Running out of things to look for

[VP1]

I just don't know what to do...
Some of you may remember my previous threads about trying to get the idle correct on my 82 GS850G. It runs well in the higher RPM range but won't hold a steady idle/ doesn't always return to idle smoothly. It hangs a bit and sort of acts like an air leak. After I rev it up, the times it'll return to idle smoothly, it then drops to a lower idle and will usually eventually die.

So far I have-
Rebuilt/ cleaned the carbs
Replaced carb o-rings and intake o-rings (except choke o-ring, can't get the choke assembly nut off)
Sealed airbox
inspected boots- they all are ok- no cracks
Synced carbs (finally gave up and bought sync tool)
New petcock

I'm running out of things to do. I still haven't checked my valves though. I'm going to check the valves today and replace the plug caps also. I don't know what else to do... This is frustrating and disheartening to say the least..
-Todd

 

[Nessism]

How many turns out are your pilot screws?

 

[Larry D]

Read bwringer's post. It may help.

http://www.thegsresources.com/_forum/showthread.php?t=135728&page=2

 

[GQROD]

Don't lose heart, you have to be methodical.

I didn't read your prior posts however this may help sort things out......

Did you check the AIR jets to make sure they are matched to your fuel jets? Are they clean?

Is the tank full of fuel? ( sometiems you get to half tank the engine shuts off cause the petcock lever has to be in the reserve position. )

Is the petcock in the correct position meaning prime then on or reserve if you don't have a lot of fuel in the tank while tuning.

Are vac hoses getting kinked when you put the tank back on?

Is your fuel line getting kinked when you put the tank on?

Do you have the correct size jets in your carbs? on mine i had to go up one on my pilot jets in order to get a good steady idle from the stock 35 to 37.5

Are you absoulutely sure all the carb passages and jets are clean?

Is your choke cable and throttle cable adjusted properly?

Are the bowls full of fuel?

Do the valve adjustment pronto!

Did you bench sync the carbs before you mounted them per the factory manual?

Are your plugs gapped properly? Are they new?

Did you do plug chops to determine what color the mixture is? this will lead you to the problem right away.

As was already asked how many turns are your fuel screws?

How many turns out are your air screws?

Have you adjusted the throttle with the throttle stop screw to get the correct idle?

Once all these questions are answered you will no doubt be closer to finding the problem just take one step at a time and eliminate as many issues as possible remembering what happened after each step was taken ie: did it make the bike run better or worse?

Hope this helps

 

[VP1]

Thanks guys, i'll answer all of the questions in just a little bit.

One question first though- Can anyone confirm that my bike has fuel screws? I know it has airscrews but I'm pretty sure there are no fuel screws.

 

[Nessism]

I always thought were called Pilot screws...and yes, your carbs have them.

 

[Dave8338]

I'm running out of things to do. I still haven't checked my valves though. I'm going to check the valves today and replace the plug caps also.

This would have been first on my list of things to do. :-\\\

That being said, once the valves are set, it can only be a mixture problem and they are quite easy to sort out. Too much air or too much fuel. :|

 

[Larry D]

I always thought were called Pilot screws...and yes, your carbs have them.

I call them idle air adjustment screws....hopefully there isn't a broken off tip in one of the carbs. Don't ask how I know....Don't screw these babies in with gorilla torque !! Just "lightly" seat them and adjust out from there.

 

[VP1]

This would have been first on my list of things to do. :-\\\

That being said, once the valves are set, it can only be a mixture problem and they are quite easy to sort out. Too much air or too much fuel. :|

I know I really should have done that sooner. Everything I've heard indicates that while the adjustment is important, it really doesn't affect the problem I'm having- hence my putting it off. I'll check them today though.

Same thing with the spark plug caps. didn't think they'd produce these symptoms but I'll replace them too.

As for the air screws- Ok, I definitely know my bike has those, but in some previous threads and also now in this thread I've heard FUEL screws mentioned which as far as I know my bike does NOT have. Anyone able to confirm that? I've had the carbs apart 3 times now so I'd think I would have spotted them.

BTW- Air screws are 3 turns out

 

[Matchless]

There is a bit of confusion due to the various names for this screw, idle mixture, air screw, fuel screw, more correctly pilot screw.
In actual fact on the CV carbs this screw adjusts the amount of fuel in the idle circuit and the amount of air for the idle mixture is static as per the idle air jet. Lean in and rich out.
Idling rpm's changing -check for leaks on the rubber intake boots and the airbox boots as well, especially if they are hard and not sealing well.

