unexplainable lean condition GS1000G

[Guest]

OK I have my GS 1000G 1980, I have had this bike for 6-7 yrs and have always run 32 mm carbs with 122.5 mains, the bike always ran good but never really pulled like it should have. Bike has stock exhaust, except the PO had drilled 4 holes in the end of each muffler, and a stock air box with a K&N filter, new airbox to carb boots, and new side cover rubber seals , also still running the snorkel on the back of the air box.
So this summer the bike developed a chirp coming from the 1 # cylinder area. I blamed the carb boots and O-rings because I had been babying them with silicone for a year or so. So I decided to buy new and replace them . Did this and relized the the 32 mm carbs didn't fit the same , so I switched to the 34mm carbs that came with the bike that I could never make the bike run smoothly with. I have stripped and dipped the carbs new o-rings , floats needle and seats, gaskets . Did a complete on carbs no stone unturned going over, put in stock jetting , ran bike flat spots and super lean , jetted it up from the stock 110 to 117.5 still lean with aflat spot at 3k, so I jumped to 125 mains took it for a ride no noticeable flat spots but plug chops showing still lean . I think I am working with blinders, am I over looking something? just does not seam that I should have to jump 7 or more jet sizes to make a basically stock bike run properly? Any ideas out there?

 

[rustybronco]

Did you make sure 'all' the numbers on the jets/needles/tubes/ect are correct for the application?

 

[resjudicata]

A flat spot at 3k while opening the throttle? I would expect the carb to be running on the pilot jet and needle rather than the main jet at that point. My understanding is that you aren't running on the main jet until the needle is all the way out of it's bore. That isn't the case at 3k rpm. Therefore, I don't think your main jet changes are solving the problem which is evident from your experience.

I would drop the main jet back down to the stock 110(?) and shim the needles up (see needle shimming on this site. Then maybe look at a couple steps larger on the pilot jet as well. I don't know what sizes you should try as I don't have the same carbs or have done this myself. I can only comment on how the carbs work in general.

Chris

 

[Guest]

A flat spot at 3k while opening the throttle? I would expect the carb to be running on the pilot jet and needle rather than the main jet at that point. My understanding is that you aren't running on the main jet until the needle is all the way out of it's bore. That isn't the case at 3k rpm. Therefore, I don't think your main jet changes are solving the problem which is evident from your experience.

I would drop the main jet back down to the stock 110(?) and shim the needles up (see needle shimming on this site. Then maybe look at a couple steps larger on the pilot jet as well. I don't know what sizes you should try as I don't have the same carbs or have done this myself. I can only comment on how the carbs work in general.

Chris

I have been going by this , chart of tuning and if you can not get color to the plug you are lean,
http://www.factorypro.com/tech_tuning_procedures/tuning_carbtune,CV,high_rpm_engines.html
I found this procedure on Bascliffs site, I have used this method before many times with excellent results, just not on this bike.
Also if you go to this sitehttp://www.iwt.com.au/mikunicarb.htm, you will see that the main jet starts to come into play at about 1/3 throttle, so yes a larger main jet will help with a 1/3 throttle stumble/ hesitation, you just don't get the full effect of the main jet until the needle is fully out , or all the way up, but it is still in use at lower throttle positions.Pilot jet by itself would never deliver enough fuel to bring a 1000 cc bike t 3-4k rpm you need the main.
Ok back to your other ? 's yes I checked the needle, and needle jet and they are suppose to be the ones for this bike, also throttle valve[jet] is a 140 like it is suppose to be and a 40 pilot, needle is a 5057.3 with a x-8 needle jet

 

[resjudicata]

Maybe I read your earlier comments wrong. I thought you had tried bigger main jets and that didn't get you richer at 3k rpm? Otherwise I guess you are on the right track.

Chris

 

[TheCafeKid]

I don't know how a larger main will make the pilot jet work any better or worse. Yes the pilot is fed through the same bore the main is attached to, but the metering agent is the pilot jet itself. I assume if the main were radically too small it could choke off the supply to the pilot, but that's not the case here.
I assume that you've assure that none of the screw tips from your adjustment screws were broken off, not necessarily by you, but by any PO and left in the body?


What about your pilot air jet? Stock size?
Tried shimming the needle??
The not stock stock exhaust will have some effect on this, but I wouldn't think as drastically as you're saying. The air box holes and added KN filter would have more effect than less back pressure.

 

[Guest]

I think I may have found the problem, I had purchased new carb to air box tubes and just pulled the old ones , cleaned up the air box and put the new ones in. Well tonight I went around spraying starting fluid checking for air leaks, and discovered that it is sucking air around the new boots where they go into the air box, so I removed the air box to investigate and low and behold the boots move all over in side the airbox, actually move enough to one side that they are not filling the hole completely. So I measured the hole and get 2 1/8 inches, measure the boot where it is suppose to seal and get 1 15/16 inches check part no,s and they are the same? So I measured the distances between the carbs and set and sealed the boots accordingly and will try it on the bike again tomorrow night. The leakage that I discovered is enough to give the symptoms that I am experiencing. Hope fully this will cure it.

