TOPIC:

(Don't do this unless your Carb is completely gas free mine had been off the bike for several months) I used a 1/4 fuel line. After wedging it into the plug hole i cut it, burned it with a lighter and smushed it together wile it was still hot.

Just a thought, please be safe!

You answered a 4year old post

HBKwaka wrote: You answered a 4year old post

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i know this is an old post but what exactly do these plugs do? I just cleaned & replaced some parts in my 83 gpz 550's carbs & mine has these plugs. they fit loosly in there respective hole & it concerned me, i wasnt sure if they needed to fit snug ie new o-rings which my kits didnt supply

I think the way the pilot passages are drilled, the plugs are needed for the proper uptake of fuel.

A metric nitrile or viton o-ring kit might have a size that will work. Kits are available at HarborFreight or eebbaayy or etc. If the caps still won't fit right & a good substitute cap couldn't be found, I'd be tempted to glue them in place w Seal-All or something --- not sure if that's a bad idea or not & wouldn't know until I tried it.

Side note: the caps seem like they would be a good candidate for 3D printing.

Where carb design has just the plug or plug-plus-o'ring, the pilot jet is supposed to receive gasoline only from the small passageway.

The plug or plug-plus-o'ring is supposed to prevent gasoline from entering the pilot circuit through lower end of the pilot jet.
















Good Fortune!

I picked up some nice pilot jet plugs from Mike'sXS. I wouldn't know if these were a stock Yama part.
Rubber pilot jet Passage Plug for Mikuni BS34 CV carbs:
www.mikesxs.net/product/48-5002.html

I know this is an old thread, but I just bought an '83 KZ440-D5 and have been rebuilding the carbs. Yesterday, I destroyed not just one, but BOTH of these plastic plugs. I'm not inclined to use the rubber plug fix, or to thread the hole and put in a bolt. Instead, I'm going to look into turning down some replacement aluminum plugs to replace the plastic ones, with the same geometry.

Does anyone have one of these plugs out of the bike and handy, and could they measure the length of the thing? I have the bottom half of one and can get the important features from down there, but the length is the most important part, since it's constrained by the tang on the float bowl.

Hopefully will have pics to follow soon.

Okay folks, an update for you. Today I was able to successfully take the measurements off of what was left of my broken plastic plugs, the critical features of the carb body itself, and the geometry from the photos of the plastic part, and then turn down some replacement plugs out of aluminum on a jeweler's lathe. The result - a fantastic replacement that seems like a perfect fit, and is much more durable than the OEM parts. Attached is a photo of the pair.



The plugs are much easier to get in there now, and I think they're going to hold up great. They take advantage of the tang on the float bowl, so I know they're not going to fall out. If anybody is interested in a pair / set of these, let me know.

Very classy
really nice job

I'd be interested in a set of four, depending on cost of course.... Pm me?

DoctorRoboto scores!
I ordered two of the plugs from DrRoboto and put them in today. They appear to perfectly match the dimensions of the plastic ones included the o-rings and went in easily, yet seated firmly. Although I haven't yet ridden any sort of distance with them, for the short ride I took around the block the bike was running well!