OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Walk Behind Lawn Mower Frames Victa Lawn Mower Frames 125cc engine compression figures

Hello all

Can someone tell me what the compression should be around for a 125cc engine. Mine is around 62psi, I am thinking thats a bit low?

Thanks

Martin

From the workshop manual in the parts list and manuals area:

It is important to note that compression cannot
be checked without isolating the decompressor.
This may be done by removing the vacuum
pipe at cylinder inlet and attaching a length
of fuel line to the vacuum pipe, whereupon
sucking gently will close the valve. The following
operation to test compression can then take
place.

Every time a two-cycle engine is serviced both
the combustion chamber and crankcase compression
should be checked. To do this open the
throttle, disconnect the spark plug lead and turn
the mower on its side. The engine shaft can then
be revolved by turning the blade holder manually.
In each revolution there should be two
positions where resistance or compression is felt.

One is when the charge in the combustion
chamber is being compressed, the other when the
charge in the crankcase is being compressed. The
combustion chamber compression is much the
higher of the two.

With a little practise spread over a number of
engines with varying degrees of wear, it soon becomes possible to form a good idea of an engine's
condition.

If little or no resistance is felt when turning
the engine it should be dismantled for further
examination so that a decision may be made to
rebore or merely fit new piston rings.

Thanks Bruce, some good info there.

I was looking for some combustion chamber compression figures from some people who may have tested there Victas before.

I tested my 125cc and found a figure of 62psi and my power torque was 75psi, and I agree a new set of rings etc may be needed, just trying to get a ball park figure before I go pulling it down.

MVC,

Ring change on the victa 125cc is not hard to do and would only take up to an hour at the most. Usually if you try to spin the blade plate and it kicks back then the rings are ok but if it spins through without any kick back then new rings.

Ok, no probs. Thanks again.