YS91 Regulator diaphram -which way up?

[malc1]

Hi
I`m still trying to get my YS91 running properly since a rebuild and today have stripped the carb and regulator to check for debris.

Not sure now which way up the diaphram goes in its plastic housing.

Anyone got any pictures?

[JimLerch]

Examine the black plastic center of the diaphragm. The flat side goes towards the crankcase, the side with the tit pushes against the metal lever arm on the regulator valve.

[DavidH]

Bump on the diaphragm goes towards the crankcase.
http://www.yspartsandservice.com/pdf/91ST.pdf

You can see the assembly on the the page above.

David

[malc1]

Mine has now been installed as per the diagram on the PDF file - with the wide flat disc on the diaphram downwards against the lever and the higher,narrow cylinder shaped plastic pip facing upwards towards the crankcase.

I was a bit confused at first as Jim seemed to say that flat disc shaped section was to go facing upwards which I think was how it was after I last assembled it and had problems with flooding,pouring fuel and hydrolic locks.

I can`t try it again now as I have just managed to distroy the hex starter coupling on the T Rex700 and have to get a new one before I can see if things start and run ok.

[DavidH]

Malc,
Yes most think the bump on the diaphragm does towards the regulator lever. But the bump goes towards the crankcase. Putting the bump towards the lever changes how the regulator determines fuel flow. It is similar to changing the timing on any other time engine.

David

[malc1]

Thanks David
As long as I have now got it right I can try again with getting the engine to idle - a bit frustrating this,being trying since last Wednesday and the engine must have been out a dozen times.