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SU H6 Carb leaking


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Had a run on Sat with local motor club, covered around 150 miles and noticed slight fuel smell....mostly when backing off throttle. Didn't worry too much and took it to show on Sunday.When fitting larger steering lock stops today noticed petrol smell once more and tracked it back to the bottom of the carb nearest to the bulkhead. These are H6 SUs. Is there a likely suspect eg bolt

/gaskets joining float to carb body or is it more likely to be in the jet area?

Is there any clever way to determine source of leak without taking it all apart? Was thinking of drying off and using a mirror.....

Any advice welcomed.

Thanks, John

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Hi John,

there is a cork 'O' ring that fits on/near the main jet underneath. This can and does shrink and leak.

 

There is a repair kit for it.

 

Roger

 

item #101 https://www.moss-europe.co.uk/shop-by-model/triumph/tr2-4a/fuel-system-induction-controls/carburettors-manifolds/carburettors-air-cleaners-h6-su-tr2-4a.html

Edited by RogerH
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Thanks Roger, I have had a look at the SU web site for repair/refurb kits but they are quite expensive,particularly if it is just one seal that has gone. Not much in any of my manuals.....can 'it' be replaced in situ?

John

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possibly the needle valve in the float chamber sticking because of a bit of dirt got through. Try a strong tap on the top of the chamber first, might dislodge it. If not top off chamber, valve in the chamber top, give it a good blow through and try it back on.

 

Mysterious misfire John

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It depends which bolt you have for fixing the float chamber to the main body.

  1. There is a bolt which has a short thread and will reach full tightening before the cork gasket is fully compressed. If so use a copper washer to increase the pressure on the cork.
  2. If the bolt has a longer thread you can get better pressure and you can use an ethanol resistant "o" ring.I bought my rings from Tom Bryant in Wiscasset , USA. They work well in replacing the large cork ring. There must be some in UK.
  3. If the leak is from the jet seal you need the updated repair kit from Burlen approx. £25.00

It can all be done with the carbs fitted in place and the mirror and a light will help a lot.

 

Good luck, Richard

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Roger wins the prize.....the cork gasket was missing a bit, probably not so bad when compressed.The gasket sets from Burlen/SU are only a tenner or so,already on the way.Not too bad removing in situ but there are a lot of small parts to lose/drop.Worth getting the gasket set and replacing all of the seals.....after soaking in petrol overnight.

Noticed that the dash pot dropped quite quickly....only about 1 sec?

Thanks for advice,

John

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Thanks Richard, the kit from Burlen is quite comprehensive.....covers all of the wee bits that may get lost.There is a note in with the cork gaskets to let them soak in oil for 24hrs.The slightly odd thing is that the smaller cork seals come already soaked in oil but the large one that caused my problem does not.Burlen say that folks did not soak the little ones, resulting in poor seals,so they do it for them.

Just got to put it back together tomorrow using my ambidiborous skills.

Never taken one apart before and am a bit in awe of the pure simplicity of how it works.....I have a Weber on a car from the dark side and have changed jets etc but have no real understanding of how it all works!

Anon,

John

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  • 1 year later...

Hi All, Methanol in todays petrol seems to cause the cork seals around the jet to leak.  It drove me mad for months.  Have a little feel around the spring above the mixture adjusting nut, and your fingers will be wet or smelly with petrol.  I have sourced some PTFE ‘o’ rings to use in place of the corks at top and bottom of the jet.  100% cure and choke slides like a well oiled clock.  David,  maddy@ukgo.com

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