Topic: For those running CR carbs

[greenjeans]

Put a new-style set of the CR carbs on my CB750 I am finishing up.   A couple of questions:

   1.  As it currently sits, the carbs are just held in place by the insulators.   Are you guys running anything additional to hold them in place ?

   2.  Hoping to find a baseline for jetting and needle position.   I am planning on taking it to a dyno to dial things in.   Would just like to not have to buy a million jets.

Current configuration:  750 bored to 836.  Stock 1969 cam.  Stock valve sizes, new serti valve job, springs, guides and seals.   Exhaust is one of MotoGP Werks 4 into 1 stainless yoshi copies.
It has a small internal baffle.     Ideally, I hope to get 2 set-ups for it.   1, running just the velocity stacks, and the other for running with K&N filters.   Any suggestions appreciated.   I bought the carbs lightly  used.   Has a 115 main jet and the needle was all the way up (moved to the middle position).    Plan on firing it up this weekend.

[turboguzzi]

rig something up to just hold their weight at the unsuspended end , say a zip tie from the top frame tube to the top carb spacing spar
a 120 main sounds more like it, but give it a try with 115. if it stumbles at high revs, go bigger

[GV1390]

I run CR26's on my CB550 and they're held in place just by the isolators. No problem what's so ever thus far.

[Haybus]

The nice thing about the modern Keihin CR carbs is how easy they are to adjust while sitting on the dyno. If you don't already have other mains and needles, ask the place with the dyno if they have stuff to try out (probably most dealers have a decent selection) before you show up. I had spare mains, needles and different stacks when I headed to the dyno. I hold mine in only with the boots and nice worm drive band clamps. They aren't easy to get on or off so I can't imagine them popping off inadvertently while in motion.

Alan

[MRieck]

rig something up to just hold their weight at the unsuspended end , say a zip tie from the top frame tube to the top carb spacing spar
a 120 main sounds more like it, but give it a try with 115. if it stumbles at high revs, go bigger

Works in both directions. To large a main jet will cause stumbling. You can tell if it is to rich by backing off the throttle. If it picks up again there is to much fuel.

[MRieck]

The nice thing about the modern Keihin CR carbs is how easy they are to adjust while sitting on the dyno. If you don't already have other mains and needles, ask the place with the dyno if they have stuff to try out (probably most dealers have a decent selection) before you show up. I had spare mains, needles and different stacks when I headed to the dyno. I hold mine in only with the boots and nice worm drive band clamps. They aren't easy to get on or off so I can't imagine them popping off inadvertently while in motion.

Alan

What turbo guzzi said about the zip tie is the solution. I did it for many, many years and currently do it with RS-34's

[greenjeans]

always the simplest solutions...   I'm gonna thread some barbs in the insulators to vacuum synch them.   This is my first set of CRs - I love that you can get to the needles and jets very easily with the carbs on the bike.

Anybody know a dyno guy friendly with old CBs in the DFW (Texas) area?

[MRieck]

always the simplest solutions...  I'm gonna thread some barbs in the insulators to vacuum synch them.   This is my first set of CRs - I love that you can get to the needles and jets very easily with the carbs on the bike.

Anybody know a dyno guy friendly with old CBs in the DFW (Texas) area?

I did that ( and shared it) about 25 years ago for the first and many times after that. 

[turboguzzi]

would give a ring to keith martin at RPM cycles, they are mainly triumph guys but did a lot of LSR bikes, from my visit there I seem to recall a dyno. they are into vintage stuff so might cooperate also on non brit bikes