Mikuni maxed out

I’m lost.

Put 22.5s, 27.5s, and 32.5s in it.
180main
2nd from bottom
No air jets

Bike does not run. It’s so rich. Just with a single kick, it will shoot a black smoke plume. My walls and shelves are covered in black splatter.

To keep it running, I have to keep the throttle cracked open, and it’s a continuous flame coming out of the pipes. Literally just off idle and it’s a continuous flame. (With 32.5 pilot)

If I try to rev it up at all it misfires and acts as if it’s drowning.

Plugs are soaking wet. And black as hell.

Idle screws and mixture screws don’t really do anything. Fuel consumption is unreal. In the few days I’ve been troubleshooting this, I’ve almost finished off my 5gal can.

How intense of a spark am I suppose to have? Maybe my ignition is weak?

My resting battery voltage is about 12.9v
At idle i measured about 13.5 (low rpm idle)
 
STOP!
IMHO For whatever reason your floats are not functioning at all, you are getting a fire hose of gas.You need another set of eyes on those carbs, forget running, you need do a fuel level in the float bowl check and find out what is WRONG with how they are set up. Seriously your cylinders are getting washed down with gas. Odds are pretty good your crankcase oil is very diluted. This all adds up to metal on metal friction and the bad things that brings in short order.
 
Seriously your cylinders are getting washed down with gas. Odds are pretty good your crankcase oil is very diluted. This all adds up to metal on metal friction and the bad things that brings in short order.

I was just thinking about this. ^^


I’ll pull the bowls off and leave the fuel line on. Then I’ll hold the float arm up and see if it stops the fuel.

But with that being said. Shouldn’t it be flooding fuel out of the carbs? Because it’s not.

It’s frustrating because these carbs are so simple. I’ll check needle/seat.
 
Pictures? show us LOTS of pics, carbs fuel lines intakes etc. with the float bowls off would be good too.
 
Literally just off idle and it’s a continuous flame. (With 32.5 pilot)

Yikes! Wow, ok...something is definitely NOT right. I'm sorry to have lead you down this path...but at least it's clear that there's something funky happening, and not standard to the general thoughts on tuning for this carb on our bikes.

As Gary suggested, pics. Can you take pics of the serial # on the carbs too? Just want to rule out that their not clones but legit Mikuni carbs that came with your bike.
 
Yikes! Wow, ok...something is definitely NOT right. I'm sorry to have lead you down this path...but at least it's clear that there's something funky happening, and not standard to the general thoughts on tuning for this carb on our bikes.

As Gary suggested, pics. Can you take pics of the serial # on the carbs too? Just want to rule out that their not clones but legit Mikuni carbs that came with your bike.

I’ll check all that tomorrow and post back.

What should I measure on the ignition system to see if it’s stout enough?
 
There are a few things that can impact your ignition. The first is to test your battery... I think initially you said you're running without a battery, is that still the case or have you bypassed that with a battery? You could trace the power to the coil and see if you're losing power along the path, and you can test your coil (There's a ton of threads on testing coils--you need to test the primary resistance and then the secondary resistance)....it's pretty straight forward. If that tests good, you could go on to try new plugs, etc. ....BUT first, have you done the basics to set the bike up: set cam chain tension/checked valves, checked timing, etc? If your timing is off, you could have similar outcomes that you're having now...and may not be completely carb related.
 
There are a few things that can impact your ignition. The first is to test your battery... I think initially you said you're running without a battery, is that still the case or have you bypassed that with a battery? You could trace the power to the coil and see if you're losing power along the path, and you can test your coil (There's a ton of threads on testing coils--you need to test the primary resistance and then the secondary resistance)....it's pretty straight forward. If that tests good, you could go on to try new plugs, etc. ....BUT first, have you done the basics to set the bike up: set cam chain tension/checked valves, checked timing, etc? If your timing is off, you could have similar outcomes that you're having now...and may not be completely carb related.


I have the bike running off of my truck battery for troubleshooting purposes. Battery is good. - resting voltage is about 12.9v and at the low rpm idle it’s about 13.5v
I checked compression, lashed valves, adjusted timing chain, and verified ignition timing. It has brand new plugs in it, but I do have to keep removing them and cleaning them.

I’ll check the coil after work. Wasn’t sure if there was anything else on the pamco that needed to be checked.
 
One thing often overlooked are the choke system.
I would check that the chokeplunge have the rubber seal at the bottom with no damage,and that it seat properly for total seal.
If you have a small leak,it will suck fuel from the bowl and mess up the jetting.
Just check to be sure I mean....
Anders.
 
The battery voltage is not really interesting. On the other hand, the voltage AT THE COIL + TERMINAL definitely is.
 
Okay. I had to work late so I didn’t get much done. But listen to this.

Yanked the stock carbs off of my buddies 75 xs650 and put it on mine.

Bike fired up and ran fine. Not rich. Ran fine. Had a dead miss on the other side this time (assuming it’s just missing from being totally fouled)

I didn’t bother to check the ignition because even when I unplugged the battery, it kept running fine. So the power it was generating was enough to run it without a battery or cap.

I took a bunch of photos of the carbs. Maybe it something obvious that I’m missing that someone can hopefully point out. Cause as of now, I’m ruling out the carbs being the issue.

Let me see if I can post them.
 
451C92E6-86A9-4DCD-B40B-A67C4C988A10.jpeg
722249A0-4D34-40D7-9C34-1226E75E5EDC.jpeg
019AA11F-BEB4-4D35-9935-FF6295FDBF3D.jpeg
48548AD7-935B-42C0-81A6-9588FC201DB5.jpeg
DAC92018-EC27-4E37-AB45-6F1D09E0F774.jpeg
7F439A0A-B5D6-4871-9762-F6EFA529D07F.jpeg
64E53E26-FD69-4801-BBA1-1D4BCCF61C48.jpeg
9A2A2FD5-B2C2-4B09-A541-5795917F8486.jpeg
92FA2702-3BAC-4424-8645-7D1558070F1A.jpeg
57DFC798-FEE4-44E5-9065-155255C89B21.jpeg
7BF3D1B3-A2A2-40B2-879A-516591B08910.jpeg
 
Um, sounds like the VM34's ARE the issue to me.
Yup. It’s killing me. These carbs are so simple, and it’s beating me lol.

Let me know if there’s something else you’d like to see or take a photo of. They’re just sitting on my shelf.

Hopefully someone can point out the issue.

I will note, when I turned the fuel off, it took a few mins for the bowls to run dry. So for sure the fuel consumption is unreal on the VM34 carbs.
 
Great pics! Thanks.
Looks like genuine late models with matched parts. All look in "perfect" condition.

Vent lines.jpg
 
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