Mikuni maxed out

[Jthomas]

Since someone asked about the fuel line setup. They originally had a “T” splitting them off of 1 petcock outlet. I put a 2nd nipple on the petcock, and ran 2 lines down to each carb.

The scale on the right is metric. So it’s at 2.3cm (23mm)


I hooked a fuel line up to a carb without the float bowl on, and lifted on the float arm. It stopped the fuel flow.

 

[gggGary]

 

[Jthomas]

Yes.

 

[gggGary]

View attachment 138251 View attachment 138252

I put a 2nd nipple on the petcock, and ran 2 lines down to each carb. ??

The scale on the right is metric. So it’s at 2.3cm (23mm)


.

 

[Jthomas]

My bad. Typo

2 lines total. One to each carb. Idk how the slides could be backwards because the cutout for the idle screw is on the correct side for each one. And I can’t flip them around because of the keys.

 

[gggGary]

My take-away from the first few pics are that the slides are in backwards. Not sure how the slide could have gotten down that far in the carb body but, the filter side is definitely closer to the bottom than the engine side of the carb.

I have seen slides in backwards before but NEVER able to go THAT far done into the carb body.

DING DING DING I think we have a winner!
I think that's it. there are left and right slides, you have them in the wrong carbs?

 

[gggGary]

You know what they say: never assume. Secondary effects of components are strong in VM and most older carbs, to the extent that a one step change in needle position will sometimes affect the idle mixture strongly enough to force a PJ change. The main circuit (slide, NJ, JN, MJ) never turns off, it's operating even at lowest idle through the slide cutaway (speaking of which, make sure your slides are installed with the cutaway facing the rear). Need to know which needle you have as well as clip position.

It might seem like a stupid suggestion but mikuni slides are easily put in back to front as in with the cut out facing closest to the engine, not sure why the made it so you can turn the slides around.

Yeah, Jay, I suggested that, maybe he checked it and maybe not. OP, you might want to do a little more research on the incompatibility of most aftermarket electronic ignitions, Pamco included, with battery-free systems. If you just have to run without a battery, consider installing breaker point ignition or a Powerdynamo system. Good luck with the project.

Edit to add Brassneck's post #27
"
↑
These have a key on them that only let you install them one direction.
That is true, but that doesn't mean that the left slide is on the right side carb, and vise-versa. Easy enough to double check.

↑
The one that opens the slide are screwed all the way in. The mixture screws are pretty much backed all the way out.

 

[Jthomas]

Oh shit. I just realized that it doesn’t matter, because you CAN flip them back to front, but ON THE OTHER SIDE, and it will work. Ouch.

 

[Jthomas]

I’ve literally “verified” them like 3 times. I was like yeah, cutout is on the correct side for each carb. Key is on correct side for each carb. Must be okay?!

But i didn’t realize that when you turn them around, and flip banks, they will fit as well!!!

 

[gggGary]

Good pics sure are useful!

 

[Jthomas]

Good pics sure are useful!

I’m in for the night. I’ll swap them after work and report back.

 

[Brassneck]

I’ve literally “verified” them like 3 times. I was like yeah, cutout is on the correct side for each carb. Key is on correct side for each carb. Must be okay?!

But i didn’t realize that when you turn them around, and flip banks, they will fit as well!!!

Ahem....Post # 27 (wink, wink)....

I don't see serial #'s on them... not saying they're not legit Mikuni...but usually they are stamped on there. Perhaps on the other side??

 

[5twins]

Yes, I can see by your pics in post 55 that you have the slides faced the wrong way, with the cutaways toward the engine.

 

[gggGary]

Old carpenter to a young buck on a job site back in the day. "Son you need to go sharpen that hand saw". Reply; "I don't have time to do that old man, I'm already way behind here"......

Who hasn't been there?

 

[Jthomas]

Alright guys.

Turned the slides 180* and swapped from left to right.
Bike runs/idles phenomenal.

Next time y’all are in southern MI, I’ll buy the beers.

Just waiting for my ignition switch, then it’s time to take it out.

Now excuse me while I go wash my mouth out with buckshot...

Thanks again!

Ps. I did change my oil. So much gas in it that I’m surprised I haven’t been taxed on it. Might as well pour it back in the tank!!

 

[Brassneck]

Seriously happy that you got it worked out...trust me, a lot of us have been there, done THAT.

I'd be curious to know what jetting you end up with after you get it tuned.

 

[Jthomas]

Seriously happy that you got it worked out...trust me, a lot of us have been there, done THAT.

I'd be curious to know what jetting you end up with after you get it tuned.

It will take me some time to get everything ironed out, but I will report back when I do.

Also, can you point me into the direction for the guide on “dead cylinder idle air mixture tuning”?

Thanks again

 

[Brassneck]

There's a whole bunch of tuning threads for VM34's...but I think this is a good place to start: http://www.amckayltd.com/vm34-36.pdf also, if you want to really learn about tuning these, get a hold of the Sudco Mikuni Tuning Manual.

And here's a quick summary of the Dead Cylinder Method (copied from a post and I don't recall who wrote this, but again, re posted below for my purposes)--BUT note, with a Pamco, you have to make sure you don't run the engine with the plugs not grounded at any time--it may fry your ignition.

Warm the engine to operating temperature, then raise the idle to around 1500 rpm. On bikes with breaker point ignitions, pull off a sparkplug cap. Electronic ignitions can be damaged by operation with an ungrounded ignition wire. To prevent that, shut down the engine, attach a spare sparkplug to a cap, ground the plug solidly on the engine, and restart. Adjust the throttle stop to hold lowest steady idle, then move the fuel screw ¼ turn each way, seeking highest idle. When you find the direction of improvement, set the screw 1/8 turn in that direction from your starting point and again move it 1/4 turn each way. As idle rises, lower it with the throttle stop, as changes are easiest to detect at low engine speeds. Set the screw at the inmost (leanest) position that yields highest idle speed. (And yes, I know; some owners advocate finding the point where idle drops due to leanness, then the point where it drops due to richness, and setting the screw at the center point. I do not concur.) Repeat for the other cylinder.

 

[Jthomas]

Hey I’m reporting back!

I’m just over 500 miles on the bike. I’ve since leaned the pilot out. I think I’m right around 20? I’d say between 17-22. I don’t recall now.
And I’m either middle clip or 2nd from top and a 180-185 main.

Sorry it’s not specific. Bikes been running so well that I’ve just forgotten about it. Any gear, any load, any RPM it’s always smooth. No hiccups or fuzzy spots. Just smooth.

Here are the plugs:

Timing band

Nice color on insulator- no speckling or blisters

Carbon goes about 50-75% around the face of the plug.

I’m actually back because it left me stranded far from home. Just shut off as if you turned the key. No spark.

I tested coil per pamco instruction- good

(Bike is kickstart only w/ PMA)

So it’s kind of hard to test the pamco itself while i kick it and hold the multi meter.

But I just measured volts DC off of my cap and kicked it, and I can’t make over 4v. Soooooo?

 

[Brassneck]

I'm not sure how you can do much testing without a battery...but perhaps check continuity? Maybe a wire has been cut/ground lost, etc. or blown a fuse? If you temporarily connect a battery, you may be able to test things better?