Topic: Keihin PD 46c Jets for a '76 CB550E??

[astrorobbie]

Hi, I have Keihin PD 46c carbs, on a '76 CB550E engine and it runs ok on flat ground with no rider on it. But when I get on her and try to move, she has no power and just dies, sometimes with a bit of a backfire. The guy who sold me the bike had 114 mains and 42 slow jets in the carbs. After a little research, the mains appear to be way too large, and I think the slow jets are correct. I am wondering:

1. What is the stock main jet size? It seems from research that it might be #90. Please confirm if you know.
2. Where can I buy these jets? The standard push-in jets seem pretty common and I have seen every other Keihin jet under the sun for sale, but no-one seems to have these screw-ins.
3. What type of adjustment should be made for 4-in-1 exhaust and pods? I'm thinking I should be running around #96 mains.
4. Where did these carbs come from? I don't think they are standard for either the frame or the engine that I have.

Thanks mucho guys (and gals).

[bwaller]

I think those carbs were used on the 77-78 model. You're right, the stock pilot jet is a 42 and the mainjet should be a 90.

I expect that 114 might be slightly large, but more importantly are those carbs clean? Take you time to do a thorough cleaning job including removing the pilot jets, soaking everything in carb cleaner and using lots of compressed air afterwards.

These carbs need to be very clean to work well.

[TwoTired]

1. What is the stock main jet size? It seems from research that it might be #90. Please confirm if you know.

#90.  It's in the carb FAQ.

2. Where can I buy these jets? The standard push-in jets seem pretty common and I have seen every other Keihin jet under the sun for sale, but no-one seems to have these screw-ins.
3. What type of adjustment should be made for 4-in-1 exhaust and pods? I'm thinking I should be running around #96 mains.
4. Where did these carbs come from? I don't think they are standard for either the frame or the engine that I have.

Thanks mucho guys (and gals).

You should read this thread:
http://forums.sohc4.net/index.php?topic=20869.msg254288#msg254288

[astrorobbie]

I have read that thread (http://forums.sohc4.net/index.php?topic=20869.msg254288#msg254288), but am still unsure where I can find these jets. They don't have them at my local shop and the last set I ordered turned out to be the wrong kind. Searching Google for Keihin PD 46c turns up nothing useful, except my own post. SCI has a rebuild kit that appears to be the right one, for a 77-78 550K3, but it comes with the #90 and due to mods, I believe I need to upsize a bit. Not to mention, I don't want to spend $200 on 4 rebuild kits for jets that may or may not work... Where did other folks get these jets? Seems many just get them at their local shops.

The carbs are very clean.

How do I remove the pilot jets? I tried a little bit with needle nose pliers, but didn't want to screw up the brass too much, or possibly crimp the tube. Any tips for how to remove the friction fit jets?

I have not yet checked the position of the needle. Is that likely to cause a NO POWER situation? I can't get ANY power out of the bike. It will idle somewhat ok, then when I roll on the throttle it sputters a little, then revs up well. Sometimes there is a backfire or two when I drop off the throttle. Then when I get on and try to move, there is no power an it dies.

Are the 114s that I have likely to be causing this problem? i.e. is that diffence in size great enough to keep the bike from having any power whatsoever, or should I be looking elsewhere?

Thanks again for any help. I am new to jetting. My other bikes have run fine with just adjustments!

[TwoTired]

I have read that thread (http://forums.sohc4.net/index.php?topic=20869.msg254288#msg254288), but am still unsure where I can find these jets.

You didn't read that Ed got his jets from Dynojet?

How do I remove the pilot jets? I tried a little bit with needle nose pliers, but didn't want to screw up the brass too much, or possibly crimp the tube. Any tips for how to remove the friction fit jets?

Grab them with hefty pliers, maybe with leather pads and yank them out.

I have not yet checked the position of the needle. Is that likely to cause a NO POWER situation?

I really don't know what that means.  Let us know what the spark plug deposits are like might help.

The slide needles dominate the mixture from about 1/8 throttle position to 3/4 position.  But, wasn't this covered int he thread I referenced?  It's a long thread with a bunch of info to glean from it.

Learn to read your spark plugs.
http://www.dansmc.com/Spark_Plugs/Spark_Plugs_catalog.html