Starter bendix not engaging

[gwav8or]

Every time I try to start my Mooney, the first start of the day, the starter bendix doesn't engage.  It just spins but doesn't engage the flywheel.  My mechanic suggested hitting the starter around the bendix with WD-40.  This seems to work a bit but doesn't last.  What are my options other than replacing the starter.  Don't really want to do that right now.

[47U]

Maintenance Manual (106) lubrication chart lists graphite and kerosene for the starter drive.  But, I would try some graphite spray.  When it dries, it won’t attract dirt.  

[Bolter]

56 minutes ago, gwav8or said:

Every time I try to start my Mooney, the first start of the day, the starter bendix doesn't engage.  It just spins but doesn't engage the flywheel.  My mechanic suggested hitting the starter around the bendix with WD-40.  This seems to work a bit but doesn't last.  What are my options other than replacing the starter.  Don't really want to do that right now.

I have this experience with more than one Lycoming.  Shooting lube into the bendix gear works, but is quickly a patch and not a repair.  Generally, I think that confirm the problem is the Bendix gear and not truly the starter itself.  You can choose to remove the starter and rebuild the Bendix gear portion.  If your labor is low cost (owner assist options) this is a viable option.  If you are paying full cost for labor, then it is probably penny wise and pound foolish to just rebuild the Bendix Gear.  

Example of the repair: 

 

[cliffy]

3 minutes ago, Bolter said:

I have this experience with more than one Lycoming.  Shooting lube into the bendix gear works, but is quickly a patch and not a repair.  Generally, I think that confirm the problem is the Bendix gear and not truly the starter itself.  You can choose to remove the starter and rebuild the Bendix gear portion.  If your labor is low cost (owner assist options) this is a viable option.  If you are paying full cost for labor, then it is probably penny wise and pound foolish to just rebuild the Bendix Gear.  

Example of the repair: 

 

Good points  given here

[EricJ]

2 hours ago, Bolter said:

I have this experience with more than one Lycoming.  Shooting lube into the bendix gear works, but is quickly a patch and not a repair.  Generally, I think that confirm the problem is the Bendix gear and not truly the starter itself.  You can choose to remove the starter and rebuild the Bendix gear portion.  If your labor is low cost (owner assist options) this is a viable option.  If you are paying full cost for labor, then it is probably penny wise and pound foolish to just rebuild the Bendix Gear.  

Example of the repair: 

 

As he mentions, silicone spray is usually the recommended lube for these.   If it starts to get sticky, shoot some silicone spray lube in around the bendix and that usually keeps it happey for quite a while.    If there's crud in there that's accumulated because other lubes (e.g., WD-40) have been used, it may take a bit to get the crud washed out. 

I used to just spray silicone lube in around the bendix whenever the cowl was off, e.g., for an oil change or whatever, and that kept it going for several years after it started getting sticky.   A friend gifted me a Sky-Tec off of a motor we removed from his airplane, so when the Bendix on my Prestolite started not responding to the silicone spray any more, I just swapped it out.    As this guy mentions, I've been going to get a replacement Bendix for my old Prestolite so that it can be a spare, since Sky-Tecs are so freaking expensive now.   

[A64Pilot]

Silicone is OK, it works because it leaves almost no residue, but because it doesn’t it really doesn’t work very well, any kind of normal lube should be avoided because it will attract dirt and dust and actually make matters worse.

I now go to dupont teflon spray for anything I used to use silicone spray for, it’s pure teflon very light powder, teflon is of course about as slick as anything and as it’s perfectly dry it won’t attract dirt, I used it on sails to get them to slide into the track and it didn’t leave any kind of stain on a white sail, it was also great for zippers etc.

Plus of course teflon is very heat resistant or it wouldn’t work in frying pans.

https://www.amazon.com/DuPont-Non-Stick-Dry-Film-Lubricant-14-Ounce/dp/B00D3G6IFE/ref=sr_1_5?crid=3UNY0P23MMZSB&dib=eyJ2IjoiMSJ9.OxOIEndmeWAC1e-9Lyy__BADWR5Pr_LUaJeBsU4Fo8VUsIfDjP9BxYfoYR2QMYriYMDWQ0zR0UZrSaa6m2yxEJ-xDahrtZXXZ70m-EYD9-b6ZnjAtt5Va2nwCJCRfl9EsXm6kjt2MVZgWHT-LpV8Zg_KaFT1rutVt65RbKNsJsd9XigsSKgKwOWBZVS6kIjcxn0_RWLe7yHyorzjzXduV9HKxywhN_oyyNVmBhhZXHQ.weZaM_YthZhFr-kbsMgAGXtIrzl0e4TiXQW7X1P37xA&dib_tag=se&keywords=dupont%2Bteflon%2Bspray&qid=1735782009&sprefix=dupont%2Bteflon%2Bspray%2Caps%2C152&sr=8-5&th=1

[MikeOH]

6 minutes ago, A64Pilot said:

Silicone is OK, it works because it leaves almost no residue, but because it doesn’t it really doesn’t work very well, any kind of normal lube should be avoided because it will attract dirt and dust and actually make matters worse.

