I recently took apart my carburetor to check out the condition after being stored for a while. But I didn't expect to find was the excessive wear on the carb slider. It's is worn through the Teflon coating on the front, but it's actually shaving aluminum off on the bottom of the back side. This type of wear is actually expected as the air flowing through the carb pushes the slide back into the body and can rub on sharp edges of the machining. It's a common issue on keihin carbs and can be mitigated by gently sanding the sharp edges of the carb body.
My question is, is this slider shot, and where can I find a replacement? The bike has maybe 35,000 mi on it and the rubber diaphragm is in really great shape. I have had a cone air filter on it for the past 10,000 or so.
The slider seems to move without binding. I still plan on filing and sanding the sharp edge inside the carb body. Would there be any issue with removing the rubber nub on the diaphragm that aligns this slider and rotating it 180° so that it doesn't continue to wear the same spot?

Photo 3

Wow!  That is a heck of a lot of slide wear.  Thanks for the photos.  Never seen one that bad.  The lower edge is really worn away.  How did it run?

A new OEM slide is $202 bucks.  There's an item I see on eBay for about $78 bucks but I have no idea if it is a quality component.  It's eBay item number 394211993714. This link should get you to it.  If not, then use the search function with the item number.

https://www.ebay.com/itm/394211993714?_trkparms=amclksrc%3DITM%26aid%3D777008...

Please let us know what you find out and how you fix the thing.

Good luck.

That's what my slide looked like when I replaced it.  Mine would stick and it created a lean condition under load.  I ordered a replacement from Partzilla.

Hey Groupus, that main jet size is unusual.  I don't think it is "153.8".  Can you double check and let us know what the actual size is.

Could you also check the size of the two orifices in the bottom of your worn out slide.  Those two holes control the velocity of the slide movement.  As you mentioned, CV slides wear out.  The CV carbs are also known for accelerated wear on the slide needles and needle jets.  The slide movement is a result of the vacuum created by the velocity of the air moving through the carb.  That air movement stops each time the intake valve closes, and starts each time the intake valve opens. So, the slide is constantly bouncing up and down as the air flows through the venturi.  Even at steady state throttle position, the slide is bouncing up & down (rapidly).  For instance, steady cruising at 4000 rpm results in the slide bouncing up & down 2000 times per minute.

To improve throttle response, some folks enlarge the orifices in the slide.   If the orifices are larger, the slide responds faster to changes in air flow through the venturi.  Problem with that is the velocity of those up & down pulsing movements also increases.  That probably increases wear.

It would be beneficial to all of us if we knew more about your slide orifices.  On a stock slide, the two orifice holes are right about .096".  A #40 drill bit just fits into the holes.  If you don't have a #40 drill bit, you can use a 3/32" and a 7/64" as "go/no go" gages. If the holes are close, the 3/32" will fit but the 7/64" won't fit.

Can you check those orifice holes and let us know what you find?  These are the holes in question.  By the way, leaving one of those screws out will also speed up the slide movement.  Are both screws in place?

I don't think I would spend any time or money on this carb....the slide and carb body are worn/damaged.  A new slide the worn carb will become worn quickly....the slide will not have a good fit in the worn carb.

I believe it is time for a replacement.  Find a good used carb or install a new aftermarket carb.

And make sure you have a filter that works properly and filters out abrasive crap.

I just don't see how a good slide is going to last in that worn/scratched slide bore.  (Open the photo link and look at the bore.)

If you watch eBay for a few weeks you can find decent used carbs for less than $300 that are in much better shape than this worn carb/slide....however you need to shop a bit as there are a lot of too expensive and trashy carbs for sale.  With a bit of cleaning and some parts swaps you could have a good working stock carb for less than $500.
https://www.ebay.com/itm/404127682204?hash=item5e17e30e9c:g:1DwAAOSwQTZj0tmW&...

As far as the main jet, here's a picture. Really looks like a 153.8. that's an odd size indeed, but I was looking for something between stock and a 155. I also removed the white spacer and replaced it with 2 washers. Pilot jet is stock and air screw is tuned to 1.5 turns out. I've done lots of tuning to this bike. It was my first bike and has lived many iterations over the past 16 years.