General carb tuning info

[the_journeyman]

In reading posts, I'm trying to figure out the signs of lean v. rich in carb settings. I've been asking a lot of questions, getting a lot of good info from everything everyone is posting. Now, I'm just trying to put things together to make some adjustments. I don't have a carbtune or colortune nor the money to purchase one.

1. Popping on decel - Lean? If so which circuit (or all) need to be addressed

2. Bogging on sudden, 1/2 throttle or more openings? Which circuit needs to be looked at?

3. Grumpy idle (idles but slows to a stop unless really warm) - Normal or something needs to be looked at?

4. When accelerating, goes from bogging to afterburner-like forward blast about 3/4 thorttle - Normal when coming on the main jet or is the needle circuit off. Which way off would cause this?

5. Starts with choke, pipes are almost instantly hot enough to radiate heat, finish looks baked off in places.

I was thinking this bike was tuned rich, in recent reading on here, I'm thinking I'm tuned lean. Possible if the PO didn't take pods & pipe into consideration.

If you need bike specific info: '85 GS1150ES, Vance & Hines pods, 4-1 aftermarket exhaust w/ removable baffle. Baffle is installed. Not sure of the brand, BUT it's a short, stubby looking muffler, pipes & muffler solid black. Only about 100 miles to the tank.

Thanks!

JM

 

[Dave8338]

In reading posts, I'm trying to figure out the signs of lean v. rich in carb settings. I've been asking a lot of questions, getting a lot of good info from everything everyone is posting. Now, I'm just trying to put things together to make some adjustments. I don't have a carbtune or colortune nor the money to purchase one.

1. Popping on decel - Lean? If so which circuit (or all) need to be addressed. Lean: pilot jets / exhaust leaks / air intake leaks / mixture screws.

2. Bogging on sudden, 1/2 throttle or more openings? Which circuit needs to be looked at? Lean: jet needle settings / under sized mains / air intake leaks.

3. Grumpy idle (idles but slows to a stop unless really warm) - Normal or something needs to be looked at? Lean: idle mixture-air screws / idle circuit clogged.

4. When accelerating, goes from bogging to afterburner-like forward blast about 3/4 thorttle - Normal when coming on the main jet or is the needle circuit off. Which way off would cause this? Lean: jet needle settings (raise the clips) / air intake leaks.

5. Starts with choke, pipes are almost instantly hot enough to radiate heat, finish looks baked off in places. Lean: shouldn't get that hot for several minutes.

I was thinking this bike was tuned rich, in recent reading on here, I'm thinking I'm tuned lean. Possible if the PO didn't take pods & pipe into consideration.

If you need bike specific info: '85 GS1150ES, Vance & Hines pods, 4-1 aftermarket exhaust w/ removable baffle. Baffle is installed. Not sure of the brand, BUT it's a short, stubby looking muffler, pipes & muffler solid black. Only about 100 miles to the tank.

Thanks!

JM

Note the red highlights for my thoughts. :-s

 

[BentRod]

the easiest trick for reading if you are lean or rich is to do a spark plug reading.

run the bike until it is hot - at normal riding temperature. stop the engine and quickly remove the spark plugs.

compare what you see to the chart on this web page

http://www.dansmc.com/Spark_Plugs/Spark_Plugs_catalog.html

 

[the_journeyman]

Looks like what I was needing. Considering there's 3 of those involving intake air leaks, I'll examine the boots between the carbs & head while I've got everything apart. I was starting to suspect lean and it sure looks that way. I'll check the plugs sometime this week too.

I'm guesing one of the previous owners never adjusted the carbs for the pods & pipe, or if they did, it wasn't right of they got tired of fiddling with it ~

Great info as usual folks!

Thanks

JM

 

[the_journeyman]

Rather than start a new thread, I'll update here ~

Pulled carbs, looks like stock needles (not adjustable, only one spot for e-clip) as well as original mains (either 32.5 or 132.5 can't decide it that's a scratch or a 1)

1. Can the factory needles be shimmed? I can't seem to figure out how if they can be. I tried removing the spacer, adding an extra spacer and the needle seems to stay in the same place.

2. I know that I can order just a set of mains and go up a couple sizes and hope it's right.

3. Should I just order the $125 Stage 3** jet kit from Dynojet rather than attempting to sort this on my own?

**I opted for stage 3 because I'm running pod filters & and aftermarket exhaust and there's some ignition mods on this bike. Based on Dynojet's descriptions, this is the best fit.

Thanks!

JM

 

[salty_monk]

Most say it's much easier with the DynoJet kit. Stage 3 is right for your setup.

You can shim the needles by putting spacers under the E clip & obviously you can change main jets. Likely to need new pilots too I would think.

132.5 is small for pods & pipe. I think most start at 140.. maybe more on an 1,100.

Good luck with it. Get some O rings from www.cycleorings.com you're prob going to need them.

