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Jetting ?s: GS1000 w/ Pods,Exhaust, and Cams

  • Thread starter Thread starter Mgriz
  • Start date Start date
M

Mgriz

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I am trying to get my freshly rebuilt engine (honed cylinders/rebuilt head) into rideable condition. I have gone through the electrical system and have fixed the problems that existed there. Now I have to tackle the carbs and I am looking for some recommendations on Jetting. Here are the details on my bike.

79' GS1000 w/ K&N Pods, Yoshimura Exhaust, Yoshimura Cam (mild), Dyna S, Dyna 3 Ohm coils, and DJ Jet kit.

Previous Carb Set Up: The carbs were chem dipped and cleaned throughly, new orings, and DJ kit installed w/ the following set up
DJ 138 Main Jet
E-Clip 4th from the top
pilot screw is 1 1/2 turns out
air is 1 3/4 turns out

Performance w/ these settings: Starts and runs OK but does not sound very good. Cylinders 3+4 are lean, If I hold RPMs at 3000k for a few seconds under no load it starts popping loudly, popping on decel, idle jumps up to 2-3k and slowly returns to 1100 occasionaly (Always happens after riding it).

Other Possible Issues: I have checked for vacuum leaks using the wd-40 method and did not get any results. Fuel slowly leaks out when shut off (bad needles).

Now I have set up my carbs according to recommendations made for a GS1000 w/ K&N pods and Exhaust. The cams might be attributing to the lean condition with these settings, what do you think? Can anyone suggest a better starting point? pilot fuel screw turned out more? Bigger main? Also whats the best place to get new needles and seats, they are pricey at bike bandit. Thanks
 
So I went through the carbs again and I found that in my attempt to make every mistake in the book while rebuilding this bike I busted one of the pilot fuel jet tips. The broken tip was actually lodged in the passage of the #1 carb. I took care of the piece but I'm stuck using the busted one until I can get another pilot screw. With that taken care of I readjusted the pilot screws to 2.5 turns out, leaving everything else the same. The bike now pops much less than it was before, no more popping on decel, only popped once when I held the rpms at 3-4k w/ no load. But I still have the idle problem, it will not return to 1100 rpms after riding it. From what I have been told/read this is a condition of a lean mixture. But which circuit is lean?? Thanks for any help you can give me.

P.S. I also checked my Cam timing and it is set according to the factory specs.
 
You are correct, popping on deceleration is generally a lean condition (or a misfiring spark). If it's the idle that's having trouble, it's your pilot circuit that is in trouble.

Just food for thought, I tried the old WD-40 trick on the carb boots one time and it didn't change my idle at all. However, two of my carb boots had cracks so bad on the engine side flange I could see light through them. New boots solved the problem, but I now no longer trust the old WD-40 trick to check for air leaks. Take those boots off and inspect them by hand.
 
As Jethro said, vacuum leaks don't always show themselves to spraying.
You DO have a classic lean condition. If it was my bike I'd replace the manifold o-rings. Apply a coat of hi-temp bearing grease to them. Replace the stock Phillips screws with Allens and torque to 6 ft/lb.
Be sure the carbs inner o-rings are in good condition too. Robert Barr sells a good/complete o-ring kit.
These carbs MUST be vacuum synched before you can take accurate plug reads and get best performance.
REMOVE the two floatbowl vent lines so the ports/bowls breath easier. This MUST be done.
Be sure the side air screws are set for best idle. Pilot fuel screws will probably want to be between 1 1/2 and 2 turns out. If not, 17.5 pilot jets probably.
I have to go to work now but will try to follow up later if you need help.
do yourself a favor and change those manifold o-rings and be sure to inspect the manifolds too.
Let us know what happens after the replacements/other checks and then we can get your jetting right.:)
 
Just to add a few thoughts...the carb with the broken tip will have to be fixed or you'll have more tuning trouble. That would obviously cause the popping and you'll just be mixing trouble shooting with jetting. All parts must be correct and the carbs set up identically before any re-jet. Ignition timing, valve clearances, etc, must be set first. Then the side air screw adjustment, followed by a vacuum synch. Your symptoms say to suspect the manifolds and/or their o-rings, as I said earlier.
2 1/2 turns out on the pilot fuel screws is too much in my opinion. But like I said, you can't really start tuning until that carb is fixed and you're positive about any intake leaks.
The mild cam may want the 142 main jet that comes in the kit. Probably will.
Once you've done the above and you're ready to jet/tune, take some plug reads first. Tape and mark your throttle and grip to be sure of position. Full throttle for the main, 1/3 throttle for the jet needle, minimal throttle for the pilot circuit, in that order. Chop off and read. Take a rag and piece of tubing that fits snugly over the plug. This will help you remove/install hot plugs. Be careful of the high speed testing. Let us know what the plugs/performance say.
 
Also, those leaking float valves must be replaced. Can't set the floats with problem valves. I always buy the factory valves but they're expensive. About $35/ea. They're much better quality than typical rebuild kits have though.
 
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