Bit of carb help please?

[Mark Hooton]

Hi Guys/Gals/Others

Aaron (the lad who works for me) bought an R65 (which he loves to bits).

We’ve had carb/erratic running problems so I put a post on and everyone was mega helpful with great suggestions like;

a) check diaphragm for splits
b) check valve clearance
c) check cable slack
d) check float height

All has been done with the floats even being replaced for new along with a float bowl gasket that looked dodgy.

It’s still running poorly however I’ve got one question and one observation -

Question - What are the ‘specified’ steering for the mixture screws? It’s got the Bing carbs fitted to it. I’ve looked in the Haynes and all it says is ‘set the mixture screws to the ‘specified’ settings?

Observation - sometimes, when drawing to a halt the bike over revs to around 2,500 rpm and also, if the bike is on tickover then out on its side stand it over revs again!

Any help and guidance massively appreciated as I’ve no idea about these beautiful airheads!

Thanks!


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[Mark Hooton]

Sorry, it should say ‘setting’ not steering!


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[Smug]

Try unscrewing half a turn to start with.

 

[Beemerboff]

i bought a poor running G/S which had defied all comers and the problem was eventually found to be poor plug caps!

FWIW the idle mixture screw has little effect on anything other than idle, there is a transition circuit which starts at a small brass jet at the LHS of the carb intake and exits from two holes just to the rear of the pinprick from the idle adjustment.

It can be checked with a pressure pack of carb clearer with the carb on the bike - just remove the tube from the air box to the carb, and you will see two small holes at the bottom of the intake. The one one the right should exit freely from around the needle jet, the one on the left from the pinpricks just to the rear os the butterfly. I remove the nozzle from the can and jam the end of the valve against the small jet.
There is an article by Mike Fishwick which periodically surfaces on the net which is about the only place you will find details of the circuit, so a search on his name and Bing might give a .

 

[Mark Hooton]

i bought a poor running G/S which had defied all comers and the problem was eventually found to be poor plug caps!

FWIW the idle mixture screw has little effect on anything other than idle, there is a transition circuit which starts at a small brass jet at the LHS of the carb intake and exits from two holes just to the rear of the pinprick from the idle adjustment.

It can be checked with a pressure pack of carb clearer with the carb on the bike - just remove the tube from the air box to the carb, and you will see two small holes at the bottom of the intake. The one one the right should exit freely from around the needle jet, the one on the left from the pinpricks just to the rear os the butterfly. I remove the nozzle from the can and jam the end of the valve against the small jet.
There is an article by Mike Fishwick which periodically surfaces on the net which is about the only place you will find details of the circuit, so a search on his name and Bing might give a .

Thanks fella


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