Topic: Better breathing options for the 500.

[Hot500]

Well, after considering the 650 head swap for my 500, I've decided to give it a miss. Too much b/s involved with the stud lengths and CR issues. My next thought was using the 650 inlet valves. Anybody tried this ? What is the valve size ? What about stem length and thickness ? Will this valve transplant straight into the 500 with a new cut seat.

I intend to go with .50 over hc pistons and a hot cam, so with some port work and the 650 IN valve (if it works) this should perk up this little motor very nicely.   

Thoughts ?

[HondaMan]

Go 1.00 mm oversize, 10:1 pistons if you can find them, increase the mainjet by 5 size. Match the intake ports and intake castings carefully, grind a pocket above theintake valves (aka "pocket porting" from the 1960s era). Open the stops on the spark advancer a few degrees (2-4 is enough) and run X24ES-U ND sparkplugs with 5k ohm caps. Add 2 teeth to the rear sprocket, if you can find it, and run a 3.50 size rear, 3.25 size front tire. Change the cam chain and tensiors parts while you're in there. If you can find one, get a cam with just 5-7 degrees more duration (forget the high lift business, it fits poorly under the cam covers on the mid-fours).

You will not recognize it the next time you flog it. 

[Hot500]

Thanks for the info Hondaman. Any advice on where to find those 1mm over valves. I've looked at the sites I know (Dynoman, KPMI) but they don't have a lot for the 500. Would 11.5 : 1 CR be OK as these pistons are easy to get hold of.

[bryanj]

MReik had a post on here about valves being made for the 500 try asking him, plus send him your head for the work, you won't get better

[dave500]

i have a spare bare head if you need one hot500.

[Hot500]

Thanks Dave500, that may come in very handy.  As I'm going to attempt the porting myself God only knows what sort of mess I'll end up with.     PM sent.

[HondaMan]

Thanks for the info Hondaman. Any advice on where to find those 1mm over valves. I've looked at the sites I know (Dynoman, KPMI) but they don't have a lot for the 500. Would 11.5 : 1 CR be OK as these pistons are easy to get hold of.

I was referring to 1.00mm oversize pistons. The stock bores shroud the inlet valves quite a bit on the wall side, but the 1mm oversize really reduces this a lot. This change picks up the breathing more than one might think. It was popular to use the 10.5 CR pistons even on touring 500s in their day, which let the riders gear up on the rear sprocket a bit to lower hiway RPM. If you went the other way and geared down a bit, the bike really woke up for stoplight chases.