Rejetting

[snyderman]

I am rebuilding the carbs on my 1978gs 750. I will need to rejet, and I believe now is the time to do it. This bike was not running when I bought it. that is an understatement. It sat for 15 years. The exhaust is completely rotted. I plan to replace it with a 4 into 1 pipe. There were mice living in the air box. I plan to replace it with pods because I like that open look. The carb rebuild is going well so far, but I need help with the rejetting. I could not find a DynoJet stage 3 kit for my bike. Is there a tutorial on rejetting? to be honest, I am not sure exactly what components I would be replacing, let alone how to select or install them. Can anyone help me? I know one of you gurus can!

Thanks!

[rustybronco]

A starting point... 125 mains, clip on the needle fourth down from the top, air screws 1-3/4 turns, fuel 1 turn.

***edit*** I would order 122.5 mains as well as the 125's

[MisterCinders]

I have pods and 4-1 on the same bike. Right now I have 122.5 mains, needle on 4th clip, and 17.5 pilot jets.

I am still working out idle kinks with fuel screws at 1 turn out and air screws out 2 turns and change. Mine seems to run a touch rich, but I suspect the coils. After a relay mod, it should be easier to dial in the mixture.

I also suspect that 125 or 127 mains will be necessary, so you should consider picking up a few different sizes to be sure.

[charbot]

hey guys,
I'm pretty much in the same boat, except I have a '77 gs400. cant find a jet kit either. The PO put on a 2-1 exhaust and replaced the airbox with a single pod and pvc tee fitting(sprayed black of course) connected to the carbs. it has never been rejetted. My understanding is that the 400 is half of a 750- if I ditch the pvc fitting and just install two pod filters, could I use these same setting as starting point ? or if Im way off, any tips/ suggestions for rejetting my bike? The carbs are stock BS34's.

Thanks

[Guest]

hey guys,
I'm pretty much in the same boat, except I have a '77 gs400. cant find a jet kit either. The PO put on a 2-1 exhaust and replaced the airbox with a single pod and pvc tee fitting(sprayed black of course) connected to the carbs. it has never been rejetted. My understanding is that the 400 is half of a 750- if I ditch the pvc fitting and just install two pod filters, could I use these same setting as starting point ? or if Im way off, any tips/ suggestions for rejetting my bike? The carbs are stock BS34's.

Thanks

Hi charbot!
A suggestion... I'm willing to bet you'll get many more replies to your jetting issue if you start a separate thread. I love to read all I can about jetting but with two issues in the same thread my brain might overheat.

[charbot]

No problem, wasnt sure of the forum etiquette.

[Big T]

The carbs are stock BS34's.

How about stock VMs?

The BS carbs weren't used until 1980

[charbot]

youre right, the '77-78 400 (and 425's) had bs carbs not vm, so I guess these setting are not for me.

[allojohn]

I am rebuilding the carbs on my 1978gs 750. I will need to rejet, and I believe now is the time to do it. This bike was not running when I bought it. that is an understatement. It sat for 15 years. The exhaust is completely rotted. I plan to replace it with a 4 into 1 pipe. There were mice living in the air box. I plan to replace it with pods because I like that open look. The carb rebuild is going well so far, but I need help with the rejetting. I could not find a DynoJet stage 3 kit for my bike. Is there a tutorial on rejetting? to be honest, I am not sure exactly what components I would be replacing, let alone how to select or install them. Can anyone help me? I know one of you gurus can!

Thanks!

Don't buy anything until you know what you have in there now. Stock main jet is 102.5 and pilot fuel jet is 15.

[rustybronco]

She'll run with the numbers given. jetted enough of them to know.

[snyderman]

Thanks!

Where is a good place to buy the jets?

[rustybronco]

Z1.... http://www.z1enterprises.com/SearchR...=mikuni%20jets

[1_v8_merc]

Good info on the jet sizes guys!!!

I also have a modified/tinkered 78 750.

I'm thinking about jetting as well.

[snyderman]

Thanks! This has been most helpful.

[snyderman]

I have pods and 4-1 on the same bike. Right now I have 122.5 mains, needle on 4th clip, and 17.5 pilot jets.

http://www.z1enterprises.com/Pilot-jet-VM28486-175-1488.aspx

Is this the pilot jet I need?