Timing is everything

[bschwartz]

My Metro 6/1 just hasn't run 'right' for several months.  It's been noiser than it used to be.  Intake making more noise.  Louder diesel knock.  More smoke etc.  Power has been fine, putting out over 3KW, but just not running the way I thought it should.
I've adjusted rocker clearances, tried removing the changeover valve and going back to a plain plug, adjusted injection timing and everything else I could think of.  I figured that I just had a bunch of carbon build up from running WVO with some several hour runs at only about 1/3 load.

Today, I was taking out the idler gear to try changing back from the brass to the steel gear.  I just like playing........
Anyway, the crank slipped, and moved while I was putting the timing gear back in, throwing off my valve timing.

I think it moved one tooth, retarding the valve timing. 

Not being quite sure, I buttoned up the engine and tried starting it.
I wouldn't start and acted like retarded injection timing.......
I advanced the injection timing via the seat of the pants 'a few turns' method.

BINGO!!!!!!  Runs like a champ now!  Quieter, easier starting, less diesel knock, no smoke etc.!!! 

I must have been running one tooth off for months.
These engines are unbelievable to be able to perform that far out of spec.

If your intake is noisy, it seems to 'knock' more than you think it should, smokes, and nothing else makes sense, try adjusting the valve timing.  These will run one tooth off!

[Veggiefuel]

bschwartz,

Thanks for the tips.
Is there an easy way to check this without dismantling too much ?
My engine does exhibit the symptoms you listed but I don't want to disturb everything if the timing is ok.
What's the easiest way to check ?

veggie

[Geno]

This pic has been around for a while. Save it to your hard drive.



Thanks, Geno

[bschwartz]

In that diagram, there is a range for each value, such as air valve opens between 4-8 degrees before TDC.  Short of rotating the cam or crank one tooth, there is no adjustment for them.  The only exception is the injection, which can be adjusted by rotating the adjusting screw/nut under the pump.  I haven't counted the teeth on the gears.  Anyone know how many teeth they have, or how far in degrees one tooth translates to?   I wonder how far advanced my valve timing was.


Veggie, I don't know a really good way to check.  I tried setting it up using the method of measuring valve lift at TDC (or something like that...).  Apparently I did it wrong months ago.

To change it, is so quick and easy, I'd say just try it.  4 nuts take off the breather plate.  One nut for the idler bolt.  Rotate the crank ONE tooth towards you, and put the idler gear back in.  If you are smarter than I am, you will make sure there are markings on your gears to line things up if you need to put it back.  After rotating the gears one tooth, I needed to advance my injection timing by rotating the screw/bolt thingy under the injection pump out to lengthen it about two turns or so.

OOOooohhh!!!!  I just remembered something that I thought was strange and NOW it makes sense.  My injector adjustment had slack in it before this last change!  If I screwed it up so there was no play, the engine would knock like a son-of-a....

Maybe that should have told me something.  Well, it was talking, but I didn't know what it meant...... now I do.

Does any of this make sense, or should I finish my coffee first......

[sframe]

Do you have spec's for the 12/1 by chance?

[Tom]

An easy way to check is to look at the valve overlap on the exhaust stroke at TDC. Both valves should be open at that position.

[xyzer]

I put an indicator on the intake lifter and refer to the numbers on Genos chart. With correct injection timing I have never got one to even run with it a tooth off! But....they are from India....