Keihin PWK 30 Carb

[Megadan]

So the adventure continues. The good news is, both intakes will technically work.

The Nibbi has one caveat to it though, it will not work with a power jet carburetor. The little protrusion from the bowl hits the frame just barely.



The other CQR intake does clear the frame and does technically work. There are a couple of downsides to this intake though.

1. It positions the carb further back, and as a result the throttle cable does not have a lot of room under the tank to work with. It functions fine, but does contact the tank. I stuck a bit of loop end velcro on my tank to reduce the potential for damage from rubbing.

2. Since it is so far back, if the idle speed and mixture on on the left side of the carb (as on the bike) then they cannot be adjusted from that side. The frame is in the way. The idle speed can be adjusted with your fingers as long as the side panel is off, but the idle mixture requires removing the carb from the socket to be able to adjust it.



If the fuel inlet, idle mixture, and idle speed were on opposite sides, it would be damn near perfect minus the throttle cable issue.

I haven't tested the main or needle jetting positions yet, but I was toying with the idle mixture. I started with a 40 just to be safe. Waaaaaaaay too rich. Stepped down to a 38, and at 2 1/2 turns out on the air screw it still surges a tad but I got it to idle decently. I am going to drop down to a 35 next, and I have a feeling that is going to be the sweet spot.

It sure would be nice to find an intake that just worked. This is kind of a frustrating experience. I want to be able to run this carburetor without having to make so many compromises.

[JerryHawk250]

This is where someone with a 3D printer would come in handy to make a custom intake like the Nibbi but at the right angle.

[Megadan]

Originally Posted by JerryHawk250

This is where someone with a 3D printer would come in handy to make a custom intake like the Nibbi but at the right angle.

I would take anything at this point lol. The intake I am now using works just fine. If everything was on the opposite side it would be perfect.

I am considering modifying the Nibbi intake a bit by cutting it down. I would lose the groove for the boot to sit in, but it should work fine without it. I could then make it as short as I want, and solve most of my problems.

If all else fails I am going to run a 32mm carb with a CRF intake.

[OneLeggedRider]

This is what I have on my Scrambler, I don't suppose you can find anything like it for the CG.

[Megadan]

Originally Posted by OneLeggedRider

This is what I have on my Scrambler, I don't suppose you can find anything like it for the CG.

I have used a UFO in the past. AFAIK they only produce them for the Mikuni round slide carburetors.

[Weldangrind]

Originally Posted by Megadan

If everything was on the opposite side it would be perfect.

The standard China bike from 10 years ago (that this forum was founded on) stuck the carb out the left side. Jerry noticed from one of my old pics that it's an unusual setup, compared to the Hawk or the XR200. Maybe you'd care to try an intake tube from a GY series bike, which would move your carb to the left side. It would be a cheap experiment.

[Megadan]

Originally Posted by Weldangrind

The standard China bike from 10 years ago (that this forum was founded on) stuck the carb out the left side. Jerry noticed from one of my old pics that it's an unusual setup, compared to the Hawk or the XR200. Maybe you'd care to try an intake tube from a GY series bike, which would move your carb to the left side. It would be a cheap experiment.

Minus having to relocate the battery at least.

[Mychel]

I have issues with my hawk 250 , I live in IL.
Mods are Exhaust system.
Mikuni carb jetted to a 115 Main, needle is at middle position. I have. 17t front 40t rear I drove it wide open at in 4th gear it stopped pulling at 50mph. In 5th gear the bike had no pull at all . I came to a stop and my engine would not idle. I rev it up engine sounded like a miss fire. I got gas let it cool down and it ran a little better.
I need to know who else has 17 40 gearing and your top speed?
I need to check my plug, and any ideas on my jetting?
Thank you.

[JerryHawk250]

Originally Posted by Mychel

I have issues with my hawk 250 , I live in IL.
Mods are Exhaust system.
Mikuni carb jetted to a 115 Main, needle is at middle position. I have. 17t front 40t rear I drove it wide open at in 4th gear it stopped pulling at 50mph. In 5th gear the bike had no pull at all . I came to a stop and my engine would not idle. I rev it up engine sounded like a miss fire. I got gas let it cool down and it ran a little better.
I need to know who else has 17 40 gearing and your top speed?
I need to check my plug, and any ideas on my jetting?
Thank you.

Have you adjusted the valves yet? Valve come set too tight from the factory. Also if you haven't already, get rid of the stock Torch plug and get a good NGK plug. Make sure you're not running on half choke. I run 17/40 gears and have done 75 mph+

[Megadan]

Originally Posted by Mychel

I have issues with my hawk 250 , I live in IL.
Mods are Exhaust system.
Mikuni carb jetted to a 115 Main, needle is at middle position. I have. 17t front 40t rear I drove it wide open at in 4th gear it stopped pulling at 50mph. In 5th gear the bike had no pull at all . I came to a stop and my engine would not idle. I rev it up engine sounded like a miss fire. I got gas let it cool down and it ran a little better.
I need to know who else has 17 40 gearing and your top speed?
I need to check my plug, and any ideas on my jetting?
Thank you.

First off, as Jerry mentioned, have you set the valve lash?
Secondly, how many miles on the bike? If it has under 1k miles, it isn't going to have a ton of top end yet, especially if you are around or less than 500.

As far as jetting, what size pilot jet do you have? I always recommend a good starting point for the Mikuni clones with an intake and exhaust with a 25 pilot, needle at the 4th notch, and 115 main. With full mods even the 25 can prove to be a touch lean so a 27.5 works better.

From the symptoms you describe, it sounds to me like you started to overheat the cylinder. Fueling will play a big role in this, and if you are at a low enough altitude you may need to step up the main jet size. I would begin with the previously mentioned jet settings though. Air cooled motors like fuel when pushed hard, it helps control cylinder temps.

A side suggestion - if you are going to push this motor that hard with tall gearing it would be a good idea to invest in an oil cooler. It makes a pretty good difference.

Originally Posted by JerryHawk250

I run 17/40 gears and have done 75 mph+

bear in mind we also have ported heads and he doesn't. Anything past 70 is a tall order for a stock Hawk with just an exhaust and mikuni clone.