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MG Midget and Sprite Technical - burning oil

The midget is going ok. Katie, my daughter who is going to be driving it for a while, has her driving test on Friday so fingers crossed.
A little problem has manifested itself though, it is burning a little oil. In fact at times there is quite a large cloud of smoke when accelerating away. There is no smoke when cruising or decelerating.
The engine (1275) has been rebuilt with a rebore and new pistons and rings. The cylinder head has been reconditioned with new guides and stem seals.
I have noticed that there is a little oil in the carbs so I am assuming that the carbs are sucking oil in through the timing chain breather. How can I prove this and how can I stop it happening?

Thanks for you help

D Brown

To prove whether it is from the breather or not simply disconnect the breather pipe to the carb.

Block the pipe going to the carb so that the carb can not pull in air while you test the theory. Your mixture will change slightly but just run the car to see if the oil burning diminishes.

Whilst testing run a pipe from the front breather into a plastic bottle or something similar to act a a temporary catch tank.

It is better to know than guess hey Dave!!
Robert (Bob) Midget Turbo

If only I had put brain in to gear before putting fingers to keyboard and I could have worked that one out for myself Doh!
If it is oil being sucked up, what is the best way to cure it?
I could leave the breather pipe in the catch tank but I will still loose some oil which I would rather keep in the sump.
D Brown

Possible causes are too much oil or blowby. The first is easy to asses the latter means or the engine isnt run in yet or there is a faulty ring:-(
Bas Timmermans

It is not too much oil as I know I have not over filled it. It could be a faulty ring I suppose. I will try disconnecting the breather first as I have seen oil in the carbs which suggests the oil is being sucked up the breather.
D Brown

It can also occur if the vent in the oil filler cap has become blocked. This results in too much vacuum in the cranckase and it then draws up oil through the breather pipe. What you are after is a regulated flow of air in through the breather on the filler cap. Too much and the rear crankshaft seal will leak, too little and it will draw out too much oil.

Guy Weller

Id just hook up a catch tank on a removeable bracket, hose from timing cover to tank from tank to carbs ...when the tank hits 1 qt mark, remove from bracket and pour oil back into engine and replace tank back on bracket where it belongs.

plus it will get you in the habit of checking fluids and engine conditions under the hood on a regular basis.


This thread was discussed between 31/08/2010 and 01/09/2010

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