I found an easy way to cut the high spot off an ez spin cam. I chucked the cam in my metal lathe and used a dial indicator to see where the high spot was. Then I put the cutter on the bottom of the lobe and turned the lathe chuck back and forth by hand to shave off the spot .This about .010 high from the bottom of the exhaust lobe to about half way up the side. Then just clean it up and blend it in with a fine file, recheck with the dial indicator and you're done. For those that don't know, the ez-spin feature slightly opens the exaust valve on the compression stroke to make the engine easier for joe homeowner to pull start. This compression loss can only rob low end power and torque. Cutting it off the cam is better then grinding the valve shorter because you are losing lift . If you want to check your briggs to see if it has the ez-spin do this. Take the head off and turn the engine by hand if you see the exaust valve open slightly on the compression stroke it is an ez spin engine. I don't know how much power loss it causes but this is something to deal with if you do are going to mill the head and stuff to get more performance .
fix an ez spin cam pictures by oldfatguy - Photobucket
after you measure and find where you need to remove material, just turn the lathe back and forth by hand move the cutter and keep going until you complete the cut. finish up with a file. if you do it right the dial indicator will hold the same measurement around the whole bottom of the cam lobe
after you measure and find where you need to remove material, just turn the lathe back and forth by hand move the cutter and keep going until you complete the cut. finish up with a file. if you do it right the dial indicator will hold the same measurement around the whole bottom of the cam lobe
I don't have a lathe so I filed mine off by hand on the HSSK50 engine and smoothed it wet and dry.
Takes forever and a day cleaning it each time and putting it back in the engine to check the clearance over and over again.
I haven't got the engine back up and running yet as I'm adding a mechanical rev counter drive to the end of the cam too.
But in theory filing off the BCR by hand should be ok if you don't have a lathe as there is no valve spring pressure/load on the base circle of the cam. The phrase valve clearance is deceptive, the main function of valve clearance is actually to lubricate between the cam before lifting the cam follower.
Takes forever and a day cleaning it each time and putting it back in the engine to check the clearance over and over again.
I haven't got the engine back up and running yet as I'm adding a mechanical rev counter drive to the end of the cam too.
But in theory filing off the BCR by hand should be ok if you don't have a lathe as there is no valve spring pressure/load on the base circle of the cam. The phrase valve clearance is deceptive, the main function of valve clearance is actually to lubricate between the cam before lifting the cam follower.
So how much of a difference is there after you cut the cam? I have a older 3hp brigs on a old go cart pull tractor my nephew won back in the 70s. It could use all of the power it can get from the 3hp. And I would like to know if cutting the cam is worth the trouble. I have a small lathe that I could cut it on.
the photo bucket link should work now .
http://vid568.photobucket.com/albums/ss125/oldfatguy/stellar mini bike h60 tecumseh/briggs001.mp4
this is a video of my 3hp briggs running after the cam was modified.
you can do it with a file too if you need to. Try using a magic marker on the cam lobe to see where the lifter is still touching.. I found that the engine is easier to start, that briggs will start on the first or second pull even after sitting for a while. It does have a milled head on it too. I would do this mod for people but the cost of mailing the cam makes it not worth it.
http://vid568.photobucket.com/albums/ss125/oldfatguy/stellar mini bike h60 tecumseh/briggs001.mp4
this is a video of my 3hp briggs running after the cam was modified.
you can do it with a file too if you need to. Try using a magic marker on the cam lobe to see where the lifter is still touching.. I found that the engine is easier to start, that briggs will start on the first or second pull even after sitting for a while. It does have a milled head on it too. I would do this mod for people but the cost of mailing the cam makes it not worth it.
