Mikuni maxed out

Yes, you read it correctly. Idle screws all the way in to give it as much air as possible.

Just to be clear, you mean the air adjust screw...vs. idle adjust screw? The idle adjust screw raises/lowers the slide...screwing it in raises the slide, adding more fuel (raising the needle and thus, raising the idle), the air screw manages the air at idle...so turning it in all the way decreases the air flow. It's opposite of the BS carbs.
 
Just to be clear, you mean the air adjust screw...vs. idle adjust screw? The idle adjust screw raises/lowers the slide...screwing it in raises the slide, adding more fuel (raising the needle and thus, raising the idle), the air screw manages the air at idle...so turning it in all the way decreases the air flow. It's opposite of the BS carbs.


The one that opens the slide are screwed all the way in. The mixture screws are pretty much backed all the way out.
 
It has not been mentioned so far in this thread, but have you verified the following before messing with the carbs?
- Valve clearances
- Compression
- Valve (cam) timing
- Ignition timing
- Voltage at the coil + terminal. Old OEM harness/ switches/connectors can cause severe voltage drop. Unless you have a magneto CDI ignition (i.e. Powerdynamo) this can be an issue.
 
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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.
 
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.

These have a key on them that only let you install them one direction.

It has not been mentioned so far in this thread, but have you verified the following before messing with the carbs?
- Valve clearances
- Compression
- Valve (cam) timing
- Ignition timing
- Voltage at the coil + terminal. Old OEM harness/ switches/connectors can cause severe voltage drop. Unless you have a magneto CDI ignition (i.e. Powerdynamo) this can be an issue.

-Ignition timing is good

Have not checked anything else. It’s on the list though. Wanted to set lash hot, and check compression hot. So I figured get it idling and do so. But it can’t idle.



For what it’s worth. The bike has 8k miles.
 
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.
Ah...ok. With your battery connected, you may want to drop the needle clip to the bottom position...which essentially raises the needle a bit...allowing you to drop the slide back to a more reasonable setting. I would up the pilot jet (try 20), turn the air screw out one turn...and see how it goes.
 
Sorry for no reply. I had to work really late the past two nights and didn’t make it into the shop.

Here’s the deal:
Attempted to start the bike as I left it a few days ago. Would not start. Kicked forever. Checked spark, none at all on either bank.
Checked connections, all good. No spark.

Hotwired the ignition off of my truck battery. Fires right up. (Ign switch must have gone bad??)

Had a dead miss on right bank.
Tested spark with engine not running. Right bank had very weak spark, or none at all.

Checked compression- 105 left and 100right

Installed new plugs- gaped to .035”
Bike fired right up in like 1/2 kick and ran as good as it ever has so far.

Bike still running rich, but I was able to warm the bike up.

Shut off bike. Lashed valves to .004 intake and .006exhaust with engine hot

Adjusted float levels to 23mm (measured @ point of float contact)

Verified slides are installed correctly

Adjusted timing chain tension

Fired bike back up and corrected ign timing

Bike runs “better”. But still runs rich

Have both needles set to the leanest clip positions as suggested previously

Fired bike up and let it warm back up. Sprayed 1/2 can sea foam into each bank in attempt to clean valves.
Pulled exhaust pipes to check exhaust valves for carbon. Also checked intake valves.
Checked compression after sea foam treatment: 120left and 115 right


Right bank will go dead after a few mins of running from running so rich. Literally blowing black smoke at idle until it goes dead on the right side. It won’t come back on it’s own. I give it a vacuum leak and the cylinder comes right back.

You can feel the temp difference in the jug between the left and right side. Right is way colder than left.

Air jets are still removed. Idle speed is still very low. Idle screws are all the way in. Idle mixture screw are still all the way out. Jets are still as listed before.

When I twist the throttle is blows flames under acceleration. (Doesn’t lean pop, just flames) it also feels like I’m hitting a rev limiter, so I know it’s running rich as hell.


The fuel consumption is crazy. I can literally watch it flow through the fuel lines as it runs. Sucks carbs dry in a matter of 10seconds or less.

Scratching my head still.
 
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Wouldn't leaning out the clip, but raising the slides as far as they will go kind of defeating the purpose? (I use drill bits for measuring, maybe start with a 1/4" for each slide opening. I also use the popsicle trick to make sure each slide is raising at the same time.)

Unless I'm misunderstanding how you have your carbs set up...I think your pilot is too lean, based on the fact that you're compensating to get the bike to run by raising the idle....have you changed your jets out yet?
 
Wouldn't leaning out the clip, but raising the slides as far as they will go kind of defeating the purpose? (I use drill bits for measuring, maybe start with a 1/4" for each slide opening. I also use the popsicle trick to make sure each slide is raising at the same time.)

Unless I'm misunderstanding how you have your carbs set up...I think your pilot is too lean, based on the fact that you're compensating to get the bike to run by raising the idle....have you changed your jets out yet?


We could be miss understanding each other. I’ll explain my thoughts, and you correct me.

I think the bike is running super rich.

Raising the slide adds air to the engine and increases engine speed. But it also raises the needle, allowing more fuel into the system. So I lean the needle out as much as possible, so the needle doesn’t come out of the seat as far when the slides are raised up.

I originally tried to set the slides about 2 turns out (.040” slide opening) and about 1-1.5 turns on the mixture screws. Couldn’t get engine to start. Twist throttle open a bit, and engine will fire up. Let off throttle, it stalls right out.
 
Right, ok, thanks for clarifying.

