Hooptie_Josh (Forum Supporter)
Hooptie_Josh (Forum Supporter) New Reader
11/14/20 12:56 a.m.

Had maybe an odd thing happen (or maybe I'm out of the loop), but asking the resident brain trust to weigh in.  Somehow my starter ate the ring gear teeth, and want to figure it out before it happens again.

The basics: 1.8l n/a BP motor, Exedy stock clutch, 1.6l ebay/amazon special 10# flywheel, aftermarket "TYC" brand NB starter.

The symptoms:  Starter has never been an issue before, and has been in use for several months and was new when installed.  The car had a pretty harsh landing last weekend (enough to strip threads from an aluminum coilover sleeve), but don't recall any issue when it was loaded up.  When starting it to remove from trailer, it sounded like a bottom end knock, but sound stopped after engine fired and starter was disengaged.  Tried starting several more times to pinpoint location of knock, always occured with starter then stopped.  Then starter ceased to engage ring gear, removed starter and found all the teeth worn in that spot.  When removed it was found that grease had come out of the starter in bendix area, but not sure if a concern.

Troubleshooting outcome thus far:  Off of car, starter functions as it should, bendix extends and retracts.  No wear on starter teeth.  Do not believe it is an issue with engine, as no sounds are present when it was running, and rotates easily by hand with socket on crank pulley.  Starter mounting was tight, all 3 bolts were used.  Transmission still in place, but it was did not seem that flywheel was loose (it was installed with ARP bolts per their directions).

My ideas:  1. It appears that there is no separate ring gear on this flywheel like a stock unit, and perhaps the teeth are not properly hardened.  Maybe this is a common issue with the cheaper flywheels I'm not aware of?  2. Possibly the landing and impact inertia caused the bendix to extend while engine was running, caused tooth damage in particular area, and knock was starter rotating past the damage until it finally stopped in that spot and was unable to engage?

Your thoughts: ?

 

Picture of flywheel carnage:

TurnerX19
TurnerX19 SuperDork
11/14/20 6:51 a.m.

A 4 cylinder engine always stops in one of 2 places. You will find a similar wear pattern 180 degrees away from what you see in the photo. Your supposition of poor tooth hardness is probably correct. Ring gear failure is common on many older cars for that reason, one of the things that the 21st century has improved! Modern metallurgy frequently escapes the cheap end of the aftermarket, it is time and resource consuming to do correctly.

Yeah, I am by no means an authority, but I'd say Chinesium flywheel failed. You get what you pay for.

To TunerX1/9: I never knew a 4 cylinder would stop in one of two places. Cooky.

KyAllroad (Jeremy) (Forum Supporter)
KyAllroad (Jeremy) (Forum Supporter) UltimaDork
11/14/20 9:52 a.m.

Nothing much to ad.  I have that flywheel in my basement now.  When the clutch disk failed I replaced everything.  If you want it, it's yours for the cost of shipping.

 


 

Hooptie_Josh (Forum Supporter)
Hooptie_Josh (Forum Supporter) New Reader
11/14/20 10:07 a.m.

In reply to KyAllroad (Jeremy) (Forum Supporter) :

I appreciate the offer, I've found a used one semi local, unfortunately the car has to be ready for The FIRM next weekend, or I will be forced to rally a Subaru, lol (no fun in that).

Did you notice any wear on starter teeth?  Yours still look pretty good from picture.  I know the chinesium risks, but perhaps I ended up with a badly treated one.

KyAllroad (Jeremy) (Forum Supporter)
KyAllroad (Jeremy) (Forum Supporter) UltimaDork
11/14/20 10:11 a.m.

In reply to Hooptie_Josh (Forum Supporter) :

The teeth seem fine.  

Keith Tanner
Keith Tanner MegaDork
11/14/20 10:37 a.m.

I mean, there are six ways to clock a flywheel on a Miata, so you could always just rotate this one on the crank so it lands in a different spot.

But I would be concerned about that flywheel overall. Failure modes on flywheels are bad. I think it is best used as a frisbee in a high-stakes game of Ultimate.

Hooptie_Josh (Forum Supporter)
Hooptie_Josh (Forum Supporter) New Reader
11/14/20 10:54 a.m.

In reply to Keith Tanner :

This flywheel is definitely destined for wall hanger at this point.  Car lives at higher revs, so not going to take that chance.

Any concern with the grease coming out of starter?  It can be seen on engine side of flywheel as well.

Slippery (Forum Supporter)
Slippery (Forum Supporter) UltraDork
11/14/20 10:57 a.m.
Keith Tanner said:

I mean, there are six ways to clock a flywheel on a Miata, so you could always just rotate this one on the crank so it lands in a different spot.

I guess as long as he doesnt rev over 200 rpms or wants no legs it would be ok cheeky

Hooptie_Josh (Forum Supporter)
Hooptie_Josh (Forum Supporter) New Reader
11/14/20 11:40 a.m.
Slippery (Forum Supporter) said:
Keith Tanner said:

I mean, there are six ways to clock a flywheel on a Miata, so you could always just rotate this one on the crank so it lands in a different spot.

I guess as long as he doesnt rev over 200 rpms or wants no legs it would be ok cheeky

6 speed and a 4.30 torsen, she pretty much lives on the limiter digging in the dirt, so I'd rather play it safe

Keith Tanner
Keith Tanner MegaDork
11/14/20 11:41 a.m.
Slippery (Forum Supporter) said:
Keith Tanner said:

I mean, there are six ways to clock a flywheel on a Miata, so you could always just rotate this one on the crank so it lands in a different spot.

I guess as long as he doesnt rev over 200 rpms or wants no legs it would be ok cheeky

We started this journey with a flywheel chosen from a random vendor hiding behind someone else's storefront and whose only selling point was the lowest possible price. So I'm making assumptions ;) It's for sure not the right solution, but it would be the fastest and cheapest.

 

wspohn
wspohn Dork
11/14/20 11:42 a.m.

You don't often see that with a pre-engaged starter as they mesh before exerting torque.  Is this a 'thing' with Miatas, or.......

TurnerX19
TurnerX19 SuperDork
11/14/20 2:04 p.m.

In reply to wheelsmithy (Joe-with-an-L) (Forum Supporter) :

Four cylinder engines always stop with the pistons mid stroke because that is where the friction is greatest. This carries over to other variations as well, a single always stops in the same place, no sharing the load at all. 

Shaun
Shaun Dork
11/14/20 2:20 p.m.

After 30 years of product development work in real manufacturing environments and more commonly now with 'brands' (some much better than others) in the in the US I identified your problem halfway through the third sentence: "Ebay/Amazon".

I learned this week you can buy fake banking apps on Amazon and Google apps for 5 bucks,  drop in a jpeg of chosen bank logo, type some fluffy numbers in there,  and send your consultant proof of payment via (fake) wire transfer. 

Pot metal flywheel!! Sure!!! Great idea!!!!

 

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