Hardened rubber on the guides , kinda like o rings, oil seals, valves. The timiing chain in my 300ex got stretched from top end rebuild. First the slapping, then the thing starts running crappy, and then stops running all together.

Checked everything air /fuel/exhaust leaks, plug, float position battery, push/pulstarted it ran crappy for few minutes and would jump time and stall !!!

Had to time it several times, kept jumping! Tore it apart found out guides were down to metal at the top of both of them.

Then I find the chain is so streched I can almost take it off the cam by hand (slop)

I look at the auto. tensioner and it's all the way out 4 complete 360 degree turns. at max tension, chain still loose!

TextHow your engine stays in time

1.The tensioner pushes against the front guide

2. The guide pushes against timing chain

3. This constant perssure from both the tensioner and guide keep the chain tight even when the chain stretches

4. When you change rpms the chain pulls when you accelerate and pushes back on the or gears when you back off the throttle when the chain is not tight. This is what the tensioner is for.

Ever wonder why you go through sprockets on the drive train and not the power train (engine) ?


If you did not have a tensioner on your engine it would go through cam gears like crazy!

They would lean one way and eventually the chain would start popping off and causing major engine damage!!!


This is why guides are so important if there wore down to far and the chain is stretched Then a new chain or taking a link out of the old one would tighting it right up. A new guide will make it quiet and add a hair or more of thickness.

My engine runs great now that I bought new guides and chain!

 

VD,
Thanks for your input. Oddly enough (after going through everything for what seemed 3 dozen times over and over) it was indeed the cam chain that was causing this very poor and confusing behavior. Sometimes a deal isn't always as good as it appears, even when just the "valves need adjusting". Oh well, lesson learned. Thanks to everyone for their help with this and have a great season of riding guys and gals.

 

Your welcome turboDS1300! Glad I could help you out.