1978 GS 1000 with 4in1 and stock exhaust - jets & settings?

[Gregory]

I posted this on the carb sticky thread, and no one responded.

Please dont scream at me for asking what has been explained somewhere before. I have read so much info on this site I have info overload.

I am lost on what additional parts or jets I may need in my situation, as well as any recommended settings I will need to start with.

• I have a 1978 GS 1000 with what I beleive are stock carbs and jets. The MAIN JET is #95 and the NEEDLE JET is a #15.
• I purchased this Bike with a Vance & Hines 4 in 1, but I dont think it was ever run or tuned on the bike. The PO may have dorked with all the exterior carb settings also.
• I am staying with the stock airbox and filter because of previous members posts saying it is best / or easiest to tune in.

One posting I read said that no new jets were needed with the 4 in1 pipe, and another said I needed bigger jets. (and if i need them where can I buy the right ones that are the best quality? Z1 ?) I am in DFW Texas so there are no altitude issues.

The Vance and Hines instructions say : GS1000 PRE '80 -Remove the stock airbox lid and increase the main jet to a 117.5 or 120. Adjust fuel screws one to two turns from fully seated.

HISTORY: The first time I cleaned the carbs (a lot of gunk) I did not take out the air or fuel pilot needles. The bike started and ran but didnt want to idle. I did not have the airbox attached and had not replaced the Intake O-Rings or carb O-Rings.

• I am now going to follow the instructions to the "T" for the VM Carb Rebuild per Paul Musser Oct 2005 v.10:
• I have purchased the O-ring kit and everything I need to seal the exhaust and intake. I will also be finding the instructions for checking the valves before I try to tune the rebuilt carbs.

Again, many apologies for asking but something that I know you all are tired of explaining to newbies like me.
__________________
78 gs1000 skunk

 

[tkent02]

I would think the 117.5 or 120 is much too large for a pipe only. 105 - 110 is where I would start, be sure to do proper testing to get it right. The same engine with pods also and the 120 would be about right.

Z1 is the place for jets, unless you want to spend a lot of money to wait a long time.

 

[GSScoobie]

I agree with tkent02. The 115-120's will be too large.
I would suggest trying 102.5, 105 or 107.5 main jets and check the plugs after 100 miles or so with each set.

 

[Gregory]

Thanks Guys, much appreciated.

I was hoping someone may already have the same exact setup and could tell me for sure. I am doing the work myself, but dont consider myself a great mechanic, and dont especially enjoy taking the carbs on and off in a quest to find the right formula.

Or maybe I should go with pods and dial it in exactly as the vance and hines manual suggests?

 

[Big T]

Tuning the carbs is an art, science and some experience tossed in

When you've cleaned your carbs and are reassembling:

1. A main jet about 105
2. Pilot jet #15
3. Fuel screw - 1 turn out (seat it gently, I'm sure you've seen the broken tip threads)
4. Air screw - 2 turns out
5. Float height at spec
6. Bench sync

Once you get tham back on the bike, you'll have to experiment a bit. Sync and tune the idle mixture with the air screws and see how it runs.

Post up your results and we can better advise you from there

Jets: Z1 or www.jetsrus.com

Oh yes, and post up some pictures of what you're doing

 

[Gregory]

Thanks BigT

I will call Z1 to order what you suggested. Then follow all the instructions on the carb rebuild pages.

I assume the "sync and tune" part of the process is also located on an instruction sheet somewhere on the GSResources site too.

I will get some pics of my basket case bike as I go. It is starting to get chilly here in Texas, so since my shop is unheated, I better get on this pretty quickly.

 

[hampshirehog]

One of my 1ks has a Marving 4-1 race pipe - she's running with 102.5 mains and standard pilots. The other has a Micron 4-1. She's running standard mains. Pass on where the aircrews are but the fuel screws will be 3/4 of a turn out.

Standard airbox on both bikes,

 

[Big T]

Thanks BigT

I will call Z1 to order what you suggested. Then follow all the instructions on the carb rebuild pages.

I assume the "sync and tune" part of the process is also located on an instruction sheet somewhere on the GSResources site too.

I will get some pics of my basket case bike as I go. It is starting to get chilly here in Texas, so since my shop is unheated, I better get on this pretty quickly.

Well, you say you've searched around, so I have to assume you've been to the BassCliff site for all the tutorials you need and you introduced yourself

 

[Gregory]

i think i got the carb rebuild tutorial from the basscliff website.....but i didnt introduce myself. i didnt realize it was a forum but will go back and check it out tomorrow. Also, I went to the jets r us website you suggested, and will place an order soon. (maybe i should tear into all the carbs first to make sure all the pilot needles are all ok)

 

[Big T]

It's the GS owners forum- just look up the forum list, it's not a requirement or anything

There's a sticky there from BassCliff

 

[Gregory]

You guys have been a great help. I DEFINITELY WILL OWE YOU ALL ONE. I am just now tearing into the 1st carb again and will be cleaning everything. Puttong in the new o-rings, and inspecting the pilot fuel screws (yes they were dirty but not broken).