 

[BassCliff]

Hi,

There's just the one screw on top. This is from the Carb Cleanup Series notes:

Note #2: Bill Kingston has brought it to our attention that the references to a Pilot Air Screw may be incorrect. He states that on these carbs use a Fuel Flow Screw instead. This means that you are controlling fuel running through the passages with this adjustment, not air. So when turning the screw counterclockwise you are increasing fuel flow and when you turn it clockwise you decrease fuel flow.

I thought you were supposed to start about 2 1/2 turns out for the 850. Are your needles and jets in good shape? I don't have the pictures handy, but check them for irregularities, pitting, grooves, flat spots, etc. And check those valve clearances as soon as you get a chance.

As for the air screws- Ok, I definitely know my bike has those, but in some previous threads and also now in this thread I've heard FUEL screws mentioned which as far as I know my bike does NOT have. Anyone able to confirm that? I've had the carbs apart 3 times now so I'd think I would have spotted them.

BTW- Air screws are 3 turns out

Thank you for your indulgence,

BassCliff

 

[Nessism]

If the idle mixture is too lean a hanging idle can result. Try 2.5 turns like Cliff suggests and then tweak from there.

 

[VP1]

Air screw, pilot air screw, fuel screw- whatever you want to call them, they're 3 turns out

 

[Steve]

Air screw, pilot air screw, fuel screw- whatever you want to call them, they're 3 turns out

At 3 turns, you should have plenty of idle mixture in there. Have you adjusted the valves yet?

Just one more statement of fact and an opinion on screw nomenclature:
My Suzuki manual calls them "Idle mixture adjustment screw". The idle mixture on the VM carbs is controlled by the pilot fuel screw (under the carb) and pilot air screw (on side of carb). You have to tweakone or the other to adjust the mixture, and both of them to adjust the quantity of the mixture. With the BS carbs like yours, the mixture is controlled by fixed jets. The air jet is in the intake throat and the fuel jet (pilot jet) is in the float bowl, next to the main jet and needle jet. The screw that we can adjust only adjusts how much of that pre-set mixture gets into the air stream at idle and very small throttle openings. Personally, I think this arrangement is easier to tune for street bikes.

Now back to the 'help' section:
To help you with your valve adjustment project, send me an e-mail with a request and I will send you a copy of my Excel spreadsheet that will help you do the math to figure out what shims you need. It will also help you keep track of what you have in there from one adjustment to the next.

Just in case you have not yet discovered this little feature, click on my name, you will see information on how to get my e-mail address.

.

 

[GQROD]

Take everyone's advice to heart, these guys know what they are doing if it wasn't for them my bike would be in the junkyard by now.

You may not think one thing is the solution to the problem but on these bikes there is no one definite cause to any problem.

Rather eveything has to be right in order to get the bike to start, idle and run right so only going through everything will the adjustments work.

Hope it works out!

 

[VP1]

Hi folks and happy new year
I poked around my GS some more this morning. Let me answer the above questions-but first- my GS has 16k miles, owner said he had it for 10 years and let it sit for the last year. By all appearances it looks to be very well taken care of. It is quite clean and definitely does not look as old as it is. I have no reason to believe the owner changed the jets ( he didn't feel comfortable cleaning the carbs himself so I kind of doubt that'd he'd be switching jets out) and we both live at the same elevation.

Ok, on to the questions

Don't lose heart, you have to be methodical.

I didn't read your prior posts however this may help sort things out......

1.Did you check the AIR jets to make sure they are matched to your fuel jets? Are they clean?

How do I match the fuel and air jets? All the jets have been soaked and throughly cleaned with carb cleaner

2.Is the tank full of fuel? ( sometiems you get to half tank the engine shuts off cause the petcock lever has to be in the reserve position. )

No, but petcock is on reserve

3.Is the petcock in the correct position meaning prime then on or reserve if you don't have a lot of fuel in the tank while tuning.

On reserve

4.Are vac hoses getting kinked when you put the tank back on?

No

5.Is your fuel line getting kinked when you put the tank on?

No

6. Do you have the correct size jets in your carbs? on mine i had to go up one on my pilot jets in order to get a good steady idle from the stock 35 to 37.5

I doubt they have been changed but unfortunately I haven't checked

7.Are you absoulutely sure all the carb passages and jets are clean?

As sure as I can possibly be. Everything was dipped and passages sprayed with carb cleaner

8.Is your choke cable and throttle cable adjusted properly?

