New used mower

[hrdman2luv]

I bought a 18.5hp OT (42A707-1238-01) MTD (13AS699G088 )the other day, I can spin the motor by hand, but it's hard. Which I think is a good thing. I changed the gears on the starter, because the one that came with it was ground down. (Not a good thing).. Anyways, the newer gear seemed to fit just fine. But, the starter (I'm hoping) is weak. Because it'll turn it over just about 1/2 a turn and then stop. The gears seemed to be sticking up in the flywheel. Since there's no way of adjusting the valves (easily) I thought I'd start with a new starter and battery first. If that doesn't solve the problem, then I'll have to do the valves.. Not looking forward to doing that. 1. Because I've never done it. 2. I don't have any calipers to know how much to grind down.
I'll probably throw in some new battery wires and definitely test the solenoid.

The engine didn't seemed to be abused. There was oil in it. And the plugs looked fairly new. Not brand new. Which is a good thing. That tells me that the problem with it starting, just started.

Also, when I remove the plugs, the engine turns freely using the starter. No knocking, bumping, ticking or grinding..

 

[bertsmobile1]

I bought a 18.5hp OT (42A707-1238-01) MTD (13AS699G088 )the other day, I can spin the motor by hand, but it's hard. Which I think is a good thing. I changed the gears on the starter, because the one that came with it was ground down. (Not a good thing).. Anyways, the newer gear seemed to fit just fine. But, the starter (I'm hoping) is weak. Because it'll turn it over just about 1/2 a turn and then stop. The gears seemed to be sticking up in the flywheel. Since there's no way of adjusting the valves (easily) I thought I'd start with a new starter and battery first. If that doesn't solve the problem, then I'll have to do the valves.. Not looking forward to doing that. 1. Because I've never done it. 2. I don't have any calipers to know how much to grind down.
I'll probably throw in some new battery wires and definitely test the solenoid.

The engine didn't seemed to be abused. There was oil in it. And the plugs looked fairly new. Not brand new. Which is a good thing. That tells me that the problem with it starting, just started.

Also, when I remove the plugs, the engine turns freely using the starter. No knocking, bumping, ticking or grinding..

Before you spend a lot of money, followed up by spending a lot more, pull the plug out and try the starter again.
If it sticks then you most likely have the wrong gear on the starter.
If it dosent then you have to adjust the valve clearances. not as big a job as you might think, it just takes a bit of time to do

 

[hrdman2luv]

Before you spend a lot of money, followed up by spending a lot more, pull the plug out and try the starter again.
If it sticks then you most likely have the wrong gear on the starter.
If it dosent then you have to adjust the valve clearances. not as big a job as you might think, it just takes a bit of time to do

Without plugs in, the engine turns over freely...

The valve's, Those are going to be a pain in the rear. You gotta remove the heads, You gotta take off the springs... I don't have calipers to judge how much to grind off...

 

[hrdman2luv]

New battery did nothing. But it wasn't a total loss, the mower didn't come with one. BUT, the new starter I got on EBAY for less than $40, worked like a charm. it turns it over like there's no plugs in it... But, wouldn't kick over.. So I checked to see if the plugs were sparking. And WOW... Yes they were. So I grab the starter fluid, give it a little shot... And nothing.

So now, I'm thinking safety switch. But then again, the plugs are firing. The plugs wouldn't spark if a safety switch was bad. So, it's gotta be either in the carb or the intake. Or both. I haven't checked to see if any gas has came through the line into the carb yet. But that makes no difference. Because the starter fluid should have kicked it off.


BTW, turned the key with thumbs on plug hole, and it blew it off. So, I'm thinking I've got a good one. If I can just get it to kick over with the starting fluid. I've gone pretty light on it. Maybe I should try more...

 

[bertsmobile1]

New battery did nothing. But it wasn't a total loss, the mower didn't come with one. BUT, the new starter I got on EBAY for less than $40, worked like a charm. it turns it over like there's no plugs in it... But, wouldn't kick over.. So I checked to see if the plugs were sparking. And WOW... Yes they were. So I grab the starter fluid, give it a little shot... And nothing.

