bendy
CBT failure
Posts: 18
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Post by bendy on Feb 21, 2017 19:05:36 GMT
Hi Guys . Need a bit of help here . Went to start the bike and noticed Petrol coming out of bottom of exhaust WTF Pulled tank of and air box noticed petrol lying on top of number 3 and 4 butterfly valves. Opened throttle and seen petrol lying in number 3 /4 cylinders around inlet and exhaust valves pulled carbs of complete strip down all floats where free cleaned main and pilot jets. All Diaphragms checked all ok . Put carbs back on and fired her up . Doing the same thing again now on number 1 and 3 Carbs .fuel lying on top of butterfly valves and inside the cylinders . I noticed when she was running there was fuel coming out of where the needle valve opens and closes with the throttle and lying on top of the butterfly valves. i thought mabey the fuel pump was putting to much fuel into the carb bowl. I am stumped her guys can anyone think what is going on here.
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Post by GAv on Feb 21, 2017 22:02:15 GMT
Strangely the engine on my old car was at last reassembled and fitted with a new clutch by a local garage was having fuel flood problems.
The same garage a mate with another old car uses and persuaded my to take it to (rather than struggling with it over the winter,when we picked up the engine with all new parts and a totally unused factory head from the 60s. A guy in Norfolk rebuilt the block etc but needing ancillory parts off my original, didnt want to refit the electric fuel pump as they reckoned it might be too much pressure for the Zenith downdraught carb. However a NOS mechanical one on Fleabay, I got post haste, they didnt put a spacer in so the end broke. I took another one I had with the thread for the screw in pipe gone west down there to swap the ends over, then apparantly it ran OK for a while but would suddenly flood, so I found another identical carb in my box of bits that hadn't been robbed for parts.
I was then told that was leaking but they put the electronic pump on and it stopped overflowing the carb.
Saturday I went for a run in the old jalopy at long last re engined, only to find after a while there was a strong smell of fuel. Having had my Plastic fantastic sportscar self combust bodied with XR3 engine catch fire last year ,obviously that was an experience I would not wish to repeat
So back home off came that old carb and denuded of the float I swapped bits over I hadnt screwed the needle valve in tightly enough(similarly the dual Mikuni carbs on my Sachs which seemingly are almost identical in design to the ones on a Humber Sceptre I had, took off and gave a good decrudding and found a needle jet was lose-the bike starts on the button again. With the current old car Zenith, It was getting dark and after putting it back on it seemed to rev the nuts off. Thinking it was the return spring not returning, left it . In the clear light of the day I could see the accelerator rod that links onto the spring loaded return flap on the throttle linkage was not seated in the orrifice so rerouted that. a rubber grommet to stop it flapping about also helped it tick over nicely I was also told the Acuspark electronic ignition wasn't working when work was nearing completion,by the same garage but I disputed that because even with the old engine down on compression, it did run 'roughly' and I did take it down to my then lockup, I think they had wrongly wired it back on and nackered it which is a given if the live lead and negative are ass about face.
I did try refitting the electronic ignition this morning but it did nothing so back to points and condensor for the time being but it is a bit uneven when the engine warms up so that will probably be another £35 quid for another electronic one.
Hope some of this may be of help but at least if nothing else you have my complete sympathy over your own trials and tribulations which hopefully you will overcome..
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Post by ollyrag on Feb 22, 2017 16:36:33 GMT
Sounds like fuel getting past needle valve seat, either that or floats set too high, causing flooding.
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