GS550 Wont Rev past 8,000 rpms

[curtie94]

My Gs550 with CV carbs has a hard time revving into the high rpms. When I hit about 8,000rpms it starts to buck and stutter. It doesn't seem to matter if I'm wot or not, wot is definitely worse then half-3/4 but not a whole lot.

The bike has sat most of the summer but starts right up. I know these circuits are not related.

So do you think it could be ignition or fuel?

The beginning of the year the bike ran good and would rev up to redline no problem, but I do remember it sputtering everyone in a while even then.

Thanks

Curtis

 

[curtie94]

I just reset timing and it did make it run better but it is still falling flat around 8-9k rpm. I have a aftermarket tach cheap so maybe that is the problem but I'm not sure, maybe I'm just revving it too high.

 

[tkent02]

Disconnect the tach to find out. The 550s love the high revs, 8,000 is about where the power starts. Mine goes well over the redline daily, has done so since I bought it.

 

[curtie94]

well I dont think its the tach. I checked the plugs and they are all white. so I will check fuel flow from the petcock. and I will check for kinks in the fuel line.

The prime doesnt work on my petcock.

 

[tom203]

If your prime doesn't work, there is a good chance that your petcock can't deliver enough fuel to carbs, get new petcock for $60 or so and rule it out. Z1 or this florida guy

http://www.georgefixs.com/brand-new...s550-gs650-gs750-gs850-gs1000-gs1100-petcock/

He also has cheaper one with less reserve which is what I wanted

 

[tkent02]

You can test the petcock to see how much it flows. It should be full flow through the hose, not dribbling.
Any chance you have an inline filter in that fuel line?
Those restrict fuel flow quite often.

 

[curtie94]

no inline filter.

I just checked the plugs after a wot run when it was stumbling and they are dark brown/black. So it is rich up top, could it be the air filter having too much oil or being too restrictive. All of the plugs where the same. I tried putting the choke on during my wot run and it made it worse. it burns quite a bit of oil by the blue smoke out the exhaust.

What else could cause it to be rich wot. The only major things I did since this started is new coils and reset the timing, but Like I said it stumbled at 8-10k rpms before just not as bad.

 

[tkent02]

What size are your main jets?

 

[curtie94]

main jets are stock. I'm not sure what number they are. but I remember that all of the jets are stock

 

[8ball]

What is your filter and (or) air box set up?

 

[curtie94]

I am running the stock air box. I did oil the filter.

I tried running it with the air box lid off and it seemed like it was sucking air. What if I remove the filter then reinstall the lid would that tell me if the filter is the problem or will it not tell me anything.

 

[8ball]

Did you pull the emulsion tubes that the main jets screw into? The small cross-drilled holes may be plugged.

 

[curtie94]

It doesnt seem carberation to me, I did replace the ignition coils so maybe I have a coil cutting out. I will look over my wires and check resistance on the coils and ill report back

 

[curtie94]

I checked the resistance of the emgo coils and it was 4.9ohms. In checked the resistance of my oem coils and they are 3.8ohms. I swapped the stock coils back on and bang I had full revs again. But just like old times it stalls at idle when warmed up. so the stock coils are junk too.

I guess ill just have to buy new coils again. What coils do you recommend?

 

[GS1000G Shopper]

I checked the resistance of the emgo coils and it was 4.9ohms. In checked the resistance of my oem coils and they are 3.8ohms. I swapped the stock coils back on and bang I had full revs again. But just like old times it stalls at idle when warmed up. so the stock coils are junk too.

I guess ill just have to buy new coils again. What coils do you recommend?

Your 1982 GS550 should have electronic ignition. It sounds like your coils have the wrong resistance. I replaced them on my 1980 GS1000G and it ran like new. The Emgo coils I ordered on eBay were like $30 each and when I tested them out of the box, I got these readings:
Primary: 2.5~2.6 ohms
Secondary: 14.3 K ohms

OEM specs for the GS1000 coils are 3~5 ohms primary and 31~33 K ohms secondary (plug cap to plug cap).

I replaced the caps and plug wires also. The Emgo PN I used is 24-37810, and they are listed in the Emgo catalog for use with H***a models that use electronic ignitions. Emgo makes a KZ/GS coil PN 24-72451 but it is listed as being for the older points ignition models only. This model had screw-on plug wire retainers so I used regular 7mm wires. Once installed, I got 2.8 ohms primary and 32~33K secondary (plug cap to plug cap).

You'd need to verify your specs via a manual, but for the OEM GS1000 electronic ignition coils are 3~5 ohms. The older points style GS lists primary resistance as 2~6 ohms.