Author Topic: Warm starting issue  (Read 693 times)

Offline Athame57

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Warm starting issue
« on: July 28, 2023, 08:27:16 PM »
These past few weeks I've found it very hard to start my engine again if I switch off with a hot engine. Keeping my finger on the starter and closing the choke usually gets me going again....any ideas?
I brake for animals!
1978 CB400F2 called Elen.

Offline 400 Cafe Racer

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Re: Warm starting issue
« Reply #1 on: July 28, 2023, 09:32:46 PM »
If you need the choke to start a warm engine, it sounds like fuel starvation or excess air. 

Could be blocked jet(s), restricted fuel flow, vent blockage on tank.  Excess air, could be flexible mounting rubbers leaking etc.

Let us know how you get on. ;)

Dennis 
Retired Automotive Engineer   MIMI, MITRE, DMS, MCMI.

Latest    - 1979 CB400/4  Cafe Racer - Parakeet Yellow
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1988-91 - Lamborghini Countach QV replica design and
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In 1956 at 12yrs old and dirt tracking
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Offline Athame57

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Re: Warm starting issue
« Reply #2 on: July 28, 2023, 09:44:35 PM »
If you need the choke to start a warm engine, it sounds like fuel starvation or excess air. 

Could be blocked jet(s), restricted fuel flow, vent blockage on tank.  Excess air, could be flexible mounting rubbers leaking etc.
Let us know how you get on. ;)
Dennis
I'm about to overhaul my carbs as it happens, just bought some bits of Julie  ;) I'll take those things into account and come back with results!
I brake for animals!
1978 CB400F2 called Elen.

Offline McCabe-Thiele (Ted)

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Re: Warm starting issue
« Reply #3 on: July 28, 2023, 10:35:49 PM »
I would have suspicions about an air leak between the cylinder head and the carbs as my first line of investigation.
Honda CB500 K1 (new pit dug out ready)
Honda CB400 four super sport (first money pit)
Link to my full restoration http://www.sohc.co.uk/index.php/topic,23291.0.html

Offline Matt_Harrington

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Re: Warm starting issue
« Reply #4 on: July 30, 2023, 10:48:55 AM »
All I can add is that the non OEM air screws (probably chinese) as so different from the OEM ones that they are almost (perhaps I should say totally!) useless.
Matt
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CB400F 1976 -  Almost finished
CB400F 1977 - On the road!
Moto Guzzi Le Mans 2 - 1981 (undergoing a spruce up)
CD175 - To be restored
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Offline Mikep328

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Re: Warm starting issue
« Reply #5 on: August 02, 2023, 09:21:06 AM »
Can you get OEM Honda airscrews/other carb hard parts like jets/needles?  I tried to find some and the few places I found them listed they were shown as "discontinued/no longer available."


Offline Matt_Harrington

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Re: Warm starting issue
« Reply #6 on: August 02, 2023, 09:53:35 AM »
Have you tried David Silver? If none there, s/hand is an option....
Matt
___________________________________
CB400F 1976 -  Almost finished
CB400F 1977 - On the road!
Moto Guzzi Le Mans 2 - 1981 (undergoing a spruce up)
CD175 - To be restored
Triumph Speed 400

Offline McCabe-Thiele (Ted)

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Re: Warm starting issue
« Reply #7 on: August 02, 2023, 11:53:03 AM »
Hopefully you should be able to clean up your existing brassware.
I have quite a few good used needles, emulsion tubes etc.

Just PM me if you need anything if yours are damaged - Ted
Honda CB500 K1 (new pit dug out ready)
Honda CB400 four super sport (first money pit)
Link to my full restoration http://www.sohc.co.uk/index.php/topic,23291.0.html

Offline Mikep328

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Re: Warm starting issue
« Reply #8 on: August 02, 2023, 12:54:28 PM »
"Have you tried David Silver? If none there, s/hand is an option...."

DSS lists the hard carb parts as pattern parts, not genuine.  No idea who the actual supplier may be.

"Just PM me if you need anything if yours are damaged - Ted"

I haven't yet gotten into the carbs but the needles/needle jets on a Norton Commando's Amal Concentric carbs wear and require replacing at, say 20k miles (or less) so I was ASSuming the same is true with these bikes/carbs.  Of course, Norton twins 'shake' a lot; Honda fours don't!  :)


Offline Oddjob

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Re: Warm starting issue
« Reply #9 on: August 02, 2023, 02:49:14 PM »
I can't remember seeing any wear issues on the brass ware on the SOHCs, not saying it can't or doesn't happen, I'm saying I personally have never seen it.
Kids in a the back seat cause accidents.
Accidents in the back seat cause kids.

Offline Bryanj

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Re: Warm starting issue
« Reply #10 on: August 02, 2023, 04:37:20 PM »
You mean you know of a commando that got to 20k?

Offline Mikep328

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Re: Warm starting issue
« Reply #11 on: August 02, 2023, 04:57:32 PM »
LOL!  Well, not with all-original parts!  ;)

Offline Bryanj

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Re: Warm starting issue
« Reply #12 on: August 02, 2023, 04:59:35 PM »
Worst were the last white ones built from spares, like the Triumph cardinal

Offline taysidedragon

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Re: Warm starting issue
« Reply #13 on: August 02, 2023, 05:03:29 PM »
Worst were the last white ones built from spares, like the Triumph cardinal

Or the 'Combat' Commando engines. ☹
Gareth

1977 CB400F
1965 T100SS

Offline Nurse Julie

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Re: Warm starting issue
« Reply #14 on: August 02, 2023, 05:06:25 PM »
NRP sell the original Keihin brass ware. But, it's very rare to have to replace any brass bits once they've been thoroughly cleaned, including the emulsion tubes.
http://nrp-carbs.co.uk/
LINK TO MY EBAY PAGE. As many of you know already, I give 10% discount and do post at cost to forum members if you PM me direct.
https://www.ebay.co.uk/sch/julies9731/m.html?item=165142672569&rt=nc&_trksid=p2047675.m3561.l2562

LINK TO MY CB400/4 ENGINE STRIP / ASSESSMENT AND REBUILD...NOW COMPLETE
http://www.sohc.co.uk/index.php/topic,14049.msg112691/topicseen.html#new

 

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