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Author Topic: Lack of revs  (Read 2556 times)

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iansoady

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Re: Lack of revs
« Reply #15 on: July 29, 2016, 10:09:32 AM »
Well spotted.

The exposed valve gear does make finding these things a bit easier as you can see it's not bobbing up and down as it should.
Ian
1931 Model 10
1993 Honda CB400 Super Four

singleminded

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Re: Lack of revs
« Reply #14 on: July 28, 2016, 09:47:58 PM »
Well that's great that you have found a fault, there's nothing worse than a fault that cannot be traced.

Andy Cubin

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Re: Lack of revs
« Reply #13 on: July 28, 2016, 04:42:55 PM »
Found it!

The carb and fuel supply were all fine.
 
On inspection of the rocker box, we found the inlet valve rocker arm had a sheared key.  No inlet air!

Off to make a new key and thanks to Chris Roberts for being a genius!

Andy Cubin

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Re: Lack of revs
« Reply #12 on: July 14, 2016, 09:14:46 PM »
Thanks for the advice Gents,

All fingers point towards the carb so, when I get back from work, I'll give it a full strip down and clean up.

Stay posted for the next thrilling episode!!!

Cheers all

Andy

iansoady

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Re: Lack of revs
« Reply #11 on: July 14, 2016, 11:35:20 AM »
Just a thought - you haven't by any chance swapped the throttle and air lever cables over?
Ian
1931 Model 10
1993 Honda CB400 Super Four

Davetom

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Re: Lack of revs
« Reply #10 on: July 13, 2016, 10:24:34 PM »
I'll second that about the pilot circuit.. My Velocette ( recent purchase in May )wouldn't start recently, I kicked it til I was sweating, then got pushed around a pub car park, and when it fired, it would die on opening the throttle. Turned out the pilot circuit was gummed up. My bike hadn't been used much for a while until I took ownership, and it seemed I'd disturbed a lot of sludge

singleminded

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Re: Lack of revs
« Reply #9 on: July 13, 2016, 10:10:25 PM »
Makes me wonder if the pilot drilling in the jet block is restricted,assuming it's a 276 or type 29.
I had problems with one and had to drop the jet block out ( you must warm the body with hot water to do this).
On the engine side of the block is a recess with a drilling going down to the base of the block, at the back of this recess is the drilling for the pilot feed. They can very easily block with what appears to be varnish , a by product of using modern fuel..John

Andy Cubin

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Re: Lack of revs
« Reply #8 on: July 13, 2016, 08:44:34 PM »
Yep - checked the needle - even shifted it up to notch 3 after a bit of advice from Vic

Davetom

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Re: Lack of revs
« Reply #7 on: July 13, 2016, 08:42:07 PM »
Are you sure that the needle is attached? If the little clip comes off, it just sits there blocking the jet, it'll run on the pilot jet but opening the throttle lets more air but no more fuel in .its hard to feel it move as the throttle has to be wide open before you can possibly get a little finger in ( depending on finger size !)
Dave Thomas

Andy Cubin

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Re: Lack of revs
« Reply #6 on: July 13, 2016, 08:34:45 PM »
yes it does Tom,

No - I have had it round the block a couple of times.

1 step forward, several back

Davetom

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Re: Lack of revs
« Reply #5 on: July 13, 2016, 08:31:10 PM »
Does opening the throttle kill the engine ? Has this just happened or has it been like this since it went back together ?

Andy Cubin

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Re: Lack of revs
« Reply #4 on: July 13, 2016, 07:59:48 PM »
She fires and runs very hesitantly for about 10 seconds - no response from the throttle - as though it is not connected.

Plenty of fuel around and the throttle slide, needle and air valves work as advertised.

Hmm??!


singleminded

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Re: Lack of revs
« Reply #3 on: July 13, 2016, 04:50:59 PM »
Is the fuel flowing through the tap fast enough..I've had a blockage above the tap before now..John

Davetom

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Re: Lack of revs
« Reply #2 on: July 13, 2016, 04:48:09 PM »
Does the throttle slide lift when you twist the throttle? You can tell just by poking your finger into the carb as you twist

Andy Cubin

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Lack of revs
« Reply #1 on: July 13, 2016, 01:17:00 PM »
Hmmm!

She starts but won't sustain.  Twisting the throttle has no effect on the revs.

Stripped the carb and float bowl and checked the needle etc.

Bit of a poser this one - anyone seen this?

Andy