Keith, Earl, your carb help is greatly needed!!

[Anonymous]

Ok, here is what I have. I have an '83 GS750E, with stock CV carbs, pod filters, and a stock Katana exhaust.

I went from a stock size of 37.5 pilots, to a 40, and a 117.5 to a 120 main to make up for the increased air flow from the pods. My bike won't idle less than 2500 RPM, no mater where I put the mixture screws. I started with them 1.5 turns out, but bike still runs too rich to get all the way into the idle circuit. I have raised the needle up by just a little too.

Should I put the needles back, and see what I get, or should I leave them there for the midrange, and just put 37.5 pilots in it again?

Also, is there 2 different kinds of jets? I ask because the stick pilots only had one hole on the end of them, where as my new ones have holes on the side of the jet too. Also, the new main jets have smaller heads, than the stockers. I dont think that matters though, becuase I think they are working just fine for my set up. I just cant get the RPMs low enough to sync the carbs right. I am pretty sure that the bike is not all the way on the idle circuit because of how far I have to have the idle screw in to keep it running. It is running so rich that it will burn your eyes if you are near the rear of the bike, and I am working in a 14 bay auto shop! :twisted:

Any help or advice you have is greatly appriciated

[earlfor]

Re: Keith, Earl, your carb help is greatly needed!!

For pods and an aftermarket exhaust such as a Vance and Hines, V&H suggest increasing main jet size by 4 increments. You have only increased by two and youre running so rich it floods a large shop with fumes and burns your eyes. That small a change in jetting would not account for it running that rich. What kind of ignition system do you have?
My first inclination is that you have your timing way retarded. I would check my timing and make sure it is exactly on the mark for the 1,4 and then for the 2,3 pickups. Ignition timing for the cylinder pairs 1,4 and 2,3 is independent of each other. One can be correct and the other advanced, or one can be advanced and the other retarded, or they could both be retarded. I think you will find your timing is off.

I would leave the jetting as is for the moment. Once timing is accurate, you should be able to synch. You can go ahead and synch to about 10-12 in Hg at 1800 to get in the mixture ballpark. At that point, you should be able to reduce your idle with the idle adjustment screw. Mixture screws at about 1.5 turns is a good starting point. I would go with that for the time being. At high rpm (beyond idle range) mixture screws dont have much effect anyway, so there isnt much point initially in trying to fine tune them before getting the ignition timing squared away and the carbs at least brought into the ballpark in balance.

Earl


[quote="slowfoxbird"]Ok, here is what I have. I have an '83 GS750E, with stock CV carbs, pod filters, and a stock Katana exhaust.

I went from a stock size of 37.5 pilots, to a 40, and a 117.5 to a 120 main to make up for the increased air flow from the pods. My bike won't idle less than 2500 RPM, no mater where I put the mixture screws. I started with them 1.5 turns out, but bike still runs too rich to get all the way into the idle circuit. I have raised the needle up by just a little too.

[Anonymous]

Earl,

I am using the stock ignition system, and an unmodified, stock katana exhaust. I didnt even think to check the ignition timing though. Do you think I should go back to the 37.5 pilot jet if the ignition is ok? :twisted:

[earlfor]

I would go back to the stock pilots. Some stock electronic ignitions were not adjustable. I think yours is, but I am not positive. If it is, you will see the 12 oclock location screw in the breaker plate going through a slot which allows for rotation of the breaker plate, hence timing adjustment. Usually the the breaker plate rotates for adjustment to timing on the 1,4 side and the plate is then locked down. Adjustment of the 2,3 side is by either a movable half plate or a slotted sensor assembly. I have found that unless ignition timing is correct for both sets, it is nearly impossible to get an even and consistant plug burn or to synch the carbs properly.

Earl

Earl,

I am using the stock ignition system, and an unmodified, stock katana exhaust. I didnt even think to check the ignition timing though. Do you think I should go back to the 37.5 pilot jet if the ignition is ok? :twisted:

[Anonymous]

OK, I have the non-adjustable ignition. I am just going to put a new set of stock pilots in, and let you know how it goes. :twisted:

[Detman101]

I would go back to the stock pilots. Some stock electronic ignitions were not adjustable. I think yours is, but I am not positive. If it is, you will see the 12 oclock location screw in the breaker plate going through a slot which allows for rotation of the breaker plate, hence timing adjustment. Usually the the breaker plate rotates for adjustment to timing on the 1,4 side and the plate is then locked down. Adjustment of the 2,3 side is by either a movable half plate or a slotted sensor assembly. I have found that unless ignition timing is correct for both sets, it is nearly impossible to get an even and consistant plug burn or to synch the carbs properly.

Earl

Whoa, I didn't know that! Thanks Earl! I've been trying to figure out why my bike keeps running rich too. Perhaps it's the timing...
I'll save up another 200 and have that done when it goes to the shop too.

Approximate Savings needed so far...500 for carb sync and adjustment...150 for timing. This is getting expensive.

Dm of mD

[Anonymous]

Whoa, I didn't know that! Thanks Earl! I've been trying to figure out why my bike keeps running rich too. Perhaps it's the timing...
I'll save up another 200 and have that done when it goes to the shop too.

Approximate Savings needed so far...500 for carb sync and adjustment...150 for timing. This is getting expensive.

Dm of mD

Wow, why dont you just buy a carb sync tool for $80, and save a whole bunch of money?? Thats what I did. Its not as hard as it sounds, I just have to get the right size jets.