Choke turns on and off smoothly and throttle has very small amount of slack.

9.Are the bowls full of fuel?

Previous times I've pulled the carbs they have been

Do the valve adjustment pronto!

Yessir!@

10. Did you bench sync the carbs before you mounted them per the factory manual?

Yes

11.Are your plugs gapped properly? Are they new?

New B8ES- .030 Gap

12.Did you do plug chops to determine what color the mixture is? this will lead you to the problem right away.

See below!
14. As was already asked how many turns are your fuel screws?

n/a

15. How many turns out are your air screws?

3

16. Have you adjusted the throttle with the throttle stop screw to get the correct idle?

As best I can but the unstable idle means I'm always fiddling with it to get the idle correct. I get the idle set, then 5 seconds later it goes too high, then 5 seconds later too low, etc..

Once all these questions are answered you will no doubt be closer to finding the problem just take one step at a time and eliminate as many issues as possible remembering what happened after each step was taken ie: did it make the bike run better or worse?

Hope this helps

So something I noticed today while attempting to do my valves (ended up not having thin enough feels guages. I'll get some tomorrow) was that

A. While turning the motor with the 19mm socket I found that the metal ring that rotates with the socket was rusty on the little tab that protudes out and spins by what I believe to be the pickups. Basically the piece of metal that passes by the pick-up was rusty, so I used some sand paper to clean it.

B. Spark plugs 1 & 4 were very black and sooty. Plugs 2 & 3 were clean and light tan colored. Cylinders 1 & 4 do fire when the engine is running.

C. Periodically while the sync gauge was hooked up, the rubber hose from boot 1 & 4 would pop off and I'd heard a cooresponding light popping noise. This stuck me as odd. If it's creating a vacuum like it should then it should be actually sucking the hose on tighter, not blowing it off. Also interesting is that it is only happening on the two cylinders with the dark, sooty plugs.

Perhaps I need to start looking at ignition things? Any ideas?
Thanks

 

[VP1]

I'm beginning to think I may need to do the coil relay mod- http://members.dslextreme.com/users/bikecliff/images/coil_relay_mod.html

 

[GQROD]

The coil relay helps and is worth doing it. I did it and it makes a world of difference in roll on performance and start up.

Check the mixture on those cylinders where it's too rich and adjust your mixture screws using the hihest idle method if you don't have a colortune.

Then check the plugs to see what the color is to tell wether you are making it better or worse.

Don't trust what the po said it could be he got into the carbs changed things for the worse and now you have problems.

Even if he was telling the truth doesn't hurt to make sure you have the right size jets in there.

 

[Matchless]

I'm beginning to think I may need to do the coil relay mod- http://members.dslextreme.com/users/bikecliff/images/coil_relay_mod.html

Before you do the coil mod, just check this:
Testing the ignition system:


Properly localising a problem with the ignition is sometimes a bit confusing and the following below should of assistance:

