Honda Race Cam. Where to set it- advanced or r.e.tarded

Tricycle Squid
Tricycle Squid
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Joined: Thu Feb 28, 2008 10:09 pm
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Location: New Zealand

Honda Race Cam. Where to set it- advanced or r.e.tarded

#1 Unread post by marsheng »

I purchased an old CB 125 Honda race bike which I use in Bucket Class. I have increased the piston size to give me 150cc the max for the class. The new compression as measured is 10.7:1. Took a bit of cutting in the piston get the clearances. The Cam in the bike is far from standard. Standard Lift 6.5mm, this one 9.5mm

No to the Business.

I measured the valve travel and this is what I got (0.050")

Inlet 22.5 Deg BTDC -55.5 ABDC Duration 258 Lobe Center 106.5
Exhauset 44 BBDC -35.5 ATDC Duration 259.5 Lobe Center 85.75

Overlap 66.5

The books I've read say the exhaust should be roughly the same as the inlet but this seems to be 20 deg out. I can't close the exhaust any later as the piston will hit the valve. The piston is only 2 mm thick in the valve pocket to give the valve to piston 1.5 mm of clearance. Would I be better with a exhaust at 106 deg and a lower lift cam ?

The cam is slotted so I have put it slightly advanced to check the motor is running well after the rebuild before I set it to the "original" settings.

The rear wheel power on the first dyno test was 12.5 HP at 11000.

The cam is asymetrical and I can find very little on full race cam info.

The bike has a real kick once on the cam.
Wallace New Zealand

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