Author Topic: Keihin CR carbs and your starting procedure (Read 10475 times)

brandEn · « **on:** June 05, 2011, 07:30:31 PM »

Just trying to find what others with CR carbs are doing to get their bikes started (before its warmed up). I have been messing around trying to find what my bike likes to get her going. So far it likes just a tiny bit of choke, crank it over a couple times and then just a small amount of throttle. Once it gets warmed up it starts no problem with a quick push of the starter button. Whats your procedure?

Rod · « **Reply #1 on:** June 06, 2011, 02:38:55 AM »

A squirt of petrol from a hand spray down each bell mouth, and the throttle just cracked open (so probably just 3 or 4ml of lift on the slides).

MRieck · « **Reply #2 on:** June 06, 2011, 04:38:11 AM »

I do not like the CR cold start circuit at all. The plunger sealing surface gets crap on it which eventually causes seating problems and weird running problems. As David Hiller can attest the starter jets are to large too.

Jim F · « **Reply #3 on:** June 06, 2011, 06:14:09 AM »

I just push the button and it fires with no choke
but I am a little rich on the bottom end.

I would like to add that if I do use the choke there is no way its going to crank
just too much fuel

brandEn · « **Reply #4 on:** June 06, 2011, 08:04:31 AM »

I have noticed the choke or starting circuit on these could use some redesign or modification. I have tried to give it full choke and no way will it start.

lordmoonpie · « **Reply #5 on:** June 06, 2011, 09:34:07 AM »

LOL! You guys don't know when you've got it easy - starting on new style Keihin CRs is a breeze compared to old style CRs with ticklers....

kos · « **Reply #6 on:** June 07, 2011, 12:55:18 PM »

Agreed, those old ticklers had you pushing them down... even after bike was fully warmed and they always allowed petrol to spill on top of engine cases, that is how I got CR Specials allowed in AHRMA, just for safety's sake alone!

Like Mike has said, the enriching circuit is too big on those, so all we did is choke and as soon as it fired...take choke off.
Mark@ M3

nokrome · « **Reply #7 on:** June 07, 2011, 07:44:37 PM »

full choke
usually starts on third kick (cold)
a bit of a PITA trying to start it if its already hot though

lordmoonpie · « **Reply #8 on:** June 08, 2011, 01:14:57 AM »

Quote from: kos on June 07, 2011, 12:55:18 PM

Agreed, those old ticklers had you pushing them down... even after bike was fully warmed and they always allowed petrol to spill on top of engine cases, that is how I got CR Specials allowed in AHRMA, just for safety's sake alone!
Mark@ M3

Great common sense Mark - I wish the CRMC here in the UK would follow suit...

burmashave · « **Reply #9 on:** June 08, 2011, 10:41:20 AM »

Full choke on a cold start, but I try to turn it down to about half-choke once it starts. It usually takes me 1-2 kicks to get it going. Hot starts are easy, but warm starts (after it's been warmed up and has been sitting for 1-3 hours) are a pain (many kicks) because I can't figgur out how much choke to use, and I'm afraid to flood it.

By the way, does anyone else find it nearly impossible to get any other choke setting other than full or minimal? When I try to set mine to half, it slides back down to low.

simon#42 · « **Reply #10 on:** June 08, 2011, 10:49:41 AM »

i put the smallest choke jets in i could buy [ i think from memory they where 35's ] needs full choke to start , i then turn it to half choke for a couple of min till its warmed a bit

brandEn · « **Reply #11 on:** June 09, 2011, 08:06:46 AM »

smaller choke jets, that's just what I need. A cold start is a real PITA everyday. My remote idle adjuster has see a lot of use and makes starting easier.

simon#42 · « **Reply #12 on:** June 09, 2011, 10:51:58 AM »

the remote idle adjuster is a must with these carbs !

davesprinkle · « **Reply #13 on:** July 10, 2011, 08:10:39 AM »

Quote from: kos on June 07, 2011, 12:55:18 PM

Agreed, those old ticklers had you pushing them down... even after bike was fully warmed and they always allowed petrol to spill on top of engine cases, that is how I got CR Specials allowed in AHRMA, just for safety's sake alone!

Like Mike has said, the enriching circuit is too big on those, so all we did is choke and as soon as it fired...take choke off.
Mark@ M3

I took a close look at the design of the starting circuit for the CRs. Simply put, as designed, you cannot lean out the choke, no matter what size starter jet you install. The starter jet bleeds fuel into a subsidiary bowl, which then feeds the choke circuit WITH NO RESTRICTION other than the choke plunger. Bad design. I've considered trying to machine threads to mount the jet between the bowl and the port. It might be possible, but the improvement might not justify the difficulty.

