Cable choke conversion for Nibbi carburetor

[superjocko]

Among my several projects is converting the operation of the cold enrichment circuit on my Nibbi carb from the detent style knob to cable operation. While having the pilot air screw on the right side of the carburetor is great, I found the placement of the enrichment knob on the left side of the carburetor inconvenient to operate, especially with a gloved hand.

After having measured the dimensions of the Nibbi enrichment plunger, I ordered up a cable actuated enrichment plunger kit on temu under the description of, "Upgrade Carburetor Performance Motorcycle Keihin KOSO Carburetor Wire Pull Damper Switch For PWK28 30 32 34 PE30 PE28 Carburetor". I'm happy to report that it fits perfectly. Edit: While it seemed to fit perfectly, it doesn't. Stay tuned for an update once I get it sorted. That said, the original choke cable from my TT250 won't work with this set up in its original configuration. It may be possible to make the original cable work, but in my opinion it would be more trouble than it's worth. Instead, I bought a Venhill throttle cable kit from Amazon that will work nicely for this installation.

Here are a few pictures to show the parts in the kit as compared to the original plunger and the part number of the cable kit. I'll post up the finished version of everything when I get it all wrapped up.

[bigdano711]

Please post links to all the parts. Very interested in this. What a pain in the ass to get to the choke on these carbs!

[superjocko]

*

Link removed because the part I thought fit fine is machined ever so slightly differently on its sealing end and doesn't work.

Venhill throttle cable kit

You may have to Shift/click those links for them to work.

The choke control that I'm using is the stock one that came on my TT250. I couldn't readily find it on CSC's website.

I hope those help.

[superjocko]

Hold off on that choke plunger kit. While it initially seemed that it would work fine, some very minor subtleties in the machining on the sealing end of the plunger cause it to bottom out in the bore before the end seals. I'm currently looking for a solution. I'll update accordingly. I'm going to remove the link from my previous post so no one goes and wastes $4.98.

[superjocko]

Okay, I'm bringing this thread back up to let anyone interested know that I got the cable choke conversion on my Nibbi PE28FL to work beautifully! The key was getting the right choke plunger.

While the kit that I bought previously had the right attachments for a cable conversion (except the cable - I made my own from a Venhill throttle cable kit), what it lacked was a plunger that is compatible with the Nibbi PE carburetor. The difference in the plungers is very minor, but enough to make it not work unless you have the right one.

The machining on the end of plunger in the cable conversion kit that I bought, which was indicated as fitting Keihin PWK and PE carburetors, may work in a Keihin, but doesn't in a Nibbi. At least the one I got didn't. It would not go down the enrichment circuit plunger bore far enough to seat on the orifice at the bottom of the bore. That meant it would be like having the choke partially on all the time. I measured and puzzled on this for some time before I concluded that the plunger just wouldn't work. This was despite its outside diameter being correct. That left only the difference on the end of the plunger to cause the problem.

I began looking for a plunger with the same style end as the one on the knob-style plunger assembly that came in my Nibbi carb. After much searching across various sources I finally found Sudco Keihin part number 021-512 which looked like a match as far as the relieved lip around the periphery of the plunger end. I ordered one and it arrived yesterday afternoon. I spent a chunk of last night and earlier today verifying its fitment and that it would seal properly where the previous plunger had not. It worked like a charm.

I took the opportunity during all this tinkering and problem-solving to fabricate what I feel is a lot more bulletproof cable retention system for the cable's attachment to the plunger, so that little related side project ate up some time. I think the results were worth it though.

Here is the link to the conversion kit that has the parts you'll need (except the right plunger) to attach a cable: Upgrade Carburetor Performance Motorcycle Keihin KOSO Carburetor Wire Pull Damper Switch For PWK28 30 32 34 PE30 PE28 Carburetor

Here is the link to the right plunger: Keihin PWK Carburetor Choke Plunger OE Part P/N 021-512

Here's the link to the Venhill throttle cable kit (again): U01-4-101-BK Universal Motorcycle Throttle Cable Kit - 5mm OD

And here's the link to some cable lining that I use when running a 5mm cable inside angled cable adapters to ensure the cable moves freely and will for the foreseeable future: Pack of 3 Meters, Protective Sleeve Slick Tube Liner Cable Suitable for Bike Gear or Brake Inner Cable or Internal Routing for Nokon Systems I've used this stuff for all kinds of different cable that I've made up and it holds up great. I just use a little silicone grease on the cable where it passes through the sleeve.

I used the original choke cable control that came on my bike. In case your bike didn't originally have a cable controlled choke, I'm pretty confident a hot-start control lever would work. The main difference would be the hot-start lever may not have the friction mechanism to keep the choke on. I don't think that would be a huge issue as you usually turn the choke off very shorty after starting a cold bike anyway. That said, I do like the fact that the friction mechanism in my OE choke control does hold the choke wherever I put it.

In case you want a link to a hot-start control lever, this one looks pretty universal: Motorcycle Hot Start Lever Rotating Bar Clamp Compatible To YZ250F YZ WR TTR RMZ RMZ250 RM RML KX100 KX KLX CR CRF XR Dirt Bike

The rest of the stuff that I used, like the plastic sleeve and flattened and expanded split washer that I used as part of the cable end retaining parts that I installed, was just stuff I had in my stash of handy parts.

See the attached pictures for the dimensions on the cable and a look at the various parts.

Oh, one other thing! Since I added that plastic sleeve to better retain the cable (and don't worry, the plastic I used is impervious to damage by fuel and heat (at least as much heat as a carburetor is going to see) I did have to slightly enlarge the ID of the cable adapter fitting that threads into the carb. I just used a drill bit and enlarged it to 8mm to a depth of about 6mm. A little deburring and polishing later, it accommodated the plastic sleeve just fine.

Anyhow, that's probably more trouble than a lot of people might want go to but when I set my mind to a project I like to try to see it through and come out with a quality result. I hope this information helps anyone that may be looking into this type of conversion and would like it to look and function like it came that way from the factory.

[superjocko]

Just the remining pictures. Each is worth a thousand words, or so they say.