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borstman · Apr 1, 2007, 04:12 PM

Hi, I have a Craftsman lawn tractor with a B&S 21 HP OHV Twin in it. The flywheel is very stiff to turn. So, today I decided to dive in and take a look. Here is what I found.

1. Drained oil that was over a year old... nothing but a little black/gray, but no particles in it. Refilled with fresh 30W oil.
2. Plugs were fine, little carbon deposit but evenly burned
3. Took off heads to inspect pistons and valves. When I took off the heads the engine freed up immediately. I thought one of the valves was sticking, but it seemed to be fine when I hand cranked the flywheel. Cleaned carbon deposits off jugs and inside of heads. Nothing that indicated anything really serious. A little scoring on the cylinders but again, nothing I haven't seen on the old VW motors I've worked on as well.
4. Put heads back on.
5. Put two new plugs in
6. Put new air filter on over the carb.
7. Once I reassembled, the motor was again stiff as heck.
8.. I did check the valves and the feeler gauge valve clearance was fine on both sides.

So, from what I've read it seems like there's a compression problem in the motor. I've read about the cam including a compression release within the case... this is my guess at this point. If this sounds familiar please chime in... and if there is another cause, please let me know.

And if it is the cam, how much would it be to fix that sucker? I'm on the East Coast.

Thanks
Andy

ballengerb1 · Apr 1, 2007, 04:21 PM

I have a 20 HP V twin and its stiff too if I turn by hand. Are you sure this is abnormal for your tractor. Twin pistons pull a good compression.

borstman · Apr 1, 2007, 04:27 PM

The starter won't turn it over... and I can turn it easily when the heads were off.

Thanks for the reply

ballengerb1 · Apr 1, 2007, 06:36 PM

With the heads off there is zero compression so it turns freely. You sound like you know your way around the engine. Any chance your battery is low? Should be about 13 vdc with no load.

borstman · Apr 1, 2007, 07:32 PM

Battery is new as of 12/06 and I checked the charge. It's fine.

The motor turned over a few weeks ago, but got increasingly stiff.

newaukumdon · Apr 1, 2007, 09:15 PM

Are you determining stiff by the difficulty the starter is having? Is the engine coming to a compression stroke and stopping? I believe ballenger is correct in his assumption you may have a voltage or starter issue. As I have stated many times on this forum even without the compression release or valves adjusted correctly the engine will still crank.
Don

borstman · Apr 5, 2007, 06:13 PM

The starter won't turn the motor... maybe it is a weak starter, but the stiffness in the motor when I turn the flywheel by hand is pretty bad. I'm going to have someone look at it for me... spring is coming too quickly.

ballengerb1 · Apr 5, 2007, 06:21 PM

When you get your fix please come back and let us know what the problem was. I have to lean with newkamundo and the weak voltage/starter approach. That 21 hp twin will be hard to hand turn since you are almost always ina compression stroke.