Vance & Hines installed on GS550ES

[Thomas Kenny]

After much pre rust removal, sand blasting, painting, polishing, I got my used Ebay Vance and Hines installed on my bike last night and fired it up this morning. WOW! What a great sound compared to stock. The bike warms up better and idles well but it needs bigger jets as it hesitates as I move up the rpm range.
Based on advice from this forum I am going to go up one size. From 102.5 to 103.5 for Cyl 2 and 3 and grom 95 to 96 for 1 and 4. Does this sound about right to those of you who have added performance pipes?

Also the pipe clears my centerstand and has a tab on it that I need to get a rubber cushion for the center stand leg to butt up against. I am glad to have found this old pipe, can, and baffle. It was worth the work. Tom

[oldschoolorange]

I didnt put a V&H pipe on my bike but modafied a 4 to 1 header with race muffler off of another suzuki to fit it, I had to go to 112.5 jets initialy and even that was slightly lean, now that it is colder and I have a UNI air filter on it I had to put in 115's

[Thomas Kenny]

Is your current jetting across all four cylinders? Or are you using smallers for 1 and 4 and larger for 2 and 3?

Don't want to start with jets too small and pay $$ for the wrong size jets!!

Thanks for the reply. Tom

[KEITH KRAUSE]

Is your current jetting across all four cylinders? Or are you using smallers for 1 and 4 and larger for 2 and 3?

Don't want to start with jets too small and pay $$ for the wrong size jets!!

Thanks for the reply. Tom

The larger main jets for the middle cylinders are required when running the stock exhaust. With a 4-1, you should use the same size mains in all cylinders.
You have the Mikuni jet size steps wrong. 2.5 is a step and 5 is a full size.
You can't always expect to get the jetting right the first time, though it's nice to do so. You may also have to re-jet the pilot and jet needle circuits but that depends on performance and plug reads. You spend the most time riding on the jet needle with some overlap from the pilot circuit, so it must be right. If your pipe turns blue after some time, that's a lean sign. Gold is acceptable.
For the pilot/jet needle circuits, you may get lucky and just have to adjust your mixture screws out an additional 1/2 to 1 turn or so. This will help richen the pilot circuit and help when you're around town at lower speeds (idle to about 1/4 throttle position). At freeway speeds, the richer mixture screw adjustments will have some overlap effect, but may not be enough to help. If your 1/3 throttle plug test says lean, then you'll have to shim up the stock jet needles. A "1/2" position richer is probably right and that would be about .022". You can use washers from a Radio Shack or a hardware store. If your model is from Canada, you have adjustable jet needles but you'll still need jetting spacers/washers to achieve a 1/2 position change. A full position change would most likely be too rich. Do what the plugs tell you.
As for the mains, I'll suggest a 7.5 to 10 increase which would be 3 steps or 2 full sizes up. Just a guess.

[Thomas Kenny]

Thanks Keith for your great reply. I am still confused on the jetting. The jets in my carbs right now are 102.5 on 2 and 3 and 95 on 1 and 4. I have the Two-Barrel Mikuni Carbs on my bike. The only adjustments that I know of on these carbs is the main jets and the idle adjustment screw on the carb rack for both two-barrel carbs. The pilots are set jets, screwed all of the way in. Perhaps I can get pilot jets with bigger holes if I need them, but I can't seem to find any other than stock sizes. You have given me alot to think about. My exaust pipes are black so I dont have a chrome finish tell tale like I do on my Magna. Thanks for taking the time to reply :-) Tom

[KEITH KRAUSE]

A bluing pipe will just make a lean mixture more obvious. Go by the plugs/performance. If you get any decel' popping, another lean condition, it may be that you didn't buy new exhaust gaskets for the pipe(?). My past experience says to replace the gaskets.
As for what's "adjustable" on your carbs, besides the main jets/pilot jets and idle adjuster screws you say you're familiar with, you also have mixture screws to fine tune the pilot circuit jetting and to a lesser extent, they have some overlap effect on throttle positions up to about 1/4. They should be on the top of the carb throat/engine side. They may still be factory capped. If you move them, be careful because they can be stuck and the heads easily stripped off. KEEP A RECORD OF THEIR CURRENT SETTINGS (from lightly seated), it may help later on. I always count/turn them in first, then pick out any crud/factory sealant with a straight pin, then clean, then a drop of lube, then start backing them out. Even then, especially if you don't have a PERFECT fitting tool, the heads can strip. Heating the carb body some will make the pot metal body expand faster than the brass screw and that will help too. Impacting can crack the carb body.
The other "adjustable" part on your carbs, actually part of the main circuit, is the jet needles. If U.S. model, yours are not adjustable but they can be raised if needed by using a spacer or washer. It all depends on how the pipe changes the flow/mixture requirements at the three jetting circuits. Plug reads and testing will tell.
As for your performance problem, hesitating as the rpm's increase, did it only start doing this after the "new" pipe was installed? Especially with your carb set up, the new pipe will require a vacuum synch. Even if the carbs were synched recently and synched per factory specs, that synch method will not be correct for the new pipe. Re-synch and test. A vacuum synch is required anyway to get the most accurate plug reads and to evaluate performance.
I assume the bike is ready to be re-jetted. The carbs will only be tunable if the rest of the bike is in good tune. Carbs come last, though you can make the obvious "ballpark" adjustments for starting purposes. I would try the 7.5 (all four) larger main jets but I'm only guessing on your specific model.
I don't know what your bikes history is but if the bike is ready for jetting/testing, I'd warm it up completely and adjust the mixture screws using the highest rpm method. This is recommended by all vacuum tool makers. Then vacuum synch. Follow the synch with another highest rpm method check in case it's needed. See if you still have the hesitation problem. If you do, then it seems obvious that the jetting's been leaned out and you need to richen it. Richer mixture screw adjustments will hopefully be enough for the pilot circuit. Test/plug reads at minimal throttle position for the pilot circuit. See if the jet needles need to be raised by testing at 1/3 throttle. Full throttle for the mains. I always "chop off" the throttle before taking plug reads. Be sure the plugs are the correct heat range/cleaned off and gapped correctly before testing. I take a rag and a piece of hose that fits tightly over the plug to help remove the last few turns and re-install the hot plugs. Be careful of cross-threading if you're not used to using a hose to start them.
Questions about the highest rpm method? Chopping off? Or?
I'm trying to keep this as short as possible and still say what I think will help.

