Carb settings for straight pipes...help please.

[Detman101]

Hello,

I have made the ultimate bonehead mistake of chopping my swiss cheese stock exhaust cans off at the point where they megaphone out.

I have since experienced hell setting the carbs up right for the mufflers I have put on the bike(H-D punched out Sportster mufflers).

What I'm experiencing is that after running for about 30 minutes the cylinders die out and lose power one by one until the bike shuts down.
I have to wait about 10 minutes until it will start again at reduced capacity.
If I let it sit overnight it runs good again till it messes up...

I know that it is running lean right now and I wanted to know if there were any suggested settings I could put the carbs at with my stage-3 kit so that I can run the stock 4-into-2 system without any mufflers.

Current settings:
Bike: 1981 GS750L with part stage-3 kit (Main jets replaced with mikuni)
Mains: 122.5 Mikuni (anyone know the dynojet to mikuni conversion?)
Pilot jets: Stock
Pilot screws: Stock
Jet Needles: Adjustable Dynojet DNT604 (at 2nd clip from top/Lean)
Needle Jet: Stock
Main air corrector: Dynojet DC0302
Adjusting washers: Not used currently
http://www.dynojet.com/pdf/3315.pdf

I don't really want to run open pipes but I can't find an exhaust for sale anywhere that will replace my chopped up one.
Suggestions anyone?

Thanks in advance,
God bless you,
Dm of mD

 

[Detman101]

I'm such a geek...Answering my own post. :lol:

Well, the guys at the shop I go to have the set of DJ130's that they took out of my bike. Apparently they never threw em out when they swapped in the 122.5's
I'm going to pick them up and see if installing them gets rid of the lean issue.

Dm of mD

 

[first timer]

http://www.macprod.orc.ca/mac-web/3x-main/suz-x3/gs7585x3.htm

try these guys for a exhaust, or look at some of billy ricks's posts, i think he used a gsxr exhaust for his 700/750. you should be able to run a straight pipe system if you have your stg 3 set up right. what are your spark plugs looking like. try turning the mixture screw out 1/2 a turn and see what that does. are you just letting your bike run in the driveway at hi rpms with no air moving over the motor until it dies, if so you are probly over heating it, try putting a big fan in front of it. are you sure the carbs are not just running out of gas. maybe you are haveing a vapor lock problem take the cap off and see if that helps, intstall a fuel filter clear one so you can watch to see if fuel is flowing , maybe your filter is not bigenough and the bike drinks more gas then the filter can filter. you pluged up the number 2 or 3 cylinder where the vacume line used to go after you replaced the petcock?

what happened i thought you got your bike all sorted out?

-ryan

 

[Detman101]

"http://www.macprod.orc.ca/mac-web/3x-main/suz-x3/gs7585x3.htm
try these guys for a exhaust, or look at some of billy ricks's posts, i think he used a gsxr exhaust for his 700/750.

I'll search billy's posts and check those guys out.

"you should be able to run a straight pipe system if you have your stg 3 set up right. what are your spark plugs looking like. try turning the mixture screw out 1/2 a turn and see what that does."

I don't know how to do a correct plug-chop test. I try riding the bike and it just dies after 30 minutes cylinder by cylinder till I'm doing 15 mph on one or 2 cylinders then it shuts down. I will check for vapor lock.

"are you just letting your bike run in the driveway at hi rpms with no air moving over the motor until it dies, if so you are probly over heating it, try putting a big fan in front of it. are you sure the carbs are not just running out of gas. "

I am usually riding the bike when this happens. It happened on the highway and it took me 4 hours to get home from baltimore stopping every 10 minutes and then only taking off again at 30 mph.


"maybe you are haveing a vapor lock problem take the cap off and see if that helps"

I will try that if it happens again.

"intstall a fuel filter clear one so you can watch to see if fuel is flowing , maybe your filter is not bigenough and the bike drinks more gas then the filter can filter."

I have a paper filter for a car installed. It never did this before I chopped off the stock mufflers and put the new ones on there.


"You pluged up the number 2 or 3 cylinder where the vacume line used to go after you replaced the petcock?"

Yes, I put a red rubber cap from the hardware store over the vacuum input on the #2 carb

"what happened i thought you got your bike all sorted out?"

I'm a dick...I chopped off the mufflers and messed it all back up again.

I totally changed the carb settings too so now it's all mucked up.
I will put it back to the dynojet settings once I go pick up my DJ130 mains this afternoon from the shop. I really want to get this bike back on the road. I've learned my lesson this time, I swear.

