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"80 GS450L running rough

  • Thread starter Thread starter ironash
  • Start date Start date
I

ironash

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The '80 GS450L is my first bike so I'm quickly learning things. Here are the specs:
1980 GS450L
Mikuni BS34 CV carbs
7,000 miles on engine, overall the body looks really good and very little surface rust.
Kept in storage a lot but driven occasionally.
So far I've put on about 400 miles and I'm starting to do some mods, gauges, clubbman bars etc to the body. I'm also starting all the scheduled maintenance, brakes, filters, cables etc.

Here is my problem. When cruising at about 5-5500 rpm the engines stutters and surges. Usually I put it in 6th gear to keep the rpms a little lower so i don't have to deal with the surging, least till I figure out the problem. Also when I give it a little throttle its jerky but if I give it a lot it goes like there is no problem, just surges when when cruising steady or slowing climbing the speed needle. I've taken apart the carbs and cleaned them but it still does it. Recently while doing the maintenance I discovered the air filter was pretty much disintegraged so I've replaced the whole air box with pods.

Two questions: any idea on the surging problem while cruising?
I've read that if you put on pods to rejet to 2 to 1 but since i'm new I dont know what that means other then change the current jets. Thanks.](*,)
 
My 'guess' is that since you put pods on and did not rejet you are running very lean and the surging you are describing is your bike starving for fuel. Be careful as an overly lean mixture over prolonged use can damage the engine.
I would suggest cleaning the carbs again (since you probably sucked in bits of the old airfilter) and putting the stock airbox on with a fresh filter.

I dabbled with pods, rejetting, and a 2-1 exhaust on my 450. It is a painstaking process of dialing in 'just' the right mixture of air and fuel (which I still don't have the way I want it).

If you really want to know what you're getting yourself into with rejetting take a look at this thread.

http://www.thegsresources.com/_forum/showthread.php?t=80632&highlight=keith+krause

Good luck man :-D

BTW: jetting 2 - 1 doesn't make sense. 2-1 denotes an exhaust that takes two headers into one megaphone. Jets have sizes like 15 or 17.5 for the pilot and 115 or 120 for the mains on a 450
 
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Put the airbox (with proper filter) back on. Re-jetting is only for experts or people who aren't experts but have LOTS of time and money.
 
I also suggest replacing the air box and renewing all seals. Not enough power gain on your 450 to justify pods only. You'll lose some low end torque too which isn't good on a smaller motor.
It sounds like you're jetting is very lean, at the least.
If you want to try, we can offer some jetting help, but jetting your CV's can/will be more than just main jets. Raising the jet needles, pilot jets, pilot air jets, possible piston/diaphragm assembly mods (lighter springs and vacuum port drilling)...then there's the basic maintenance/tuning that must be done before any re-jet.
 
Thanks for all the help offered, right now I'm also dealing with a striped screw on the clutch adj cover plus cosmetic parts so It'll be sitting for a week. As a temp solution what If I just covered up some of the pods to limit air intake instead of rejeting right away? Does this sound like a viable temp solution to try? I looked around and found a dynojet kit for an 83 450 but I havent' found specs on the 83 to compare it to the 80 engine.:-k
 
Partially covering the pods with a baggie and tape will obviously help richen the mixture. Hard to say how the bike will run over it's entire range though. It's better than doing nothing.
I suggest keeping your trips short though. Longer rides will heat things up and you could damage things. Lean mixture can cause pre-ignition and you'll hole a piston or burn valves. Besides the outside air, your motor completely depends on the fuel in the fuel/air ratio for cooling.
Because it will help a little, I suggest turning OUT the mixture screws an ADDITIONAL 1/2 to 1 full turn temporarily. This will richen the mixture and help with lower throttle positions. They should end up about 2 to 2 1/2 turns out at that point. If for some reason the bike doesn't like the adjustments (shouldn't), keep a record and simply return the screw to their previous positions.
Typically, going to pod filters requires richer mixture screw adjustments anyway.
 
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