To be Banned from this site?

[Anonymous]

pretty new to this forum. However, where do you get the CORRECT specs for adjusting the original carbs. I have a 82' GS1100L with CV carbs. MY Clymer book saynothing about the pilot screws, air screws or the fuel needle height hanging from the slides, etc. Just talks about the sync screws. The carb clean up is very nice, good pictures, where does it mention air, fuel adjustments?

It seems NO one on this forum, (reading various threads) agrees as to the correct settings, or even what they do? Me included. I see NO advantage to using a vacuum sync tool. I think it causes trouble. Forgetting the CV part of the carb, the throttle plates should be syncronized to allow an equal amount of air into each cylinder. I believe the accuracy would be GREATER if the carb pack was put on a bench the throttle opened part way, and a drill bit fit between each throttle plate (like a feeler gauge) and adjustments made until all throttle plates are open equal. This insures an equal amount of air to each cylinder. Using the vacuum tubes could really cause some way out adjustments and inbalance as one tries to compensate for other fuel and ignition abnormalities while the engine is running. Fuel balance should be a whole differant senario, and pilot scres?? are they not more for fuel mixture during idle and throttle transition. If the throttle plates are set equal, the CV slides should take care of the remaining fuel issues. All this talk of changing jets and needles seems to be way off base. The ideal fuel and air mixtures are carefully calculated to match the engines breathing. Unless you change cams, valves or exhaust, and the like, there should be no reason to change fuel jets. (maybe extreme altitudes). Is every one going down the wrong road? or just me? Just look at the issues posted on this forum, a great % is due to carburetion.

[shaftzuki]

So Victor ... Are you asking for help?? Or just expressing your opinions?? 8)

[Jethro]

Yup. Totally in the dark myself re. the carbs. I recently rebuilt using factory rebuild kits, and now the bike is doing strange things. Seen my post called "What does it mean when..."? It seems everyone here works on the trial and error method. Maybe it's the only thing you can do when you are working with so many variables.

[Anonymous]

requesting FACTORY settings as stated in the first part.

observation as stated in the second part, encouraging either support or oposition for my point of view. I really don't think i am that far off from correct, and if i am incorrect, invite some one to clear it up.

[Billy Ricks]

Factory jetting was usually on the lean side to meet EPA restrictions and resulted in dips and peaks in the power curve. Aftermarket filters and exhausts made these conditions more pronounced. Jet kits helped smooth out the powerband.

[KEITH KRAUSE]

requesting FACTORY settings as stated in the first part.

observation as stated in the second part, encouraging either support or oposition for my point of view. I really don't think i am that far off from correct, and if i am incorrect, invite some one to clear it up.

I don't know if this helps, but with so many different carbs out there, some
carbs have very minor changes from year to year and sometimes the changes are not included in any manual, especially emissions adjustments. I believe your CV carbs do not have seperate air mixture screws and pilot (fuel) screws. You have a MIXTURE screw. When you adjust it out, you get more mixture of air/fuel, not just air or fuel.
These are set at the factory using an emissions analyzer, you cannot re-set them exactly if you disturb them. They are set according to each cylinder on the bike. So sometimes you will have all 4 set at different settings. No two cylinders will be exactly the same inside, so these screws are the fine tuning. Your stock needle is not adjustable because it only has 1 groove to hold the clip. You cannot adjust the carbs by eye, nearly as accurate as you can with a vacuum tool.
I don't own a bike with CV carbs, so my knowledge is limited. What carbs do you have? Mikuni 34mm CV's? Is your bike stock?
As for getting different opinions/advice on repairs, we are a forum.
So you're going to get good advice and some not so good advice. There is a lot of room for error in so many ways. Correct terminology is a problem.
Discriptions of a problem may leave out important info. Some problems can be caused by several things. The fact that these bikes are old and may have had several people work on them does not help matters. Each bike is different in many ways, but the same in many ways. So it can be confusing.

[Jethro]

I have the CV carbs with the mixture screw. If it controls the total mix, how do I make the bike run more lean or rich?

[KEITH KRAUSE]

I have the CV carbs with the mixture screw. If it controls the total mix, how do I make the bike run more lean or rich?