I now go to dupont teflon spray for anything I used to use silicone spray for, it’s pure teflon very light powder, teflon is of course about as slick as anything and as it’s perfectly dry it won’t attract dirt, I used it on sails to get them to slide into the track and it didn’t leave any kind of stain on a white sail, it was also great for zippers etc.

Plus of course teflon is very heat resistant or it wouldn’t work in frying pans.

https://www.amazon.com/DuPont-Non-Stick-Dry-Film-Lubricant-14-Ounce/dp/B00D3G6IFE/ref=sr_1_5?crid=3UNY0P23MMZSB&dib=eyJ2IjoiMSJ9.OxOIEndmeWAC1e-9Lyy__BADWR5Pr_LUaJeBsU4Fo8VUsIfDjP9BxYfoYR2QMYriYMDWQ0zR0UZrSaa6m2yxEJ-xDahrtZXXZ70m-EYD9-b6ZnjAtt5Va2nwCJCRfl9EsXm6kjt2MVZgWHT-LpV8Zg_KaFT1rutVt65RbKNsJsd9XigsSKgKwOWBZVS6kIjcxn0_RWLe7yHyorzjzXduV9HKxywhN_oyyNVmBhhZXHQ.weZaM_YthZhFr-kbsMgAGXtIrzl0e4TiXQW7X1P37xA&dib_tag=se&keywords=dupont%2Bteflon%2Bspray&qid=1735782009&sprefix=dupont%2Bteflon%2Bspray%2Caps%2C152&sr=8-5&th=1

Not saying that stuff doesn't work well, but is it Teflon?

Your link says it's boron nitride:

 

[A64Pilot]

I went out and looked at the can I have, it’s does have BN in a green symbol on the can with the words ceramic technology, but the ingredients aren’t anywhere on the can. It’s logical of course to assume this BN is Boron Nitride.

You learn something every day, apparently in 2021 Dupont no longer sells Teflon (PTFE) and replaced it with Boron Nitride. The following is I guess a gun site and for some reason you have to be 18 to view it.

So I guess it is NOT Teflon, but Boron Nitride, it seems to work the same anyway.

https://blog.roninsgrips.com/use-dupont-ceramic-dry-film-lubricant-in-your-steel-and-aluminum-pistol-rifle-and-shotgun-magazines-to-smooth-their-operation/

[Bolter]

Tri-Flow is recommended for some of the Mooney lube points, so something worth having on hand.  It also includes Teflon, and probably works well for the Bendix gear.  Again, that is a patch, and eventually you will get tired of climbing out and lubing the starter, and one day it may not work anymore.

[Pinecone]

DuPont has never "allowed" or recommended using Teflon in a liquid lubricant.

USMC Rifle Team stopped using TriFlow when they noticed excessive wear.

[AJ88V]

I always used TriFlow spray on the starter shaft, but was thinking of switching to graphite spray per @47U's suggestion.  Found this cheaper at Home Depot than Amazon

https://www.homedepot.com/p/Blaster-5-5-oz-Industrial-Graphite-Dry-Lubricant-Spray-8-GS/202597501

Opinions?

[Bob K]

Had a similar problem with the Bendix not driving out to engage the ring gear about 5 years ago. Following the recommendation of another Mooney driver, I have not had another issue after lubing the drive with Deep Creep (made by Seafoam). 

[PT20J]

I would think a dry film lube would be best on the starter. Evidently DuPont used to make Teflon lubricants, but as @A64Pilot said, its current products utilize boron nitride. A friend showed me a spray can of boron nitride he got years ago in Japan, so it’s been around a while (I don’t know who made it: all the writing was in Japanese). It sprays out as a white powder (so it’s a little messy) and is very slippery. 

[Fly Boomer]

31 minutes ago, PT20J said:

Evidently DuPont used to make Teflon lubricants

Quick search suggests that DuPont still make PTFE, but may be trying to keep a lower profile due to nasty effects caused by a chemical used in production, fairly recently swapped out for a new chemical which has been investigated less.