New Boom Vader - Need help converting to Mikuni carb

[prismways]

Hello, just received the Vader and still assembling it and waiting for the MCO.

In the meantime, I've seen some of the mods that people have done on youtube and on here and I was wondering if anybody can send me a link to a step by step walkthrough of replacing the stock carb with the Mikuni carb.

It looks straightforward but don't want to risk making a noob mistake. I was more concerned about what to do with the existing air filter and all the hoses coming in and out of it.

Thanks in advance for any assistance!

[Lucas@Air_Lift]

Any reason you are going mikuni and not something like a cable choke pz26?

[prismways]

I guess based on what I've seen, the Mikuni was a good option.

[Skin Mechanic]

The ease of installation depends on 2 things; the size of the new carburetor, and whether or not you live in a state with strict emissions laws. Since Alabama doesn't have mandatory vehicle inspections I was able to toss the stock airbox and related emissions crap, though I do need to run the PCV hose to the air filter.

I installed a Mikuni VM26 606 on my little monster. I picked it over a comparable Keihin carb because I've had prior experience with Mikunis. I purchased a kit off ebay that included an intake, adapter, foam filter, and throttle cable. Note: I didn't need to use the Mikuni throttle cable because the stock cable end fit the Mikuni's piston valve assembly, YMMV. The new carb has a choke button instead of cable actuation which wasn't an issue for me, the idle speed thumb screw makes up for that.

[prismways]

So I installed the Mikuni kit that I purchased off of Amazon. It was this one:

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1



It was actually a straightforward install. I had tried to install PZ26 (with cable choke) but it couldn't fit due to the position of the choke being on the opposite side compared to the stock carb and it was jammed up against the starter. I tried to make it work but ended up going with this kit.

Now I have all these extra hoses that I do not know what to do with. I believe they may be relating to the emissions control system. If you can confirm, that would be great.



So I believe this silver thing attached to my crankcase breather and the large hose was originally connected to the airbox. I connected to a uni filter. But this extra hose was connected to an inlet on my original intake pipe but the new intake pipe didn't have a connection and I'm not sure what to do with it.

Next, this hose was connected to the airbox on one of the inlets on the filtered side. What do I do with it?




Finally, I have this extra hose that was connected to the carburetor, I think which was an overflow inlet. What should I do with it?




Any help you guys can give would be appreciated.

[Skin Mechanic]

Welcome to the fun world of aftermarket modifications, be forewarned, it's a slippery slope


That's the EGR assembly, an ancient device invented by the automotive industry to appease the emissions gods before the the advent of the catastrophic converter, you can get rid of it.





This one looks like the Positive Crankcase Ventilation. Crank the bike and put your finger close to the end. If it's blowing air, it's the PCV hose. Route it somewhere around the frame(pointing up) so that air flows across the end of it.





You won't need this one either, since your new carb already came with a drain hose.

[Skin Mechanic]

You can ditch the EGR entirely, though you'll need to remove the fitting and block off the opening with a metal plate. Note; mine came that way from the factory. A small mending brace from a hardware store should do the trick.





As for the Evap can you can toss that crap as well, except for the aforementioned PCV hose. Mine is attached to a fitting on top of the crankcase, next to the left engine mount (behind the starter). Your's should be in the same location.The fuel overflow line can be run down the side of the engine and zip-tied somewhere near the side stand.

[prismways]

thanks for the tips.

Isn't that plate you're asking me to cover up the crankcase?

Don't I need to use a filter for the crankcase breather?

I thought that is important.

Originally Posted by Skin Mechanic

You can ditch the EGR entirely, though you'll need to remove the fitting and block off the opening with a metal plate. Note; mine came that way from the factory. A small mending brace from a hardware store should do the trick.





As for the Evap can you can toss that crap as well, except for the aforementioned PCV hose. Mine is attached to a fitting on top of the crankcase, next to the left engine mount (behind the starter). Your's should be in the same location.The fuel overflow line can be run down the side of the engine and zip-tied somewhere near the side stand.

