Topic: Synchronizing CR Specials

[kmoll70]

Could someone help me out with the proper procedure for synchronizing CR Specials?

[Jerry Rxman Griffin aka MuthaF'er]

First thing you need to do is install some syncing ports to hook up a sync tool. The CR's do not come equipped as such. The easiest way has been to drill holes into the intake manifold rubbers and install the ports. A few of the guys have done this and documented the process. I don't have that link for you but I'm sure when you do a search you won't have any problem finding it. My CR's should arrive early this coming week so I'll be interested in finding it myself.

[co425]

From what I understand. After you install your vacume ports you pull the carb tops. Undo the lock nut and adjust your slides. That sets the sync. But...as far as I understand these are set at the factory. I have about 50 miles on mine and they run awesome. Just bolted them on and ran. Except for a half throtle bog. I think that will come down to needle posistion though. As a side note make sure that your chokes are all seating properly mine werent and it ran like kaka #$%*y until I figured that out. The choke lever should be all the way down.

Any tips on that half throttle bog would be appreciated. I cannot remember if I need to go up to lean it or down to richen. Thanks.

[MRieck]

After removing the tops....the screw is the lock down...the nut adjusts the slide up and down and controls vacuum.

[Doctor_D]

The clip goes down to raise the needle, which richens the half-throttle mixture, and vice versa.

[co425]

Now is a mid throttle bog lean or rich?? Been a while since I started with a fresh carb.

[MRieck]

Now is a mid throttle bog lean or rich?? Been a while since I started with a fresh carb.

 Rich 90% of the time. You also know with no accelerator pump you can't grab a handful of throttle. Those neefles are usually set to high when you receive them. They are not synched from Sudco. Synching carbs is an absolute must do it especially if you are establishing a baseline.

[co425]

Cool. Thanks for the info. May the morning project begin.

[co425]

Well took the needles out. They were set at the second to top notch. Moved them to the top notch hope that works out.

[co425]

Tried leaner no dice. Went one slot down from the start. I'll try that in a bit. Very smooth in the lower end but with slow throttle application it bogs more in the top slot.

[Doctor_D]

Sorry to hear you're chasing your tail. Here's a refresher on the carb circuits at play for various throttle positions:

Tip-in is controlled by slide cutaway (0-1/8th throttle).
1/8th-1/3rd is controlled by the needle jet.
1/3rd to 2/3rds is controlled by the needle taper, which can come on earlier or later depending on the needle height
2/3rd to wide open throttle is largely on the main jet.

The circuits overlap and influence each other to various degrees.

Hope that helps.

[co425]

Got it figured. Raising the needle got rid of the bog.

[kos]

yep... lean in the middle.

KOS

[kos]

Now is a mid throttle bog lean or rich?? Been a while since I started with a fresh carb.

 Rich 90% of the time. You also know with no accelerator pump you can't grab a handful of throttle. Those neefles are usually set to high when you receive them. They are not synched from Sudco. Synching carbs is an absolute must do it especially if you are establishing a baseline.

Mike is quite right about getting started with a baseline....

You would be surprised at how close on new sets of carbs you can get them sync'd... by using your fingers against the slides with velocity stacks out of the way, not for beginners, but I was taught this method when I attend the first Honda CB750 KO school way back in time. they did not have the sync gauges from Japan yet, so we had to do something. And, the KO's with 4 cables always needed to be reset. What a mess.


 And just think...everyone wants a KO?

KOS

[kmoll70]

Is there a particular sequence that should be followed?

i.e. match the right two together, then match the left two to the right two?

[co425]

Set your idle then pick one. Sync all to that one cylinder then reset idle.

[Jerry Rxman Griffin aka MuthaF'er]

Co425,

Were you doing plug chops to read your plugs or just flying from the seat of your pants? Serious question, I have a set of CR31's on the way and hope to do it properly.

[co425]

Plugs. Gona pull them tomorow. I just did a nice long ride this afternoon. Fresh top end and carbs. Pretty sure the jetting is spot on. She runs like a top now that the needle is in the right spot.