[Thomas Kenny]

Keith, Bless you my good man. I just looked at my Carbs and cannot find mixture adjustment you are talking about. I will look some more as you suggest they may be covered from the factory. The only obvious things on the carb are the vacuum plugs for synching, and the idle adjustment knob on the carb rail. I started it last night from cold to see how it would warm up, and the bike began to run erratically. I switch from choke circuit and it died. Now I start it up and it appears to be flooded as I open the throttle all of the way, and it fires and zooms in RPM then it begins to struggle, and I am dropping cylinders. So I will begin the check off on reading my plugs which are new irridium, check my coils and high voltage wires and caps. Re-adjust my valves, check all grounds. I did a compression test with a thoroughly warmed up engine and WOT and I am reading 123-125 PSI across all four. With a teaspoon of oil in each cylinder hot and WOT they all read just under 200 PSI. The normal range for this engine is 142 to 199, so I may need new rings or a bore and new pistions and rings. Thanks for staying with me on this.

Best Regards, Tom

[KEITH KRAUSE]

You don't say what year your 550 is but here's a pic' of an '84 550.
Your carbs are kind of unusual but there has to be a mixture screw as I mentioned.
Bikebandit lists #42 as a "pilot screw", which is the closest to correct terminology of the mixture screws I mention. #42 seems in the wrong location though. #34 is only listed as a "screw" but seems closer to normal location but still not in the top/center location as most other CV carbs. If you look at the other carb, a hose is attached to the spot where 34 is.
Neither 34 or 42 physically looks like a mixture screw, at least in their diagram. Not long enough?
I've never had these carbs in my hands so I have to go by these diagrams.
Perhaps someone with these carbs can tell you exact location but it must have mixture screws and they must be engine side and approx' where I said.

[KEITH KRAUSE]

Sorry for the big pic posted before. I'm not a computer buff so I didn't know it would come out like that. It also failed to show the parts list/discription that was right below the diagram.
Back to your problem(s) description.
Sounds like you have more going on as you post, not just hesitation.
Besides a new pipe, it seems like other things have happened since it ran well?
Maybe it has sat unused? Old fuel will clog up the carbs sooner than you think. Electrical connections get loose/dirty, etc.
If your model info says the measured compression is below service limits, you'll have to fix that. You can't tune with poor compression.
Sounds more and more like the bike needs a good going over. You do mention that though.
Let us know how you progress and we'll try to help if needed.

[Thomas Kenny]

Thanks Keith, yes I have been reading up on ignition, etc. I ride the bike at least every other week, keep it on a battery tender in the garage when not riding. It has always run pretty strong. I checked it yesterday for spark and I get good spark on 1,2, and 3 but on four I got some spark and then none. Coil one fires 1 and 4, and coil two 2 and 3 on this bike, so I am going to check the spark plug cap and high tension lead on #4. It has done this before but only a couple of times and then runs fine. My bike is a 1984 GS550ESE

I will look over the carbs again. My Haynes manual does not give any procedures for adjusting idle jets etc. I bought a complete used set of carbs off of Ebay carburetor cleaned them well and plan to use them for spare parts. I will pull the carbs off of the bike and rebuild them. The sliders in the carbs now on the bike are going to be replaced by the ones in the spare carbs as the ones in the bike are worn, and the used ones appear to be almost new. I do have the exploded view from the parts fische with the description. I live in Seaside Oregon and work in Portland at the PDX airport 90 miles away so I only have a little time on weekends to pursue my passion. However I have 12 weeks to retirement from the Government and then I will have time to lay out the project and put some quality time into a good rebuild of the engine. My bike has just over 25,000 miles on it. The PO did not take good care of it. I bought it for $200.00 with a bad tranny, got that fixed and have put about 5000 miles on it myself. Oh I am 62 years old and also ride a 1995 Honda VF750 Magna and a 1975 Kawasaki Triple that I have restored. My boys got me into riding, sold my 1932 Austin Bantam streetrod and bought my first bike. They now say they have created a monster :-) Thanks much. Tom

[Thomas Kenny]

Keith here is a picture of my unrestored 1984 Suzuki GS550ES. I am trying to attach it using manage attachments but may not go as I am not a slave to computer geekdom. Tom

[KEITH KRAUSE]

Nice looking bike.
Let us know if you need help.