Vance and Hines recommendations ...

[rebeldart]

Got my V&H header today .... purdy thang, too. V&H tech sheet that came with the header states they have had good luck with the following (if not using a DynoJet kit) : 80-83 GS1100 - Remove stock air box lid and increase main jet to 125. Pilot jet should be to raised to 42.5 - I'm at sea level here in Florida - anyway, anybody disagree with this starting point ? Also, I've never cracked into carbs but turn wrenches every weekend (car hobby) , any links to step by step procedure, if out there, would be helpful. Thanks.

[chef1366]

The pilot jet would be raise to 47.5 since stock is 45.
I'd go with a 117.5 main with a K&N filter in the airbox with lid removed.

[TeamDar]

Got my V&H header today .... purdy thang, too. V&H tech sheet that came with the header states they have had good luck with the following (if not using a DynoJet kit) : 80-83 GS1100 - Remove stock air box lid and increase main jet to 125. Pilot jet should be to raised to 42.5 - I'm at sea level here in Florida - anyway, anybody disagree with this starting point ? Also, I've never cracked into carbs but turn wrenches every weekend (car hobby) , any links to step by step procedure, if out there, would be helpful. Thanks.

That looks like the recommendations for a GS1000 1980-81. The GS1100 1980-83 calls for removing the airbox lid with a 122.5 main and a 47.5 pilot.

[twr1776]

Do you have the two valve per cylinder 1100? If so there is no airbox lid to remove. I have a V & H street megaphone on an 81 1000 two valve with the K & N filter in the stock airbox. The stock jetting is the same for the 1100 two valve and on my 1000 I bumped the pilot one size 42.5, mains two sizes # 120, and shimmed the needles. The plugs read a bit rich but do not foul. Some here have been able to keep the stock 40 pilot and take it out additional turns with good results but I prefer to run it slightly richer. The 1100 two valve should be similar enough with the megaphone pipe and stock airbox to use this as a starting point IMHO. Post up what you end up with, each bike will be slightly different but at least it will give others a good starting point.

[KEITH KRAUSE]

I never saw the reasoning to remove the lid as part of an exhaust change. Meaning, either go all the way with pods/pipe or just run the richer jetting needed for the pipe only and stock airbox. But to each their own.
The pipe alone won't effect the jetting nearly as much as removing the lid. Easier to jet for. Probably 5-10 higher on the main jets and maaayybeee a tad richer on the jet needles but may not be needed. Removing the lid changes things to where you can have air jet issues and throttle response issues. Not only are you significantly changing the main circuit A/F ratio, but also the jet needle and pilot circuits. If you get that into it you should just get pods and do a complete re-jet and gain as much top end as you can.

[rebeldart]

I don't necessarily need to remove the lid - doubt I'll notice a difference as I'm not an "aggressive" rider. So say I leave the lid on the box - bump the mains maybe (what size?) , but all else could stay stock ? This is all a "for now" situation - may go for more performance at a later date, had to have the header as stock exhaust was in poor condition (for my taste). Thanks.

[chef1366]

I'd start with the 117.5s

[rapidray]

I would start with NO lid, 47.5 pilots, & the 125s to keep from bluing the pipes right off the bat. If the 117s are lean it will blue the pipes. If the 125s are rich you can go down & not blue the pipes. What do I know, I've only done over a hundred or so of them. Ray.Ray.

[chef1366]

I would start with NO lid, 47.5 pilots, & the 125s to keep from bluing the pipes right off the bat. If the 117s are lean it will blue the pipes. If the 125s are rich you can go down & not blue the pipes. What do I know, I've only done over a hundred or so of them. Ray.Ray.

You know more than I Ray.
I can only speak from personal experience.

[rapidray]

Not bagging on you Bill. It's just better to start rich & go leaner than to start lean & blue the pipes immediately. We all know how EASY that is to do! Ray.

