[Al Posts: 880 Status: Offline WWW]

The starter motor was the problem, new one fitted and it turns the engine over quickly :-)

[Steve Holland Posts: 1582 Status: Offline]

I've started painting the joints in starter motors, a couple of coats of anything is fine, I used the quick dry hammerite type paint, it looks naff, does seem to stop the creeping ingress of salt.....so far.

[Al Posts: 880 Status: Offline WWW]

Hopefully this will sort out my engine cranking issues.  Courier brought me a new starter motor this morning.  I got this one off of eBay for less than £60, so a bargain compared to the £150 + other sellers are charging

[Al Posts: 880 Status: Offline WWW]

Been having hassle again with the engine not cranking.  Done all the electrical checks as suggested by JR and everything seemed OK.  I also removed spark plugs, so no compression and still it wouldn't turn over, so I removed the starter motor again and tried direct to the battery and solenoid worked as it should and also the starter motor turned over quickly when the live was put on the stud where the braided cable goes to.  The next time I tried it wouldn't spin over.  Tapped the starter motor and it span over again.  I'm pretty sure it's to do with the brushes in the starter motor, so I have now ordered a new starter motor, as I hate unreliability 

[edwadee Posts: 156 Status: Offline เรารักในหลวง]

https://youtu.be/ggV0wS6VMSs
Looking on youtube a very common problem.

[Al Posts: 880 Status: Offline WWW]

Thanks John.  Helpful info

[John Robertson Posts: 5130 Status: Offline WWW]

... and fit an isolator!  In a salty environment corrosion will eat anything connected to the +ve battery terminal.

[John Robertson Posts: 5130 Status: Offline WWW]

Too much speculation and too little data.

1. Measure the voltage between the battery -ve and the starter body WHEN the motor is stalled
2. Measure the voltage between the battery +ve and the starter solenoid power terminal WHEN the motor is stalled.
3.  Measure the voltage between the battery +ve and the starter MOTOR power wire (usually a short braided wire) WHEN the motor is stalled.
4. Measure the voltage between the battery -ve and +ve terminals WHEN the motor is stalled.


If 1 and 2 aren't the same (within 200mV or so) then there is a problem with whichever cable (or connections) has the highest voltage.

If 1 OR 2 is more than 1.4V then the cable is too small cross section (a car usually has less than 0.5m of cable so you need to x4 the cable section that's used in a car to get a low enough voltage drop/resistance - or shorten cables/move battery/etc.).
 

If 3 is more than 0.2V HIGHER than 2 then the solenoid/contactor is dirty or damaged (some types can be disassembled and cleaned, if sealed then you can buy a replacement if you get the manufacturers number (Denso, etc.)).

If 4 is less than 10.2V then the battery is flat/defective.

[Al Posts: 880 Status: Offline WWW]

Battery was new.  No isolator fitted, so that's ruled out.  I think the starter & earth cables are probably too thin.  I actually mentioned  to a mate of mine a couple weeks ago, that I wondered if the battery cables were too thin, as they were quite a bit thinner than what I fitted on previous hovers.   


I've just measured battery cable to the starter and it is about 8.5mm diameter including the PVC coating, which I think is the 16 square mm (110 amp).  I cant remember what I used previously on my Sevtecs, it was either 170 amp (25 square mm, 9.75mm diameter) or the 240 amp (35 square mm, 12.15)


I haven't measured the length as hover is covered in 6 inches of snow, but assume length will be about 2 to 2.5 metres from battery to starter & to engine earth

[John Robertson Posts: 5130 Status: Offline WWW]

The Briggs service guide (including the method used to set the valve clearances) is HERE.  The cranking will be simple issue - doubtful it's the starter if its been rebuilt properly - there isn't much to them (a couple of coils, brushes, and crude bearings - all easy to check).  Much more likely to be a poor battery (get it tested), dodgy isolator or deficient cables (too small).

[edwadee Posts: 156 Status: Offline เรารักในหลวง]

My Briggs had an automatic decompressor which kept the exhaust valve open
until the engine was turning over at whatever speed, I don't know how common
that is but if you have one then it is impossible to set the tappet clearance as
the valve is always slightly open until speed is reached. If you set the valve
clearance (as I believe you did) with this system you would no longer have
the decompression and also the valve opening would be wrong once the engine
did get going.
I don't know how to check this apart from taking the engine apart but I'm sure
someone will !!

[Al Posts: 880 Status: Offline WWW]

The Briggs engine in my marlin doesn't always turn over when I turn the ignition key.  The engine will start to turn, maybe 1/4 a turn or when it hits compression then it wont push past the compression.  If I push the fan back until it hits compression the other way, more often than not it will turn the engine over quickly and start.


Battery is fully charged.
Checked all connections to the starter motor & engine earth lead.
Battery connections are clean, tight and greased.


I'm thinking that maybe the starter is too weak or has a problem and not able to flick it past the compression stroke if it only has a short travel distance before compression.  A new starter motor is upwards of £150 so I don't want to buy one unless I know that is definitely the problem



Does anyone have any ideas as to why this could be happening?