I am to the point in the instructions regarding taking apart the SLIDE ASSEMBLY. If it looks clean from the outside and has free range of motion... is there really any reason I should take it all the way apart?


Also,I just got through taking all of them apart and I think I may have one fuel screw with a tip that is not as sharp as the others....so i will order a new one.

Here are the specs on what was removed:

Carb 1 - Pilot Air 1 1/4 turn, Pilot Fuel 1 1/4 turn
Carb 2 - Pilot Air 1 3/4 turn, Pilot Fuel 1 3/4 turn
Carb 3 - Pilot Air 0 0/0 turn, Pilot Fuel 1 3/4 turn
Carb 4 - Pilot Air 2 1/4 turn, Pilot Fuel 1 3/4 turn

 

[Gregory]

Tuning the carbs is an art, science and some experience tossed in

When you've cleaned your carbs and are reassembling:

1. A main jet about 105
2. Pilot jet #15
3. Fuel screw - 1 turn out (seat it gently, I'm sure you've seen the broken tip threads)
4. Air screw - 2 turns out
5. Float height at spec
6. Bench sync

Once you get tham back on the bike, you'll have to experiment a bit. Sync and tune the idle mixture with the air screws and see how it runs.

Post up your results and we can better advise you from there

Jets: Z1 or www.jetsrus.com

Oh yes, and post up some pictures of what you're doing

When you refer to the main jet #105 and pilot jet #15 are you talking about the main jet and the needle jet that is attached to it....

.... Or are you saying the pilot jet#15 is the Bleeder(pilot jet) which is what my bike has already set up from stock

I am trying to order today and i am confused which ones to pick and order...and there is no help line at jetsrus

 

[Big T]

When you refer to the main jet #105 and pilot jet #15 are you talking about the main jet and the needle jet that is attached to it....

.... Or are you saying the pilot jet#15 is the Bleeder(pilot jet) which is what my bike has already set up from stock

I am trying to order today and i am confused which ones to pick and order...and there is no help line at jetsrus

Main jet is self explanatory

Pilot jet is next to the main jet and, yes, stay with the stock #15

As to your question about the slide disassembly, not really needed, but -look in there for the needle - you should confirm that the clip is on the middle setting, plus you may have to move the clip later on for tuning

 

[Gregory]

Since I have never done this before, I know the Main Jet should have been self-explanetory...but since it is directly attached to the needle jet, I didnt know whether that had to be changed out also.

Cool on the slide assembly ! Yes needle looks clean and pitless and appears to be mounted in the center position. MANY THANKS

BTW: For other newbies trying this... I just learned that a person SHOULD remove the bowl gaskets before submerging in Chem-Dip for 24 hours. I will be needing those too.

 

[Gregory]

Ok I just put the carbs all back together with the new o-rings, 105 Jets and new pilot fuel screws.

When reading up on bench syncing it implies that there is a way to change the heights of the floats.... but mine are already fixed in place with bolts that go through the throttle pulley knob. (VM 26mm)

All appear to be very close in comparison to each other.

Is there anything else I should check before putting it back on the bike?

Also, I found a tiny extra broken part but have no idea what it is, and cant seem to take a picture clear enough to post. It is a small threaded brass piece consisting of 4 threads (sheared off from whatever it was) and it has a hole in the middle... I guess it will probably have to remain a mystery

 

[tkent02]

Since I have never done this before, I know the Main Jet should have been self-explanetory...but since it is directly attached to the needle jet, I didnt know whether that had to be changed out also.

It's not. The needle jet stays in the carb. The tube the main jet screws into is not it.

 

[allojohn]

When reading up on bench syncing it implies that there is a way to change the heights of the floats.... but mine are already fixed in place with bolts that go through the throttle pulley knob. (VM 26mm)

Are you mistaking the slides for the floats? How about a picture or two.

The floats are under the carbs in the bowls.

 

[Big T]

Are you mistaking the slides for the floats? How about a picture or two.

The floats are under the carbs in the bowls.

Yeah, that bracket that pivots on the pins with the two floats attached to it

Height adjustment there is critical


The height of the slides is changed by loosening that nut on top and screwing the bolt in or out - that's how you sync the slides, whether on the bench or with the sync tool

 

[Gregory]

Yes i am sorry i did mean slides, they are fixed to the throttle assembly.

I put everything back together and guess i will try starting and "tuning it" (according to the instructions)tommorrow afternoon.

 

[hampshirehog]

Yes i am sorry i did mean slides, they are fixed to the throttle assembly.

I put everything back together and guess i will try starting and "tuning it" (according to the instructions)tommorrow afternoon.

The slides are adjustable and you need to do a bench synch before you put things back together. The manual shows you how to do this plus if you take a look at the pages below you'll see wherethe adjuster and lock nut are:

http://members.dslextreme.com/users/bikecliff/images/vm_carb_rebuild.pdf