Rover Sports Register Forum

I finally have the engine running and it sounds quite nice.The exhaust flange and downpipe is great.The only thing its,I notice that the tick over isnt as steady as I would like,it ticks over fine,but tends to speed up slightly in bursts,as though your`e pressing the accelerator slightly it then settles down for a few seconds.Any ideas anyone,Also I actually moved the car in the garage first time for a year.I bought the car a year ago this week, Time flies when your`e having fun !!!!
Is there a way to check the float level in the cars the manual usually shows how the put a rod between the "fingers" and the case ? I have a feeling mine not be correct,when I bought the car and checked the float,the fingers were in a position where the needle could fall out Len

Good morning,I went onto the Burlen SU pages and they recommend,that if the float is braas,then the gap should be 5/16" a common drill size I reset it to this and there seems to be an improvement.However after standing idle for a year,the engine needs to be fine tuned. The exhaust flange and flei section works a dream ,no more blowing.Len

Hi Len,

The erratic tick over you have described suggests a carburettor issue. On an SU the throttle operates a butterfly, allowing in more air. The draw of air creates a vacuum within the carb that moves the slider and needle, letting in more fuel. At least, that is my understanding. On an old carb it is likely that the butterfly, spindle and spindle seats will be worn, letting extra air causing erratic tick over.

It’s possible the slider may be sticking due to lack of use. Worth checking but, at tick over, the slider shouldn’t be moving and this is when you set the mixture with the hex nut on the jet. There is no oil damping on a downdraft SU but it can be lubricated through the oil cap. With the filter removed you can move the slider with a screwdriver to check free movement.

Probably the best thing to do is get a SU service kit from Burlen Services or Southern Carburettors. This will give you a new jet, butterfly, spindle, float valve and all the required seals including the felt ones that the jet is sealed with. Stripping the carb and rebuilding with all these bits is an easy enough job and far cheaper than paying to have it reconditioned. About £50 I think, from memory. Be careful with your needle as they are easily bent and specific to your model. Should you need to get one though, the number is on the flat end which fits into the piston. Jets are all the same and you get one of those. They supply a diagram so you know where the bits go. Worth buying a can of carburettor cleaning spray as this will help get things looking like new.

Good luck,

Tony.

Thanks at the moment I set the float level using a 5/16 drill between body and "fingers" of the lever which controls the valve and it seems to be a fair bit better already.Ill check the tick over next week Len

Len,

Good to get the float setting right but it won’t have any impact on the way the engine runs unless the valve is stuck closed, cutting off the supply. I’ve never worried too much about the floats and valves in my cars, providing they operate such that fuel doesn’t overflow. After all, the float chamber is simply a reservoir taking petrol in the top and feeding the carb through a hole in the base. Much like a toilet cistern. So as long as there is petrol in it the engine should run fine. Fuel starvation due to a stuck valve or float would result in the engine spluttering to a halt as it runs out of fuel, rather than the speeding up you described earlier.

However, while you have the float chamber top off, it’s worth squirting carb cleaner through the hole in the base to ensure no dirt has collected in the tube feeding the jet. Be careful not to get the cleaner on the new paint though as it might not do it any good!

Setting the mixture is a simple matter of using the hand throttle to get a tick over of about 1000 revs and adjusting the the hex nut that moves the jet so that the fastest running is achieved, then back it off just a little bit. You need to set points gap and static timing first, of course. That is about all the fine tuning you can do, but it should be running like Swiss watch by then!

Let us know how it goes.

Tony.

Thanks again for the useful information Len