Can't figure these carbs out

[Guest]

I've been having trouble getting my carbs adjusted correctly. I've got a '78 GS1000E. The motor is virtually new from a parts bike that was parked at less than 4.000 mi. The tank and petcock are new, coils and caps are new, timing on the Dyna S ignition is spot on, valves are in specs, boots have been replaced, O-rings are new in the boots and the carbs. The carbs were initially built by a company that supposedly specializes in these carbs. I replaced the improper jetting with a DJ stage 3 kit set up per instructions from Keith Krause, and am still having trouble. With the pilot fuel screws set at 1 1/4 turns out from lightly seated, and the side air screws out 1 3/4 turns, idling at 1,000RPM, I'm not getting enough change in the side air screws to set a good highest idle. I can close #1 and # 3 and stall the bike. Closed #2 and #4 will not stall the bike. The adjustments don't make enough difference to really determine a highest idle. Adjusted with Color tune, I can make the bike purr at an idle, but it will foul plugs if I try to accelerate through the 5 to 6,000RPM range where it stumbles and does not pull smoothly to red line. If I lean out the fuel screws, it will go through the entire RPM range to red line as smooth as glass, but won't idle well. There doesn't seem to be a happy medium. THE BIG QUESTION is, should I toss these Wired George Carburetors in the bin and start a new rebuild, or is this symptomatic of something that can be fixed.

 

[Danjal]

Sounds like you're running too rich. Hows the exhaust look? You might just need smaller jets. Are your chokes sealing properly?

 

[Nessism]

The fuel and air screws are only for the low speed mixture. Set them where you get the idle and low speed throttle response you want and then mess with the needle and main jets to tweak the high speed running.

 

[Guest]

I have two questions then. What about the lack of adjustment response in # 2 and # 4 and Keith says with the 138 jets the third clip is too lean. I lost one motor that way already. Is there a way to drop the needles half a clip?

 

[Danjal]

I wonder if your 2 and 4 carbs are clogged or air screws are broke off.

 

[Guest]

The air and pilot screws are fine. I checked them when I went through and checked the O-rings. At this point I don't know what to do except maybe rebuild another set.

 

[stain]

I have a set with a fresh Dyno-jet kit installed with brand new APE filters if interested.

 

[rustybronco]

Make or buy a fuel bowl adapter and check the wet fuel levels.

 

[Guest]

They are coming off tomorrow for a float level check and to check out all the passages. I have a gauge and gaskets now. I've got an idea I shouldn't have trusted anything that Wired George did. I wasted $440.00 on this set through ignorance, thanks for the offer stain. I have the original set off of this motor that I'm going to start rebuilding, and another set that doesn't look too bad. I intend to thoroughly understand these carburetors before it's over.

 

[Nessism]

VM carbs are pretty simple and reliable, I seriously doubt there is anything wrong with the carbs other than the jetting (and maybe broken off fuel screw tips stuck in the carb bodies as already suggested).

I'd set the fuel screws to 1 turn and the air screw at 1.75 and stop worrying about the highest idle adjustment method. In my experience the engine idle doesn't always respond to the tweaks (can't explain why). From this base line you can tweak the screws maybe a 1/4 turn each way to fine tune the mixture for the best idle and the low speed running. After you get that where you want, you need to focus on some different carb circuits by doing plug chops. There are lots of different threads around here on what to do so you might want to do a search to learn more. Just remember to not make too many changes all at once.

Good luck.

 

[Guest]

Will switching the nylon spacers on the needles drop them some?

 

[Guest]

Three of the float levels were off, set them all to 24mm and one Pilot fuel needle slightly bent. I robbed two from a spare set of carbs. They were the same needles but had a longer screw end. I put those in #2 and #3 that are hard to reach. It will be easier to make any adjustments being able to see those screw heads. It fired right up and idled nicely with good throttle response. I'll see if I need to mess with the needles after I ride it tomorrow.

 

[Guest]

Thanks Nessism. I was still having the same problems so I dropped the needles to the third clip. That seemed to cure the transition stumble. The soot is starting to burn away and the center of the plugs are becoming a chocolate brown. #2 needs to be leaned out a bit to bring the exhaust temp. up with the other three at an idle. It runs through the RPM range effortlessly now, so I think its time to sync the carbs and start racking up some miles.

 

[Don-lo]

OldVet, your method of checking sounds reasonable, so I am suggesting one possibility: stock cams in the early bikes can be poorly degreed. I think Suzuki was so concerned with getting impressive 1/4 mile times (top end) that they designed the intake cam to open early. I remember one bike that was actually rattling the slides of some CR33s (blowback) until we degreed the cams, after which it ran incredibly well all the way to redline.

Degreeing the cams can be a chore, but I think it is one of the best things you can do for the bike, regardless.

 

[Guest]

Thanks Don-Lo. I was reluctant to drop the needles because Keith Krause was so adamant that the third clip would be too lean. So far I haven't seen any indications of "too lean", either in spitting through the carbs, or plug color. I've been riding to work in some pretty nasty 90 degree weather, and it's not missed a beat, except once when the front end easily came up and surprised me, I chopped the throttle. That was not an elegant evolution, but not the bikes fault. It would have happily reached for the sky if I had let it. Might have had something to do with my new saddlebags loaded with liquid refreshment. The weight, I swear, I hadn't had a chance to partake yet. I'll be keeping a close watch in case I have to shim up half a notch. Mileage went from 37 to just a touch over 40 MPG. I'm happy. I'm sure I'll eventually degree the cams, but right now I'm still in the toddling stage of learning these bikes.

 

[salty_monk]

You can use small washers from Radio Shack to get a "half" setting if required

 

[Guest]

Thanks, there is a Radio Shack near where I work, I'll have to check them out just in case.