'83 GS550 Idle Going Crazy

[BigD_83]

I have been looking into getting a small inline filter, but my bike (as well as a number of other GS models, I assume) is vacuum-fed, so won't it cause fuel feed problems?

Also, how small can the filters go? I don't have a lot of room directly under the tank. Thanks!

My understanding is that the petcock is vacuum actuated, but the fuel feed is gravity fed. PRI bypasses the vacuum and allows fuel to flow directly to the carbs. This meshes with my check of the system as when negative pressure is applied to the vacuum line I can hear the petcock opening and then closing once the vacuum is taken away.

I just had this discussion with the elder statesman at my local Suzuki shop, and his answer to whether the inline filter is affected by the vacuum was a resounding "No!" and that he had installed an inline filter on his 650GD and other bikes with no problems. The only pitfall is to make sure that the fuel isn't travelling uphill at any point in the system.

There is a discussion about this on the Kawasaki forum:

http://www.kawasakimotorcycle.org/forum/vintage-motorcyle-info/137434-line-fuel-filter.html

I ended up with the same fuel filter in the above discussion (the same as the ones from Z1 Enterprises). I suppose that placing it closer to the tank protects the fuel line from accumulating rust, but it might swing or bounce around a little more than if it is nestled amongst the carbs.

I think I'm going to mount it lower down, between the carbs rather than higher up, but I don't see much danger in it being in either location. I'll let you know how it goes for me once I get my 650 back together and have run it for a while.

[GS550ED]

My understanding is that the petcock is vacuum actuated, but the fuel feed is gravity fed. PRI bypasses the vacuum and allows fuel to flow directly to the carbs. This meshes with my check of the system as when negative pressure is applied to the vacuum line I can hear the petcock opening and then closing once the vacuum is taken away.

I just had this discussion with the elder statesman at my local Suzuki shop, and his answer to whether the inline filter is affected by the vacuum was a resounding "No!" and that he had installed an inline filter on his 650GD and other bikes with no problems. The only pitfall is to make sure that the fuel isn't travelling uphill at any point in the system.

There is a discussion about this on the Kawasaki forum:

http://www.kawasakimotorcycle.org/forum/vintage-motorcyle-info/137434-line-fuel-filter.html

I ended up with the same fuel filter in the above discussion (the same as the ones from Z1 Enterprises). I suppose that placing it closer to the tank protects the fuel line from accumulating rust, but it might swing or bounce around a little more than if it is nestled amongst the carbs.

I think I'm going to mount it lower down, between the carbs rather than higher up, but I don't see much danger in it being in either location. I'll let you know how it goes for me once I get my 650 back together and have run it for a while.

Well it's settled then. I'll be going in for a fuel filter as soon as I can. Thanks for clearing that up.

[BigD_83]

Well it's settled then. I'll be going in for a fuel filter as soon as I can. Thanks for clearing that up.

Of course, I'm open to other suggestions if someone with more experience lays out a good explanation. Been wrong before, and I'm sure I'll be wrong again in the future...

[skreemer]

Have you tried a vacuum synch of the carbs yet?

Are your fuel air mix screws drilled out? (if so what are they set to) IIRC they need to be between 3 and 3.5 turns out(check that with the haynes/chiltons/factory manual I'm getting this from memory). Lastly take a look at the knob between the carbs, it's the idle adjust and it just slightly tweaks the angles of the butterflies... if it's been over adjusted to have them open you'll be chasing the idle issue all over the place...


BTW in the 4 - 1 stage 3 dyno jet kit they never change the pilot jet size. They increase the fuel air mix slightly and up the main jets...

At idle though you should be on the fuel air mix screws/pilot jets and not much else...

[GS550ED]

Have you tried a vacuum synch of the carbs yet?

Are your fuel air mix screws drilled out? (if so what are they set to) IIRC they need to be between 3 and 3.5 turns out(check that with the haynes/chiltons/factory manual I'm getting this from memory). Lastly take a look at the knob between the carbs, it's the idle adjust and it just slightly tweaks the angles of the butterflies... if it's been over adjusted to have them open you'll be chasing the idle issue all over the place...


BTW in the 4 - 1 stage 3 dyno jet kit they never change the pilot jet size. They increase the fuel air mix slightly and up the main jets...

At idle though you should be on the fuel air mix screws/pilot jets and not much else...

I'm having a friend synch the carbs in a couple days. The fuel-air mixture screws are still untouched with their covers on them. I haven't changed the idle jet or main jet size, just replaced them with new ones.

[JEEPRUSTY]

So I spoke too soon in the thread I last posted saying that the bike ran fine. I recently installed some aftermarket Accel coils on my 1983 GS550ED and it ran fine except for running extremely lean and bogging bad. So I took the jets back out and upgraded them to one above stock (stock is 95 & 102.5 so I upgraded to 97 and 105) Strangely enough, the jets in the bike when I bought it were like 85's and 87's...

Anyways, after putting it back together, as well as replacing the idle jets with new ones of the same size and a new float valve seat and needle, and new O-rings all around, it started up after spraying in some carb cleaner. But after this the idle became extremely erratic even after it warmed up. It would leap up to 4-5k, and after I naturally turned down the idle, it would idle fine at 1200-1500 until I revved it, when it would then get stuck at 4-5k, or kill itself. I've played with the idle adjust for hours and I seem to find a sweet spot only for the bike to not like it 10 minutes later.

I cleaned the carbs very thoroughly and even tried using the stock number (95 and 102.5) jets just today, but with no luck. It won't stick with an idle. I'm at the end of my rope...I must have screwed up the carbs somehow.

take the idle jet screws out. PITA but I bet that the cavity is filled with corrosion and that the o-rings are shot. That woul make adjusting idle impossible.
When I did mine recently I found a huge difference in performance just by replacing the tiny washers and o-rings.

You should check the throttle cable for binding. You need to be sure the carb throttle plates are full closed when the throttle is in the close position. You can accidentally have the cable jump in the twist tube which will have the throttle cracked open.

[GS550ED]

take the idle jet screws out. PITA but I bet that the cavity is filled with corrosion and that the o-rings are shot. That woul make adjusting idle impossible.
When I did mine recently I found a huge difference in performance just by replacing the tiny washers and o-rings.

You should check the throttle cable for binding. You need to be sure the carb throttle plates are full closed when the throttle is in the close position. You can accidentally have the cable jump in the twist tube which will have the throttle cracked open.

I cleaned the cavity with very fine steel wool and compressed air. My carbs actually do not have O-rings or washers in the channel where the idle jets go. They are a one-piece assembly. I did replace the washers and O-rings everywhere possible, though.

The throttle cable was extremely tight but seems to be in the correct place.

Thanks for the troubleshooting, though! I got an okay idle earlier today and I hope to perfect it!

[JEEPRUSTY]

I cleaned the cavity with very fine steel wool and compressed air. My carbs actually do not have O-rings or washers in the channel where the idle jets go. They are a one-piece assembly. I did replace the washers and O-rings everywhere possible, though.

The throttle cable was extremely tight but seems to be in the correct place.

Thanks for the troubleshooting, though! I got an okay idle earlier today and I hope to perfect it!

I think I meant the steel needle valves. Are you talking about the small brass jets in the underbody of the carb?

[GS550ED]

I think I meant the steel needle valves. Are you talking about the small brass jets in the underbody of the carb?

Oh, the needle valves. Yes, I replaced the washers there and also thoroughly cleaned the channels with steel wool and air.

I actually have got the bike running fairly decent. I think I need a fuel filter but besides that I think I've got the carbs good and synced.