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Post Info TOPIC: Carb repair


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Carb repair
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Hi all I am just checking my carb before putting it I'm my bike and I understand by reading other post that when you open the throttle it should spray  petrol out, but mine is not doing this have any of you guys come across this before if so is it an easy fix?

I have checked the diafram that's still in one piece just leaking now that I have disturbed it. Any help would be much appreciate 

 



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1996 (N reg)Yamaha TTR 250



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Have a quick look through this thread - shows you where the accelerator pump nozzle is.

www.ttr250.activeboard.com/t55374798/rebuilding-a-ttr250-teikei-y30p-carburettor/

With the carb bowl full of fuel, when you twist the throttle a jet of fuel should squirt out towards the intake duct. If it doesn't you either have a blockage, (tricky to fix 'cause there is not a "straight path" you can poke a wire down), or your diaphragm is torn (yours is not), or the o-rings in the diaphragm plate are leaking badly/not seated properly.

The o-rings have a habit of going hard and not sealing and are easily replaced, and the face of the backplate can corrode - easily fixed by cleaning it up by rubbing it on a piece of abrasive paper on a flat surface.

Good luck,

Simon.


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Simon has almost certainly nailed the answer(s) but, just in case, if you go here and scroll about a third of the way down the page you will see a photo showing a check valve that is supposed to be sitting under the float bowl gasket. There is a remote possibility that yours is missing which would also explain your carb symptoms.



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Thanks Simon for your reply, I have since given it a poke with a strand of wire, like you say not a easy task😉and I have put back together put petrol through it and twisted the throttle, and nothing but as you say could be because I have a rubbish seal around diafram because it did leak around there, maybe worth buying a new diafram because mine is a it stiff and a rebuild kit

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TTRfan wrote:

Simon has almost certainly nailed the answer(s) but, just in case, if you go here and scroll about a third of the way down the page you will see a photo showing a check valve that is supposed to be sitting under the float bowl gasket. There is a remote possibility that yours is missing which would also explain your carb symptoms.


 Thanks Brian Ill also check under the seal for check valve, do you get a new check valve in a carb rebuild kit or is it just jets

 



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I've just checked the check valve and it's still in there, so hopefully just a blockage 😉

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Was the check valve working? It's a one-way valve.



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I've just been and checked it an it is now fully working, think it may have been blocked a couldn't blow through it to start with but I can now and as you say only works 1 way.
Would that have caused my carb not to work if it was blocked

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Possibly...... I think it prevents the petrol returning to the float bowl when the diaphragm is depressed. So, if it does what I think it does, that may explain why no petrol squirting out the nozzle in the throat of the carb. Possibly.....



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All sorted carb is fully functioning, in the end I brought a new diafram as mine was abit stiff (thanks Steve for the parts😉)
Put all back together now it's working as it should.
Thanks for your help guys 👍👍👍



-- Edited by Martinm on Saturday 24th of November 2018 09:45:16 AM

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