rebuilding/rejetting 77 750 carbs, HELP!!!

[Tarbash 27]

Well when I used to run my 750 with pipe and pods, I only ran 115 mains. I think 125's is a little too much. On my 1085 with smoothbores, pipe, pods, cams, I have it running well with 120 mains.

To go from 102.5 to 125 is a little too much I believe, but if your plug chops come out good, so be it.

[Beaver]

The sizes mentioned in this thread are for Pipe AND PODS...dont put those sizes in there if you're running an airbox...generally you SHOULD only have to go about 2 sizes up for just a pipe...

The pods are in the post, so I am needing to know how big the jets will need to be. It may well be that there are 102.5's or 105's in it now because of the pipe I don't know but working out from that the engine had 100 as stock and when I am finished it will have both pods and pipes I am thinking I am needing to order somewhere betwee 110 and 115 size jets...

Next, is a carb rebuild kit nescessary (Float Bowl Gasket, Float Needle & Seat, Carb Top Gasket) $14.95, or just a float bowl gasket for $3 as recommended in the carb cleaning guide? (O-rings are in the post too)

Cheers

[rustybronco]

I am thinking I am needing to order somewhere betwee 110 and 115 size jets...

Just for reference, my post about a '77 gs750... http://www.thegsresources.com/_forum...d.php?t=139768

If I was doing it again I would order both the 122.5's and 125's, I would start out by using the 122.5s because of the plug color when jetted with the 125's, but your mileage may vary.
I have stopped by Bplubin's place a couple of times trying to find out what the final plug chops looked like, but he hasn't been home the times I had been there.

the required jets can be sourced from Z1 enterprises.

http://www.thegsresources.com/_forum/showpost.php?p=995444&postcount=6

pertinent carb info... http://www.thegsresources.com/_forum...9&postcount=43

4 sizes or 10% gives me 110's, 6 sizes 115's and this thread is talking about 122.5-127.5.

using 100 for an example, 1/2 size=102.5, 1 size=105, 2 sizes=110
5 sizes=125... (someone please correct me if I'm wrong)

Next, is a carb rebuild kit nescessary (Float Bowl Gasket, Float Needle & Seat, Carb Top Gasket) $14.95, or just a float bowl gasket for $3 as recommended in the carb cleaning guide? (O-rings are in the post too)

Cheers

The kits are NOT necessary, only the o-rings and "possibly" the bowl gaskets.

[Beaver]

Legendary!

Thanks I had misunderstood the sizing as I hadn't realised that there was such a thing as ½ sizes. I couldn't find the jets on Z1 either as they aren't listed under GS750 parts so your link was a big help too. I am ordering them now...

Cheers

Angus

[rustybronco]

Legendary!

No, that would be Keith Krause! (If that man speaks, you'll do well to listen)

where do you hail from?

[Beaver]

New Zealand originally, but Denmark now. Cursed with vehicle 'afgift' (it is like a fee penalising you for owning something that pollutes, making cars and motorcycles here some of the most expensive in the world) and living in an apartment with no yard of my own, nor garage. It doesn't make embarking on a 'project' particuarily easy

[beergood]

Every now and again I get asked what jets I ended up with in mine. I wish I was organized to keep a log.

If I remember correctly, I jumped up to 125 on the main. I tried 17.5 on the pilot, and that was too much, so went back to the 15. And I think I moved the needles up one notch (tried two and it was too much). It pulls pretty strong through the whole band, and I haven't been fouling any plugs this year (so far).

Someone far more organized than I should make a spreadsheet of user, bike, pipe/filter configuration, and main, pilot, needle settings. I think we would probably populate it with a ton of data that would be useful to track what works with what.

[TheCafeKid]

Every now and again I get asked what jets I ended up with in mine. I wish I was organized to keep a log.

If I remember correctly, I jumped up to 125 on the main. I tried 17.5 on the pilot, and that was too much, so went back to the 15. And I think I moved the needles up one notch (tried two and it was too much). It pulls pretty strong through the whole band, and I haven't been fouling any plugs this year (so far).

Someone far more organized than I should make a spreadsheet of user, bike, pipe/filter configuration, and main, pilot, needle settings. I think we would probably populate it with a ton of data that would be useful to track what works with what.

