1980 GS850G with 4 into 1 V&H and K&N filter - what main jets?

[Guest]

Hey guys, my 82 GS850G has a Vance and Heins 4 into 1 pipe and a K&N Air filter. And it's breaking up badly after about 1/2 throttle. I opened the choke during the break up and it got worse and fell on it's face so I'm pretty sure the main jets are too small.

I have not opened up the carbs yet but was wondering if any of you that have an 850 and slapped on a V&H pipe and an air filter.. what Jet's did you end up using? (Figured I'd save some time trying new ones)

Stock is as follows:
GS850 (80) the specs are for the CV's

idle.................... 1050 +/- 100 r/min
carb................... mik BS32SS
id no................... 45120
bore size ............ 32 (1.26)
float height ......... 22.4 +/- 1.0 (0.88 +/- 0.04)
fuel level ............ 5.0 +/- 0.5 (0.20" +/-0.02")
VALVE SEAT........ 2.0
STARTER JET....... 32.5
PILOT SCREW ..... 3.5
PILOT AIR JET ..... #200
pilot jet............... #42.5
jet needle........... 5D57-3 (the -3 3rd notch)
needle jet .......... X - 6
pilot outlet........... 0.7
BY PASS............. 1.0, 0.8, 0.8
MAIN AIR JET...... 1.7
main jet............. #115

 

[Big T]

Half throttle is the needle, and the main jet had little effect
Most people go to a jet kit, like Dynojet to get a better needle

 

[steve murdoch]

Easiest solution would be to go back to a stock filter and you can use the stock jetting.

 

[Steve]

Is your "K&N filter" a single filter in the stock airbox or is it four individual pods?

What baffle is in the V&H pipe?

Both of those will have a BIG impact on what jets to use, but a DynoJet kit will likely cure either situation.

.

 

[Guest]

Is your "K&N filter" a single filter in the stock airbox or is it four individual pods?

What baffle is in the V&H pipe?

Both of those will have a BIG impact on what jets to use, but a DynoJet kit will likely cure either situation.

.

Single filter in the orig sealed air box, and full baffle, The bike is not loud.

Thanks in advance.

 

[Steve]

There is a decent chance you may not have to re-jet. :-k

The airbox is more of the restriction in the intake side than the filter itself, so nothing changes there.

With a quiet baffle, flow might not be much more than stock, so not much will change there.

At worst, you might have to go up one size on the main from a 115 to 117.5 and maybe shim the needle a bit.

I have a K&N insert in my stock airbox, along with a quiet 4-into-1 pipe. I am running stock jetting in the carbs. I think I still need to turn my pilot screws in from when I rebuilt them. They might still be at 3 turn out, they likely need to go in half a turn or so.

.

 

[ged]

My sons red 1980 GS850 with a Vance and Hines and K&N filter I only changed main jet to 120 and 2 1/4 Turns out fuel screws. Carb needle jet standard position middle NO3. Have you the rubber intake boot/snorkel attached to the rear of the air filter box? I found when mine was not attached I had similar problems that you are experiencing. Regards.

 

[Guest]

There is a decent chance you may not have to re-jet. :-k

The airbox is more of the restriction in the intake side than the filter itself, so nothing changes there.

With a quiet baffle, flow might not be much more than stock, so not much will change there.

At worst, you might have to go up one size on the main from a 115 to 117.5 and maybe shim the needle a bit.

I have a K&N insert in my stock airbox, along with a quiet 4-into-1 pipe. I am running stock jetting in the carbs. I think I still need to turn my pilot screws in from when I rebuilt them. They might still be at 3 turn out, they likely need to go in half a turn or so.

.

Excellent info thanks!

 

[Guest]

My sons red 1980 GS850 with a Vance and Hines and K&N filter I only changed main jet to 120 and 2 1/4 Turns out fuel screws. Carb needle jet standard position middle NO3. Have you the rubber intake boot/snorkel attached to the rear of the air filter box? I found when mine was not attached I had similar problems that you are experiencing. Regards.

I will double check this! Thanks!

 

[salty_monk]

I used that setup on a 1000G. I liked it. Better than pods.

You don’t need to go up much. I think I ran 122.5 (stock 117), pushed the needle up a bit using washers and ran the air screws at about 3 turns out. I am at sea level.

 

[wymple]

I had that snorkel on the airbox problem and it indeed caused problems.