1. Basic test, remove spark plugs. Fit them to the plug HT leads and ground them to the engine. Turn engine with starter and see if plugs spark. If any one spark plug does not spark swap it out. If the spark seems good on all 4 plugs, the ignition system is very likely in order. If spark is not present or very weak proceed with the following tests.
2. Remove the tank, left side cover, seat and signal generating unit (pickup) cover at bottom right of engine.
3. A good habit is to check the coils and igniter to see if they do not get very hot once the ignition is switched on, as this will most likely be the indication of a failed component of faulty connection or wire.
4. If the spark is weak but present, inspect the HT leads and plug caps. Suspect coil wires and spark plug caps, or voltage at the coils and thus the battery condition. It could also be due to coils with partially shorted windings, but do not jump on this cause immediately, and they may get hot.
5. Overheating coils with no spark may also be due to them getting a permanent full ground either from a faulty igniter or a grounded and pinched wire. Disconnect the coil plug connectors and proceed with tests.
6. Measure the battery voltage directly across the battery terminals. If lower than approximately 12.6V first charge battery fully before proceeding.
7. Next measure voltage over the coil connector plug, orange/white wire and the battery negative terminal. If lower than 12 Volt inspect the wiring for poor contacts and localise cause of voltage drop.
8. Again measure directly across the battery, but pull off the spark plug leads to prevent engine from firing and swing with starter. While starter is turning the voltage should stay at least above 11 Volt. Also swing the starter with the headlights on to see that the voltage does not drop significantly at the coils while the starter plus headlights load the battery, which could prove that even if your battery is fully charged, it cannot give full or sufficient current and is on its way out or your starter may be drawing excess current (usually unlikely if starter is spinning at full speed) and pulling the battery down. If it drops much lower, charge battery fully or have it load tested and replaced if faulty.
9. If all is well up to here you can assume your battery and the positive feed to your coils are in good order.
10. With the coil plug connectors disconnected, use an ohm meter and measure the resistance of both windings on each of the coils. Exact resistance measurements are not too important, but continuity of the windings close to the approximate resistance values given indicates that the coils are in good condition. It must be noted that it is possible for the coils to only show up a fault when at higher operating temperatures, but this does not happen frequently.
    Ignition coil resistance:
    Between the two HT plug caps of the same coil, secondary HT winding, approximately 30 – 35 K ohm
    Between the orange/white and white on the first coil and orange/white and black/yellow on the second coil, primary winding, approximately 2-5 ohm. If this test is within limits you likely have two good coils.
11. Locate the igniter and disconnect the plug with the blue and green wires coming from the signal generator (pickup) at the right bottom of the engine. Test the resistance across these wires coming from the signal generator pickup coils, it should be approximately 250 – 360 ohm. If this is in order you have proved the pickups and the wires to be good.
12. The little back box or igniter is now tested as follows. With the ignition on, kill switch on, test for 12 Volt DC between the orange/white and the black/white wires in the plug going into the igniter. This proves that it is getting the correct voltage.
13. The next step is to prove whether the igniter is powering your coils. Remove all 4 spark plugs and connect the HT lead caps to a spark plug #1, #2, #3 and #4 which is grounded and located to enable you to see the spark. Ensure all the connector plugs are back in, except the one with the green and blue wires from the signal generator.
14. To simulate the small voltage generated by the pickup coil, prepare an ordinary 1.5V dry cell with two wires red for positive and black for negative. Connect the negative black wire from the dry cell to the blue wire on the connector plug going into the igniter. Switch on the ignition and kill switch to power the igniter and briefly touch the red wire from the dry cell positive to the green wire connector going into the igniter. You should see a spark on plugs #1 and #4 when you touch the wire and on #2 and #3 when you remove the wire. If this works your igniter is in a working condition.
15. One other check that is often overlooked. Run the bike at night with all lights off in a dark area and check that no sparks are jumping from the HT leads to the frame or tank. If so they may need replacing.
16. At this stage if all tests have passed you MUST get a spark at all the plugs when everything is reconnected and the engine is turned with the starter.
17. If a spark that was previously missing has mysteriously appeared, have a very good look at your wiring and connectors, as something may be making intermittent contact and corrected itself temporary when you moved the wires.
18. If there is a spark, but the engine will not fire, it could be due to ignition timing, valve timing or fuel problems. Ignition timing and valve timing problems are more likely on a bike that has not run yet after being disassembled and more unlikely to be the cause if the bike was not taken apart and was running before.
19. A quick test with a few drops of fuel directly into the cylinders before replacing the spark plugs and then trying to start will prove it to either the fuel system or ignition system.
    1. If the engine then starts and runs for a few RPM's the ignition is correct and you need to look at the fuel and carburettor side.
    2. If the engine does not fire, but occasional gives one load pop through the carburettors or even exhaust, it may be igniting when the valves are open, the valve timing may be a problem, cam chain or swapped wires from pickup – plugs firing at wrong time.
    3. Other reasons could be extremely low compression, too tight valve clearances, thus not closing fully (usually unlikely on all cylinders at the same time, but plausible), carburettor faulty or dirty, fuel line, filter or petcock faulty. Filter can cause an airlock if not positioned properly to allow free gravity feed.
    4. Then finally the ignition timing must be set properly. At less than 1500 RPM connect a timing light to #2 or # 3 spark plug and check that the timing marks line up for 2-3 on F, then move to #1 or #4 spark plug and check that marks line up for 1-4 on F. Check the advance by pushing revs up to 2350 RPM and the timing marks should both line up on the 45 mark behind the signal generator mounting plate through the sight hole at the top. The three mounting screws can be loosened and the mounting plate can be moved slightly in the elongated holes to meet this.

 

[bdalameda]

A quick rule of thumb for any motorcycle float bowl carb. If the mixture screw is on the engine side of the slide assembly the screw controls fuel flow for the low speed circuit. If the adjustment screw is on the airbox side of the carb slide the screw controls air flow into the low speed circuit.