V twin hoglet questions

[neil_1821]

I have a couple of questions relating to my build of the Hoglet, as I know a lot of people have experience with them.

I've done the valves, but i'm not overly happy with how they seat on the face of the head, on one in particular its almost like the chamfer on the head is slightly out of centre so the valve has to be in a certain orientation to sit flush (I'm slightly concerned that the valve might rotate during running). For lapping the valves in i've applied some metal polish, placed the valve in a collet chuck on the lathe and turned it on while i apply slight pressure to the head. Is there a better way of lapping the seat for the valve or is this adequate?

My other question is, where does everyone get the small sprockets, chains and gears from for these engines? I know the plans give you the serial number for an american website but i'm based in the UK.

 

[tornitore45]

A large seat will leak because there is more opportunity for sneak path to meander around the seat surface. As a rule valve seat should be as thin as possible on the order of 0.01". With a thin seat a minimal lapping with the finest compound will do it. You know you are done when the dull ring formed in the contact zone is all around the valve and the seat. As the engine run the first few explosion the seal increase.

 

[Cogsy]

For lapping in valves I normally leave an inch or two of material on the head end of the valve to hold on to and rotate the valve (with suitable lapping compound on it) about 180 degrees back and forth by hand. Then rotate a full 90 degrees and repeat. I do this about 4-5 times and it's normally enough. For valves into brass seats I usually just use toothpaste as the lapping compound although some say it's not abrasive enough, but it works for me. As Mauro says, once the engines starts to fire the valves achieve a better seal reasonably quickly by themselves.

 

[tornitore45]

Toothpaste is a very mild abrasive often useful for polishing and valve seating, another product is a what in the USA is marketed as "Bon Ami" used to scour sinks and porcelain, I believe is pulverized pumice. Mixed with oil can be used as abrasive paste.