Topic: 1974 cb550 Keihin 27mm Carb- need bigger pilot jets!

[badsheep]

So I know what size pilot/slow jets I need but I can't seem to find them anywhere.  The stock are #38 and I need to upgrade to #42's.  I have been searching all over for these jets but only finding #38's.  Does anyone have them, know where to find them, or know how to drill them out. What size bit would I use?

Thanks

[bwaller]

First I'm curious about the 27mm carbs, are these stock 550 carbs? If so they're 22mm...but no bother.

I enlarged the #42 pilot jets (PD46 carbs) to 46 using a tapered jet reamer. First double checked orifice size with gauge pins, then used the reamer, removing material from both ends of the jet. It's trial & error removing some material then checking the size, etc.

I can't say this is better than drilling, this is my first experience, but it did the job.

[badsheep]

Well that is what it measured- if any thing they are 28's.  where do you get jet reams then?

[HondaMan]

Well that is what it measured- if any thing they are 28's.  where do you get jet reams then?

Umm...28s on a 550? Is it a big bore kit, or something? Carbs that big on that little bore, with the teaspoon-sized intake valves, will be mighty tough to tune...just my 2 cents, there.

You can get a set of tiny drill bits from MSC for around $10. They come in a tiny drill index, just like their bigger brothers.

[mlinder]

Where did you measure them at, sheep?

[TwoTired]

The stock carbs are 22mm at the venturi.  At the exit bore they are about 27mm.

#38 is the standard idle jet for 550's.  They are #40 for the 500.

Hard to imagine what mods were done that it requires #42 pilots.

http://www.motorcyclecarbs.com/Keihin_Pilot_Jets_C72.cfm?UserID=2208070&jsessionid=ee309515172c225d7a5c


Cheers,

[badsheep]

I think I found them!  Thanks for all the help and thanks to the person who posted the link!  ONE step closer......

Oh and the 27mm was not the correct measurement... it was 22- I measured the wrong part

[SteveD CB500F]

You still haven't told us why you need #42 pilots sheep - what is non-standard about the bike?

[badsheep]

Well the air box was screwed when I bought the bike and new/used we more than I wanted to pay. So I went with pods but once the filter oil dried out after a few weeks of riding the bike wouldn't run without the choke being on.  I checked the carbs (which had recently been professionally rebuilt) to see if there were any clogs but there was none.  I had noticed the midrange lag and had replaced the mains.  I figured since I was at it I should up the pilots as well.  I realize this is not what everyone would do but it is what I wanted to do.  But I have not found any larger pilots so I guess I'm going to put the carbs back on soon and see what the increased mains do.  Perhaps the problem will have already been fixed!