I'm such an idiot.
Dm of mD

 

[first timer]

set it back to what settings you had that worked last for you. basilly put it back to your stg 3 settings then go and wrap your carbs with barb wire so you don't touch them agian.

-ryan

 

[Detman101]

Will do captain.
I'll not touch the carbs again.
I feel so stupid....like an addict that fell from grace again.


Dm of mD

 

[Detman101]

Welp...I put the bike back at Dynojet settings of

Mains: 132
Needle: Groove #4 from the top
Mix Screws: Three turns out

The bike now makes a "Whuffle-whuffle-whuffle-whuffle" sound and dies at stoplights if I don't keep the revs higher than 2500. It has also run through 1/4 of a tank in 10 miles.
Very very rich....

I'm going to try lowering my needles this lunch period today and see if that helps any. The idle mixture settings seem to be good...better rich than lean I guess. But I think the over rich needle setting is causing the idle mixture to be too rich.
And it would hit wide open throttle if it could get there without stumbling, smoking and almost fouling out in the mid-range. I couldn't highway test it last night because I couldn't get over 50 mph without it stumbling and almost dying. I cut the ignition with the off switch at 3000 rpm and stopped to check the plugs and they were all fouled sooty black. (Super rich)

Why can't I be super rich instead of my bike's fuel mixture?

:x
Dm of mD

 

[Detman101]

Oh another note....
I tried to buy a 4-into-1 pipe yesterday.
No one has any...not vance & Hines, not mac, not jardine, none of the retail stores, smaller stores don't have any either.

So, I'm pretty much screwed and will not be able to do anything the right way like I want to. It's funny, I finally have the money for a 4-into-1 exhaust and no one f'kn sells any...

Such is life...I just know I'm carrying the "Bundy" curse.
I should shoot myself now.


Dm of mD

 

[first timer]

is your bike a 2v or a 4v ? what were the setting you had on the bike when it was working right? use them.

-ryan

 

[Detman101]

It's the 4-valve version with TSCC.

The settings I had the bike on when it was working is apparently too lean for these mufflers. That is why I went with the dynojet settings last night thinking that they might be better for the engine. Apparently not...they're too bloody rich.

Stock holey mufflers with pods
Mains: Mikuni 122.5
Pilots: stock
Mixture screws: 3/4 turns out
Needles: Groove #3 from top

Dynojet setting (current)
Mains: DJ132
Pilots: stock
Mix screws: 3 turns out
Needles: Groove #4 from top

:?:
Dm of mD

 

[first timer]

what was your good setting with the stage 3?

try these guys
http://www.cyclewareables.com/pages/exhausts_hines_megaphone/hinesmegaphone.htm CWV12001

here is one place, the exhausts are out there you just need to look harder.

-ryan

 

[Detman101]

Jesus christ!!! 300 dollars?!?!
I will have to save up and get it from them next friday.

Thank you for the link Ryan, and for putting up with my stupidity.

The stage-3 kit never did work with the stock exhaust. I took it to the shop when i got fed up and they replaced the DJ130 main with the mikuni 122.5 main jet.

I thought that perhaps it (stage-3 kit) would work now that the stock mufflers are gone.

Guess not...


Dm of mD

 

[Detman101]

Ah well, new pipes on the way. DJ132 mains installed, I'm running open pipes for the bike's final trip home.
I'm gonna throw these stupid harley mufflers as far as I can throw them.

:lol:
Dm of mD

 

[Anonymous]

Hmm, I am running 122's on my 77 GS750 with open V/H 4-1 exhaust and velocity stacks on the carbs. Needles are all the way up, but I only run 1/8 miles drags. I does run nicely around the pits though.

 

[Detman101]

Are those mikuni 122's or Dynojet 122's???

There is a difference in size between the two manufacturers is why I'm asking.

:?:
Dm of mD

 

[Anonymous]

I never heard of that. The sizes are supposed to be standard. Why would one company make it different for the brand of carbs they are supporting?

 

[Detman101]

I don't know dude. When I look at the Mikuni main jets and the Dynojet Main jets the size numbers increase at a different rate.

For example...

Mikuni = 102, 102.5, 122, 122.5....
Dynojet= 102, 104, 106, 108, 110, 112...

:?
Dm of mD

 

[Anonymous]

I guess I was wrong, see this post:

http://www.thegsresources.com/_forum/viewtopic.php?t=23337