Advance-Retard Timing /w Stage 1 HC on Rap?
#2
#6
Advance-Retard Timing /w Stage 1 HC on Rap?
I have an 01 Raptor with a 11:1 wiseco piston (std bore), hotcams stage 1 cam, staintune full stainless exhaust (Australian built). And an opened up airbox, and rejetted.
I retarded the cam 1 tooth which equates to 17.1 degrees retarded in crankshaft degrees. The raptor has a cam sprocket with 42 teeth so 1 tooth change = 360/42 = 8.57 camshaft degrees hence multiply this by the 2:1 reduction which = 17.142 degrees crankshaft change. By retarding the cam the exhaust valve to piston clearance is reduced, but the wiseco comes with 1mm deeper valve reliefs in the piston compared to the flat top std piston. I checked the exhaust valve clearance by pressing on the exhaust valves while rotating the engine over near top dead centre and could feel a fair bit of clearance. I didn't measure this with a dial indicator though so i dont know the exact value.
The result. It flies. Conservatively i'd guarantee it' given another 500 rpm, but i reckon it's closer to 1000 rpm of top end power. It pulls hard and keeps revving instead of the power dropping off.
The jetting becomes much leaner at idle and i have wound out my mixture screws a fair bit and it now idles beautifully. I will fit 25 or 27.5 pilots when they come as i am now well past the recommended 3 turns max out.
I have noticed a little drop in bottom end power but the raptor has never had a shortage in this area anyway. If you have a wiseco or JE piston which has the deeper valve reliefs, and a stage 1 then you would be stupid IMO to not try this. If you have a stage 2 cam then you should only attempt this (to see if any benefit exists, it may not) if you are experienced enough to measure the exhaust valve to piston clearance with the springs removed and a dial indicator, as the stage 2 has more valve lift and might result in dangerously close contact.
By retarding the cam the top end increases as the intake valve closes later to take advantage of the momentum of the intake air and similarly with the exhaust. All i can say is that i am rapt with the quad now, and it has been one of the biggest gains in power that i have done. Same sort of gains as the piston and exhaust combined.
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I retarded the cam 1 tooth which equates to 17.1 degrees retarded in crankshaft degrees. The raptor has a cam sprocket with 42 teeth so 1 tooth change = 360/42 = 8.57 camshaft degrees hence multiply this by the 2:1 reduction which = 17.142 degrees crankshaft change. By retarding the cam the exhaust valve to piston clearance is reduced, but the wiseco comes with 1mm deeper valve reliefs in the piston compared to the flat top std piston. I checked the exhaust valve clearance by pressing on the exhaust valves while rotating the engine over near top dead centre and could feel a fair bit of clearance. I didn't measure this with a dial indicator though so i dont know the exact value.
The result. It flies. Conservatively i'd guarantee it' given another 500 rpm, but i reckon it's closer to 1000 rpm of top end power. It pulls hard and keeps revving instead of the power dropping off.
The jetting becomes much leaner at idle and i have wound out my mixture screws a fair bit and it now idles beautifully. I will fit 25 or 27.5 pilots when they come as i am now well past the recommended 3 turns max out.
I have noticed a little drop in bottom end power but the raptor has never had a shortage in this area anyway. If you have a wiseco or JE piston which has the deeper valve reliefs, and a stage 1 then you would be stupid IMO to not try this. If you have a stage 2 cam then you should only attempt this (to see if any benefit exists, it may not) if you are experienced enough to measure the exhaust valve to piston clearance with the springs removed and a dial indicator, as the stage 2 has more valve lift and might result in dangerously close contact.
By retarding the cam the top end increases as the intake valve closes later to take advantage of the momentum of the intake air and similarly with the exhaust. All i can say is that i am rapt with the quad now, and it has been one of the biggest gains in power that i have done. Same sort of gains as the piston and exhaust combined.
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#7
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#9
Advance-Retard Timing /w Stage 1 HC on Rap?
Originally posted by: raptor03
what do you think Gary...
what do you think Gary...
#10
Advance-Retard Timing /w Stage 1 HC on Rap?
I think I saw Grant from australia post that on this or another forum.
I have always thought of this way - moving the cam gear counterclockwise advances it. If you turn the motor over the cam is "advanced in time" where the crank firing position and TDC have stayed the same. The cam is 1 toother "sooner"
I have always thought of this way - moving the cam gear counterclockwise advances it. If you turn the motor over the cam is "advanced in time" where the crank firing position and TDC have stayed the same. The cam is 1 toother "sooner"