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Triumph Twin Carburation Problem.


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Hello there,


My 3ta engined trials bike has suddenly decided not to run unless on full choke.

I've stripped and checked the carb a couple of times, float and needle are OK, tank and carb. filters are clear, tank cap breather is clear, replaced jets, needle and gaskets but no joy, it splutters out as soon as I begin to open the choke. Exhaust pipes are tight, can't find any evidence of cylinder head leaks.The plugs are obviously sooty black with the choke on.

The bike has a Rex Caunt ignition system.

Any suggestions would be welcome, no matter how unlikely they may sound!.




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First, take off the air filter completely and try the bike. If it makes no difference, you now know the problem is most likely in the carburettor.


If working through the air-flow path step by step logically doesn't throw up the culprit, then I would check the ignition, daft as it sounds, because even with the sooty plugs suggesting over-rich mixture, my two 3TA motors were always very critical of the ignition timing, particularly checking each cylinder firing point separately to make sure they were at exactly the same point.........



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Hi I think it's definitely carb problems, this crap they call petrol nowadays.is the carb fitted with a pilot jet or the 16 thou Bush at the end of the pilot fuel mixture screw.

If it's a Bush type card they are a pain to clean,carb cleaner and compressed air required.

Hope this is of use.

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Deryk, I did have a look at the timing marks, they are where they were but as you suggest it may be necessary to investigate further.


Whinger, It's a concentric with the bush, I didn't have access to a compressor yesterday just the carb cleaner aerosol. I'll try the compressor on it today and hope your right.


Thanks for your time guys.


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Was the bike parked up for a long period between working well and not?  If the pilot does turn out to be blocked, then it sometimes needs the jet prodding clean with a .016" guitar string.....never had to do this myself, but have read about it on various Brit bike forums.

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