cub timing gear marks...Help

Sun Jul 20, 2014 7:14 pm

Good evening everyone. My name is Rob and Im new here. I need some advise and or direction from the pros. We have a 4-h group and are rebuilding a cub for fair this year. The kids are doing awesome and making great progress on the old girl. I fear that the gears may not be aligned correctly. The crank was in and rotated to #1 TDC, there was only one dot. The cam was installed and the one dot was aligned with the crank dot (actually a tooth behind or ahead, sorry) the idler gear had no marks and was installed to mesh with the other 2 gears. The timing cover was installed and the pulley is now on as are the valves. When I roll her over to #1 TDC on compression stroke (the head is off) the mark on the pulley (notch actually) is just about 1/4" before the pointer, not 13/16 AFTER like the book states. Oh yeah the gov is out too. Am I okay Or does she need to come apart? The kids are coming back on Wednesday evening and are hoping to get her to fire that night. As for the mag, I believe Im supposed to install the gov in a position that the slots would allow me to have the mag pointed at number 1. Just kinda freaking out about it. Don't want to let the kids down. :? ANy help or advice would be greatly appreciated.

Thank you all

p.s. its a 1949 Cub

Re: cub timing gear marks...Help

Sun Jul 20, 2014 7:52 pm

my idler has no marks, I popped out the seal and checked from the mag side. I found the one on the gov though

Re: cub timing gear marks...Help

Sun Jul 20, 2014 10:18 pm

Here is how the marks should go. If you have a magneto, the idler and governor timing are critical, if a distributor, you can always pull the shaft out of the drive unit and compensate. The camshaft timing is critical though. Sometimes the governor mark which is on the seal side of the idler are pretty shallow.

Image

Re: cub timing gear marks...Help

Sun Jul 20, 2014 11:05 pm

Welcome to the board!
motornutz wrote:my idler has no marks, I popped out the seal and checked from the mag side. I found the one on the gov though

With #1 at TDC on the compression stroke, the pointer and notch should line up exactly.
There should be a timing mark on the mag side of the idler gear. You will only see it when the #1 cylinder is at TDC on the compression stroke. When the dot is visible and in the center of view, the pointer should be lined up with the notch on the pulley. The scribe in the photo below is pointing to the timing mark on the back side of the idler gear.
Image
If you can't see the mark with the pointer and notch lined up, have someone slowly rotate the engine as you look in from the Magneto side to try and locate the mark.

After installation of the governor, the drive should look like the photo below. As John said, if it doesn't, you'll never get the ignition timed right with the Magneto.
Image

The GSS-1007 located here: http://www.cleancomputes.com/Cub/Blue%2 ... Engine.htm
The last five pages are where you are at now.

Re: cub timing gear marks...Help

Mon Jul 21, 2014 8:17 am

I cleaned the gear and found the mark....wrong spot :( . I guess she needs to come apart right? The crank and cam are right, just not the idler. Would it be possible to install the governor in the right orientation, install the mag and where the rotor is pointed that be number one? My cam gear had only one dot when we installed it and was at the tooth not between.

Re: cub timing gear marks...Help

Mon Jul 21, 2014 12:50 pm

That will work. it may take a little trial and error.but you can do it.

Re: cub timing gear marks...Help

Mon Jul 21, 2014 1:48 pm

John *.?-!.* cub owner wrote:That will work. it may take a little trial and error.but you can do it.

It may be quicker to pull the front cover back off (depending on where the engine is). The next guy to own the Cub will definitely benefit from having it set up correctly.

Bob