Wiseco Piston & Mugen Cam XR500

[Mudnut]

Hi

I'm new to the forum & need to pick some brains, I'm re-building a XR500 motor (early 1979 /80 ) which is in my JBR500 . It originally had a Protec piston & Mugen cam  installed as standard from John Banks in the late 79 .

The Protec piston is well past its sell by date & Ive purchase a new Wiseco Piston :

Compression Ratio - 10.5 :1
Model -4117M08950
Displacement -503cc
Stroke-80.00mm

I'm still want to run the original Mugen Cam , how ever what kind of clearance do I need to allow between the piston & the valves so on possible valve bounce there is no collision .

The Wiseco has a larger crown compared to the original Protec

Ive done various searches on the net on the subject to no avail . Ive read all the links on XL & XR 500 on the forum & there is some tidy Honda 500's out there , some one must of had the same issues over the years . Its a costly mistake if you F up 

I'll post some pix of the restore if any body is interested , just wondered is there any more JBR's out there in Australia

Cheers  Mudnut 

[TT5 Matt]

try mugen for the valve to piston clearence failing that dummy up the motor with the old protec piston and measure the clearence using resin cored solder put in through the spark plug hole and turning the motor over

[Mudnut]

Thanks Matt , for a minute there I thought you were calling me a dummy . I'll give Mugen a go, but your suggestion of building up the motor as was is the best idea . I'm glad I have not re bored the barrel for the Wiseco piston yet.

Mudnut

[eric318]

Oooohhhh I would love to see that camshaft and the whole bike
----

[eric318]

OK, here is the head on my C&J in exchange

[John Orchard]

Man they're big lobes  :-)

All the 14,000 rpm 1000cc 4 cyl and V-twin engines that I've ever built up I've always run a minimum of 1mm, checked with plasticene.  Although with the piston chasing the exhaust valve home I may opt for 1.5mm on it (just incase I get a bit of valve-float) :-)

[John Orchard]

And such a big-bore with a heavy piston I'd run a minimum of 1mm squish (piston to head).  I'd also run a 1mm radial clearance from valve to valve and valve to edge of the piston valve pocket.

I perfer to use plasticine over solder as I can check more areas after one dummy assembly.  I build a layer of about 2mm over the top of a dry piston, I might put a light smear of oil over the head & valves so the plasticine doesn't stick to it and get pulled up when the engine is turned-over.

When I take the head off, I slice the plasticine a strip at a time to measure all areas with the verniers.