GS850GZ carb settings after top end rebuild

[LJR47]

Hello all,
I'd say this question has been asked a hundred times but this will be question 101.

I've just rebuilt the top end of my 1982 gs850gz, new pistons 0.5 over size, new valves, timing chain and all the associated bits and pieces, basically a new top end.
I've also installed Dyna Coils, stage 3 jet kit, 4 into 1 vance and hines pipes, macs pods etc.

When installing the jet kit, the instruction called for 165 main jets, along with the enhancements listed above, seemed excessive to me but I followed the instructions to a T.

They also call for the mixture screws to be set at 4.5 turns from closed.

Started the bike for the first time the other night, started up first push of the button, extremely happy.

To help me with tuning the bike, I am a novice and really getting a kick out of this high learning curve, I purchase a Gunson Colour tune and Carbtune Pro.

The engine ran ok, small amount of smoke after blip of throttle, to me she smells rich, also infrequently a small back fire through a carby.

I've seen on this forum that a lot of members have also done these performance enhancements to their bikes, would appreciate any feed back / help with setting the bike up with the correct jet / tuning settings.

I haven't ridden the bike as yet, only started up in the garage, still playing with wiring and linkages etc, should be on the road in a month.

Any feed back much appreciated.
Regards
LJR47

 

[Steve]

Many of us will end up with the mixture screws about 2.5 turns out from lightly-seated, but each bike is different. Heck, each CARB is different, as you might not have the same setting on all of your own carbs.

I will also say "good luck with the Color Tune". It seems to work nearly perfect on the older VM carbs, but not so much on the BS (CV-type) carbs on your bike. The color is supposed to change with a change in mixture. I have observed that on the VM carbs. I was inspired to try it on my BS carbs, but did not see a change in color. The flame sputtered a bit, became more itermittant, then finally went out as the screw was turned in. Turning the screw back out, the flame sputtered a bit, then finally became steady, but never changed color.

Was that a Dynojet Stage 3 kit? I find the 165 suggestion interesting because my list does not show any DJ jets ending in "5". :-k And if they do have a 165, it would be the equivalent of a Mikuni 155. Coupled with the other changes they provide, it's probably pretty close. On the other hand, might that be a 165 AIR jet?

.

 

[LJR47]

Yes agree with you on the colour tune, tried it out and also didn't notice any change as i turned the screws.

Yes Dynojet stage 3 kit, here's the link to the instruction page they provide http://www.dynojet.com/pdf/3306.pdf

Thanks for your help.
Regards

 

[lurch12_2000]

As posted in my 1982 GS850 thread here, I am running Dynojet Stage 3 160 main jet with pods and stock exhaust now. I removed the 4 into 1 to experiment. The PO indicated that he had jetted for the stock exhaust before installing 4 into 1 this year, and turned mixture screws out 3.5 turns(paper work says 4.5 turns). It was running fine at idle and on cold starts but too lean on open throttle and bogging some with the headers. Runs great with stock exhaust now after 20 mile test ride including up to 80 mph and whacking the throttle. I did have to synch the carbs to dial them in more but I believe the 165 main jets would be needed for the free flowing headers. You'll suffer in gas mileage too. I had the luxury of having the stock exhaust to re-install. It is definitely more responsive in my present setup with stock exhaust, and smoother and quieter. I have the actual paperwork and remaining Dynojet stage 3 kit too. 155 and 165 still in box along with original 175's(stock #) and needles. What level did you set the needles at? Their instructions say to set at groove #3 but I can't remember what the PO said he did.

Note: I have the receipt for the 4 into 1 exhaust from the PO. Over $350 and from Niche Cycle Supply in FL, US but no brand name. It's sitting on my garage shelf now looking nice!

 

[lurch12_2000]

Many of us will end up with the mixture screws about 2.5 turns out from lightly-seated, but each bike is different. Heck, each CARB is different, as you might not have the same setting on all of your own carbs.

I will also say "good luck with the Color Tune". It seems to work nearly perfect on the older VM carbs, but not so much on the BS (CV-type) carbs on your bike. The color is supposed to change with a change in mixture. I have observed that on the VM carbs. I was inspired to try it on my BS carbs, but did not see a change in color. The flame sputtered a bit, became more itermittant, then finally went out as the screw was turned in. Turning the screw back out, the flame sputtered a bit, then finally became steady, but never changed color.

Was that a Dynojet Stage 3 kit? I find the 165 suggestion interesting because my list does not show any DJ jets ending in "5". :-k And if they do have a 165, it would be the equivalent of a Mikuni 155. Coupled with the other changes they provide, it's probably pretty close. On the other hand, might that be a 165 AIR jet?

.

Yes, the Dynojet kit comes with 155, 160 and 165 main jets...and original in carbs was 175.

 

[LJR47]

Hi,
Yes as previously mentioned I am currently running the 165 mains and have set the needle as per the instruction sheet at the 3rd clip position, carbs have had a compete rebuild as per the detail procedure on the Bascliff web site, new "O" ring set, float levels bench set, full strip down and clean, new diaphragms etc all running fine, running the MS pods with the Vane & Hines 4 into 1 header etc.
Played with the colour tune, not very successful, didn't see much of a change in flame colour as I turned the mixture screws.
Engine seems to be happiest a present with the 4.5 turns on the screws as quoted in the Dynojet instructions.
At present only giving engine a quick start up in the garage after full top end rebuild, proof will be when I get her out onto the road.
Regards