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Cam timing
http://www.mudmotortalk.com/mmt_v2/viewtopic.php?f=3&t=72398		 Page 1 of 1
Author:  MSM60 [ Tue May 01, 2018 8:23 pm ]
Post subject:  Cam timing
Need some help thinking through a problem with my prodrive. When I got the 36 block (to replace the cracked 32 block) I took it apart to hone the cylinders, new rings, gaskets, seals, etc. Put it together and put it on the frame and it wouldn’t run. To condense many hours of wondering what the hell was going on, the ignition timing is 180* off from the cam timing (magnet passes coil at end of intake stroke when piston is at bdc, on the compression stroke the magnet is 180 degrees away from the coil). I’ve been thinking through this for a while now but I can’t figure out how this could happen. The flywheel can only go on one way and I’m 98% sure that I lined up the marks on the cam and crank correctly. Is there another mark on the other side of the cam? What am I missing? Im going to double check the flywheel key tomorrow and if that looks fine then I’ll pull the motor back off and check out the cam but I’m hoping somebody comes up with an easy answer before I do that :D
Author:  Will C [ Wed May 02, 2018 7:24 am ]
Post subject:  Re: Cam timing
The engine actually fires twice per "4cycles" if your cam is exactly 180 out the engine won't know the difference. The crank spins twice for every one turn of cam. Now if the teeth are off other than 180 then that's different . Are you using a factory cam or aftermarket?
Author:  MSM60 [ Wed May 02, 2018 9:02 am ]
Post subject:  Re: Cam timing
Author:  MaXXis85 [ Wed May 02, 2018 9:20 am ]
Post subject:  Re: Cam timing
stock engines fire about 22-23* BTDC in a non cdi motor which you have. With that being said take cylinder #1 and put at TDC of the compression stroke (both rockers will have lash /valves closed). The left side of the magnet will have past the left pole of the #1 coil. You also have to remember these engines also have a WASTE spark so they also fire on the exhaust stroke as well.
only two things can be wrong.... the cam timing is off or the flywheel has rotated on the crankshaft shearing the key.
Author:  MSM60 [ Wed May 02, 2018 5:33 pm ]
Post subject:  Re: Cam timing
Flywheel key was sheared. That’s what I thought originally but then I got to thinking too much. Put another key in it and it ran fine for a few minutes then sheared again. I’m taking it home and impacting that bitch on next time.
Author:  MaXXis85 [ Thu May 03, 2018 7:02 am ]
Post subject:  Re: Cam timing
150' pounds is the TQ spec. I use an impact... You also need to make sure there are no high/low spots on the flywheel taper and crank snout taper.
Author:  50fps [ Thu May 03, 2018 8:50 am ]
Post subject:  Re: Cam timing
Throw some lapping compound on the shaft taper and work the flywheel without the key.
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