Really struggling with my 1964 CB72

Paul Strassmaier · Post by **Paul Strassmaier** » Thu Apr 30, 2009 3:43 pm

I restored the bike in 2003 and it ran very nice until you hit higher rpm's and then it would shoot black smoke (seemed rich). (This is the square bowl type with the extra jets). I've pulled it apart and have been able to replace all of the jets except I don't have new needle jets. Does anyone have them? Any ideas? Thanks, Paul

rbaselt · Post by **rbaselt** » Thu Apr 30, 2009 6:42 pm

You could try emailing Sirius to see if the part you need can be obtained separately or as a component of one of their kits. It sounds like your main jet is too large, or you need to lower the needle from its current position. Could also try hotter plugs. I'm assuming timing is OK and the ignition system is functioning well. --Randall

Paul Strassmaier · Post by **Paul Strassmaier** » Fri May 01, 2009 10:28 am

Thanks, yes, I've tried moving the needle, haven't tried hotter plugs. The timing is right on. All of the other jets are new, so I'm thinking the needlejust isn't matched right to the seat.

rbaselt · Post by **rbaselt** » Fri May 01, 2009 10:32 am

What main jet and needle are in there now? They should both have numbers on them. --Randall

Paul Strassmaier · Post by **Paul Strassmaier** » Tue May 05, 2009 11:37 pm

I looked and couldn't find a number. I think they've been replaced. In looking through my other needles for CL72, I did notice some wider and some narrower. Also, some are lighter and an aluminum color. I checked the parts book and it shows just a 16151-268-004. I do have the 35 slow, 100 main, and 90's on the super jets.

rbaselt · Post by **rbaselt** » Wed May 06, 2009 10:10 am

You could try going to 105 or 110 main jets to see if that helps. Alternatively, you could try running without air filters and muffler baffles. Have you done dynamic timing with a strobe light to make sure you are getting proper ignition advance as you increase revs? --Randall

LOUD MOUSE · Post by **LOUD MOUSE** » Wed May 06, 2009 10:15 am

Are ya working with the 22mm power jet carbs?
I now see ya are and the power jets are (inside under screw 160 and external 90) the Power Jet carbs I have use 130 and 35 inside jets and I suspect your needle is not correct as you say no numbers. Early needles are aluminum and similar to the difference between the CB/CL77 needles will be a little shorter and thicker than the CL77 needles and not the same as the CL72. . ............lm

Paul Strassmaier wrote:I looked and couldn't find a number. I think they've been replaced. In looking through my other needles for CL72, I did notice some wider and some narrower. Also, some are lighter and an aluminum color. I checked the parts book and it shows just a 16151-268-004. I do have the 35 slow, 100 main, and 90's on the super jets.