There are two ways of running too rich.
One, is an incorrect amount of fuel to air ratio.
The other, is introducing too much mixture into the cylinder for good combustion.
The same applies to running too lean, except you introduce too little mixture.
With a single mixture screw, you can adjust out to introduce more mixture, which can be considered "richer".
If you adjust in, you will decrease the amount of mixture, this can be considered "leaner". The mixture screw has an effect at idle/lower rpm's.
This is the only adjustment on your carbs, unless you change jets.

[Anonymous]

Keith Krause

Thank you for your reply.
Yes the bike is stock.
does the MIXTURE screw have an effect through the entire throttle range?

[Billy Ricks]

Victor,
Give this site a try. It explains things pretty well.

http://members.hometown.aol.com/ffastcbr/factorycarbtune.htm

[Anonymous]

Billy

thank you!

[KEITH KRAUSE]

Keith Krause

Thank you for your reply.
Yes the bike is stock.
does the MIXTURE screw have an effect through the entire throttle range?

No. The mixture screw helps control idle/lower rpm's. There is an "overlap" effect with the jet-needle up to approx' 1/5 throttle. Then the needle takes over the jetting. Another overlap at about 3/4 throttle with the main, and then the main takes over.

[Anonymous]

i agree with you keith one problem with victors theory of tuning with out vac gauges is that the setting of each slide will be slightly different because compression will vary between cyls
ozman

[Anonymous]

and compression will vary with engine speed and with cylinder temperature and with ambient temperature. Many Multi carb engines are set relative to throttle plate position. Throttle body and multi-port fuel injection fires injectors with a pulse width ?on time? to deliver the same amount of fuel to all cylinders, Detroit diesels are adjusted to synchronize each fuel injector (air is always wide open, no throttle plate) with each other, (called running the rack) not influenced by each cylinders ability to produce power, but to deliver an equal amount of fuel to each cylinder so potentially each cylinder can produce the same amount of power, resulting in a stronger, smoother, more efficient engine, and with equal mechanical loads.
If the mechanical foundation of each cylinder is not "sound" or varies from its sister cylinder, attempting to "adjust" the problem away with syncing the carburetors will do more harm than good. Differences in combustion per cylinder do occur. Adjust (1) carb and the other carb will change. The ONLY time that vacuum adjustment will be correct is at the same conditions it was adjusted at. These engines don?t run at one speed under one condition. Plug gaps are different, valve timing can be different just from differences in valve stem clearance. I can see HUGE differences made to ?synced? throttle plate positions by trying to compensate for something like a plugged idle passage, or worn intake valve guide, but crack the throttle, enter a different fuel circuit, (transition, needle? main fuel jet?) and now everything is going to be very wrong. Maybe in a perfect world with a perfect engine and all cylinders pumping exactly the same, can vacuum tuning have an advantage. If you set all the throttle plates to pass the same amount of air, the CV part of the carb will compensate for the per cylinder variations. Using the engine, with 4 separate pumps with varying pump characteristics, and trying to have them "pump" equally by varying the throttle plate position is backwards.

Mechanically, on a bench, adjusting all throttle plates to have the same opening and using a drill bit as a gauge will give better overall performance results than ?compensation adjustment? on a running engine.
If one wanted to improve the vacuum synchronizing method, you may do better, to flow each carburetor in the rack with a shop vac. That would probably improve accuracy over the drill bit method.

Not looking to argue, just can?t put the thoughts down to rest. Perhaps if I have time I will try both methods. Right now just theory. I haven?t made any adjustments. But I intend to over the winter.

Any ideas on what affect a permanent balance tube joining all the vacuum ports together may have? I think it would increase idle stability and smoothness and transition during throttle opening.

[Anonymous]

if i fit a detroit deisel to my bike i will remember to consult your post .i do know a little about those i have a 430hp d-dec 3 fitted in one of my b-doubles(thats a 34 wheel 2 trailer truck) in the mean time you seem to be trying to reinvent the wheel do you think that thousands of mechanics are all stupid .the tuning methods used by most have been learnt over many years and i am fairly sure that if a balance tube was the go it would have been done a long time ago . i could not be bothered trying to explain the down side and total impracality of the idea. i will post no more on this thread