'79 gs1000 jetting for pods and open 4:1 pipe - recommendations? & aftermarket jets?

[garyS-NJ]

'79 gs1000 jetting for pods and open 4:1 pipe - recommendations? & aftermarket jets?

On my '79 gs1000 with the VM26 carb set, I'm just getting it running after the PO said it used to run before it sat... I put in new manifold O rings and cleaned the carbs, running K&N knock off oval pods, a home made 4:1 header, and an open 3" pipe I made myself. the carbs has #20 pilots (stock should be 15) and #112.5 mains (stock is 95). fuel screws set 1 turn out and air screws 2 turns out. After vacuum sync, it idles and revs in neutral. On a test ride, it pulls hard off the line but then as I open it up. it seems to starve for fuel. Someone on here said I needed at least 122.5 and I read someone had 130's (or just over) in his gs1000 with the VM26's.

So I'm preparing to buy more jets but theres got to be a few people on here with GS1000, pods, and 4:1 open pipe// WHAT JETS YOU RUNNING?

Then if I abosolutely must do my own figuring out, It's going to get pretty expensive going up one jet size at a time and buying mikuni jets instead of the aftermarket jets.. ANY REASON WHY I SHOULD BUY THE GENUINE MIKUNI JETS INSTEAD OF AFTERMARKET?

Lastly, in below table, in the Mikuni column, I see my 112.5Jet but not a 122.5?? Now from what I'm reading here, I should have large round head jets style n100.604. My stock main jet is P/N 09491-9505. From some Basscliff table I found a bike that uses the 122.5 Main in a VM26 carb (the 1985 GS700) and looking up thatcarbmain jet, I find P/N 09491-24013. So I'm thinking this is my main jet size 122.5...

Keihin, Dynojet, Mikuni Jet Size Cross Reference

All Hole Diameters Are in Inches

Hole Dia?---Keihin # -- DynoJet # -- Mikuni #
0.0350---- 92.5--------- 92----------- 86.3
0.0360---- 95----------- 94----------- 88.1
0.0370---- 97.5--------- 96----------- 90
0.0380---- 100---------- 98----------- 91.9
0.0390---- 102.5------- 100---------- 93.8
0.0400---- 105--------- 102---------- 95.6
0.0410---- 107.5------- 104---------- 97.5
0.0420---- 110--------- 106---------- 99.4
0.0430---- 112.5------- 108--------- 101.3
0.0440---- 115--------- 110--------- 103.1
0.0450---- 117.5------- 112--------- 105
0.0460---- 120--------- 114--------- 106.9
0.0470---- 122.5------- 116--------- 108.8
0.0480---- 125--------- 118--------- 110.6
0.0490---- 127.5------- 120--------- 112.5
0.0500---- 130--------- 122--------- 114.4
0.0510---- 132.5------- 124--------- 116.3
0.0520---- 135--------- 126--------- 118.1
0.0530---- 137.5------- 128--------- 120
0.0540---- 140--------- 130--------- 121.9
0.0550---- 142.5------- 132--------- 123.8
0.0560---- 145--------- 134--------- 125.6
0.0570---- 147.5------- 136--------- 127.5
0.0580---- 150--------- 138--------- 129.4
0.0590---- 152.5------- 140--------- 131.3
0.0600---- 155--------- 142--------- 133.1
0.0610---- 157.5------- 144--------- 135
0.0620---- 160--------- 146--------- 136.9
0.0630---- 162.5------- 148--------- 138.8
0.0640---- 165--------- 150--------- 140.6
0.0650---- 167.5------- 152--------- 142.5
0.0660---- 170--------- 154--------- 144.4
0.0670---- 172.5------- 156--------- 146.3
0.0680---- 175--------- 158--------- 148.1
0.0690---- 177.5------- 160--------- 150
0.0700---- 180--------- 162--------- 151.9
0.0710---- 182.5------- 164--------- 153.8
0.0720---- 185--------- 166--------- 155.6
0.0730---- 187.5------- 168--------- 1575
0.0740---- 190--------- 170--------- 159.4
0.0750---- 192.5------- 172--------- 161.3
0.0760---- 195--------- 174--------- 163.1
0.0770---- 197.5------- 176--------- 165
0.0780---- 200--------- 178--------- 166.9
0.0790---- 202.5------- 180--------- 168.8
0.0800---- 205--------- 182--------- 170.6
0.0810---- 207.5------- 184--------- 172.5
0.0820---- 210--------- 186--------- 174.4
0.0830---- 212.5------- 188--------- 176.3
0.0840---- 215--------- 190--------- 178.1
0.0850---- 217.5------- 192--------- 180
0.0860---- 220--------- 194--------- 181.9
0.0870---- 222.5------- 196--------- 183.7
0.0880---- 225--------- 198--------- 185.6
0.0890---- 227.5------- 200--------- 187.5

