Topic: Isle of Man Cam setup

[bambuhiphop]

Hello,

I am getting ready to degree my Isle of Man B grind on my 550 and was hoping someone may be able to assist with a question. Through various searches I have found the below specs:

In opens 27BTDC-closes 57ABDC lift 9.00mm
Ex opens 56BBDC-closes 27ATDC lift 8.55mm
Yoshi part# YH600-122-00
Valve clearance street-0.10mm race-0.15mm,
Ignition Timing +5 advance

My question is in regards to the advance. Was this cam advanced when made meaning I should put TDC at 0 or should I advance off my TDC reading and put at +5?

Any help would be appreciated. Thanks

[bwaller]

They're asking for 5 degrees more ignition advance, not advancing the cam. Testing ignition sweeps on a dyno, and turboguzzi as well, we both found that we were able to retard the ignition timing down to 28 degrees for best power. This is with increased compression and tight squish, but regardless the small 500 chamber is quite efficient and I never understood the need to add ignition lead.

[bambuhiphop]

They're asking for 5 degrees more ignition advance, not advancing the cam. Testing ignition sweeps on a dyno, and turboguzzi as well, we both found that we were able to retard the ignition timing down to 28 degrees for best power. This is with increased compression and tight squish, but regardless the small 500 chamber is quite efficient and I never understood the need to add ignition lead.

Great, thanks!