Carburettor issues

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pablotrini67
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Carburettor issues

Post by pablotrini67 »

Carburettor issues
Over the winter I had restored a 1979 CBX , it included a complete engine overhaul ,new wire harness ,dyna ignition ,pingel full flow fuel valve and complete carb overhaul .So far I have ridden 1800 kms without any mechanical issues .
The problem I am having which IMO is carburettor issues .the bike will start only when the choke is fully closed ,this includes even when the engine is hot ,it won't idle , and therefore I have to partially close the choke when stopped to keep the engine turning over . I did increase the idle speed but this does not help .Once moving @ lower rpm it feels like its starving for fuel untill the rpm builds,@ hi-way speeds @ 4000 rpm if I roll on very hard it seems like it's starving for fuel untill the rpm builds ,if I roll on slowly the power builds smoothely & steadily without any lag .At speeds above 5000 rpm it pulls normally & no sign of starving for fuel.During the re-build I never checked to see if the accelorator pump was functioning (apparently there is a way to check with the carbs off the bike ) never checked the float bowl height .Any ideas as to what's causing this issue would be welcomed as I am preparing to remove the carbs .
One other thing I have noticed is the wire from the main harness which connects to the starter solenoid mini harness gets warm-hot ,I am running LED 30 watt headlight.

daves79x
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Re: Carburettor issues

Post by daves79x »

You didn't get the idle/slow-speed circuitry clean. The pressed-in #35 jets need removed and cleaned, as well as verifying all idle passages are open. Lots of other little things to trip you up with these too.

If a connection is getting warm, there is excess resistance somewhere in the circuit. Every connection needs taken apart and thoroughly inspected and cleaned.

Dave

pablotrini67
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Re: Carburettor issues

Post by pablotrini67 »

Got the carbs re-built & back onto the bike ,what a difference ,starts easily once warmed up , idles smoothely but slight clutch rattle tells me will eventually need a carb sync , pulls strongly through all gears with no lag .
What I found : THE GOOD :When I had originally re-built the carbs the bowls were very clean and all jets were open & not plugged so I just changed the float valve & seat but never checked float height & re-built with new o-rings .This time I purchased a proper air nozzle which came with attachments which were ideal for blasting the jets with compressed air as the nozzle fit snugly in most of the jets & thx to Devin "shiskowd" who lent me Mike Nixons carb overhaul manual & also loaned me the small tap & extractor. I removed the pressed in jets ,they were clean & no sign of dried out gas , also removed the main jets which were also clean and not plugged , also made sure the nozzles for the accelorator pump system were clear & once the carbs were re-built & during the wet bench test I checked there was a stream of gas exiting each nozzle when blipping the throttle.
THE BAD : When I initially re-built with new float valves I never checked the float height ,this time I checked the float height & found that the float heights were way out this was due to the fact that the small shock absorber pin on the new float valves was longer than the original float valves causing the float height to be way out ,also around I found all the small filters which are attached to the float seat completely disintegrated & some in pieces , I replaced these with the original filters which were in good condition.. Also found that the idle jet screws had two o-rings instead of the required one o-ring. ,in Mikes manual he notes that these o-rings are like tree rings & can tell how many times the carbs have been re-built ,& also more than one o-ring will greatly effect the idling . I set the idle jet screws @ 13/4 turns out

daves79x
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Re: Carburettor issues

Post by daves79x »

You really should have gotten Keihin float valves and re-used your original seats and filters. There are about a million cautions here about using aftermarket float valves.

Dave

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Re: Carburettor issues

Post by CBX-tras »

FYI to everyone reading this thread:

We usually have the correct Keihin (brand) float needles in stock along with the best rebuild kits, new screw kits (include Vessel JIS driver bits) in either bright zinc or nickel plated and connector boots.

I said "usually" because at times we'll have a run on these components and are temporarily out of stock with more on the way.

Send an inquiry to: sales@KMCarburetor.com

New website coming soon at: http://www.kmcarburetor.com

Larry Zimmer
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Re: Carburettor issues

Post by Larry Zimmer »

Thanks, J.R.
Larry Zimmer
cbxlarry@sbcglobal.net

pablotrini67
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Re: Carburettor issues

Post by pablotrini67 »

Thx for the info on any future purchase of cbx carb parts ,I had inquired at the local Honda dealership about the float kit ,the price was $90.00 cdn for each kit so decided to use the same float valve & seats and just replaced the disintegrated filters with the original ones which were in good condition.have attached a photo of the filters which weren't 3 mnths old & the tools which helped me with doing the re-build correctly.
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daves79x
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Re: Carburettor issues

Post by daves79x »

Lots of sources for Keihin float valves. Kurt here carries them < $100 for six. You just get the valves - you re-use your old seats, which are fine.

Dave

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