Topic: Carb Issue, makes NO sense.

[fletcha221]

I was planning on backing the IMS down to 1 and see what happens. I'm guessing it's still going to be way fat.

[fletcha221]

Ok, got home and screwed the mixture screw one turn out from closed. Same symptoms, even MORE black smoke than before........ Makes no sense at all.

Regardless, I looked at the carbs, the serial number is PD 428APG7

The last digit might be a "p" or a "7" or something in Japanese? What the heck bike did these come off??

[fletcha221]

http://www.hondachopper.com/garage/carb_specs/carb_specs.html

Well, according to this link, the carbs came off a 78 750k. Also, stock mains are 110's. However, with the pods and exhaust, the 120's should me ok....

[scottly]

Have you checked the fuel level in the float bowls with the clear tube method? It's REALLY easy with PD carbs; all you have to do is fit clear tubing to the drain spigots on the bottom of the bowls, hold the tubing next to the carb where the bowl meets the body, and open the drain screw. BTW, IMS screws shouldn't have a great enough affect to cause black smoke, at least not lots of it.

[crazypj]

Hey PJ, there is only one screw on the carb, sooooooo, I'm not sure what you are talking about.

 The position of the screw will determine if it's air or fuel
 I've found all Kei-Hin carbs get more critical of exhaust length when you fit 'pods'

[flybox1]

Hey PJ, there is only one screw on the carb, sooooooo, I'm not sure what you are talking about.

 The position of the screw will determine if it's air or fuel
 I've found all Kei-Hin carbs get more critical of exhaust length when you fit 'pods'

for his PD carbs the screw is on the engine side, so clockwise leans the circuit.

[lucky]

You cannot run pods and a performance exhaust and NOT change the setting of the slide needles.
It will never run right.

It probably has the non adjustable needles.
#42 slow jets will be right unless the baffle has a
lot of back pressure like those fiberglass stuffed things.

I would use ONE .020 thousandths shim on top of the pocket in the bottom of the slide.
That pocket is .012 thousands deep so the slide will get raise .032 thousandths.
About one clip position if it had the adjustable clip on the needle.
My advice is try to get a set of 1976 slide needles with clips and make your life easier.

The advice to go with #120 mains differs from Brewsky but remember he has 4 one inch diameter holes drilled in his stock airbox with his set up.  He mentions that  on his data chart. 1.5 turns on the mixture screw sounds right to me too.

One more thing. Only use the "clear tube method" to check your float levels AFTER...AFTER....AFTER you have set them my measuring like the workshop manual shows you.
If the float needles are old or you have tried to resurrect them by polishing them with steel wool or tooth paste all bets are off.

[brewsky]

OK................SO I'm the idiot.

I got to thinking that when I got the carbs, the slow jets were missing. I remembered I ordered them from Sirius Consolidated. I went back and checked what I ordered. Guess who picked the #42's instead of the #35 by accident.

No wonder the goddamed thing won't idle correctly.

SO, Off comes the carbs.

D'oh.

So, a really rich condition CAN cause the bike to bog under load at higher RPM? I've had bikes run rich and not get much out of the top end, but never bog the way this does.

Just to add to the confusion, note that the Sirius push in slow jet sizes don't seem to correspond to the Keihin sizes. The Sirius jets flow more than a corresponding sized Keihin. (at least the ones I tested did) see here:
http://forums.sohc4.net/index.php?topic=112370.0

[fletcha221]

Hey guys, thank you for all the good advice! I think I will start from a baseline and go from there. I'll put the #35's on, and start with 1 turn out from seated. I'm OK with it running a little rich, but not to the point it is now. She's a real dog. The bike is being sold to a friend of mine, who will likely beat the piss out of it. SO, running a little on the rich side might give the motor a shot of not exploding within the first year. If she still runs super rich, I'll work with the shims.

BTW, why on the PD's did they not make the needles adjustable? Seems silly.

[mrrch]

They were adjustable the year before.

[crazypj]

BTW, why on the PD's did they not make the needles adjustable? Seems silly.

EPA

[fletcha221]

Damn EPA.

Another quick question:

Are the cams different from a K5 to K8?

[mrrch]

Cam changed in 77, PN#14101-392-000. I don't recall what the exact difference is but it was used in the 76 F model as well.

[fletcha221]

Well, I wonder what the outcome will be with this bike. 75 motor with the old cam, and the newer carbs designed to run was the new cam? It's likely negligible....

[flybox1]

yeah, my PD carbs run my stock K1 motor just fine