 

[resjudicata]

That makes sense. You can't really tune the jets, etc. until the intake and air box are sealed. Or, as sealed as they are intended to be.

BTW, are the 32mm carbs stock or the 34mm?

Chris

 

[Guest]

Bike came stock with 34mm carbs. When I first got it I could not get it to run correctly, so I put a set of 32mm on and have ridden the bike about 8000 miles or so with no problems until the intake boots started to split this summer, I had been patching them for a couple yrs , just decided it was time to replace them . But found that the 32's didn't fit into the new boots very well . Never noticed a problem with the old boots. but the spacing between the 32's and 34's are a bit different. I would not have thought that the carb to air box tubes would have been such a loose fit kind of surprised me.

 

[Guest]

Well back to the drawing board , tried the bike tonight and it is still lean, real lean. I have the carbs back off and am going to start over for the third time. Something is amiss here and I can't seam to find it. I know if I ride the bike as lean as it is I'll cook it. I have done some cross checking between Basscliffs site with the spec sheet and my Factory Suzuki spec guide and there is some conflict on what is stock and what is not

 

[resjudicata]

Well back to the drawing board , tried the bike tonight and it is still lean, real lean. I have the carbs back off and am going to start over for the third time. Something is amiss here and I can't seam to find it. I know if I ride the bike as lean as it is I'll cook it. I have done some cross checking between Basscliffs site with the spec sheet and my Factory Suzuki spec guide and there is some conflict on what is stock and what is not

Are the different references listing different jet sizes? Maybe post asking what other 1000G owners have for stock jetting.

I know it isn't a perfect comparison, but my 850G is running a V&H pipe (less restrictive than yours) and K&N factory style air filter in the stock airbox (same as yours) and it didn't have that lean a condition. I bumped my mains from 102.5 to 110 for top end help. But, the bottom didn't need anything other than maybe mixture screw adjustment.

So, it does sound like maybe there are still the wrong jets in the carbs or maybe the low speed ports aren't clear.

When you did the tear down and clean up of the 34mm carbs did you blast through from where the mixture screw goes to make sure you got a good flow of the carb cleaner from the low speed ports in the throat of the carb?

Chris

 

[Guest]

Are the different references listing different jet sizes? Maybe post asking what other 1000G owners have for stock jetting.

I know it isn't a perfect comparison, but my 850G is running a V&H pipe (less restrictive than yours) and K&N factory style air filter in the stock airbox (same as yours) and it didn't have that lean a condition. I bumped my mains from 102.5 to 110 for top end help. But, the bottom didn't need anything other than maybe mixture screw adjustment.

So, it does sound like maybe there are still the wrong jets in the carbs or maybe the low speed ports aren't clear.

When you did the tear down and clean up of the 34mm carbs did you blast through from where the mixture screw goes to make sure you got a good flow of the carb cleaner from the low speed ports in the throat of the carb?

Chris

The carbs have been stripped twice and dipped in Berrymens , twice, the passages all have been blown out with compressed air and had carb cleaner spared through .Your 850 has VM carbs on it and the ability to make 2 different screw adjustments to dial them in , These are cv carbs , and a little different to dial in. I am in process of going through these one more time , and if I can't get them I am going to shelve them and get another set. As I stated in the first post I played with this set last year and could not make the bike run correctly so I had a set of 32 's I used and the bike ran fine. These carbs came with the bike when I got it , not on it , with it. The bike was a frame ,a motor, and gauges, and shaft, without wheels or bodywork. so they are a true unknown. The differences between Basscliffs chart and the factory spec guide are as follows
factory Basscliffs
Mains 115 110
jet needle 5D58 5d57-3
Needle jet X-6 X-8
pilot jet 40 40
pilot air 160 160,
Now the specs that I am getting are from the Suzuki Tech's quick reference manual. It is a hand book that Suzuki dealers use to get for shop quick reference info. So unless this is a miss print there are some discrepancy's between the two. Although I don't believe even these will cause this condition. Also this lean condition is on all cylinders equally so it kind of directs to the air supply .

 

[resjudicata]

My analogy between our bikes was just meant to say that your bike configured the way it is shouldn't need much change, if any, to run well with stock'ish jets.

I agree with you, after dipping twice and blasting the ports properly if it still isn't running right on those carbs then maybe something is damaged inside and that is why the PO had them loose.

The reason I brought up blasting the low speed ports with carb cleaner is that most people I run across don't do that. They just dip the carbs and think that's good enough. Sounds like you already know that it isn't and is why you go the extra steps.

