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Carbs finally on....bogs like a bitch....

  • Thread starter Thread starter Johnny K
  • Start date Start date
J

Johnny K

Guest
Ok, my sig is my bike. I have 180 air mixture screws. 155 main jets. 47.5 pilot jets. That's been on my bike for over a year since my mechanic installed the Stage III dyno-jet. After getting the all the same intake boots and completely assembling the carbs and doing one carb/one day the berryman way. Washed and carb sprayed clean each part. I have new float needles and fixed every float to spec. All new o-rings from Robert Barr. New intake o-rings alone with new intake boots. I set the screws to around 2 1/2. I primed it and started it and it idled to my surprize cuz for almost a year I had a vacuum issue. Anyways, it idled and let it warm up. I took it for a ride and let out in first and bog, bog, bog. From start to finish. Little throttle to any and I almost fell over cuz it was no go. So I parked it in my shed and revved the engine where it was all bog throughout the rpm's. Everything is nice n snug with clamps. Took the tank off and turned in to slightly seeted and then 2 turns out. It idles around 2000 and anything lower starts to stall like a leak. But on the other hand, at 2000 I can give it throttle and it responds. Not well, but enough to actually make me go. Havent rode on that new adjustment screw cuz it started to rain. But tomorrow I will ride on that. Any ideas about mixture screw turns and was wondering how do you fiddle with the screws once the gas tank is on?? Thanks.
 
I think the Dyno Jet instructions say to set the screws to 3 turns out.

I've been fighting with boggin as well. No I haven't found a way to adjust these screws with the tank on, unfortunately. Keep us up on what you find- but check the DJ instructions for the jet kit. again, I think it says 3 tuns out and the needle on the 4th position from bottom.
 
Last edited:
Hi Johnny,

Sounds like you did a fair amount of work to be so disappointed.

You didn't mention if you sync'ed the carbs after your clean/rebuild/reinstall. It sounds like that could be the problem.

Once you get the mixture screws & the idle right, the carbs will need to be sync'ed - it won't run for crap without that crucial final step.

Follow the link for more info:

http://members.dslextreme.com/users/bikecliff/images/carb_sync_notes.html

Good luck,

Mike
 
The 47.5 pilot is too big. Try a 45.
Your jet needle isn't set right. See where it's at
The main is about right
Is the press in main air jets installed?
 
Johnny K said:
...and was wondering how do you fiddle with the screws once the gas tank is on?? Thanks.
Click to expand...

I remove the 2 mounting bolts (and associated rubber mounts) holding the tank rear to the frame. Then, with the tank pulled "slightly" back but still engaged into the 2 front mounts, I lift the rear end up & stick my "special" wooden shingle between the rear mounting "ears" and and the metal tabs that hold the front of the seat down. Of course, your fuel line needs to be long enough to to this.

Now you have enough room to get a small screwdriver under the tank to adjust the mixture screws while the bike is running (don't forget to keep a fan blowing on the engine!!)

BTW, when you do your carb sync, you have to plug off the vaccum line from the #2 carb ( the line that goes to the petcock). You can simply put your pertcock on prime to flow gas to the carbs during the sync job, as the tank will need to be removed from the bike to get access to the sync screws.
 
My mechanic has synched them prolly twice. But that was when it had a vacuum leak and I couldnt pin point it out. The air press is drilled/different size holes if that is what you are referring to. What would u suggest Chef for how many turns for the mixture screws?
 
Johnny K said:
My mechanic has synched them prolly twice. But that was when it had a vacuum leak and I couldnt pin point it out.
Click to expand...

Hmmmm... I thought you took the carbs apart & dipped them and sealed all the air leaks and such... did your mechanic sync them after that??
 
Oh no. I just put them all back together today. I had to wait for new intake boots and o-rings. I plan on getting to him when I get to at least running point.
 
Well then, as Chef pointed out, maybe your jets are incorrect and you definately NEED to sync them before the run right. Learn to do it yourself & you'll save money & do a better job.

Good luck
 
My mechanic wont charge me for the synching. I just can't affod to pay for the manometer. I'll have to try 3 turns out and see what it does tomorrow.
 
Johnny K said:
I'll have to try 3 turns out and see what it does tomorrow.
Click to expand...

Adjust them while the bike is running - listen to the exhaust. start at 2.5 turns & turn each screw out one at a time until the engine stumbles, then turn in back in slowly while you listen & feel it smooth out. Move on to the next carb & repeat. Keep re-setting the idle adjustment back to about 1500 or so after each carb adjust.

When you've done them all, start over & fine tune then some more, listen to the exhaust & try to get that deep, mellow, smooth sound. Takes practice & lots of patience... you'll get it. Don't forget to use the fan!!
 
Yeah, the fan I will remember. What about the idle screw? At some point, it's going to be very low. I guess just wondering if there would be a set point where the idle screw would be turned and then adjust the mixture screws? Or more of just feel it out kinda?
 
You could have the screws out 20 turns and you shouldn't have the bogging you have.
Rich on the pilot jet and needle circuit?
What does your spark plugs say?
 
Maybe the floats need to be leaned out. The mains sound too big 155DJ would be like 145 Mikunis. I have 142.5 Mikuni mains on a 1229 with pods. And is 180 air jet not stock? Maybe trying a stock size if all else fails. People here always mention removing the float vent tubes with pods if you haven't already.
 
I went and played with my mixture screws. I tried each one out at 2.5 turns, got the bike started and the fan going. On each carb I turned in till it started to bog and then slowly turned out to make it idle. I couldn't get to that spot because every time I wanted to bring the idle down by the mixture screw to below 2000, it would just barely run until I turned the screw out and tried to make it idle. Almost every time I went to play with the screw and it was almost going to stall, I revved a little with the throttle and it would kinda hang up there when it went past 2000rpm. Especially if I went to 4-5000rpm, it would hang and slowly come down. I still have almost like a vacuum leak which is really annoying me right now. If the bike falls past 2000 it will slowly start to bog and then die. So everytime I went to play with the screw and try to let it go to about 1500rpm, it would just die. Okay on a sidenote. If I were to color a pointy edge on a flat head and have that colored edge face me, and turn it until it reached me again is one full turn right? I just dont want to be turning it too many times in and out thats all. But any ideas about the vacuum issue?
 
Thanks. I havent checked my spark plugs yet. But just wondering about the whole vacuum isue thing. I shouldnt have any and i hope that it isnt a vacuum issue rather a tuning issue. But tomorrow I will tackle it again.
 
Johnny K said:
...I wanted to bring the idle down by the mixture screw to below 2000, it would just barely run until I turned the screw out and tried to make it idle.
Click to expand...

I'm confused by this statement... the idle is set by the idle adjust screw, it's the large bronze colored knob located near the bottom of the carb rack on the airbox (or pods in your case) side. Turning it clockwise (in) will open the butterfiles on all the carbs & increase the idle - conversely, turning it the other way (CC wise), will lower the idle.

Playing with the mixture screws is to adjust the proper mix of air/fuel for each individual carb - the overall engine idle will indeed be affected by these changes After each carb is adjusted, reach under and set the idle to 1500 or so. Keep doing this (adjust the carbs, reset idle) until you have a happy bike.

Perhaps your assumed vaccum issue is really a mis-adjusted carb.

Good luck
 
Ok. Good point. But i need to bring it down to 1500 without it stalling and dying. I can't get to that point yet. Im trying to get ideas on why I cant, ya know?
 
Also when playin with the mixture screws im gettin a lot of popping from the intake boots. Kinda shocked at first when i see and hear it happen.
 
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