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Carburator Blues

  • Thread starter Thread starter Redliner
  • Start date Start date
R

Redliner

Guest
Hi Gang,

I own a 1979 GS750E that's basically stock except for a Vance & Hines 4 into 1 pipe (the one sold by Dennis Kirk for all these old 70's Japanese muscle bikes)

She has K&N individual air filters, and Mikuni carburetors came off of a 1979 Kawasaki 750. I had them rebuilt, and I have had them professionally synced on a flow bench at a bike shop 6 years ago.

I recently changed the oil, I changed the plugs (yes I used the correct plugs with the correct gap) I cleaned the air filters, and I put a bottle of fuel injection cleaner in with a full tank of gas to give the carbs a good scrubbing. (I've always done this before without negative consequences)

I've owned this bike for 15 years, and she's dead reliable (never left me stranded, and she's always gotten me home) :)

All the things I've just mentioned I've done for years, and I've never had the reaction that I've gotten over the last few rides.

She starts, and idles fine - up through 1st, 2cnd, and 3rd gear - she's great. Once I hit 4th gear, and I'm between 50 and 70 miles per hour she starts to spit like she's either starved for fuel or air. Once I'm up in 5th gear above 80 miles per hour she smoothes out again.

She's never done this before and I'm really getting aggravated with her because she feels like she wants to cut off but doesn't. I give her gas, and she just bogs down until I get past 70 miles per hour - then she launches forward without the spitting.

I should mention that when I took her out of the shed after last winter and went through my spring regiment to get her ready for the summer, there was some type of obstruction with the carbs, and the fuel wasn't moving through the fuel tube into the carbs.

I had to take them off, and blow all the ports out with carb clean in order to get the fuel moving again.

I don't know if there's something restricting the fuel from getting into the carbs, or if the air/gas adjustments are all totally out of whack or if the plugs have prematurely fouled (which I severely doubt) or if the packing in the muffler is shot. I don't know what's wrong.:confused:

The last time she acted just like what I'm going through now was because of a vapor lock from fuel tank. I drilled a hole in the gas cap to relive the vapor lock, and she's been fine all these years???..up until now.

I'm at my wits end, and I know the solution is to just buy some new CR Keihin's - but I don't have $800.00 right now for new carbs.

Any and all advice would be greatly appreciated.

 
I was thinking about the valves, they haven't been adjusted in about 6 years. The weird thing is that before I cleaned the air filters and put in the fuel injection cleaner - she ran great. I put too much filter oil on the filters and I originally thought that was the problem.

I re-cleaned them, and I didn't put any oil on them the second time around, and she ran good for 100 miles, and then back to the spitting problem.

You would think that if the valves were bad or if the carbs had a major problem, the spitting would have persisted no matter what I did.
 
Don't take this the wrong way but if you haven't adjusted the valves in 6 years I don't understand why you are even asking; do the valves regardless.

Regarding the carbs, the cleaner you added may have loosened sludge in the carbs and plugged them up. It never hurts to treat your bike nice and freshen the carb o-rings, so consider this an opportunity to do something nice to a deserving steed.
 
Greetings and Salutations!!

Greetings and Salutations!!

Hi Mr. Redliner,

I'd like to give you the unofficial "mega-welcome". Please pay particular attention to the "Top 10 Common Issues", the Carb Rebuild Series, and the Stator Papers. Let me roll out the welcome mat for you...

Please click here for your mega-welcome, chock full of tips, suggestions, links to vendors, and other information. Then feel free to visit my little BikeCliff website where I've been collecting the wisdom of this generous community. Don't forget, we like pictures! Not you, your bike! :D

Thanks for joining us. Keep us informed.

Thank you for your indulgence,

BassCliff
 
Your right Nessism,

It's definitely time to get the valves adjusted along with a solid rebuild of the carbs. I think I want to get a new ?cam chain tensioner? as well.

I ditched the points, and installed a Dyno electrical ignition system about five years ago, and that's made a world of difference as well. After I installed it along with some new coils and wires she ran much better.

I don't think I need to mess with the stator; I'm leaving that sleeping dog alone. I?ve seen a bunch of conversations on how original stators have given lots of people lots of problems, but I've never had any charging or dead battery issues in 15 years.

Thanks for the advice, I'll definitely follow through........

Thanks for the welcome BassCliff, I play Bass myself.............

I'll try to attach some pictures of the bike.

Ciao...............

 
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