Good luck. Sorry these carbs have been such a problem.

Chris

 

[Guest]

My analogy between our bikes was just meant to say that your bike configured the way it is shouldn't need much change, if any, to run well with stock'ish jets.

I agree with you, after dipping twice and blasting the ports properly if it still isn't running right on those carbs then maybe something is damaged inside and that is why the PO had them loose.

The reason I brought up blasting the low speed ports with carb cleaner is that most people I run across don't do that. They just dip the carbs and think that's good enough. Sounds like you already know that it isn't and is why you go the extra steps.

Good luck. Sorry these carbs have been such a problem.

Chris

No offense taken,I have been missing with these for years(20-25) and every now and then you run across something that just throws you a curve ball. And apparently this is one of those. Tonight I am going to throw a set of 140 mains in just for the knowledge of if I can make it run rich , If I can't get any color with them I'm going to build another set of carbs for it. I am almost thinking they must be sucking air through the shaft seals or something, I taped off the 8 holes that are on the bottom of the air box and it was still lean, the other thing I am trying is raising the float height to almost flood stage. I did also notice last night the bike will not pull redline in third gear kind of acts like it is running low on fuel. Boy I need to buy a DYNO.
And no I do not have a inline filter and yes I am running a 7mm fuel line, with good flow from the NEW fuel petcock

 

[gustovh]

My money is on carb mount "O" rings. If they are not sealing well no matter what you do to the carbs it won't help that much. just my 2 cents
V

 

[don]

Because I experienced this with my 1100, kind of, ..... I went from 115 to 125 mains due to open pipes and because the pocelin was showing way too lean when I did that. After the change they were still lean. I raised the needles to having no washers and still.....I opened the pilot screws about 1/2 to 3/4 turns from where they were and I now have beach sand brown colored porcelins and no lean pop on decel.

I'm with you on the whole "complete sepperation of fuel circuits" thing. Both circuits work at all throttle positions. Adjusting the pilot screws DOES make a change in the main circuit and because these carbs feed the plugged pilot circuit through the main, the main DOES affect the pilot circuit.

My soap box 2? worth.............................

 

[Suzuki_Don]

Why don't you try it with the stock air filter element in place of the low restriction K&N filter and just see if that makes any difference. Also spray around the head where the boots mount to see if there is any leakage there. Head could be warped -- who knows. Desperate times deserve desperate measures.

 

[Guest]

Why don't you try it with the stock air filter element in place of the low restriction K&N filter and just see if that makes any difference. Also spray around the head where the boots mount to see if there is any leakage there. Head could be warped -- who knows. Desperate times deserve desperate measures.

I thought about trying a stock air filter but I do not have one , I tossed it 5 yrs ago when I put the K&N in the bike. I have sprayed the whole area , boots , carbs, air box boots [ that is how I found the new carb to air box tubes were leaking] sealed them up. I am thinking that the carbs are sucking air around the throttle shafts and causing the lean condition. I put a set of 140 jets in and raised the floats as high as i dare but have not had a chance to try it with the storm and all. Tomorrow is suppose to be good. Also took the K&N filter out sprayed it heavily with filter oil and put a foam sock over it lets see what that does.If that don't work may have to plug it's nose and stuff a rag in the snorkel

 

[Suzuki_Don]

I thought about trying a stock air filter but I do not have one , I tossed it 5 yrs ago when I put the K&N in the bike. I have sprayed the whole area , boots , carbs, air box boots [ that is how I found the new carb to air box tubes were leaking] sealed them up. I am thinking that the carbs are sucking air around the throttle shafts and causing the lean condition. I put a set of 140 jets in and raised the floats as high as i dare but have not had a chance to try it with the storm and all. Tomorrow is suppose to be good. Also took the K&N filter out sprayed it heavily with filter oil and put a foam sock over it lets see what that does.If that don't work may have to plug it's nose and stuff a rag in the snorkel

Try spraying around the throttle shafts if that is possible. It will be interesting to see the results after your next ride.

 

[Guest]

Well I took the bike out tonight and tried it,
1st trip floats raised as high as I dare, 125 mains,needles raised .040 Pulls like a train the entire rpm range but snow white lean.the air mixture screws 3.5-4.25 out
2nd time ,floats raised as high as I dare,140 mains , needles raised .040 would not rev past 5500rpm rich
3rd trip floats the same , needle same 132.5 mains , stumbling around 6000 rpm and have some color on 3 of the 4 plugs a little rich
Going to try some 127.5 and 130 tomorrow night I am getting closer
I bet when I get this dialed in I won't have the 50 miles to the gallon I was getting with the 32mm carbs on it, but it does pull alot harder, and is quicker out of the hole.