Ive thought of doing that BG..but its SOOO dependent on whats going on with the bike at hand...While the chart would get you CLOSE, in the ballpark, final settings would still require testing and retesting... Altitude, state of tune, type of filter etc etc... So many variables..

[beergood]

While I agree that it is difficult to get your bike 100% in tune (personally, I think this is pretty much impossible in the average garage), being in the high 90s is within the grasp of a little work. Which is where I would guess most of us are.

By the way, these numbers aren't based on anything concrete, just a gut feeling.

Sure altitude, temperature, barometric pressure, changes in the wind can all effect the final results of your efforts, but I don't think most of us worry about these fairly negligible effects. These bikes are workhorses, not surgical instruments. They were built 30 years ago and sold around the world. The fact that we are all able to keep these things running points to their sturdy and forgiving design.

We know the bid deals: timing, valve clearance, good voltage, keep your carbs synced and clean.

When it came time to change the jetting I found a post by Keith where he threw his best guess at a similar question, so I went with his advice and it got me pretty darn close. Almost but not quite close enough. But without his advice I bet I would have spent a heck of a lot more time shooting in the dark.

Now I am pretty happy with the results. I am sure I could probably dial it in a little more if I felt like putting in more effort, but I think I am at the point of diminishing returns.

I also think it would be kind of nifty to have a running list of members, and what they have going on in their rides. I think I will start a new thread asking just that.

[Daffyd]

Jets

Hi mate, jets are the bain of my life too, so I will tell you what little I have found out......google suzuki carb jets, somewhere on here there is a chart for Mikunis. The setup it recommended was 115 main, 22 pilot.
The advice I"ve been given is upgrade by 10%, so depending on what standard jets you have, (Haynes manual says it depends on your engine number), go up from standard 10%,start from there. Then fiddle around, see my thread "jet sizes AAAAArrrghhhh", sound advice there

[KEITH KRAUSE]

Hi mate, jets are the bain of my life too, so I will tell you what little I have found out......google suzuki carb jets, somewhere on here there is a chart for Mikunis. The setup it recommended was 115 main, 22 pilot.
The advice I"ve been given is upgrade by 10%, so depending on what standard jets you have, (Haynes manual says it depends on your engine number), go up from standard 10%,start from there. Then fiddle around, see my thread "jet sizes AAAAArrrghhhh", sound advice there

For a typical pipe/pod set up, 10% will get you nothing but a very lean running bike. That would be saying a typical VM equipped 1000 with a stock 95 main would require a 105?...just won't work. Most 1000's require a 130 or slightly larger main for pipe/pod mod'. 750's/550's won't run well either on that 10% suggestion.
Haynes isn't a reliable source when it comes to jetting.

[chuck hahn]

In post 18 Dale posted a link next to pertinent carb info. In that chart is say the mixture screw settings.. i always get confused on the technical names here. The MIXTURE screw is the one found inside the carbs bowls and the AIR screw is the external one on the side of the carbs...right???

[rustybronco]

Correct... The fuel/mixture screw is on the bottom and the air screw is on the side.

[chuck hahn]

and if i remember it is to the left of the main jet seat inside there?? Was wondering cause when i found all that gunk in the #4 carb on my 77 i took that out and blew some air and carb cleaner thru the passages..i just never really was sure i had reset it correctly. Have to check it out next time i go up north...Thanks Dale.

[vladdmd]

Sorry guys... Newbie here.

Hi guys, I am trying to figure out what adjustments to do on my 77 gs 750. I added pods and High compression forged ARIAS pistons, and I retarded the timing about 3 degrees. Stock exhaust. Bike is running, yet at full throttle it bogs down. My first project and learning as I go. I already.. rebuilt the top half with ARIAS high compression pistons, added a copper gasket, had a valve job done, re did the electrical, duneage's RR and 81 GS 850 magneto and RMstator's stator, rebuilt front and rear calipers.... Carbs scare the crap out of me. A shop wants 300 to jet and sync the carbs.... seems like a lot. I was told that I am running stock jets. Plugs do NOT look white. They like they have normal wear and tear. Also in terms of exhaust heating up (I dont know if it matters) number 2 and 3 heat up first, with 4 then 1. Could that be from poorly calibrated carbs? Also since I am breaking in the engine, I should have an even compression +- 15 psi, before I jet right?

...Overwhelmed.

-Vlad