Dan

 

[the_journeyman]

Sounds like I'll be ordering the kit, more than I wanted to spend BUT it'll be work it when she runs like she's supposed to. Looks like a previous owner changed stuff but never bothered to adjust the carbs to work properly with the changes that were made.

JM

 

[the_journeyman]

Looks like the Dynojet kit comes with a 138 main. It also specifies where to set the needle and such. I may go one notch richer on the needle, and just see how it runs in the midrange.

I just wish I knew what kind of cams were put in. The PO didn't know, he only knew they had been changed. I've got the originals, but they've got a nice layer of rust on them for not being stored properly.

JM

 

[Steve]

Looks like the Dynojet kit comes with a 138 main.

Would that be the DynoJet 138 or Mikuni 138? :shock:

I am under the impression that they are different sizes and not interchangeable. Yes, they are interchangeable in the sense that you can install the DJ jets in a Mikuni carb, but the DJ 138 jets are NOT the next size larger than a Mikuni 135. Not sure how they relate, but they are not the same.


.

 

[Guest]

Get the Dynojet kit. We'll help you dial it in. In mikuni land the jets are sized by fuel flow. Dynojets are sized by actual size of fuel port.
Dan 140 is pretty fat for his bike. I run a Dynojet 138 which is near a 130 in Mikuni land and i have an 1166 kit. But he has 36mm carbs compared to 34mm like our 1100s.

 

[the_journeyman]

Dynojet kit Stage 3 kit ordered, yes, the 132.5 is in Mikuni sizes and the 138 is in Dynojet sizes. The adjustable needle in the kit should prove useful too. Currently, the bike runs best at WOT. It's grumpy everywhere else in the rev range. I'm interested to see how this bike will run when properly tuned.

JM

 

[the_journeyman]

My jet ket arrived yesterday afternoon. I'll put that in, using the Dynojet recommended settings and go from there. I feel like I'm about to turn a monster loose when I get the right amount of fuel flowing! Going out of town this weekend, so it'll be next week before I can acutally see if there's a difference ~

JM

 

[the_journeyman]

Jet kit installed! Took the bike out for a shakedown run. Here's the results:

Flat spots? Nope.
Popping on decel? Nope

2 things I still notice:

1. If I flip the bike in neutral, the idle hangs at about 2K and eases it's way back down to just about 1100

2. Still a slight stumble when opening the throttle from coasting in gear with the throttle closeed. Doesn't happen when in neutral opening the thottle from idle.

Otherwise, the bike is noticable smoother running and the exhaust doesn't smell bad, just smells like normal exhaust. Once the bike passes about 5,000RPM it like it lights a jet engine.

Any input on 1 & 2?

Thanks!

JM

 

[Guest]

Either rich or lean on the needle. Since the throttle is hanging I'd say lean. Raise the needle one notch by putting the clip one notch lower. Dynojets jetting info seems to be on the lean side anyway.
Do you have any intake leaks?

 

[TheCafeKid]

Im excited...my new mains and intake rings should be here tomorrow...maybe by the end of this week ill have her dialed in....\\/

 

[salty_monk]

Chef,

Could it be the pilots?
I would try to richen up the pilot circuit using the screws first, I read somewhere on here that having them slightly rich helped the transition from no throttle to some throttle (makes sense cause more petrol in there already when you open it up then).

Certainly having those screws too lean on my bike made the idle hang as you describe. Something to try before you mess with the needles again...

Dan

 

[Guest]

Chef,

Could it be the pilots?
I would try to richen up the pilot circuit using the screws first, I read somewhere on here that having them slightly rich helped the transition from no throttle to some throttle (makes sense cause more petrol in there already when you open it up then).

Certainly having those screws too lean on my bike made the idle hang as you describe. Something to try before you mess with the needles again...

Dan

Could be but since he wasn't popping on decel I didn't consider it. I jumped from stock 45 pilot to 47.5 pilots but I also jumped up to 170 on the air jet from 160.

 

[the_journeyman]

OK, I'll go another 1/2 on the screws and see where that happens. I couldn't find any intake leaks and and just checked the valves (all in good shape). If the pilots don't do it, I'll richen the needles by one clip.

I set everything per the Dynojet instructions, so if they tend to be lean, I didn't use the pilot air jet they say is optional. According to the instructions, I don't need it, AND it leans out the bottom.

I haven't done a Synch, which I know might smooth things out a bit more. I don't have the equipment nor the money to purchase so I'll have to do without for now.

Thanks for the input!

JM

 

[Guest]

I did not use the Dynojet air jet either.
Sync those carbs. Could be the issue.

 

[salty_monk]

There's a link on here for making your own. I downloaded the PDF. Basically a board, some tubes & some connectors. Should be cheap enough.....

Let me know if you want me to email the PDF to you.

Dan