 

[howardshane2]

I saw your reply on my other post but figured I would just respond on yours. I have decent carb knowledge but not a lot of experience with vm's but I will try to help. When I was deciding on jets for the 1000 I decided to go with a dynojet kit and in my opinion it takes a lot of the guess work out. The jet that comes in the kit for these bikes is equivalent to a mikuni 130 so you could save yourself some money and buy that size mikuni jets but the greatest thing about the dynojet kits is their needles and the different taper that they have over the stock needles. If you think your bike is starving for fuel as you open it up I would think that your problem is going to be you are to lean on your needle clip position and not actually on the main jet fully. My clip is on the 4th position from the top but I haven't done any road testing yet, it's still on my lift.

 

[garyS-NJ]

one cheers for GS1000 rejetting recommendations

one cheers for GS1000 rejetting recommendations

OK great thanks, that's twice I'm hearing main jet 130 ish for a GS1000 with pods and 4:1 open pipe!!! This is the first I'm looking into a VM carb and it's not clear how I move the clip on the needle. Does anyone have a link or procedure, or can tell how to do it? (hope I don't have to mess with my Synchronization). I'm thinking I should get the bigger main jet before adjusting the needle clip position.

I saw your reply on my other post but figured I would just respond on yours. I have decent carb knowledge but not a lot of experience with vm's but I will try to help. When I was deciding on jets for the 1000 I decided to go with a dynojet kit and in my opinion it takes a lot of the guess work out. The jet that comes in the kit for these bikes is equivalent to a mikuni 130 so you could save yourself some money and buy that size mikuni jets but the greatest thing about the dynojet kits is their needles and the different taper that they have over the stock needles. If you think your bike is starving for fuel as you open it up I would think that your problem is going to be you are to lean on your needle clip position and not actually on the main jet fully. My clip is on the 4th position from the top but I haven't done any road testing yet, it's still on my lift.

 

[Guest]

The Dynojet stage 3 jet kit has a needle that is designed for smooth transition, the stock needle will never do it properly for this application. I am running the DJ 142 jets that are equivalent to the Mikuni 133.1. Every motor is different so you might need the smaller jet provided but the magic of the kit is the the shape of the new needles provided. You will regret the open pipe. My baffle fell out of my old Vance and Hines 4-1 never to be seen again and the sound was so annoying to me that I parked the bike in prime riding weather until the new baffle came in. It's easier to tune with proper back pressure unless you are going to race it or tool around a farm, then it won't matter if it's smooth or not. Taking it on the road will annoy anyone behind you and it's noisy as hell on the bike.

 

[garyS-NJ]

Howardshane 2, did that 130 jet come with a stage 2 or stage 3 kit? and does anyone know the difference between the dynojet stage 2 & stage 3 kits? their website is smoke and mirrors.

 

[Guest]

DJ 3304 stage 3 jet kit for what you are doing $120.00 at Z1 Enterprises.

 

[howardshane2]

If you get the stage 3 kit it should come with two different sizes of main jets for you to try.

 

[garyS-NJ]

wow, long time but I got the mikuni 130 mains and now she runs right up to way to fast for my current suspension (I need to look at the front forks) without starving for fuel. idles fine and pulls off the line with a slow roll on just marginal.. (seems a little boggy as if the 20 pilots are a tad big). If I twist it hard she pulls hard off the line.. And with the 130's in the midrange and even opened up pretty good on the highway she seems a little on off- ish as if I'm turning the throttle on and off but actually I am constantly feathering on and off to try to ride through it.. Plugs were kinda light so I put tape around each pod covering about half closest to the carbs (trying to restrict the air a little AND get more velocity). The Pod tweek helped some but not enough so I'm thinking go up one more on the mains (and then maybe down on the pilots to get better off idle performance) or just spring for the dyno jet stage 3 kit. Is changing the needles a difficult procedure? I took a quick look when I cleaned the carbs as I lubricated that linkage and it didn't seem obvious.., Can anyone point me to a procedure for swapping the jet needles? And is anyone running mains larger than mikuni 130s on their GS1000 with VM26s?? How much larger (and is it worth buying the aftermarket mains from jets are us?

 

[Big T]

To get at the needles, you need to pull the slides from the lifting arms and you'll see the top of the needle. Pull the needle out, move the clip one notch closer to the tip and reinstall

This will affect the 1/4-1/2 throttle response

You can try turning the fuel screw in 1/8 turn for the off idle response, but some 17.5 pilots will probably work better