New Bike: Various Starting Problems

[Anonymous]

I just purchased a 78 GS550 that was in storage for like 5 years. It has nearly 47000 miles. When I purchased it it wasn't putting out spark. I bought 2 new coils and now it has spark. At that point it would start but only idle for a few seconds with the choke on. I cleaned the carbs and it would pretty much run the same way. I thought it might need some intake restiction so I put shop rags over the carb inlets and it ran almost perfect. So I purchased 4 pod filters and now it won't start at all. It fires a bit but wont catch. It has also started backfiring.

The left exhaust pipe blows a little blue smoke when it does run and this is the side that backfires. The spark doesn't look particularly strong but it seems to be enough. I have cleaned the carbs around 6 times. The pilot jet on the bottom was set to 2.75 turns. The owner before me has cut the baffles off the pipe. Could this just be a jetting problem?

I would like some suggestions on where to look next.

[Anonymous]

Re: New Bike: Various Starting Problems

I just purchased a 78 GS550 that was in storage for like 5 years. It has nearly 47000 miles. When I purchased it it wasn't putting out spark. I bought 2 new coils and now it has spark. At that point it would start but only idle for a few seconds with the choke on. I cleaned the carbs and it would pretty much run the same way. I thought it might need some intake restiction so I put shop rags over the carb inlets and it ran almost perfect.

Do I take it that you are running the machine without any breather box or air filter? The GSes are known for not running properly without the stock airbox.

So I purchased 4 pod filters and now it won't start at all. It fires a bit but wont catch. It has also started backfiring.

Tell-tale sign of a lean condition i.e. too much airflow through the pod filters.

The left exhaust pipe blows a little blue smoke

Usually indicitave of oil leaking into the cylinders (head gasket?)

when it does run and this is the side that backfires. The spark doesn't look particularly strong but it seems to be enough. I have cleaned the carbs around 6 times. The pilot jet on the bottom was set to 2.75 turns. The owner before me has cut the baffles off the pipe. Could this just be a jetting problem?

I would like some suggestions on where to look next.

Be forewarned that I'm only speaking from what I've heard: It's well known that putting pods on a bike will require rejetting. So yes, you should probably rejet. However, you should keep in mind that the main jets have the most influence on the mix when the throttle is fully open. And they have very little, if any, effect on the machine at idle.

Here is some more reading on carburetion:

http://www.motorcyclecarbs.com/jetting/carbs101.pdf

http://www.bob2000.com/carb.htm

[Anonymous]

so it would be a good idea to revert to the stock airbox?

[Detman101]

Yes, unless you want to go through the hellish but educating process of rejetting.


Dm of mD

[Anonymous]

Well I thought it was kind of strange that it stopped starting all together so I went poking around the carbs and found that the pilot jets had beenovertightened. This caused them to be broken or rounded off. The guys at the local bike shop said that the carbs are probably junk because the carb body is probably messed up. Do you think this is true?

[Anonymous]

Not necessairly true. I did the same thing trying to get my pilot jets out. Buy a reverse drill bit at a discount tool store and you will see it come out easily. (in most cases)

[Anonymous]

I got most of the jet out but there aren't sharp anymore. They have a really rounded tip and are missing maybe 5mm of the point. I think that part may be in the carb body.