QL 1000 shutting down when hot - Page 2

J-Mech · #11 09-07-2014, 01:53 AM

Quote:

Originally Posted by cubby102

Man just gotta remember these are old machines and issues do come up once in awhile. Dosnt take much to fix the valve problem most of the time pulling the valve and cleaning it up does the trick. Just a evening with some tools good luck man

Guitar Guy · #12 09-07-2014, 02:00 AM

Thanks for the encouragement, but I'm not really a mechanic, and don't really have a lot of tools, so this will likely require hauling it back to the guy who did my clutch, and waiting for him to get time, probably several weeks, and who knows how much $$.

Regarding the "low ash" oil ... I'm not familiar with it. Is that what is recommended? I thought the manual just recommended SAE30.

JT

cubby102 · #13 09-07-2014, 02:31 AM

To be honest man literally a few different sizes of wrenches or sockets will pretty much get the job done. Only big tool needed is a valve spring compressor which can be rented from autozone and u get the money back when you return it. I use the automotive type that looks like a big C clamp. Hope it works out for ya and good luck with it

cadzag72 · #14 09-07-2014, 03:10 PM

Don't sweat it too much, it's cheaper working on these old tractors than keeping the family car up and running when Murphy's law takes effect. I had the joy of dropping $1000 on my wife's car last week, and that was with me doing all the work.

sawdustdad · #15 09-07-2014, 11:17 PM

I would suspect a fuel restriction before a sticking valve. Running for a period may accumulate debris will plug up the fine mesh screen on the tank valve. Clean or Replace that and clean out the tank before you pull the head. The fact that pulling out the choke helps is the key here. That wouldn't happen with a sticking valve.

J-Mech · #16 09-07-2014, 11:28 PM

Quote:

Originally Posted by sawdustdad

That wouldn't happen with a sticking valve.

Actually, it would.

Just as he described,

Quote:

and it seemed to keep running a little longer,

When the valve starts to stick, the engine would suddenly have a lot more air, which would lean the fuel. Pulling the choke would reduce the air coming in and bring the mixture back up. With the description of the problem that was given, it sounds like a sticky valve to me.

sawdustdad · #17 09-08-2014, 10:34 AM

Quote:

Originally Posted by J-Mech

Actually, it would.

Just as he described,

When the valve starts to stick, the engine would suddenly have a lot more air, which would lean the fuel. Pulling the choke would reduce the air coming in and bring the mixture back up. With the description of the problem that was given, it sounds like a sticky valve to me.

How does a sticking valve results in more air into the cylinder? would that be drawing backwards through the exhaust?

J-Mech · #18 09-08-2014, 10:56 AM

Quote:

Originally Posted by sawdustdad

We were talking about a sticking exhaust valve I think. At least that's what the discussion was about. If either valve sticks open, you'd either lose compression or be backfiring/chuffing out the carb. Didn't hear anything about that.

I'd go looking for the simple/more probable issue first.

If your theory is correct, can you explain how a sticking valve results in more air into the cylinder?

The particular situation will only result if it's a sticking exhaust valve. (I'll come back to that.)

If it is a sticky intake valve (which is rare BTW) it would dump the compression out the carb and "spit" the fuel back into the air filter killing it immediately. On a single cylinder motor a sticky intake is pretty much a "direct kill" (engine will die).

Back to the exhaust valve: If the exhaust valve sticks, depending on at what point in the lift it sticks (how far open it is) will determine how fast it dies. If it is staying open just a small amount (like it does in compression release mode) when the engine is on the intake stroke it will pull air in through the exhaust valve as well as the intake. Thus, leaning the mixture. Pulling the choke would help in this situation. Even though it is dumping compression, it isn't dumping it all, so it would continue to run for a while. The condition that the OP describes fits this set of conditions.

Frank, I too am not usually convinced of a sticky valve and like to look for simple first. However, this time, by description and what the OP says about the parts that have been changed and what he has done with the fuel system, the exhaust valve sticking is the next most likely diagnosis. If it was my machine, I'd be ready to test compression next time it dies. With my experience I would probably be able to tell just by the sound it makes cranking, and not need a gauge, but most probably can't tell the difference just by sound.

olds45512 · #19 09-08-2014, 11:09 AM

With a stuck exhaust valve it will turn over faster when trying to start it almost like it doesn't have a spark plug in it.

J-Mech · #20 09-08-2014, 11:14 AM

Quote:

Originally Posted by olds45512

With a stuck exhaust valve it will turn over faster when trying to start it almost like it doesn't have a spark plug in it.

Depends on how far open it is. If it's open just a small amount (like it is with the compression release) it may not sound all that different than normal. But I do agree with you Tim.

NOTE: It takes more compression to start a motor, than it does to run one. If you can get them started, they will run with pretty low compression. Not well, but a motor will run.