[KEITH KRAUSE]

I don't necessarily need to remove the lid - doubt I'll notice a difference as I'm not an "aggressive" rider. So say I leave the lid on the box - bump the mains maybe (what size?) , but all else could stay stock ? This is all a "for now" situation - may go for more performance at a later date, had to have the header as stock exhaust was in poor condition (for my taste). Thanks.

Pipe change only I'd try 1 1/2 sizes richer (7.5) than whatever is stock. I doubt one size (5) is enough. Two sizes up (10) might work too but I'm trying to guess right the first try. I doubt more than two sizes would be necessary.
So my suggestion is a 7.5 increase and test at full throttle and chop off/read the plugs. Do what the plugs/performance say.
Once the main is good, test the jet needle at 1/3 to no more than 1/2 throttle. Cruise in top gear at that throttle position and note any surging or hesitation issues. Roll on the throttle and note any throttle response issues. Now run it at 1/3 to 1/2 about a 1/2 minute and chop off and read the plugs. If a little on the whitish/lean side then you'll want to richen the jet needles by raising them. You'll need to get some small washers. How much richer will depend on the plug color/performance. This can be a bit of work if you've never done it and it may be trial and error. You may have to try more than once to get the jet needles right.
As for the pilot circuit/pilot jet, I doubt a larger jet is necessary in your case. You MAY need to richen the mixture screws a 1/2 turn or so. Again, test at mimimal throttle openings/just puttin' around town about 35/40 mph. Check the plugs again and note any performance issues such as too much decel' popping or poor idling.
Your pipe mostly effects the upper rpm range. Not much change in flow below 3/4 throttle. Around 7K rpm and above is where the pipe will add some power (properly jetted), though it's full potential won't be realized with a stock intake feeding it. That's why your jetting won't need much richening except the mains. Now if you remove the lid then that effects things more and the jetting could get harder to set because all three jetting circuits and other components such as the air jets are effected much more. Throttle response/vacuum issues are more pronounced. You'll even most likely lose some torque at lower and mid-range.
Like I said, either pipe only (lid on) or go all the way with pods. Something in between makes little sense. Just my opinion.

[rebeldart]

Thanks for all the advise - great site, great guys ......

[Katarat]

If you clean the inside of the pipes with a grease remover then paint a full can of hi temp header paint down all the tubes it will help on the bluing also. If you do mostly short rides the fiberglass in the baffle will hold moisture & eventually rust out. I remove it but to each his own. Also taking the battery out and removing the bolts will get you a little extra room to fight the air box boots too. There is also a difference between Mikuni & Dynojet jet sizes for the same number main jet

[1_v8_merc]

Good question got me thinkin.

My 82-650g runs really lean after I freed the exhaust more open.
(just punched some holes in the back, now it's too lean, lol)

What main jets should I upgrade up to , and pilots?

Somebody mentioned it before but can't find it now!

[Steve]

Good question got me thinkin.

My 82-650g runs really lean after I freed the exhaust more open.
(just punched some holes in the back, now it's too lean, lol)

What main jets should I upgrade up to , and pilots?

Somebody mentioned it before but can't find it now!

When known changes are made, such as installing a name-brand header or pods, there are enough other people that have done that particular change, there is a pool of experience from which to draw and make a reasonable suggestion.

You punched some holes. Great. How big? How many? How much did it enhance air flow? What shape was the system in before you punched the holes? How much of a change did it really make?

Too many unknowns. My only suggestion for jet sizing would be to get some that are probably two sizes larger, then do some plug chops and then do what the plugs are telling you. They are the only ones that can tell you with any accuracy what is going on in the combustion chambers of YOUR bike. You should only have to change the main jets. Unless you have gone hog-wild with pods, pipe, cams, etc., your stock pilot jets are OK. Even with all those mods, you would only go up one size on the pilot. You will likely have to shim the needle to richen the mid-range a bit with any jetting change, how much you shim it will depend on what your plugs tell you.

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