6 replies to this topic

[Ollie's going to the mayfair]

Just rolled the mini out for the first bit of sunshine and started it after the winter.

i have a 1985 mayfair 998

car starts fine and idles fine, but as soon as you give it any throttle is misses and eventually cuts out. Its better if you feed the throttle in slowly, but would be un drivable at the pace you have to feed it in.

we have set the timing up, new plugs, new leads, new points (set to correct gap) and dizzy cap and still the problem persists.

Just before it cuts out it makes a sort of sucking, throaty noise from the carb/air filter side of things.

Any help would be greatly appreciated, im scratching my head and cant come up with anything.

Ollieseaton.

[iwatkins]

Enough fuel getting to the carb? Does sound as though its leaning out then eventually running out of fuel.

I.e. could be a blocked fuel hose or blocked float valve etc.

[BennerW]

Agree with iwatkins

Sounds Possibly like it might be going to lean when the throttle is opened. This is because a large amount of air is sucked through due to the vacuum created behind the throttle and and to my knowledge the piston in the carburettor is let up slowly as to disallow too much air without the appropriate fuel mixed with it.

Is this what the dashpot oil is for?? as it restricts the speed the piston can move in the carb?

Just found this on MossMotors Forum,

"Extra mixture richness for acceleration is provided by a classically elegant means; the upward motion of the air piston is retarded by the oil damper within the piston guide rod. This condition causes greater fuel flow out of the jet in relation to the air flow. This is why the oil in the dashpot is essential. Return of the piston is, in most SUs, aided by a spring, the tension of which is critical to proper functioning of this system."

Check the dashpot oil and then possibly the the function of the piston in the carb itself

Edited by BennerW, 12 April 2013 - 06:28 PM.

[Ollie's going to the mayfair]

awesome. going to have the fuel pump off, make sure that is clear and free from blockages and then top up the dashpot oil.

ill keep you all informed of any progress.

[Ollie's going to the mayfair]

turned out it was as simple as the dashpot oil - jeez!

[cal844]

did you check the engine ofr water and oil levels?

[johnnyblaze]

thats cool you sorted it , dont ya just hate when its realy simple things, i was going to suggest the age of the fuel , gas these days goes off pritty quik