• Required reading for all forum users!!!

    Welcome!
    Register to access the full functionality of the GSResources forum. Until you register and activate your account you will not have full forum access, nor will you be able to post or reply to messages.

    A note to new registrants...
    All new forum registrations must be activated via email before you have full access to the forum.

    A Special Note about Email accounts!
    DO NOT SIGN UP USING hotmail, outlook, gmx, sbcglobal, att, bellsouth or email.com. They delete our forum signup emails.

    A note to old forum members...
    I receive numerous requests from people who can no longer log in because their accounts were deleted. As mentioned in the forum FAQ, user accounts are deleted if you haven't logged in for the past 6 months. If you can't log in, then create a new forum account. If you don't get an error message, then check your email account for an activation message. If you get a message stating that the email address is already in use, then your account still exists so follow the instructions in the forum FAQ for resetting your password.

    Have you forgotten your password or have a new email address? Then read the forum FAQ for details on how to reset it.

    Any email requests for "can't log in anymore" problems or "lost my password" problems will be deleted. Read the forum FAQ and follow the instructions there - that's what we have one for...

  • Returning Visitors

    If you are a returning visitor who never received your confirmation email, then odds are your email provider is blockinig emails from our server. The only thing that can be done to get around this is you will have to try creating another forum account using an email address from another domain.

    If you are a returning visitor to the forum and can't log in using your old forum name and password but used to be able to then chances are your account is deleted. Purges of the databases are done regularly. You will have to create a new forum account and you should be all set.

To be Banned from this site?

  • Thread starter Thread starter Anonymous
  • Start date Start date
A

Anonymous

Guest
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.
 
So Victor ... Are you asking for help?? Or just expressing your opinions?? 8)
 
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.
 
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.
 
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.
 
Victor Mierta said:
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.
Click to expand...

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.
 
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?
 
Jethro said:
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?
Click to expand...

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.
 
Keith Krause

Thank you for your reply.
Yes the bike is stock.
does the MIXTURE screw have an effect through the entire throttle range?
 
Victor Mierta said:
Keith Krause

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

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.
 
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
 
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.
 
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 :lol: :lol: :lol: :lol: :lol:
 
I have tried using a drill bit to get the carbs statically within the ballpark. Every time vacuum guages are need to get the balancing adjustment right.

If you consult the factory workshop manual the procedures for synching the carbs are described using vacuum guages. It only takes very fine adjustments to get them right.

If you also read the manual, it describes that there are conditions to be met before synching..compression within set limits between cylinders, valve clearances etc. All this is not news!!!
 
Victor, you seriously think thousands of automotive engineers and mechanics are wrong and you're right?! I envy your self-belief!

Having read your post I have to tell you that you are basing your "theory" on one or two false assumptions.

Carb synching is done for exactly the reasons that you say it shouldn't be; that is as a final calibration (as well as is acheivable) to get all 4 cylinders producing the same amount of power. Its easier and cheaper than making the engine so accurate that doing the drill-bit thing would work alone.

Good luck with that wheel.
 
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.
Click to expand...
I don't ahve any experience with Detroit diesels, but I did work a bit with the engineers at Cat when they were designing one of their new ECU's. Their diesels run at a constant air/fuel ratio, no matter the load. This to me excludes any comparison of diesel to gasoline induction systems.
 
Its not self-belief. Reading many of the threads here i think many riders are getting themselves into deeper trouble believing the power of vacuum tuning.

OK. This is my last reply.
I appoligize, didn't intend to be so brash. Just thought provoking.

Visualize this.

4 containers, equal size filled with water, (engine cylinder). On the bottom of each container is a hose that runs too a single variable valve (power demand). Above the containers is never empty tank filled with water and with 4 petcocks on the bottom (carburetor throttle valves), 1 each over each of the containers. The valve (power demand) on the bottom of the containers opens and water flows equally out of the 4 containers feeding the requested power demand. We open the 4 petcocks (carburetor throttle valves) above the cylinders to fill water back into the cylinders to maintain the proper level.

Vacuum Sync
Now, (1) of the containers has a little leak. So we now sync the 4 petcocks and open the one above the leaking container more to maintain the level in that needy cylinder. We open the single (power demand) valve fully. In response we now open the 4 synced petcocks (carburetors) fully, BUT only the one we previously adjusted greater can reach full open. The other 3 can not open fully because the adjusted petcock reached throttle stop preventing the other petcocks from opening any further. Now you have 1 cylinder that maintains the full level, but the other 3 can?t keep up cause they can?t reach the full open position and there respective cylinders can not maintain the water level.

Mechanical Sync
If you set all petcocks to open equally you would have at least 3 cylinders maintaining full cylinders, during full power demand. The fourth wouldn?t be far behind especially since the small leak at idle will diminish percentage wise as the demand for flow increases, and may not have any affect as you demand full flow. All 4 petcocks when open fully together have the potential to flow enough water to maintain the demands of the power requested.

All things considered, the age of the engines, degree of maintenance and abuse, we might be better to set the carbs mechanically, then locate and fix the leaks that cause a flow imbalance, if needed.

I think we may see more grinning faces, and less head scratching.
 
i know i said i would not reply but you are right it is thought provoking theory is great but it is only theory.. practise is what we do and it works i have been building and tuning bikes for 25 years we often set the carbs to a set height before fitting. :evil: it makes them easier to sync there is very few that don't run better when you sync them with vac gauges. so as you can see we already do as you want then find a improvement by further adjustment...the experiment has been done YOU ARE WRONG this is the provoking part of your thought .. :evil: :evil: ozman
 
You must log in or register to reply here.
Back
Top