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Where to set the cam timing

RacingJake

RacingJake

Forum Sage
With 13.5-1 pistons and stock cams what would be the best setting for degreeing the cams. 100, 105, 110, 115 ?

Thanks
Jake
 
Re: Where to set the cam timing

RacingJake said:
With 13.5-1 pistons and stock cams what would be the best setting for degreeing the cams. 100, 105, 110, 115 ?

Thanks
Jake
Click to expand...

I would be conservative and go with the 100...after setting, slowly turn the motor at least through two revolutions with a wrench on the crank to insure that there is no contact between the valves and the pistons. The when you crank it up, and ride it a little, note if there is any pinging or rattling when you are accelerating or loading the engine. If there is not, then you might want to advance the cams to 105 and try it again. 13.5-1 pistons could be a problem with even high octane gas. You may have to adjust you ignition timing.

Hap
 
I don't think there is a magic #. The higher the lobe center #, the higher in the rpm range, the power will come on. With lower lobe setting #'s, the more torque, or bottom end power you will have, also a longer power curve. Trial & error is the only way to find what works best for you. I had a GS 1100 E with 11:0 to 1 pistons, 1150 carbs, & almost stock cams. The best settings for me were "98" on the in. & 104 on ex. Set this way, the torque was unbelivable, cruising at 60 or 70mph, in 5th, I was always pulling up on the shifter, thinking I was still in 4th. And street racing, I was shifting just under redline. and running better against the competition than I was with the previous owner's settings of "115" and I was having to shift at 500rpm past redline. For me, lower settings ment more fun to ride caused by the higher torque, and long power curve, less abuse to the engine by less rpm, & better performance. Everybody is different, the previous owner must have liked the less torque, a shorter power curve, & higher rpm. Set them at what works best for you. I think the factory settings for the early GS 1100 E's were 107 in. & 109 ex.
 
You are going to have to run 110 racing gas. You must check the clearances either use a dial indicator or modeling clay on the top of the piston. You can change the thickness of the base gasket to increase clearence/ will also lower compression. YOU don't want to guess on the clearances
 
As previously stated, the higher you set the cams, the more the horsepower increases but you sacrifice torque. To me, on my '79 1000, the best compromise is 106 degrees on each. Nice wide powerband, good torque and good top end. If you are more interested in racing, then you would be happier with a higher setting.
 
This is a drag bike and I going to run C14 fuel and was thinking 110 degrees on the cams would work best at the strip. I don't care about bottom end power cause when launching, the RPM is between 6-8 grand when I'm slipping the clutch. But with the higher compression I was'nt sure if a different setting would be better.

The previous owner of this 1166 piston and block was using GS1100 ported stock head with stock valves and G3 cams and 36 carbs. Ran a 5.68 in 1/8 so there won't be to much guess work for me in the future.

Thanks
Jake
 
Greg returned my email from Cope Racing and said 108 on the intake and 110 on exhaust. So that's what I'll try.

Jake
1100E
 
Can you post some pics of the 13.5 to 1 pistons? I'm curious how the tops look. Another way of measuring the squishband and clearances is using a bit of thick solder through the sparkplug hole.
 
robinjo said:
Can you post some pics of the 13.5 to 1 pistons? I'm curious how the tops look. Another way of measuring the squishband and clearances is using a bit of thick solder through the sparkplug hole.
Click to expand...

Just tab on my WWW tab at the bottom to see the pistons in the block.

Jake
 
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