DragBikeMike:

Since you are located at Sea Level.....your #55 Pilot Jet might be an acceptable level of "rich:".

For those of us who live at higher elevations - it likely would be overly rich.  On most of the bikes I have worked on a #50 works fine - only on one bike did I feel that the #52.5 ran better.  (The elevations where I live range from 500MSL down at the Ohio River - to 825 MSL at the hilltops, and I have never needed to use a #55 Pilot Jet).

Great comment Dave.  I’m glad you brought up elevation, and also glad you shared your view on pilot jet size.  My neighborhood is 627 feet above sea level.  I do my acceleration tests at 1014 feet above sea level.  My riding is limited to a range of about 5 feet above sea level to 1168 feet above sea level.  You’re correct, I’ve got a pretty good column of atmospheric pressure and can probably tolerate a little more jet than the folks in Denver.

I was curious why you recommend a pilot jet smaller than 52.5.  Then I remembered that the early model carburetors were set up a lot different from the later models.
 
The parts fiche shows that the carbs from 1986 through 1995 came with a #47.5 pilot jet.  Only one pilot air bleed is shown.  It’s piece 12 and is identified as a #70.  The factory service manual lists the pilot air bleeds as a 2mm and a #67.5.  That tells me the early model carbs had a fixed 2mm air bleed (probably just a drilled hole) and a replaceable pilot air bleed (#67.5 or #70).

I have a 2016.  My as-delivered pilot jet was a #52.5, and my pilot air bleeds were #45 & #230 (pieces 12 & 40, both removable jets).  That thing ran about as lean as you could get and still be able to operate.  As delivered, it ran terrible.  It didn’t care if it was at sea level or all the way up on the Pali Lookout 1168 feet above the ocean.  It took forever to warm up to a point where it could be ridden, and even then, it ran terrible.  I can’t imagine putting a smaller pilot jet in that thing.

Note that my air mixture screw remains at 2 turns, exactly where I found it when I drilled out the plug.  My idle starts to drop when I turn the screw in ½ turn.  I think that’s just about right.  There’s almost no afterfire.  I can get a puff of black smoke if I start continuously blipping the throttle (it starts about the fourth or fifth blip).  That’s just the muffler loading up.  Idle is smooth and steady.  Response is excellent.

Do you think it’s possible your experience with the stock carburetor is associated with an early model carb, the one with the different pilot air bleeds?  Do you think I’m overlooking something?  Most comments I’ve seen on the forum report extremely lean as-delivered mixtures, so switching to a smaller pilot jet doesn’t seem logical.  I’m not trying to be a jerk; I just want to make sure I’m not missing something.  This is a good discussion, and it deserves a little more exploration.

In the case of the stock carb, I believe it's important to have the 'air horn' at least the length of the rubber duckie between the carb and airbox to straighten out the air flow.  But it maybe needed to make the 'eyebrow' port work correctly.

Dave:

It sounds like those carburetors you worked on were all pre-1996.  By any chance, did you take any photos?  I think it would be a valuable piece of info to capture and share.  Seems to me, the older versions (pre-1996) need a #50 pilot jet, while the newer versions (post-1996) need a #55 pilot jet.  That would be good info to share.  Since the factory service manual and parts fiche aren’t perfectly in agreement, photos would be the best reference to differentiate between the old & new versions of the carb.  This is the pilot air bleed arrangement for the late model carbs.  Two removable pilot air bleeds, a #45 and a #230.  If anyone has photos of the pilot air bleeds on an older carb, please post so we can all see what it looks like.

Hiko, I'm glad the mod worked good for you.  Sounds like you ended up with a .06" washer (1.52mm).

Can you tell us what year your bike is?  Do you have two removable brass pilot air bleeds under the diaphragm, or only one pilot air bleed?  Can you tell us what size your pilot air bleeds are?  If you have an older carb (pre-1996), can you post pictures of the area under the diaphragm?  Is your slide needle the older style 5C16 with three grooves?  If so, what groove is your e-Clip installed in?

Thanks for the feedback.

Best regards,

Mike

Thanks for sharing Hiko.