding back out. Well this leaves almost 1/4" of play between the top of the air cleaner element and the bottom of the airbox ceiling seems this cant be right or what good would the air-cleaner do? looks like I need to pick up some weather stripping but is there supposed to be some sort of actual rubber gasket here? couldn't see one in the bikebandit parts breakdown? Has anyone run a GS engine without the airbox installed? Will it still idle or does it absolutely NEED the airbox installed to hold enough negative pressure to run at all?

 

[cowboyup3371]

None of the folks who have tried running their bikes without the air box/filter on it have had any success. The most you could do is wrap rags around the carbs for a short term thing but otherwise get the air box back or find some pods and start fighting that mess to jet.

 

[veedub]

Did the airbox rebuild with no change to the bike. I believe the tightest valves were about .001 when I had the cover off. While this is tight and needs to be fixed it should not stop the engine from running. Its got to be something else but I am out of ideas as to what