Have a 15.5 HP B&S on an early 2000's craftsman rider. Last year was difficult to start, this spring, impossible. When turning over, it hits a spot where it just can't go further with the starter. Have replaced starter, solenoid, battery, plug, and adjusted valves (which move freely-I have had the head off as well). If I hold the lever that operates the compression release ("easy starting" mechanism), then it turns over really well, but won't start. As soon as I begin to ease the lever into the position it should be in, the motor backfires through the carb and exhaust really badly, and becomes unable to turn over again. Obviously it has something to do with a timing problem or a compression-release problem, but I can't figure it out.
I don't think you are holding the compression release. That is inside the engine and you can't get at it. Where is this lever located and what is it hooked to.
It is located near the rear of the motor, very close to the bottom. It is connected by a lever to the throttle. When I push the throttle up far enough, the throttle mechanism that is connected to the carb pushes this lever a bit.
That is the governor control arm. When you push on it you are opening the throttle. I think you have a fuel problem. Spray a little carb cleaner into the airhorn with the throttle wide open. It should fire butnmay not run. Let us know.
Thanks, I forgot to mention that I have had the flywheel off to check things out in there, no problems. It sure is acting like it's out of time somehow, though.
Just tried to "prime" the thing. Problem is, it is simply too hard to turn over. When I turn the key, the flywheel turns just so far, then the compression is too hard for it to keep going. Once in a great while, it will fire, and when it does, it is through the carb or the exhaust.
By the other posts I have seen with similar problems, it sure seems like I have eliminated everything except a bad cam.
Thoughts?
#7
OzRanga
Take the rocker cover off and check the following...as process of elimanation:
Ensure both rockers are operating about the same (there was a bad batch of cam lobes wearing at one stage but unlikely). This will also check any bent or broken pushrods
Check the bottom rocker is opening the inlet valve ever so slightly on the compression stroke (opens valve only a thou or two)
Double check valve clearance on both valves is at 0.003-0.005" with piston 1/4" past TDC on power stroke.
At least I know that I was on the right track at one point here. I have checked the push rods, they are fine, and the valves open both the same. I have set the valve clearance to .005" on both. I just tried determining with a feeler guage whether the lower valve is opening on compression stroke. It seems like it is not.
From you description I would say that the compression release on the camshaft is broke and will require a new cam to be installed. Have one in the shop right now where the flyweight on the camshaft broke and was lying in the oil pan.
This is my first time this deep into a small engine. What is the flyweight? I have completely disassembled the motor. On the cam, the little lever still has a spring around it, but it doesn't look like it would do anything. I found pieces of metal in the pan and all over inside the crankcase. Some are small, but several are quite large, like 1/8" thick and 1/2" long, look like a piece of a large, tapered washer or something. It is cast metal, and is not aluminum. I have inspected all the parts inside that are cast metal, and none are damaged. It has to be something that is so damaged it is unrecognizable and missing from wherever it is supposed to be.
I would recommend that you go to either the B&S website or one which sells parts on line and download a breakdown of you engine. It would greatly help you to understand the parts and what you are looking for.
The flyweight on the flywheel looks like a 1 1/2" finger near the gear on the camshaft. When rotated moves a small half moon rod that bumps the intake valve off of its seat for starting. the spinning flywheel causes the flyweight to move out for running and the spring returns it to its resting position when the engine is shut off for starting the next time.
Sounds like the pieces that you found are from a broken flyweight.
I meant to say on the camshaft not the flywheel. sorry for the miss communication. Murphy of Murphy's law has been plaguing mean for about 3 days now. He usually sticks around about a week before moving on.
Wednesday was doing the camshaft broken compression release weight problem and went to open the new sump gasket package and the paper package tore wrong and tore the gasket in two. Yesterday was getting ready to put a new battery in a WE261 riding mower and the battery I got from the Poulan distributor had superseded to a incorrect battery, currently waiting on new battery and call tag for incorrect battery to be sent back. Also yesterday was going to put a new diaphragm on a small push mower and one of the carb mounting screws that bolts in to the fuel tank caught the edge of the diaprhagm and tore it. Customer came to pick up his rider yesterday and the voltage regulator quit at start up so I had to change it with the customer waiting.
