four stroke assembly
01-23-2007, 06:39 PM
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four stroke assembly
I was given a Magnum 80fs that is in a box in a bunch of peices. The guy said that it ran before he tore it down but he wanted to see how it worked. When he went to try to put it back together he couldn't get it to run. My question is this, how do I make sure that the valves are installed right with the right valve moving on the right stroke? This is my first four stroke and I dont know much about them. I have messed with two strokes for years but this is a whole different ballgame.
Thanks
Matt
Thanks
Matt
01-23-2007, 07:42 PM
#2
Senior Member
RE: four stroke assembly
Matt, does the 80 have the cam in front or in back?? If the cam is in front, you will find a small drill mark on the outside of the cam. With the piston at TDC, the mark on the cam points down. You can check with magnum service, they are great at answering questions. Other than the cam timing, the only other issue is adjusting the lifters. You want 0.002" tight, 0.003" loose and you have them set. Not much to it.
Don
Don
01-24-2007, 01:08 AM
#4
Senior Member
RE: four stroke assembly
Matt, don't know why I said what I did on the lifter adjustment. It should have been 0.002" loose, 0.003" slight drag.
Check with Golobal or Hobby People on the cam mark. I just went back over some of the old post and some are saying that it should straight down at TDC and others are saying it should be in line with the lifters. I timed mine with the lifters and it ran sort of OK, good high end but not so good at idle. I sent it into Magnum for service and they said the cam timing was wrong. When they were through, it ran good on high end but not so good at idle, in other words no change. It wouldn't hurt to get another opinion on the exact timing.
Don
Check with Golobal or Hobby People on the cam mark. I just went back over some of the old post and some are saying that it should straight down at TDC and others are saying it should be in line with the lifters. I timed mine with the lifters and it ran sort of OK, good high end but not so good at idle. I sent it into Magnum for service and they said the cam timing was wrong. When they were through, it ran good on high end but not so good at idle, in other words no change. It wouldn't hurt to get another opinion on the exact timing.
Don
01-29-2007, 03:22 PM
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RE: four stroke assembly
OK, The service department at Global said the the proper way to set the timing was..........
CRANK PIN AT 12 O'CLOCK (STRAIGHT UP) AND THE TIMING DOT ONE TOOTH AHEAD OF BOTTOM, ABOUT THE 5:30 POSITION.
This may help someone else a little later.
Matt
CRANK PIN AT 12 O'CLOCK (STRAIGHT UP) AND THE TIMING DOT ONE TOOTH AHEAD OF BOTTOM, ABOUT THE 5:30 POSITION.
This may help someone else a little later.
Matt
01-29-2007, 05:05 PM
#7
RE: four stroke assembly
The guy said that it ran before he tore it down but he wanted to see how it worked.
Not laughing at you, but the prior owner.
I once went to look at a 1940's Ford 8N tractor advertized in the classifieds as: "Runs GREAT!" When I arrived he started walking me around his garage and introducing me to the pieces scattered all over.
"How do you know it runs great?"
"It did when I took it apart. I can have it back together in a week."
"Here's my number. Call me when it runs great again and we'll talk."
Never did find out if he got her back together.
Did you check to see if there is a downloadable exploded diagram on their website?
