This Forum is now CLOSED use the link to get more details viewtopic.php?f=3&t=13924#p102587
User avatar
By Slappy
Good morning all
Been a while since I have posted on here
So I have finally nearly finished building my bike and I am now in to the reassembly of the top end
So the bike is a 91 Bullet 500 all the parts are from our host, they are as follows
Alloy barrel matched to the standard Omega forged piston, the ring gaps have been set ready to go, i have the competition vavle set the guides and new valve seats have been professionally fitted with all the specs suplied
I am also running the alloy rocker set
My question is would i be looking at any clearance issues valves to piston and would the pushrod clearance still be
Many thanks Slappy
User avatar
By Adrian
I can't see any reason to vary the normal pushrod/tappet clearance, just enough for the rods to spin freely with both valves closed at top dead centre on the compression stroke.

As for worries about the valves hitting the piston, are you using high-lift cams? You can always do a dry build with a lump of plasticine on the piston crown to check valve head to crown clearance, and retard the inlet cam by one tooth if necessary. With a high comp 500 piston you won't lose a lot of bottom end grunt and might get a bit more top-end performance, as well as reduced vibration.

User avatar
By stinkwheel
My 612 has the hitchcocks high compression 535cc forged piston, tuned head, longstroke crank and high lift cam.

With just a 3mm compression plate under the barrel, it still had a (measured) piston to valve clearance of 5.5mm. Even if I took the plate out, (which would leave the engine with an utterly unfeasible negative deck height and 13:1 compression), piston to valve clearance would still not be an issue, minimum is stated as 1.3mm.

I measured that using the blu-tak trick.

With the high performance cams, they usually recommend having a small but measureable tappet gap (as I recall, 0.015" on the inlet and 0.03" on the exhaust). That's what came with the literature for my build kit in any case.
User avatar
By Slappy
Thanks for the replys gents
I am just on standard cams, so just valves alloy barrel and omega forged piston, I will try plasticine trip just to be sure

Thanks Slappy

Shop for accessories at Hitchcocks Motorcycles