Perry Shooter / Small Engine Experts

Dads3040

I replaced the rod and piston in my 8 HP I/C B&S that powers a Troy Bilt Horse Tiller. When I went to time the cam to the crank, I found that there is no mark on teh crank gear because the roller bearing obscures it. The online forums mentioned a mark on the crankshaft couterweight that is used to align the cam to the crank. I aligned the mark I found with what I thought was the corresponding tooth on the camshaft.

When I try to start it, I get nothing. Spark is good. Fuel is good. But it seems to spit back through the carb. As I turn the engine over by hand, there doesn't seem to be much compression built up, but it will blow my finger off the plug hole.

I put a degree wheel on the crank, and did a quick check of valve timing using my fingers in the valve/pushrod access cover.

What I get is the Intake valve beginning to open at 35* BTDC and closing at 30* ABDC. The Exhaust valve begins to open at 70* BBDC and closes at 10* BTDC.

This is of course the valve beginning to move, so it makes the duration longer than a normal cam duration measurement, but it seems that the beginning points of movement are a tad early...like maybe I am a tooth off?

Any thoughts? I am trying to avoid tearing the stupid thing back apart before I am sure that is the problem. Thanks All.

fordsix

carb spitter is out of time

Dads3040

The carb spitter is an option on this model.

redneckandy

I bet you are out of time. It ran fine before the rod/piston failed right? That eliminates fuel and ignition problems. The only thing that could of changed is crank/cam timing.
Crack the case apart, pull the bearing and be sure the timing marks are aligned.

iceracerx

Your cam timing might be off 180 degrees.

Cams run at 1/2 crank speed so turning the cam 180 will keep the valve timing as you noted but on the 'other' (of 4) stroke.

This will (might) get your ignition times and valve timing where they should be.

perry shooter

wow hard to tell but Cam timing is most likely off make sure the when piston is at tdc both valves are completely closed and then should start to open equal degrees away from top dead center turning both CW and CCW

320090T

Timings wrong

mogley98

Apparently you need to reset your watch!

Don

[:D]

Dads3040

Having checked my watch (Thanks for the tip, mogley [;)]), I am going to tear the infernal contraption back apart.

I see no point in chasing possibles. I might as well just bite the bullet and go in to check to see if the timing or something else is off.

Thanks for the input.

Mr. Perfect

Is it not possible to transfer the mark to someplace you can see?

Dads3040

quote:Originally posted by Mr. Perfect
Is it not possible to transfer the mark to someplace you can see?

There is a mark on the crankshaft counterweight, but it wasn't well defined and there is more variation in how the 'alignment' is judged than there is when a tooth is marked to correspond with a space between two teeth.

I should have been more careful when I took it apart, but the case was stuck pretty good and the cam popped out when I opened it up.

Tearing it back apart isn't the end of the world, since it is a one lung B&S, but it just annoys me. I was ready to be done with this thing and get it sold. The 5 HP Troy Bilt Pony I got from my FIL is all the tiller this fat old man wants to wrestle around these days.