drivability questions

[Iceman71]

Hi all, here's the info - she's a 82 gs850glz, low kms (29000), full tune up 2 mths ago (plugs, wires and boots), recent oil change, new air filter, recent muffler change (from stock megaphones to factory HD FX muffler, sorry guys they were all I could lay my hands on quick and cheap), new intake boots and orings, as well as a valve adjustment at the start of this season, rebuilt petcock and new fuel lines at the start of this season also.

And here's the problem (sorry about the long post but it's nessessary to get the full picture) - it started before I put the new mufflers on with a noticable drop in mileage (220 kms per tank to about 190 before reserve) and engine noises ( a low seated "knocking" under no load coming from directly under cyls 3 and 4, and a higher pitched "rattling" like a ball bearing in a can at cruise with little load), so I put the new mufflers on and noticed substantially more heat radiating off the engine as well as number 2 header pipe started to blue at the first bend. SO I removed and reset the cam chain adjuster (seemed to get rid of the rattle) and reset the pilot air screws directly in front of the carb just before the head. At this point I noticed that #3 and 4 pipes not eminating any heat when idleing after start up (though they did seem to be working just fine under load and when warmed up), but did blow hot air out the exhuast when you snapped the throttle. I checked the temp on the pipes with a thermometer 110* on 1, 170* on 2, 110* on 3, 100* on 4. I also checked the firing voltages on the wires all were between 7.5 and 10 Kv, with no miss indicated, I checked the plugs and all 4 were reading just between white (not blistered) and slightly brownish tinge. I am also getting a backfire on the right pipe (fed by 3&4) on decel since the pilot screw adjustment. And the lower end knock is still there (maybe a minor main knock caused from 3 and 4 not having proper load on the piston?)

I am a class A mechanic but haven't had much expieriance with bikes yet, and at this point in time this bike is my only ride back and forth from work. I am debating whether to drop in another set of plugs before I readjust the pilot screws (the reason for the readjust is when I adjusted the screws the first time I noticed the lack of hot air from the right pipe and didn't connect the dots that the bike wasn't warmed up yet...hence should do another adjust fully warmed) or do the readjust first?

I am just about at the end of my rope and from the looks of it in over my head!

ANY help or advice would be appreciated, thanks in advance.

[chef1366]

You might have to raise the jet needle a bit and raise the main jet for the free flowing pipes. Also set each idle mixture screw with the highest rpm method. After you get that dialed in synchronize the carbs. (very important)
Did you do the valve adjustment?

[Iceman71]

Chef,

I checked the pipes before installing them and they looked more restrictive then the previous pipes (I know that isn't the best way to check but I could see some light through the old pipes and none throught the new ones, as well I seem to have slightly less airflow through the new pipes), so by lifting the main jet I will richen the mixture slightly, right?
Quick question, as I haven't quite figured these carbs out yet (they are CV's BTW), where and when do the main circuits of these carbs come into play..start is obvious, but what about idle, main metering and power?
I used the highest RPM method the first time I did the pilot asjustment, but meathead that I am didn't clue in to the fact all cyls weren't fully warmed up...so will have to repeat this step.
When I checked the valves they were within suzuki specs....I wrote them down, I just don't have them handy. If I remember correctly they were within .001" of being bang on spec and still within tolerances.....now even though they were in spec...was there anything else I should have done? (as I know that sometimes there is theory and there's reality)

Thanks, the help is much appreciated!

[chef1366]

The pilot circuit sucks gas through the main jet and diverts it through the pilot jet since the main has the needle jet blocking it. (idle) Once you start giving throttle the needle starts to lift out of the main and you run on the pilot and needle circuits. At about 3/4 throttle the needle is all the way out of the main so it's the main source of gas. You do most of your driving on the needle circuit.
Do a search for "plug chops". This will teach you how to dial in each circuit by reading spark plugs. Remember these carbs are dialed in thinking of throttle positions and not RPMs.

[Iceman71]

Chef,

Thanks, I think I am starting to get a picture of how these carbs work (it's just too bloody bad these thing don't run Rochester Quadrajets..those I know like the back of my hand!)...unfortunately for me I really need to understand how something works before I can begin to diagnose and repair. I think I'll leave the plugs as they are and head for the adjustments first then re-evaluate the 3-4 cyl problem if it still exists. Any thoughts on the lower end knock or the #2 pipe blueing issue? (I hope I'm not being too bothersome)

[chef1366]

Check for fuel in the vacuum line from the petcock leading to the #2 carb. I've always bought new petcocks and thought the rebuild kits were rather poor.
Pull the #2 spark plug. Is it black from a rich condition? Even though blueing usually is caused by a lean condition it can also be from a rich condition by fuel leaking out of the petcock and firing fuel on the exhaust stroke. The plug still fires on non compression strokes.
The knock could be from the carbs being out of sync.
Compare the needle rising out of the main on the CV carbs and the secondaries opening on a Quadrojunk. On the quadrojunk the throttle position releases the secondaries and the intake vacuum pulls the butterflies open. On the CV carbs the intake vacuum pulls the slide up and the needle with it.

[Iceman71]

Excellent, will check the petcock..plug iundicated white with traces of brown evenly distributed...and don't be so hard on the Q-jet, I'd take one over a Holley doorstop anyday. LOL
Will get back in the morning or sooner if theres a problem..

Thanks again.

[chef1366]

Sorry, just a little pet name we use to call them back in Ohio. What? You don't like Holleys? You don't like messing with them every day?

[Iceman71]

yeah, just love spending time turning screws...lol. Anyways, did a comp test , which came back ok, readjusted pilot mixture screws, and put new plugs in...and 3 and 4 are warming up a little quicker but still lagging behind 1 & 2 for warm up time (they still go warm when you snap the throttle) and number 2 is running even hotter than before and number 1 exhaust temp has increased as well.
I think that I am going to have to take the carbs off the bike tomorrow night and thoroughly clean everyting as the only thing that I can think of that would make only one cylinder run hotter than the rest is a lean mixture cuased by a plugged jet. (come to think of it...what tipped me off to the decrease in mileage was the fact that last year I went almost 220kms and still never hit reserve and this year I have hit reserve, just about draining the carbs before I got the tank switched over, several times...possibly drawing some fine silt off the bottom of the bowls into a jet?
What does everyone think...getting warmer or on the wrong path entirely?

[chef1366]

Clean those carbs. See here
Then do a carb sync.
So no fuel in the petcock vacuum line?

[Iceman71]

no, diaphram developed a hole last year and I wasn't able to locate a rebuild kit so I disabled the vacuum shut off part of the petcaock and added an aftermaket dhut off valve as well as plugging off the vacuum supply line from #2 carb..it still flows proper in all positions, just the vacuum shut off function has been disabled.
Speaking of which I just found a guy bout 2 weeks ago who has one brand new still sealed in the bag for a reasonable price. Just have to go pick it up.