I am sure this has been discussed before, so apologies . Henk has told me that these pumps can be problematic, but mine does seem very stiff. I have fitted it back into my rebuilt engine, which was turning over like a swiss watch and the pump is so stiff its restricting it from freely rotating now. It may free up when it has been running but with all the counter weight on the flywheel I would have thought it should rotate a bit easier than that! Should I bite the bullet and strip it, or is this par for the course? thx Andrew

email (option): andrew.honychurch@btinternet.com

Andrew you must attend to the pump. The Mazak swells up with age and will cause the pump to bind. Then the worm teeth will wear or strip. Each individual gear should be inspected and turn freely in the pump body. You can use fine grinding past on the shafts and turn them back and forth with pliers. It's tedious but doesn't take long. Also make sure the gears aren't binding against the end caps. Just make sure each gear is free individually before assembling all four....and be careful not to over tighten the bolts. Ron

email (option): ronpier@talk21.com

Also check the pump for free rotation after fitting..when the two bolts that hold it to the crankcase are tightened the pump can go tight again. If that happens you will need to do a bit more lapping in. Remove the crankshaft pinion and try to turn the pump with the drive spindle after fitting.
The pump should turn freely by hand, although you may well find it is a bit less smooth when rorated in the opposite direction to normal running.
Don't forget two fit new spring washers to the pump retaining bolts.
A useful point for future reference...when I am building these engines, after the bearings and fixed fitting are in place the next thing I fit is the pump and drive..it is a lot easier to access the drive shaft before the rest of the engine is assembled....Ian

thanks very much Ron. are there gaskets I will need in the pump, or is it all face to face?

email (option): andrew.honychurch@btinternet.com

Hi Andrew..It's all face to face...fit the pump/crankcase gasket dry or just smear some light oil on it...Ian

thanks Guys. Its out with the pump again tomorrow then and try to get it all smooth running. I am awaiting a new set of Valves and piston rings so no need to hurry . thanks , as always for you help. I am really looking forward to getting the old girl going again soon.

email (option): andrew.honychurch@btinternet.com

Wouldn't it be great if one of the boffins on this forum could make some new bodies for these pumps. !!

Anyone ?

Job

email (option): Jonnyob1@googlemail.com

Hey John, Draganfly does make steel bodies for these pumps.
Cheers, Mick.

email (option): mick@motorbikemike.org.uk