This thing again

[sefu]

I need a little help.

Background:

I just bought a used 78 GS1000 a month ago, and if the odometer is correct, she has just a little under 30K miles on her. I'm the 3rd owner. The 2nd owner bought the bike a few months ago, basically brought it back from the dead with new plugs, battery, tires, dyan 2 ignition pickups and original stock coils and caps, etc. The bike's only noticeable issues are it's rusty tank and no vaccum port from the petcock which means that I run off the pri position which means that the carbs are not OEM.

Issue:

Tank was contaminated, drained and put in fresh fuel. Rode around the block and after about 2 miles she gags and bangs and acts like she's running out of gas. After taking the carbs apart and cleaning them out (I've seen worst carbs work better) I put them back on and she starts and idles fine. But in gear, under load, and when you give her the gas, you hear a gaging noise and she won't go above 4500 rpm. Removed plugs 1 & 4 with no drop in idle, 2 & 3 there is a drop in idle. All 4 plugs are black and sooty 1 & 4 seem dryer than the others the spark seems to be equal all 4.

What I've done so far:

- Cleaned the plugs.

- measured the spark plug cap resistance (only) and got 0 ohms from 1 & 4 and 8 ohms from 2 & 3. Got a spare from another old bike in the yard and one read 8 ohms and the another read 0 ohms so which one is bad, if either.

- need info on how to measure the coils because what I've seen is very confusing to me. When I measure resistance from the signal input wire to the plug wire I get nothing on either coils. But when they are runnig I have spark from both. And although the caps read differently I still see not a blue spark but a whiteish spark from both. The spark from the plug wire to ground is better than the spark at the plug on all 4 wires. I have 12v's going to both coils

[Steve]

After taking the carbs apart and cleaning them out ...

Still sounds more like a fuel issue than ignition.

How did you "clean them out"? Did you just spray around to get out the crud that you could see, or did you dip them (preferably overnight) in Berryman's carb cleaner dip? With a tank that has been visibly rusted like yours, there is going to be a fair amount of rust that has made it past the token filters that Suzuki put in the fuel system. This rust could easily clog the small ports in the carbs, giving you the problems that you are encountering.

Cleaning the plugs works in a limited number of cases. When you have major problems like this and are trying to diagnose a problem, sometimes it's just better to have new plugs.

PM me with a phone number, I can help you on the phone or maybe even come down to have a look-see. 8-[

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[sefu]

Carb cleaning

I just did a basic once over with a spray can and a guitar wire. With a few squirts and a few pokes. But like i said Ive seen carbs in worst condition work better. I'd appreciate some help if you have the time. Oh and those plugs were new, they just got sootty.

[doctorgonzo]

You're gonna need new plug caps (among other things). They should (probably, I think a couple of bikes vary on this) 5 Ohms. 0 Ohms would be no problem, (except for screwing up your neighbor's radio or maybe your own ignition if electronic), but if they read 0 and are supposed to read 5, then they are probably old and crappy. If there is a difference in the condition of plugs in 1 and 4 as compared to 2 and 3, then possible coil issue. If they are stock coils, you might also have a plug wire issue. is there visible cracking in the covering when you bend it? Is there resistance in the wire only (not the cap) wire should have 0 resist. Second on the carbs as well, probably gonna have to pull therm and clean them for real with a soak.

[Steve]

You're gonna need new plug caps (among other things). They should (probably, I think a couple of bikes vary on this) 5 Ohms.

Is that 5 ohms or 5K ohms?

I have always thought it was 5K, but have never had problems where I suspected the caps, so have never really measured them. 8-[

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[doctorgonzo]

Is that 5 ohms or 5K ohms?

I have always thought it was 5K, but have never had problems where I suspected the caps, so have never really measured them. 8-[

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5K ohms, my fault.
Literally every link in the ignition chain on mine had SOME kind of issue, from low voltage at the coils to resistance in a cracked plug wire, to a rusty mechanical advance, to a bad cap. The cap read the right resistance, but was of unknown age. The second I replaced it, that cylinder's firing problems went away.