[prismways]

So this device is part of the EGR assembly?

the skinny hose connected to the pipe connecting the carb to the engine.

The other was connected the airbox and the last one to the engine directly.

[Skin Mechanic]

The opening that's covered on my engine is part of the head. Yes, the silver box is the Emission Gas Recycling. It improves emissions by cycling some of the unburnt exhaust gases back thru the carburetor. It's attached to the head between the exhaust valve and manifold. The hose going from the air filter mixes with the exhaust gases and cools them down to prevent overheating the engine.

Ideally the crankcase breather hose should be attached to either a vacuum port on the intake, or air filter box. If your new carb has a vacuum port on the side you can attach the PCV hose to it. If there isn't a way to attach the PCV hose to the intake you'll have to draft it. By mounting the end of the hose perpendicular to the air flow, it creates a draft that draws blow by out of the engine.

Originally Posted by prismways

So this device is part of the EGR assembly?

the skinny hose connected to the pipe connecting the carb to the engine.

The other was connected the airbox and the last one to the engine directly.

[david3921]

The carb isn't installed correctly. The intake should be curving toward the rear rather than the front. The carb should be pretty much in line with the shift lever. The bowl tube exits at the rear of the motor.

[prismways]

so does this pretty much mess me up if I need to get it inspected in MA?

They do require an inspection and I assume some type of EPA regulation.

Originally Posted by Skin Mechanic

The opening that's covered on my engine is part of the head. Yes, the silver box is the Emission Gas Recycling. It improves emissions by cycling some of the unburnt exhaust gases back thru the carburetor. It's attached to the head between the exhaust valve and manifold. The hose going from the air filter mixes with the exhaust gases and cools them down to prevent overheating the engine.

Ideally the crankcase breather hose should be attached to either a vacuum port on the intake, or air filter box. If your new carb has a vacuum port on the side you can attach the PCV hose to it. If there isn't a way to attach the PCV hose to the intake you'll have to draft it. By mounting the end of the hose perpendicular to the air flow, it creates a draft that draws blow by out of the engine.

[Skin Mechanic]

My stock carb was aimed at the clutch cable, I flipped it forward before getting the Mikuni. It ran poorly in either direction. If my new carb would fit on the taller stock intake I would swap it out just to get it further away from the engine. Hmmmmmm, maybe I can cut the mounting flange off the stock intake and use it as a spacer.

[prismways]

What size jet did you end up going with? Do you think 120 is too big for this size engine? Would I need to adjust any of the smaller jets if I went with this one? thanks

Originally Posted by Skin Mechanic

My stock carb was aimed at the clutch cable, I flipped it forward before getting the Mikuni. It ran poorly in either direction. If my new carb would fit on the taller stock intake I would swap it out just to get it further away from the engine. Hmmmmmm, maybe I can cut the mounting flange off the stock intake and use it as a spacer.

[prismways]

So I changed the main jet from 120 to 100. The air/fuel mixture screw is turned two full rotations from the closed setting, which I believe is close to factory.

So I was able to get my bike to start and run but I am noticing that it only starts with the enricher plunger lifted up (which means it is adding extra fuel). It starts easy but it's revving super high at around 3,000 rpm.

I try to lower the idle by turning the idle screw counter clockwise and it does not lower the idle. But if I turn it clockwise to tighten, I can eventually increase the idle further but that's not what I want.

I lower the enricher plunger to about halfway and the idle slows to between 1500 to 2000.

If I lower the plunger all the way, the bike dies. I know that ideally, the plunger should be closed after the bike warms up and this should be the normal operation state.

At half way, when I apply the throttle, it feels like it is struggling to generate power. It's sluggish and this is without a load on the engine.

I am thinking it might be one of the following causes:
- stuck throttle
- air leak somewhere
- air/fuel mixture screw
- pilot screw (but I haven't messed with this)