1980 gs850 jetting

[Guest]

I know this topic has been hashed to death but anyway----My 1980 GS850 project is oh so close to being done and all I have left is to jet the carbs. I have a vance/hines 4 into 1 and emgo pods. Any quick clues on a jet combo? I really don't want to buy the dyno-jet stage three kit but will if it comes to it. Reinstalling stock air box is not an option. Any help is GREATLY appreciated.

[gs_kiwi]

dyno

as i dyno turner my self don't waste your time it is too hard to fully load the bike up and jet it riding on the street you will save money have more fun riding and the bike will run right all the time. trust me i see it all the time you will save money doing a dyno

[RobGS850L]

Having rejetted my 850 with a kit I can tell you that if you did what you said to your bike you need to also adjust the idle mixture and getting those screws to move may be a real adventure. The advantage of the Dynojet kit is the new adjustable needles, the air restrictors, the right drills and the jet assortment. Plus the "how todo's". I'd say leave it stock and save your money but it's too late for that. Check the screws and see if you can get them to move and if not they will most likely have to be drilled out. I tried to run my bike without moving the idle mixture screws and it was not too good to say the least. Not trying to rain on your parade but it's better to know what you may be up against than not.

[stain]

All the screws are free on my bike. anyway I said heck with it and purchased the dyno-jet kit. After looking at the kit ,the stage three settings are quite detailed. I don,t think I could have come up with a similar set up my self in a timley manner

[RobGS850L]

Love to hear that the mixture screws were loose. You lucky dog. Mine were glued tight and it cost me about 150 bucks to get it all fixed. Add the kit and I was sunk to the tune of 250 samolians. I'm sure you will be happy with your performance increase. The 155 jets from the Dyno kit seem to be good for me but I started high and worked down. I didn't want to start lean and start getting the engine too hot and blue the pipes real bad. One cool thing is getting the carbs in and out with the pods is a whole lot easier. Good luck and have fun.

[stain]

Did you use the 155's and leave all the other settings as instructed? I started with the 165's and it is way to rich even with the clips in the 2nd groove. I was going to leave the clips and try the 160's but am interested in your settings.

[stain]

Well I just installed the 160DJ jets with needle in #2 position. It's raining out and don't really want to test in the wet, will report back later

[Zooks]

Well, what happened????

[stain]

I went with 142.5 mikuni jets and left the clips in the # 2 position. It runs almost perfect with a VERY slight bog above 75mph and whacking the throttle wide open. Backing off to about 7/8th throttle takes care of it. I am probaly not going to fool with further as my wife has comodeered the bike!!! This also made me sell my FZR400 as she would rather ride the GS!!
Come to think of it Ijust installed a complete DYNA ignition upgrade and should see if this helps

[KEITH KRAUSE]

I started with the 165's and it is way to rich even with the clips in the 2nd groove. I was going to leave the clips and try the 160's but am interested in your settings.

I don't know why you're combining main jet and jet needle performance. They are separate. The main controls 3/4 to full throttle, the jet needle approx' 1/4 to 3/4 throttle. You test each circuit at the throttle position it's intended to regulate.
I'd do yourself a favor and take some positive plug reads after running in the appropriate throttle position. I think you're running lean with the jet needles in position 2. I also think your main jet choice is too lean. Just saying from experience.
Lean mixtures can ruin your motor.

[stain]

Not combining needle with main jet circuits---thats just where I ended up after repeated tests. Plug checks look good, a nice coffe brown.
Thanks for the input--your opinion is respected.

[80GS750]

the dynojet kit is the way to go. i will always buy this kit now... after messing with my 750 it was just way too easy not to

the kit makes it easy and is way worth it

[stain]

I bought the dynojet kit and it was WAY to rich. I was surprised because I too have had good luck with these kits.
I am running the 142.5 mikuni jets in the Dynojet kit instead of the recomended jets.

[KEITH KRAUSE]

I went with 142.5 mikuni jets and left the clips in the # 2 position. It runs almost perfect with a VERY slight bog above 75mph and whacking the throttle wide open. Backing off to about 7/8th throttle takes care of it.

OK. But just for your consideration, your bog description suggests a lean symptom. Also, you're partly describing the classic "roll off" test of determining jetting. If you roll on the throttle fully and it bogs, but backing off approx' 1/8 throttle IMPROVES performance, that's a classic lean symptom, since rolling off the throttle this way actually creates a temporary richer condition.
Another old school way of thinking, if a symptom is as noticable as you describe, you're not even within 1 jet size of being correct yet. Your bike shouldn't be doing what it's doing, not if it was really jetted right.
Just curious, what mains are stock in your models carbs? I realize you don't want to play with the jetting anymore, but I'm just curious because I have a pretty good idea of what the typical increase is for your specific mods.

[stain]

Stock mains were 115. I started at 165DJ and it would bog terrible in the higher Rpm range.. The lower I went with the jets, the less the problem became. I am also running Emgo filters, not K&N. I have left the remainder of the DJ kit intact. I don't mind fiddiling with these carbs some more if some one has a better set up. In the dyno-jet directions they suggest the top end flat spot to be a rich condition and to drop the jet size