I went back to a 37.5 pilot today, but have not had time to run the bike like that yet. I had to repair the intake boot again. I am hoping my high temp silicone repair will last untill I can afford new intake boots. :twisted:

[KEITH KRAUSE]

Intake boot leak? I don't think you should waste your time doing temp intake repairs. They ALWAYS come back to haunt you.
The intake leak could be the reason for your high idle or a poor carb sinc. Does the idle go up quite a bit more when it's warmed up, or all the time hot or cold? I think you need to start over and probably replace the manifold o-rings and the manifolds too if necessary. Then do a good manual sinc to the carbs and turn those mixture screws to about 1 1/2 turns out. Then do a vacuum tool sinc. You can't sinc carbs with intake problems. You can hook up the tool and make compensating adjustments, but the bike won't run right or idle correctly.
It's always difficult to guess on the jetting when you install pod filters, but the pipe is not necessarily a "free-flow" design. I would have to say your main is still too small. The jet needles should be raised, but you don't have adjustable needles, right? What exactly did you do to raise the needles? What thickness of shims? Did you re-install any existing spacers in exact order? Your pilot jet increase makes sense.

[Anonymous]

Alright, here is what I did today.

I put the stock size/style 37.5 pilots in today, and after the bike warmed up, it will idle at 1500 RPM. The problem is that now cyl's 2 and 4 are not fireing at full power. RPM's will go all the way up to 10K easy. But now 2 and 4 are too rich. This is only since I put the 37.5s back in. I am not sure if they were fireing good with the 40s or not. I do know that with the open exhaust, all cyl's were working. Why would 2 and 4 suddenly die when I put on the stock style Kat exhaust? That doesnt make since to me.

I also know that the intake manifolds have small leaks in them, ether told me so. Should I get new manifolds and try again?? :twisted:

Matt

[earlfor]

As Keith said, you cannot adjust carbs with ANY leaks in the induction system. Until you have taken care of the leaks, its a complete waste of time and effort!!!!! Fix the leaks.

Earl

I also know that the intake manifolds have small leaks in them, ether told me so. Should I get new manifolds and try again?? :twisted:

Matt

[KEITH KRAUSE]

Most of the time, it's the o-rings inside the manifolds that cause the leaks. They are cheap, the manifolds are not. Look at the o-rings and manifolds for cracking. When installing the new o-rings, apply some hi-temp bearing grease to help them last. Torque to around 6 ft/lb. You should replace any Phillips head screws with hex heads.

[Anonymous]

Ok, after reading about a correlation between timing and plug burn, I decided to try something.

When I first got my bike, the timing was retarded as far as it would go. I fixed that right away with a timing light, thinking nothing of it ..

(this bike has stock electronic ignition)

I've been fighting a lean problem for some time now - I'm up to 122.5 mains from 115s, Removed any inline fuel filters, cleaned the p i s s out of the carbs, etc etc to assure fuel delivery and made sure there were no airbox or intake leaks.

Plugs still just slightly off white .. just makes no sense. Nothing I do, that SHOULD drastically increase fuel delivery, makes much of a difference. No pods, and a mildly modified exhaust.

I should add that while jetting up didn't change the plug burn much, it DEFINITELY lowered my fuel economy.

Now, on to the interesting part. Just for kicks, I tried setting the timing back to the full retarted setting.

After checking my plugs this afternoon, they have a perfect burn. Thing is, the retarded timing leaves me a little sad in the acceleration department.

Any ideas as to what might be going on here?

[KEITH KRAUSE]

I would put the timing back to what Suzuki calls for. Then, if the mixture screws are missing their caps, I would adjust them to 1 1/2 to 2 turns out. Then I would do a manual carb synch followed by a vacuum tool synch.
Poorly synched carbs will cause major mixture problems. Be sure to set the timing correctly before the synch.
Also, if you removed the jet needles during the carb clean, did you put any spacer(s) back in the exact order? Are you sure the diaphragms are seated correctly?
Your results from retarding the timing make perfect sense. A bike with a lean mixture will fire too soon. Retarding the timing counters the lean mixture firing. Retarding the timing is only compensation for the real problem, and compensation never works.

[Anonymous]

Done and done.

The pilot screws are 2.5 turns out, the needles are in their factory position. I've tried shimming the needles, and that does not help either. I've done mechanical then vacuum sync with a Morgan Carbtune, and the sync is dead on. Diaphragms are intact, soft, and seal well. This just doesn't make sense... But, at least I have a workaround for the time being, so I can ride without worrying about holing a piston.

Anyone have any more ideas? Could the acutal problem be with the ignition itself, or with valve timing?

[Anonymous]

I am going to replace all of the intake manifolds. I had to put all of them together with high temp silicone, and I just want to replace them so that I can rule those out of my porblem. I rode it around the block today, and 4 was working much better, but 2 is still dead. I have the 54mm emgo pods, and I have them tight, but I saw Earl say somewhere, to someone else, that they were too big for their cv32 carbs. I dont remember what mine are, right off hand, but I am wondering now if that could be a problem too. I am sure there is no shortcut to fixing those is there? The whole thing is frusterating. I took the bike from a piece of old broken metal, and am so close to being done. All I want to do is ride the damn thing, and everytime I get close, something else pops up!!

One more thing, does having the vent tubes on or off make a difference. I just noticed today that I forgot to put them back on, but didnt have time to take everything apart and try again,.....