will not rev

[spaceman]

could anyone throw a light as to why the diaphrgam will not open when ask to will rev to 5000 but no more??

the head has had a bit of work done to it and 600 inlet rubbers fitted (swopped for 400 but no change) got it for sale and could do with trying to sort or tell the buyer what it may be.

[DonTZ125]

Is it one slide that's stuck, or all four? Try lifting the slides with a finger, see if they move freely. The slide grooves could be corroded / fouled / laquered up (not liquored up - that's the rider!)

The diaphragms could be perished, hardened, torn; the vacuum passages could be plugged; there could be a family of mice living in the diaphragm chambers. The diaphragm caps could be loose. I believe there is an o-ring that seals the passage at the top; if it's missing, no vacuum = no lift.

[spaceman]

checked all that wish it was that easy its on a race bie so every thing check after meeting etc