Drive Chain = Brain Drain

[Jeff McKelroy #55A]

The 40 stamped on the sprocket is the number of teeth on the sprocket  not what size chain its for put the chain on the front sprocket look at how it sets down on the teeth then do the same thing  with the rear sprocket if it doesn't look the same on both its for a different size chain

Okay. I measured the thickness of the front sprocket, at .284", the rear sprocket at .253".  It is a 40-tooth, 40 pitch sprocket according to the stamping.

Tank, the numbers were lined up like you suggested.  But, you can roll the chain up and over the sprocket (new chain, BTW) and it climbs off the sprocket.

Sounds like wrong chain. Are you sure its 40 chain on 40 pitch sprockets. Something is bad wrong to bend a tooth over on the sprocket that or sprocket is wore slap out.

George, I think the chain is okay. I went to a local cart shop, they didn't have 40 anything, but I saw 35 and 50 pitch, and my sprocket looks somewhere in the middle of them.  So I am pretty sure it's somewhere near a 40, unless it's a 41?

check your sproket holder.....a 40 tooth sporket will only fit on a certain holder or the side plates of the chain hit the sproket holder and it will not allow the chain to sit in the sproket all the way. i know i had this happen.

You know what, you're right. it does exactly that.  The front sprocket allows for no movement of the rollers when the chain is seated, however the rear sprocket does allow for some movement.  You can see where the chain rides directly on top of the carrier.  No Bueno.

Here's what I', going to do fellas, and I appreciate all the input.  I am going to replace the rear sprocket with a 42 tooth, but refigure my math to keep the ratio the same.  I think another sprocket with a tad more diameter will do the trick...I hope.

Thanks everybody, I love this board! Everybody's so willing to help.

[more4les]

Bigger sprocket might be a good idea in 2 ways. I was running smaller sprockets trying to lose rotating mass but ended up destroying chains - fast. I've since went to bigger sprockets which reduce the strain on the chain. I now change my chain halfway through the season 'just because'.

Lester

[RoMow]

Jeff,

   I haven't seen this suggested yet, so try it:
1. Jack up the rear of the mower so the wheels are off the floor.
2. Disconnect your chain's master link.
3. Lay the chain over the axle sprocket and slowly rotate the sprocket forward and backward while watching for the chain "jumping" teeth.
4. Put the transmission in neutral and repeat this with the transmission sprocket. 
5. If the chain matches the sprockets, the chain rollers will smoothly follow the sprocket teeth as the sprockets are being rotated.
6. If the chain jumps teeth on both sprockets, you have the wrong size chain.  If the chain only jumps teeth on one sprocket, whichever sprocket jumps the chain is the wrong sprocket.

Sincerely,
Rodney Rom
Rom's Reworks
Butler, MO

[Rooster]

Jeff,

   I haven't seen this suggested yet, so try it:
1. Jack up the rear of the mower so the wheels are off the floor.
2. Disconnect your chain's master link.
3. Lay the chain over the axle sprocket and slowly rotate the sprocket forward and backward while watching for the chain "jumping" teeth.
4. Put the transmission in neutral and repeat this with the transmission sprocket. 
5. If the chain matches the sprockets, the chain rollers will smoothly follow the sprocket teeth as the sprockets are being rotated.
6. If the chain jumps teeth on both sprockets, you have the wrong size chain.  If the chain only jumps teeth on one sprocket, whichever sprocket jumps the chain is the wrong sprocket.



Sincerely,
Rodney Rom
Rom's Reworks
Butler, MO

[Caudy155]

I had this issue when we built my father s/s imow tractor last winter the chain wouldn't seat all the way and wasn't sitting in the sprocket after about a 1/4 of a revolution... the chain would "jump out" and this was on a 46 tooth sprocket... come to find out it got better once you played around with the sprocket flipping the halves around and such but never was quite right... got it close tightened the chain and let it wear itslf in... it was a cheap sprocket... but eventually it wor itself in and fit great...

[Jeff McKelroy #55A]

I am almost home from my road trip from EC after talking with Sir George (I can say that now, else he would've charged me double, lol) the 40 tooth was a bad idea.  As soon as I get in, I am going to try the 42 tooth first, with a 13 tooth trans sprocket.  I'll keep y'all posted, need some sleep first!

[George Herrin]

Jeff was nice meeting you!!! Hope you enjoyed the tour.

[Jeff McKelroy #55A]

I had a blast!  I'll have to make it my annual pilgrimage I think...

By the way, I have to ask:  You only get, what, 2 1/2 hours of sleep per day? 

[George Herrin]

sometimes 3

[Jeff McKelroy #55A]

UPDATE:

Well, all rested up, installed a 42-tooth sprocket on the axle and a 13-tooth sprocket on the transmission - and WOW, this thing runs mui fantastico!!  I haven't done anything to the engine yet except for carb stuff, so the torque at the bottom end really carries it through!  By the time I get to the turn, I am nowhere near 5,200 rpm, which is great for the olde oppy.  However, my testing is on a 500-foot asphalt parking lot, a world of difference from a real race.

Anyway, THANKS SO VERY MUCH for all the input fellas, basically the 40-tooth axle sprocket requires a special carrier for those wanting to run one.  Russ, you were right on about that one.  Rodney, good feedback about the chain-over-the-sprocket test: with the 40-tooth sprocket installed, the chain walks up and over, but not with the 42-tooth.  Both sprockets were new, and are the same pitch, thickness, etc.  it was just the combination with the standard carrier that caused the issue.

Now, to find a truck to carry this thing to Oil City!

[russell jennings]

thank you. i sometimes get one right. glad i could help. good luck with it,sounds like a runner!!