Another 34 Pic 3 Build!

[dan filipi]

That transition from idle to primary can be a tricky spot to get right. What size is the primary jet?
Be certain there are no vacuum leaks. They will throw everything off.

 

[fivestring]

The primary has no markings on it but it is very near a 126. I haven't changed it yet. I want to road test it before I start experimenting with the top end.

I was surprised to see how much the idle speed screw setting affected the 2-3k range. Didn't expect that.

I got new front brake and clutch levers mounted today along with a new horn/turn/high beam switch wired in. I have headlights to mount and come up with front turn signal mounts for the LED lights I am going to use. After all that then I can start road testing in earnest.

 

[fivestring]

Tried riding it today. Not good. That flat spot just off idle is back and is making it near!y impossible to start out from a dead stop. I have to feather the clutch and rev it up to keep from dying. And as I putt around my yard the engine will pull me all over the place as long as I am idling. If I hold rpms at anything just above idle, within about 10-15 seconds it begins losing power and will stall. BUT! If I give it a tiny bit of throttle (accelerator pump squirt) it will take off again. I am guessing it is running out of fuel just off idle.

I adjusted the small mix screw in 1\2 turn increments between each test putt around the yard. I went from 1.5 turns (low idle) to 4.5 turns out with only a very slight improvement.

Next I am going to drill out the idle jet to .50 and see if it changes.

I checked for vacuum leaks using butane around intake with no change in idle as I did it.

Please comment your thoughts.

 

[slabghost]

4+ turns out? I agree the jet needs to be larger.When the jet is right the mix screw should be close to 2-2 1/2 turns out.

 

[fivestring]

I'm now at .50mm on the idle jet. I got the flat spot to eventually get almost completely gone but I am again over 4 turns out. Taking off from stop got a good bit easier but maybe a little of that was me. This bike seems to have a tall first gear.

I suspected I still may have a vacuum leak so i checked again with carb cleaner. Still no leaks showed up.

Pretty soon I'll be right back at the original original .55mm. Goosing the throttle brings her to life right quick but I still haven't gone beyond 15 mph. Just didn't have a rescue person available today. And I still need a headlight and front turn signals.

 

[slabghost]

If it has an air jet in that circuit maybe closing it up just a tiny bit will help.

 

[fivestring]

it doesn't to my knowledge. There is the idle mix and idle speed mix screw which as I understand adjusts fuel input to the idle circuit.

 

[dan filipi]

Not knowing that carb specifically I can't be a lot of help but I would trace the off idle gas circuit to see where it comes from. Possible there is another jet or some other adjustment.

 

[joedrum]

i think this carb has a hole in the throttle plate ...that can be pluged or open how is yours carb at the moment

 

[dkl]

My 82 GL1100 with stock Jets on the VW 34 pict 3 carb, and using the single runner PVC Manifold, electric choke hooked up
and working correctly, vacuum line hooked up at front of carb, side port plugged....this is my carb setting...​

Small screw 4 turns out--Large Screw 3/4 turn out....
After it warms up a bit it does not smell rich.....Made two trips on this set-up, both bikes ran well​

 

[fivestring]

Thanks for all the replies! Gotta love this site.

Before going inside and modifying things I want to run the full range of jetting possibilities. So, I am going to resize to the original 55 idle jet at start out at 2.5 turns this morning as I can see I'm getting closer as I continue to go bigger and richer. I have a pretty good idea I'm going to end up right where DKL is. And I should have a chance for a quick actual road test this morning instead of laps around the yard.

All this fiddling is just part of the process. I'm enjoying the journey. Very interesting experiment. And I love how easy this carb is to rejet and adjust.

 

[fivestring]

OK. First, I am man enough to admit when I did something dumb. So here we go.

I never checked the initial setting on the high idle screw that rides against the electric choke cam. Everything I read was "after initial adjustment, don't touch it, it is not how you adjust idle!!" Yeah, I never touched it. Like never. I didn't do the initial adjustment. This screw holds the throttle plate open to spec at warm idle, which is .004. Well, I found mine was open significantly more than that which would certainly allow too much air at idle. I now have it adjusted to "touching the last step of the cam, plus 1/4 turn". I had to back it off about 2 full turns. Duh.

My idle jet is now .55mm. I don't feel like this is too big even after adjusting my throttle plate setting. Heck without that adjustment, I may have ended up at a much larger idle jet hole to compensate!

I started out at 2.5 turns but the engine still wanted a little more for a smooth idle so I went to 3 turns. Putted around the yard, seemed pretty good. Helmet on, hit the road. There was still a little hesitation on initial take off. But I eased through the first few gears just dandy. Smooth cruising around 45 mph, still a little hesitation when giving small throttle inputs. I took my screwdriver with me so I stopped twice to add a little more fuel to the idle circuit. Better off idle throttle response now. Now it's at 4 turns. No backfiring on long decels. And a very nice steady 1200 rpm idle.

I'm getting some slow response while giving large throttle inputs but I am certain I'm approaching the main jet influence at this point. That will be addressed as soon as I get time. I have to drain the bowl to change main jets. I feel very confident in drilling to different sizes. If I can drill a 0.35mm hole, I shouldn't have any problem with a 1.30mm hole.

 

[joedrum]

hmmmmmm i wonder if this carb accelerator pump has a jet in it that can change ..some carbs do if so you might be able to clear slow response deal could be not enoufg squirt or to much squirt going on there

 

[fivestring]

Good thought, Joe. It has a screw right on the side for squirt adjustment. Haven't touched it yet. Think I should try that before main jet changes?

34PICT3a

• fivestring
• Aug 15, 2016

Accelerator pump adjustment 34 Pict 3 carb

 

[joedrum]

well it should be adjusted id say ...once idle is good ...and not rich it should be adjusted to try and cure flat spot ...all this is before main ...im very happy your going at this so good ...this may be the dialing in deal for the carb

 

[slabghost]

Sounds like a good plan to me.

 

[fivestring]

Then that's what we'll do! She's getting close to being on the road. :Egyptian:

I may have time tomorrow evening to 'play motorcycle' again. Work work work.

p.s. I have begun assembling another manifold. Instead of 1" PVC like this one, I am using 1.25" but copying DKL's single runner v2.0 design. The i.d. of 1.25 PVC exactly matches the 34mm throat of the carb whereas this 1" PVC necks down the airflow from 34mm to 26mm right out of the carb. Once I get this first setup dialed completely in and log all my settings, I want to swap to the bigger pipe to see what happens.

 

[slabghost]

Sounds like a good plan.

 

[dkl]

The 34-3 is almost impossible to get right with out the Electric choke hooked up and adjusted properly, I did the same thing on the first one I messed with. It also makes cranking so easy. Good Job..

 

[Ansimp]

:clapping:
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