Anyway, here's the starting procedure for my 400 with 26s:
-- Very slightly crack the choke, just open it off the seat. Leaving throttle fully closed, kick the engine through. You'll hear a hiss through the choke circuit. The engine will not start, but this first kick will load the port with fuel.
-- Close the choke fully. Crack the throttle roughly 1/8 open. The engine will start on the next kick.

brandEn · « **Reply #14 on:** December 02, 2011, 02:13:23 PM »

So I am going to order some new start jets, what size can anyone recommend? I see Simon mentioned 35's...

brandEn · « **Reply #15 on:** December 02, 2011, 02:44:00 PM »

Sudco is backordered on the #35 starter jets, anyone got a set they can part with?

Terry in Australia · « **Reply #16 on:** December 02, 2011, 02:52:57 PM »

After selling my troublesome 29mm CR's and enjoying the OEM 28mm Keihins for street use I missed the ability to rev my 836cc engine way past redline in each gear as I could with the CR's, so I've bought a set of 31mm CR's and just about every jet/needle combo that Sudco lists.

These carbs are "as new", the eBay seller bought them for something called a Yamaha Maxim, something that I've never seen before. Anyway, bottom line is that the PO realised that 31mm CR's were too big for a stock 700cc engine so leaned them right out with smaller jets and needles, but they were still too rich, so removed them.

What size needle/main jets combo's are you guys here with 31mm CR's on 836cc engines using? Also, I'm going to use a remote idle screw assembly, the stock CR setup is no good on a CB750, is there an "off the shelf" item available, or do I need to make my own? Cheers, Terry.

brandEn · « **Reply #17 on:** December 02, 2011, 02:57:07 PM »

There is one you can buy that is made for them. I know Sudco and Jet R Us sells them here Stateside.

brandEn · « **Reply #18 on:** December 02, 2011, 02:59:11 PM »

link
http://www.jetsrus.com/individual_parts/018_778_su.html

BLUE71TURBO · « **Reply #19 on:** December 02, 2011, 03:01:02 PM »

Mikuni needs to make 29 smoothbores again !

Doctor_D · « **Reply #20 on:** December 02, 2011, 05:32:32 PM »

Quote from: Terry in Australia on December 02, 2011, 02:52:57 PM

What size needle/main jets combo's are you guys here with 31mm CR's on 836cc engines using? Also, I'm going to use a remote idle screw assembly, the stock CR setup is no good on a CB750, is there an "off the shelf" item available, or do I need to make my own? Cheers, Terry.

I'm using 30mm velocity stacks, 130 mains and YY7 needles (one clip position leaner than middle). The open stacks and 4 into 4 open meggas can take quite a bit of fuel. If you're running K&N's and a four-into-one pipe, you might want to try 125's to start, and stick with the YY8 needles.

Terry in Australia · « **Reply #21 on:** December 02, 2011, 07:06:54 PM »

Quote from: brandEn on December 02, 2011, 02:59:11 PM

link
http://www.jetsrus.com/individual_parts/018_778_su.html

45 bucks for a screw? Oooer, last time I paid 45 bucks for a screw she showered me, dressed me, and kissed me goodnight!

brandEn · « **Reply #22 on:** December 02, 2011, 07:09:04 PM »

haha! Thats a good one. I made one from the idle screw that they come with and a ZRX adjuster. It was nearly identical. Gave it to another forum member.

brandEn · « **Reply #23 on:** December 02, 2011, 07:11:53 PM »

This would work
http://www.ebay.com/itm/1997-HONDA-CBR600-CARBURETOR-IDLE-ADJUSTER-SCREW-CABLE-KNOB-/330645970124?pt=Motorcycles_Parts_Accessories&vxp=mtr&hash=item4cfc091ccc

Retro Rocket · « **Reply #24 on:** December 02, 2011, 07:30:37 PM »

Quote from: Terry in Australia on December 02, 2011, 07:06:54 PM

Quote from: brandEn on December 02, 2011, 02:59:11 PM
link
http://www.jetsrus.com/individual_parts/018_778_su.html

45 bucks for a screw? Oooer, last time I paid 45 bucks for a screw she showered me, dressed me, and kissed me goodnight!

Its good to see our $45 dollars going a little further in the current financial climate....

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Author Topic: Keihin CR carbs and your starting procedure (Read 10475 times)