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Float valve not seating
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Jonny_on_the monorail
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August 15, 2020 - 6:24 pm
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Evening,

I've recently bought a 1966 D7 Super (the metallic red one) as a project. I'm used to working on old cars but this is my first bike.

My plan is to get it running first before I even consider spending any time and money on cosmetic stuff.  I bought a repair kit from Burlen to service the 375 Monobloc carb. Following reassembly, I primed it only to discover that petrol was pouring out. If I carefully push the float valve into its seat it seals fine but pushing the float up to move the valve, the float touches the tickler before the valve seals. Removing the tickler, the float touches the chamber body before the float seals. 

The float needle came with the service kit so should be correct for the 375 Mono. Its quite possible that the carb is made up of someones left over parts and I could be chasing my tail.

 

Any thoughts?

Cheers  

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Stoo63
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August 15, 2020 - 9:41 pm
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Hi,  jonny and welcome to the forum. Floats are a common nuisance. As you say,could be a mish-mash of parts you're dealing with. I'm sure that someone will have an answer for you. Just to get you started: 

You will find just about everything you could ever want on the Forum via the FAQs and technical sections;  ** Please log in to view **

And if you're logging in, DON'T use your email- it won't work. Only use your username that you've registered - saves a lot of frustration 🙂

Have a really good nose around the forum and enjoy yourself. Looking forward to seeing your progress.

Good Luck!

All the best,

Stewart

 '55 D3 Battery; '58 Square Four (project); '59 D1 direct lighting plunger; '59 Tiger Cub; '60 5TA;  '76 FS1-E; '97 Honda Sky SGX50.

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stubaker58
Sunny Felixstowe
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August 16, 2020 - 3:07 pm
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Hi,

im just cleaning up a Monobloc for fitting to my D7 mongrel so it’s currently in pieces.  The only way that I can see you having the problem you described is if the needle valve seat is not screwed fully home (washer far too thick?) or the needle is the wrong length.  On mine the float gets very close to the tickler but just misses, it goes nowhere close to the top of the float chamber.

Hope that helps.

Post a picture or two, it always helps to see the issue.

Regards.

D7/14 hybrid (4 speed with D7 crank etc.) on the road, D10 Bushman awaiting rebuilding.

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Alan.Moore
Leicestershire
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August 16, 2020 - 5:37 pm
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Hi,

A few thoughts:

Did it fail to seal with the old needle?

Is there a fibre washer under the needle valve set? If there is remove it and try again. If that works you can make a thin gasket from some brown paper and use a bit of gasket sealent.

Did you get the kit with the newer type black plastic float or are you using the original float? if using old float maybe incompatibility with the new needle.

Have a look at this previous topic  ** Please log in to view **

 

Bests of luck

Cheers

Alan

1939 Ariel VH, 1942 Ariel WNG, 1951 Triumph 6T Thunderbird, 1970 BSA Bantam B175, 1980 Honda CB250N, 1986 Yamaha SRX600

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Jonny_on_the monorail
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August 22, 2020 - 9:36 am
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Morning,

Thanks for the replies chaps.  I'll take a look at the carb again today.

The float needle and washers came with the repair kit so in theory should be correct. However, nothing is ever that simple is it?  Agreed, if the needle is correct then the seat is too high so Ill try your suggestion of removing the fibre washer. I'll also compare old and new needles.  Its the original brass float so I'll give it a submergence test and see if any petrol ends up inside the float. Good point on the compatibility with the new needle.

Another thing thats been bothering me: The carb only has a single cable (throttle) and no choke. Is this standard or should this model have a choke cable? There is no choke control on the handlebars (but to be fair there wasn't a throttle control either until I bought one! )  

 

I'll try and upload some pictures later...

 

Cheers

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Jonny_on_the monorail
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August 22, 2020 - 9:52 am
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Thanks for the link Alan. Certainly appears to be the same problem as mine thumbs-up.

Cheers

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stubaker58
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August 22, 2020 - 3:14 pm
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Hi,

as to the choke, it was normal for there to be no handlebar control.  The choke was usually part of the air filter housing, when closed for starting the vanes cover the slots, when open for running the vanes sit out of sight and the slots are open.

Regards

D7/14 hybrid (4 speed with D7 crank etc.) on the road, D10 Bushman awaiting rebuilding.

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Jonny_on_the monorail
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August 22, 2020 - 4:19 pm
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Success! With the fibre washer removed, the float valve seats fine now. Thanks chaps. 

Thats interesting with the choke.  I thought the bike may have been missing even more parts. Its got compression and a spark so just need a battery now so I can give it a go at starting....

Cheers

 

  

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Jonny_on_the monorail
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August 22, 2020 - 4:25 pm
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BSA-carb-1.PNG

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