MGB & GT Forum

Downside with the intertia starters is the way they engage is somewhat hit and miss.. the most common issue is chewed up teeth on the starter ringear.. neccesitating engine and flywheel removal to rectify ... UNLESS..you fit gear reduction starter, which engages from opposite side.. However.. current replacement ringears have the first 3/8" of the gear teeth on front side shaved down.. which can't be good for the starter teeth if using a front engaging (as per gear reduction) starter..

a properly working inertia starter is no harder on the ring gear than a pre engaged one.

Not true. An inertia starter, by design, has the pinion gear spinning prior to, and during, engagement with the teeth on the flywheel ring gear. As such, the gear teeth necessarily wear, often dramatically. With a pre-engaged starter motor, the pinion gear is, by definition, "pre-engaged" with the teeth on the flywheel gear before the gear begins to spin. Damage to the flywheel teeth when using a pre-engaged starter is rare...

Dick

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Errabundi Saepe, Semper Certi
(Often wrong, but always certain)

that's where u wrong. it is not turning until it comes up to the ring gear. it either goes in & turns the engine, or the bendix spring compresses until the gear moves a hair & pops it into mesh & the engine starts. that's how it works.

"a properly working inertia starter is no harder on the ring gear than a pre engaged one"

Sorry, but respectfully, this is incorrect. A properly working inertia starter begins spinning the pinion gear as soon as the starter switch is activated. The spinning pinion gear then spools toward the stationery ring gear and "crashes" into it by design, thus turning the flywheel. A pre-engaged starter does not energize and spin the starter motor until the electromagnetic solenoid has fully engaged the starter pinion with the ring gear. So there's no "crash".

The '68 and later MGB pre-engaged starters are fine and have plenty or torque to spin a stock engine over. The pre-'68 Lucas M418G inertia starters are sketchy even when working as-designed. They wear the ring gear every time they engage, and once the ring gear is worn past a certain point, the starter pinion can hang up in the ring gear, which jams the starter. That's why the M418G has a removable cap on the end which covers the squared end of the armature shaft-it allows the unfortunate driver to turn the shaft with a wrench thus winding the pinion back out of the ring gear. These starters are also enormous and weigh about 15lbs. The modern ND gear reduction starters weigh a fraction of the weight of the Lucas inertia starters, do not wear the ring gear, and spin the engine much more briskly than the Lucas starter.

I guarantee you will not see a stock Lucas inertia starter on any MG/TR/AH/Sunbeam, etc. racecar.

Proof is in the pudding... its very rare to find a buggered up ring gear on a post '68 MGB.. and very common with the MGA and '62-'67 MGB.. unfortunately the replacement ringears have the teeth cut back on front edge ..(can't be good for a gear reduction stater which throws in same as the 're-engaed' later set up ..from the front) ..but its a no brainier on an MGA or early B with ORIGINAL ring gear that is chewed up on rear edge.. its really a very good solution to inertia starter woes..and offers huge savings over engine removal and ringear replacement.. plus much easier starting..

ok, put an inertia starter in the vice, wind the gear all the way back. get a piece of 1 X 2 &create some friction on the gear. power up the starter, & tell me when the gear starts making sawdust.

Frank,

I admire your passion for the crash starter. I think you should keep and enjoy yours. You are entitled to express your opinion.

When the crash starter was designed, the factory just didn't know any better. I suspect engineering learned from their mistakes and eventually took a better approach for starter design. For me, I'll have nothing to do with a crash starter, way too expensive and troublesome to own.

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Edited 1 time(s). Last edit at 2021-11-29 03:12 PM by geezer.

listen, i fixed the bloody things for a living for 40+ years, all shapes & size's, no preference, just don't waste my time telling me how they work. cheers.

Then perhaps you can explain to us why crash starters chew up flywheel ring gears and pre-engaged starters don't...

Dick

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Errabundi Saepe, Semper Certi
(Often wrong, but always certain)

WHOAH !..If a man knows more than others...he becomes lonely !..



Anyway I have been going through this conundrum over the last few days...thinking , .
.just which direction to go ?..Doing clutch replacement plus all the may as wells ! ..and I have been having a high percentage of jamming now..
I pulled the engine with everything attached apart from the valve cover and fan..but I thought I would see what all the fuss was about with removing the inertia starter in situ..( I put the distributor back in prior to engine removal ) ..
After looking at the ring gear condition and the starter removal PITA .( especially with the steering shaft making it awkward ! ) .a GR starter it will be...so my question is..
I was going to get a new ring gear and a GR starter..
But after reading a couple of threads on the subject I ascertained I can leave the ring gear because of front meshing but might have to chamfor the leading edge of the ring gear..
Now it appears that the ring gear is NOT to be chamfored ??..is this correct and I can just simply install a GR starter without altering anything on the flywheel..???? Cheers



Edited 1 time(s). Last edit at 2021-11-29 04:52 PM by little G.

Pic of a badly worn MGA ring gear.....courtesy MGA Guru.

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Buz

“Every problem, has a gift in its hands for you”

it will have the same wear 180 degrees over, on the other side.

We all know that. It's engine compression that stops the crankshaft and flywheel in certain positions.

So we'd still like to have you explain to us why crash starters chew up flywheel ring gears and pre-engaged starters don't...

And why do they call them crash starters if they're not spinning when they contact the ring gear?

Dick

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Errabundi Saepe, Semper Certi
(Often wrong, but always certain)

u are forgetting one thing, yes the gear reduction starter engages from the front, but the ring gear teeth aren't beveled on that side & can be a problem. usually sharpening the starter drive teeth helps. one reason inertia starters can be hard on the flywheel is the fact that clutch dust & some oil gums the drive up so that it doesn't move freely, & then it is turning when it reaches the ring gear. if it was pulled & serviced when this started it wouldn't be so bad. that is a weakness of inertia starters. also most guys that did repair it would clean & oil everything, put it back in& it worked great. only one problem the drive assembly should go together dry so that clutch dust doesn't turn into putty. this happens on pre engaged starters as well, but they just don't start. that is not an issue with the nippon denso.