17.5 requires ether to start (follow up questions)

turbofiat124

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This is a follow up post to a question I asked awhile back but turned into a spark plug thread so I'll just recap.

17.5 B&S. I don't know the exact model number but it's a fairly new engine. I mean built in the last 10 years.

The float valve stuck on the carburetor stuck and it filled the crankcase with gasoline. I took the carburetor apart and changed the oil. I mowed with it the rest of the day.

Since then, this engine requires starting fluid or carburetor cleaner to "jump start it" when cold. Once it runs for awhile it starts right up and runs fine.

Things I've checked so far:

1) Installed new spark plug
2) verified that the choke is working.

I know the choke is working because I can close it and stall the engine.

3) Checked the solenoid in the fuel bowl. It did not appear to be working so I broke the tip off the plunger. Sure enough when I turned the ignition off KAPOW!. So whether it was working or not does not seem to be the cause.

4) Plenty of fuel flow to the carburetor. New filter.

Possibilities:

Choke is out of adjustment after reinstalling the carburetor and when fully closed is completely shutting of the flow of air so no fuel can be pulled up through the jets. I have not tried to crack is open a bit but will.

Trying to start a hydrolocked engine over has bent the valves (but would it run smooth and fine afterwards)? I initially thought this was due to a weak battery until I started seeing fuel dripping from the muffler.

This same thing has caused the valve clearance to get out of adjustment (is that possible)? I think I read on here somewhere that if the valve clearance is not correct, the engine will either not start or requires starting fluid to initially get going.

What other possibilities could there be?

I've got the shop manual for the B&S 21 hp OHV engine. Are the valve clearance specs pretty much the same for the 17.5 hp model? I will get the model number off the engine. It's in my yard barn in from of my Husqvarna right now.

Just looking for some generic B&S OHV troubleshooting tips to ponder over.
 

turbofiat124

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No replies? I figured at some point or another someone has had this happen.

I'm going to check the valve clearance this week.
 

pugaltitude

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Yes you could try valve clearances.
Clearances on the 17.5hp (model31-33?) would be 0.003"-0.005" inlet and 0.005"-0.007" ex.

Could be a head gasket or even a valve not seating properly.
 

turbofiat124

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Thanks. I was just wondering if it was worth checking or I should be looking elsewhere. I was afraid I might have damaged it somehow by trying to start it hydro-locked when I thought it was a weak battery.
 

bertsmobile1

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Usually you blow the head gasket on inteks when trying to start a hydro locked engine.
It is a design weak point to prevent major engine damage
 

Tinkerer200

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Thanks. I was just wondering if it was worth checking or I should be looking elsewhere. I was afraid I might have damaged it somehow by trying to start it hydro-locked when I thought it was a weak battery.

Your model number should be stamped into the valve cover.

I can send you detailed instructions on valve adjustment and a Service Manual as well IF you like. Address below, put in proper format and remind me engine model number and what you want.

Hint - try removing the gas cap, place mouth against fill opening and blow, pressurize, the tank, do not inhale fumes and decrease pressure before removing mouth or you will get blow back. See if this helps starting and post results for solution.

Walt Conner
wconner5 at frontier dot com
 

turbofiat124

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Your model number should be stamped into the valve cover.

I can send you detailed instructions on valve adjustment and a Service Manual as well IF you like. Address below, put in proper format and remind me engine model number and what you want.

Hint - try removing the gas cap, place mouth against fill opening and blow, pressurize, the tank, do not inhale fumes and decrease pressure before removing mouth or you will get blow back. See if this helps starting and post results for solution.

Walt Conner
wconner5 at frontier dot com

I downloaded a service manual for the 21hp model. My guess is it coveres the 17.5 model. I seem to think the 21hp version is an Intek engine, not sure about the 17.5 hp version.

Due to yard work I have not had a chance to look at my MTD with the cold starting issue.

The blown headgasket sounds logical but unlike my 21hp model which blew a headgasket after I overfilled it with oil, it is not smoking and burning oil. Another possibility is I bent a pushrod so when I pull the valve cover off, I'm going to pull the pushrods and have a look at them while I'm at it.
 

turbofiat124

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Update:

I haven't had time to check the valve clearances on this mower but did try something Saturday.

So Saturday while I was mowing my yard, in the meantime I hooked a battery charger to the mower I was having issues with just to see if it would start.

On a side note: I mentioned previously I can't seem to get more than a couple of years out of these lawnmower batteries (on any mower I've owned since I've lived here). I can get almost 10 years out of a car battery with a 2 year warranty as long as I keep it topped off with DI water once a year and hook it to a trickle charger if the car sits for more than a month. My guess is because my yard is so bumpy, the constant bouncing must be damaging the batteries somehow? Or they are just cheap batteries. When I owned a Snapper, the battery on that mower lasted one year. So after that I just used to recoil starter for about 10 years until I sold the mower.

Anyway, the battery on this MTD must have a bad cell in it because after a day or so, it tests around 11 volts. But after a few hours of charging, it has enough juice to turn the engine over.

So after a few hours of charging, I hit the starter and it fired right up without starting fluid.

I think the problem maybe the battery itself. The battery may have enough balls to spin the engine over, just not fast enough. But because starter fluid is more volatile, makes it easy to start on a slower spinning engine. Now as to why the same battery will start my B&S 21 HP Husqvarna just fine, I don't know.
 
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bertsmobile1

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Update:

I haven't had time to check the valve clearances on this mower but did try something Saturday.

So Saturday while I was mowing my yard, in the meantime I hooked a battery charger to the mower I was having issues with just to see if it would start.

On a side note: I mentioned previously I can't seem to get more than a couple of years out of these lawnmower batteries (on any mower I've owned since I've lived here). I can get almost 10 years out of a car battery with a 2 year warranty as long as I keep it topped off with DI water once a year and hook it to a trickle charger if the car sits for more than a month. My guess is because my yard is so bumpy, the constant bouncing must be damaging the batteries somehow? Or they are just cheap batteries. When I owned a Snapper, the battery on that mower lasted one year. So after that I just used to recoil starter for about 10 years until I sold the mower.

Anyway, the battery on this MTD must have a bad cell in it because after a day or so, it tests around 11 volts. But after a few hours of charging, it has enough juice to turn the engine over.

So after a few hours of charging, I hit the starter and it fired right up without starting fluid.

I think the problem maybe the battery itself. The battery may have enough balls to spin the engine over, just not fast enough. But because starter fluid is not volatile, makes it easy to start on a slower spinning engine. Now as to why the same battery will start my B&S 21 HP Husqvarna just fine, I don't know.

yep. I will go with that, just remember ;-
too much valve lash defeats the decompression which causes the engine to crank slowly so it will not start.
It also stuffs the battery and is none too healthy for the starter motor either.

Genuine USA made mower batteries have a thicker grid and a stronger binder in the paste.
better ones are AGM & PVR
adsorbent glass mat , provides more support for the pates
Pressure valve regulated , stops gassing and vastly reduces the self discharging.
The Rolls Royce solution is to fit a spiral cell battery, either a Cyclon or Optima
The Optima has a massive CCA rating and ca be charged at a very heavy rate 20+ A/hr
The slightly lesser alternative is a heavy duty motorcycle battery.
Same story made to take rough stuff.
 
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