Stens solenoid failure

[SamB]

If OEM solenoids are failing it is usually a sign of another problem
I am yet to come across one that has failed for no external reason.
The most common one is an out of tune engine so the owner cranks it till the battery goes flat ignoring the 30 seconds max printed in the owners manual
the most common failure is the plastic melting allowing the internal parts to no longer make contact .

They would be better made from a thermo setting plastic ( bakelite to some ) but that would cost three times as much .

I agree that is usually the case. Most mower owners are not very mechanically inclined. The pesky B&S compression release that won't work with the valves out of adjustment or it being broken will damage a solenoid and starter in short order. Overdoing the cranking can and will melt the solenoid and also melt the brush holder in the starter. Blame this on the engine and starter being 'underbuilt'. A proper starter wouldn't need a compression release. My brother's Super Bee 440 six Pack is 11.5 to 1 and the starter spins it just fine without a compression release. All my mowers are "vintage" with the oldest being 1984 and the 'new' one being a 2005. Others somewhere in between. Sometimes things just wear out. The replacement solenoids I use are metal and rated 200A and continuous duty.

 

[VRR.DYNDNS>BIZ]

I've had 3 failures of stens solenoids this year, same part numbers as well. and one on my own equipment just the other day.

Stens 435-864​

I keep several of these on hand as i service a few older kawasaki Mule's which use the solenoid shift starters.
anyway i replaced three total in 2021, one of which was on my Mule.
i repaired one mower back in the spring, March i think... that solenoid failed in July. i then went back with a OEM Kawasaki part.
i replaced another one in May, an it failed in October.
i replaced the on on my Mule in august and it failed last week.
Now the kicker is, they all failed the same way, you turn the key, and it doesn't retract or anything. just barely moves... i load tested the trigger wire by using a 12v30W tailight draw on it and it never dimmed. or flickered. So it appears the solenoid just gave up, and all in the same manner.
so it seems to be a stens/supplier issue.... so far the OEM kawasaki's are doing good.

Shift fork is worn and therefore does not travel far enough to engage contacts or flywheel teeth mis meshed.

 

[StarTech]

Shift fork is worn and therefore does not travel far enough to engage contacts or flywheel teeth mis meshed.

Not always the problem. For me it is the electrical contacts inside the solenoid being burned not allowing the starter motor to even get any juice. I do just replace the complete as normal the whole unit is worn enough to justify it.

 

[bertsmobile1]

I agree that is usually the case. Most mower owners are not very mechanically inclined. The pesky B&S compression release that won't work with the valves out of adjustment or it being broken will damage a solenoid and starter in short order. Overdoing the cranking can and will melt the solenoid and also melt the brush holder in the starter. Blame this on the engine and starter being 'underbuilt'. A proper starter wouldn't need a compression release. My brother's Super Bee 440 six Pack is 11.5 to 1 and the starter spins it just fine without a compression release. All my mowers are "vintage" with the oldest being 1984 and the 'new' one being a 2005. Others somewhere in between. Sometimes things just wear out. The replacement solenoids I use are metal and rated 200A and continuous duty.

It is a chicken & egg thing
Because these engines are made as cheaply as humanly possible ( cheap & nasty ) only Hondas have a fuel cut off tap
Because carb overflows have to be internal you now are set up for a petrol hydro lock .
A stronger starter will blow the head gasket & bend the con rod with a strong hydro lock.
So you fit a low strength starter .
Better quality engines ( Honda ) do not have this problem .
And of course a flimsey starter only requires a flimsey mounting point both of which reduce costs.

 

[SamB]

Hmmm. I don't even bother replacing the solenoid as I had good luck with the starters from DB. Beside the Kawasaki starter is only $75 from them with free shipping.

I've purchased a number of items from DB,both mower and automotive, and have always been pleased with the quality and also the price. I would recommend them highly.

 

[SamB]

It is a chicken & egg thing
Because these engines are made as cheaply as humanly possible ( cheap & nasty ) only Hondas have a fuel cut off tap
Because carb overflows have to be internal you now are set up for a petrol hydro lock .
A stronger starter will blow the head gasket & bend the con rod with a strong hydro lock.
So you fit a low strength starter .
Better quality engines ( Honda ) do not have this problem .
And of course a flimsey starter only requires a flimsey mounting point both of which reduce costs.

Again,I have to totally agree with bertsmobile1. A strong starter and a poor carb needle valve + a weak design head gasket is a recipe for disaster.
A stronger head gasket would not be a good solution either. Then ,if in the event of hydro lock,you'd get a bent rod or at the very least.a sheared flywheel key. Maybe even broken flywheel teeth.
So I guess the (cheap) weak starter is the best solution to all of the above worst case scenarios. I have fuel shut-offs on my mowers but I might forget from time to time to turn that petcock handle. Electric NC valve might be a wise addition to the ones with gravity flow tanks