So now, I'm thinking safety switch. But then again, the plugs are firing. The plugs wouldn't spark if a safety switch was bad. So, it's gotta be either in the carb or the intake. Or both. I haven't checked to see if any gas has came through the line into the carb yet. But that makes no difference. Because the starter fluid should have kicked it off.


BTW, turned the key with thumbs on plug hole, and it blew it off. So, I'm thinking I've got a good one. If I can just get it to kick over with the starting fluid. I've gone pretty light on it. Maybe I should try more...

Safety switches work 2 ways
1) prevent the starter from turning by interupting the power , or more common now days the earth to the starter solenoid.
2) The other type earth out the magneto so there is no spark.

So with deer stalker on lid & pipe in mouth we can therefore eliminate any external wiring problems.
We now need to have a close look at the engine.
The easiest thing to verify first is the flywheel key as it only requires the removal of the top cowl , debris screen & fly wheel nut.

If that looks good then next thing to eliminate is the carb.
Remove both spark plugs and give each cylinder a good squirt of starter fluid then replace with new plugs fresh out of the box.
Give it a spin and see what happens.
If it fires then pull both plugs, remove the fuel pump from the front of the carb and give the engine a spin.
If you get a petrol bath all is well with the fuel pump, the pump used on the horizontal opp B & S gives a lot of trouble and because they pump directly into the carby float bowl are a bugger to diagnose
If you haven't already done so pull off the air box and give the engine a good squirt of starter fluid past the choke. cross your fingers while doing so.

If no joy then pull off the carb.
Don't bother with it yet but while it is off pull off both valve chests

 

[bertsmobile1]

Opps pressed the send button too soon.

with the plugs in, turn the motor over slowly by hand and watch and listen.
Watch the valves going in & out listen to the air being drawn in then blown out.
Check the valve clearences on both sides several times with couple of rotations between each measurement.
WHile flat tops are a PIA to adjust valve lash, it is a job very seldom needed to be done.
While there take a close look at the area under the cylinder, if it ooks oily then you need to replace the head gaskets and if one is gone the other is not far away.
Buy a full gasket kit, you can get aftermarket ones and I use the Stens ones all the time with no problems other than a large accumulation of sump gaskets.
If the valves need adjustments, just grit your teeth & get into it.Do not try to shortcut things by using any mechanical device.
I have tried just about every thing including a valve stem grinder and you always end up either taking off too much metal or grinding a facett on the end so have to grind down the seat to compensate.
The Briggs manual gives the clearences for the valves, spring off & spring on so you only need to replace the valve springs once.

 

[hrdman2luv]

Thanks for the tips Bert.

Just a couple of questions.

1. The safety switches. If I had a bad safety switch, the coil wouldn't spark right? I'm getting good spark. Especially after I cleaned the plugs. They all work through the key switch, which works through the kill wire on the magneto. Right?

2. If no safety switch problem, what could be causing the starter fluid to not ignite in the cylinders? I've removed the plugs and even squirted fluid into the cylinders. (quickly re-installing the plugs and trying to start the engine) But to no avail. The plugs themselves don't look bad. They weren't bad when I first got the mower.

 

[ILENGINE]

MTD uses the safety switches to prevent the engine from turning over, but wouldn't prevent spark. I would check compression next, the opposed twin has a bad habit of dropping the valve seats, and loosing compression. Have seen a few cases of stuck open valves, as well as odd wear on the cylinders.

 

[hrdman2luv]

MTD uses the safety switches to prevent the engine from turning over, but wouldn't prevent spark. I would check compression next, the opposed twin has a bad habit of dropping the valve seats, and loosing compression. Have seen a few cases of stuck open valves, as well as odd wear on the cylinders.

But wouldn't the starting fluid still ignite?

 

[ILENGINE]

Not without proper compression it will no ignite starter fluid.