Your pilot jet is too lean. Get a bigger pilot, drop the slide back to your settings you originally tried leave the needle on the bottom or 2nd from bottom clip, and air mix out 1-1 5 turns.
 
Right, ok, thanks for clarifying.

Your pilot jet is too lean. Get a bigger pilot, drop the slide back to your settings you originally tried leave the needle on the bottom or 2nd from bottom clip, and air mix out 1-1 5 turns.

Will do. Be right back
 
2nd from bottom on needle.
17.5 pilots (biggest I have)
2 turns out on idle screws
1.5 out on mixture screws

Bike fires, stumbles then stalls out.

I think I need a bigger pilot.

Going to max the needle in rich position and try again.
 
Maxed needle out in rich position.
Stumbles- won’t idle
Installed the air jets (2.0)
Stumbles a little more- won’t idle

I’ll go pick some more pilots up tomorrow.
 
There's a thread on here somewhere that shows a bunch of VM set ups that have worked (all based on each person's location, bike configuration, etc...) which boils down to each bike is different and what works for some may not work for others...that being said, there are a few common traits that seem to be consistent. The biggest one I saw was that most people ended up with pilot jet's being closer to 25... I copied this summary for my own purposes when I went to VM carbs this year... it helped me get a general starting point and what size jets to get in anticipation of tuning needs. Here's the list I came up with (Again, stolen from a thread which actually has a lot more info, but condensed for my purposes). Might help you as well:

Mikuni VM combos

MJ = Main Jet
PJ = Pilot Jet
NJ = Needle Jet (emulsion tube)
JN = Jet Needle
Slide = Cutaway number
_________________

Roy Fisk
Carb: VM34
MJ: 190-200
PJ: 22.5
NJ: P6
JN: 6DHS, 3rd slot
Slide: 2.0
Air jet: 2.0?
Air screw: 1.25- 1.75
Float height: 25mm
_________________

Richard, from the Aussie site
Carb: VM34
MJ: 180-190
PJ: 20-25
NJ: P5, P6
JN: 6F9, 3rd slot
Slide: 2.5
Air jet: Removed

Dwayne, from the Aussie site
Carb: VM34
MJ: 180
PJ: 25
NJ: P6
JN: 6F9
Slide: 2.5
Air jet: 2.0?

Bob Hart, from the Aussie site
Carb: VM34
MJ: 180
PJ: 27.5 - 32.5
NJ: P5, P6
JN: 6F9
Slide: 2.5
Air jet: Removed

Yamaman
Carb: VM34 with Ramair pods, Triumph silencers ,Halco 1 1/2" pipes.
MJ: 185 - 190
PJ: 25
NJ: P6
JN: 6DH4, 3rd slot
Slide: 2.0
Air jet:

gggGary's Pristine, never had gas in them yet.
Carb: VM34
MJ: 180
PJ: 25
NJ: 159-P6
JN: 6F9, 3rd slot
Slide: 2.5
Air jet: ?
Float valve 3.3

gggGary's Unknown
Carb: VM34
MJ: 260
PJ: 40
NJ: 247-Q2
JN: 6DH4, Top slot
Slide: 2.5
Air jet: ?
float valve 1.5
 
There's a thread on here somewhere that shows a bunch of VM set ups that have worked (all based on each person's location, bike configuration, etc...) which boils down to each bike is different and what works for some may not work for others...that being said, there are a few common traits that seem to be consistent. The biggest one I saw was that most people ended up with pilot jet's being closer to 25... I copied this summary for my own purposes when I went to VM carbs this year... it helped me get a general starting point and what size jets to get in anticipation of tuning needs. Here's the list I came up with (Again, stolen from a thread which actually has a lot more info, but condensed for my purposes). Might help you as well:

Mikuni VM combos

MJ = Main Jet
PJ = Pilot Jet
NJ = Needle Jet (emulsion tube)
JN = Jet Needle
Slide = Cutaway number
_________________

Roy Fisk
Carb: VM34
MJ: 190-200
PJ: 22.5
NJ: P6
JN: 6DHS, 3rd slot
Slide: 2.0
Air jet: 2.0?
Air screw: 1.25- 1.75
Float height: 25mm
_________________

Richard, from the Aussie site
Carb: VM34
MJ: 180-190
PJ: 20-25
NJ: P5, P6
JN: 6F9, 3rd slot
Slide: 2.5
Air jet: Removed

Dwayne, from the Aussie site
Carb: VM34
MJ: 180
PJ: 25
NJ: P6
JN: 6F9
Slide: 2.5
Air jet: 2.0?

Bob Hart, from the Aussie site
Carb: VM34
MJ: 180
PJ: 27.5 - 32.5
NJ: P5, P6
JN: 6F9
Slide: 2.5
Air jet: Removed

Yamaman
Carb: VM34 with Ramair pods, Triumph silencers ,Halco 1 1/2" pipes.
MJ: 185 - 190
PJ: 25
NJ: P6
JN: 6DH4, 3rd slot
Slide: 2.0
Air jet:

gggGary's Pristine, never had gas in them yet.
Carb: VM34
MJ: 180
PJ: 25
NJ: 159-P6
JN: 6F9, 3rd slot
Slide: 2.5
Air jet: ?
Float valve 3.3

gggGary's Unknown
Carb: VM34
MJ: 260
PJ: 40
NJ: 247-Q2
JN: 6DH4, Top slot
Slide: 2.5
Air jet: ?
float valve 1.5
Brass, got a link to the thread.
 
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