I have a 1976 xlh, the Kiehin butterfly carb that came with the bike was pretty ratty. it was missing the choke. I believe this was the original carb, it said HD on the side. I bought another carb very close to the one I had from ebay, this carb is very clean and has all the parts. I think my new carb came from a newer bike because it has double cables.

My real problem is were do I start with jets? My bike has no motifications except a K&N air cleaner. The carb I took off had what I think was a 68 on the slow jet and I could not read the fast jet. With these jets my bike back fired and shot blue flames from the exhaust.Adjusting did not help. The new carb had 52 slow jet and could not read fast jet. The bike started, but would stall after a few seconds.

I went to the dealer and he said 42 slow jet and 165 fast jet was stock. I bought them and installed but have not started bike yet. Does going from a 68 to 42 sound right? Does any body have a idea were to start for these old Keihin butterfly carbs

 

My '83 came with a 52 and a 160 in the stock Keihin carb. Different years came with different jets, but I don't know if it was a difference in the carb designs or just an EPA thing. A 42 soundspretty small to me. You can compensate some with the idle mixture screw if your slow jet size is a little off, but I'd look up the carb part number, find out what year it is, and look up the stock jet sizes for that year carb (which, hopefully, is what the dealer did).

Are you sure the replacement carb you have is clean inside, and the float, accelerator pump, etc. are all working properly and the idle mixture screw is adjusted right? Are you sure the manifold's not leaking air? Lots of things to check.....

 

Sounds like your valves are too tight it ought not backfire like that. Check your timing too. Get yourself a S&S carb and don't worry about it any more.

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I forgot you ought to be able to use the jets out of your old carb. make sure everything is real clean

 

Thanks to everyone for their input. This weekend I will try the 42 slow jet (I think it is to small)and work my way up to 52, or beyond. I will post what works best for me.

 

Pull the spark plugs and inspect them closely. If they are a wettish-black in color, you are running rich. It never hurts to have a few sets of spare plugs on hand while carb tuning. I keep about 15-pairs in varying heat ranges......it sucks not having spares!

 

Hi, Bryon,

My old 76 XLH, long gone, had the original Keihin and jetting. They were jetted much bigger than later Keihins, to do with proper P cams, rose tinted days before EPA regsetc...

Iddle was 1.00 (1mm diameter), main jet was 1.65 (1.65mm). The parts book listed main jets up to 1.80 if you really like your throttle...

Patrick

 

Also adjust valves and for manifold leaks. manifold leaks have driven me crazy