Plausible Carb Issue

[Tim Tom]

First a little background story. So while I was riding my 850G earlier today I open up the throttle in 5th to pass. The bike pulls smooth up to 8 grand on the tach. Then i hit a small bump in the road and my gear indicator light goes out. I loose power then get it back, then it goes out. I notice that my key had been bumped out of the vertical posistion by about 10 degrees. I turn it back and my lights come back and i get power back. This all happened in a matter of seconds.
I continued on my merry way but when i went to make the next pass I noticed hesitation in the throttle at 5 grand. Power would surge, then drop, then surge, then drop etc. I've ridden the bike 2000 miles in the one month since i started riding. Never noticed anything like this before. The hesitation contined all the way back home another 50 miles. After the bike had cooled i went to take a look at it. In neutral with steady throttle it would still hesitate. I could hear the RPM's drop about 5-600 right around 4500.
I'm thinking it is related to the tuning of the carbs. I've never had the bike apart, it was last serviced in December by the dealer before I bought it. I am mechanically inclined, but new to bikes. Currently gearing up for a valve adjustment and 2000 mile service.
I'd appreciate any advice on what to do.

 

[Steve]

Just one question, if you don't mind. :-k

Which side street were you on when you hit 8 grand in fifth gear?

On all of the 850s I have had, that's about 110 mph.

.

 

[BassCliff]

Hi,

After the "bump" you mentioned, I would start by inspecting the wiring in the headlight bucket and then take off the tank and check the wiring under there too.

My bike started running funny one time and upon inspection I found this...

Thank you for your indulgence,

BassCliff

 

[lord1234]

As BC says, my bet is you bumped or cut a wire loose. Pain in the ass to track, but definitely doable.

 

[kinnet]

I am absolutely no expert by any stretch of the imagination, but have you checked to ensure that the connections on the battery are nice and tight?

When I was messing with my 550, I didn't have one of the connections to the battery tight and I was noticing that the light would dim and brighten as I turned the throttle, then eventually, the bike wouldn't start.

TCK figured out that the connection wasn't tight, fixed it, and we didn't have any more problems...

Anyway, just a thought and easy enough to double check. Hope you figure it out!

 

[Tim Tom]

Just one question, if you don't mind. :-k

Which side street were you on when you hit 8 grand in fifth gear?

On all of the 850s I have had, that's about 110 mph.

.

There is stretch of road in South Jersey called Route 72. It runs perfectly straight for about 30 miles. There are very few intersections and cross roads and it doesn't see much traffic. I'd say I was running at least 110, I had my chin on the tank, and am on the skinny side of the scale. I was definably moving. Quicker than I care to do again for a while :-\\\

PS. Sorry for the enormous delay in responding to your question Steve, I sort of forgot I started this thread...

 

[Larry D]

So.....did you find the problem and get it fixed ?

 

[Tim Tom]

Yes i did fix it. As it turns out, it was electrical in nature. For some reason, (a short in the harness, old wires, etc) I was not getting enough volts to the coils. They would not deliver a potent enough spark (sometimes no spark) so I would have unburnt gas in my cylinder, then when it did ignite it was a larger explosion than usual, resulting in the "bogging then boost" I was experiencing.

In order to fix this I modified the wires running to the coils with a relay and a wire from the battery. This Coil Relay Mod is well documented on BassCliff's site, and did the trick.

Plus my bike now starts on the first push every time
Its amazing the difference getting 2 volts back can do.

My troubleshooting and repairs are in the thread below, if anyone is having similar symptoms they might want to read through it

http://www.thegsresources.com/_forum/showthread.php?t=161351

 

[Steve]

Thanks for posting your resolution. :clap:

Too many times, all we see are questions and suggestions, but not the resolution.

.

 

[srsupertrap]

The coil relay modification solves a lot of things but I think you were experiencing a electrical cut out/short like bwringer described perhaps in the ignition swtch or the wires running to it. Perhaps it will be okay if the bad connection was in the wires running to the coils since you eliminated that loop with the coil relay mod. It's a worth a look at the ignition switch wiring.

I believe your your diagnosis if off a little, it was not a matter of weak spark but rather spark cutting out altogether for a milli second at 4500 or 8000 rpm which caused your symptom