running at max revs

[ant-fto]

hey guys
i have been putting a mini engine back together and now its all in and the carb is connected when the car is started it goes to max revving and i cant work out why... have i not connected somthing properly and just cant see what it is?
any advice?

cheers

[revingtosh]

It might sound obvious, but disconnect the accelerator cable from the carb amd see if it stops.

If it does, then you may have the linkage connected up wrong.

What carb are you using? If its an SU, remove the air filter and stick you finger in the back to check that the piston has fully dropped. It it hasnt, the needle might be bent.

[oakdale]

A sticking piston on an SU carb will not cause the engine to rev if the throttle butterfly is closed properly.
Is it the type of SU where the pull off spring goes between the arm operated by the throttle cable and a plate sandwiched between the carb and manifold ? And if so, is it fitted?

Edited by oakdale on Friday 9th January 20:18

[GTOBEN]

The butterfly must be open? The engine could not achieve the max revs if not. Check the linkages and throttle cable and that the return spring is connected up properly.

[Cooperman]

Check for an air leak on the induction side after the carb. That, combined with the choke being fully on coulkd cause this if the leak is large. If you have fitted an LCB manifold, the manifold flanges can hold the inlet manifold away from the head and cause a very large air leak.

[ant-fto]

iv found that the piston in the carb is sticking up.. taken it apart and the needle seems to have a lot of play.. do they usually have play?
im thinking of fitting a webber 45.. would this be straightfoward job? the webber is off of a mate and it has the manifold with it.

[Cooperman]

A piston sticking up would not cause the high-revs running. It would cause the mixture to be well over-rich, but the throttle butterfly would be closed and the mixture would not be getting into to cylinders. However, a sticking piston combined with a big air leak would do exactly that. Check the manifold flange thicknesses - it's a common problem for a new exhaust manifold to cause an air leak.
Fitting a weber entails cutting away the bulkhead and welding a metal box in place to provide clearance for the Weber. If you have a centre mounted early-type instrument cluster you will need to move that as well. You will need an angle grinder and a MIG welder plus the nerve to cut the bulkhead away.

[guru_1071]

nerves of steel!

[cone]

I'm not giving you any more money !

[Cooperman]

It's the first cut with the angle grinder as it goes right through the bulkhead which stimulates the adreneline!
A friend of mine came over to do this to his rally Clubman 1330 a few years ago. I helped him to move everything out of the way, but then I had to go out and I left him in my workshop with the angle grinder and some spare cutting discs. He was still looking at it with apprehension when i returned about 90 minutes later. I just scribed around the box and cut 0.75" onside the outer flange, then welded the box it. It worked out fine, but it does need a bit of courage the first time you do it. I always wonder if it's worthwhile for a road engine and if twin SU's are not an easier option.