Hi Gang,
I received a new trainer from TH with the 46 ABS engine.
First thing I noticed was crankshaft end play appx 18-20 thous. of an inch but the split cone takes it away.
I mounted the prop and tightened it GOOD.
I tried turning the engine by hand and it seemed locked.
I added some oil and it loosened up but at the compresson stroke it gets tight and squeeks as if you cross threaded a nut on a bolt and was forceing it.
Do I have a bad engine?
Also because of the split cone how do I mount the spinner?

This is normal for a OS40LA series of engine.

The crank end play is from a bushing crankshaft. Without the drive washer, you are seeing the clearance between the crank pin and the rear cover.

All ABC engines are tight at the top of the stroke when new.

Jim

Hi Jim,
Thanks for easing my mind on that engine.I called TH and they told me the same
But I told them there was no way I can ever start it like it is so they told me to put oil in the Glow plug hole and keep hand proping it until it gets loose.
I did and then I put the electric starter on it and spun it a few times after adding more oil.
I think I can hand start it now if I had to.
WOW!!!! That engine was TIGHT!!!
Just didn't seem normal.The end play really had me worried.
They sure must run some close tolerance on those small engines.
Thanks for the info.Really appreciate it
AF2Q

Make sure you have not lost the drive washer. I lost mine and it seized up. No damage to the engine but scared the crap out of me!

Jeremy

You should be able to place the spinner back plate between the prop and the drive washer that has the cone inside it?

maybe i have the wrong term, but there is a very thin washer between the engine and drive washer (cone)

Leave the very thin washer in between the drive washer/cone and engine. You put the backplate for the spinner between the prop and the drive washer/cone.

Thanks for the post Guys.
Guess what.
Thats the first thing I looked for.
I have none.
The cone rides up against the face of the bearing race.
I hope this photo comes out OK.
The bearing goes into the housing and the cone rides on the bearing part that turns.
Photo looks OK.
Take a peek

bullfrog,
I just posted a picture of the engine break down of the parts.
There is no this washer

Yes,
Thats just how it's setup.
But when I tried to tighten the nut as per the instructions I could feel it wanting to give so i'm leaving it as is until I pick up a aircraft grade locking type nut.

my os 46LA had one, i lost some how and it caused my engine to go stiff, sorry my info cant help you good luck

Jeremy

The parts breakdown you've shown is a Tower 46. There is no washer behind the prop driver that I know of?

Bullfrog,
I can't put in what is not there.
Even the picture showing the breakdown of parts don't show it.
OOOoooooohhhhh,
I just read the parts list and they list it as 1 part called Drive washer cone.
Well,I don't have one so I guess I have to call TH.
They did send me 2 extra head gaskets.
They trying to tell me something about this engine?

Whirley Bird...if that parts view is correct for your engine then it's ball raced so won't have the shim washer. It seems there was an assumption made that you have a plain bearing engine and they're the only ones that need that shim (they don't use a split cone either).

What I'm curious about is if the engine feels free to turn (other than at the top of the stroke) without a prop and then gets hard to turn when the prop is put on and tightened. If so then there's a problem with bearing clearances in that tightening the prop forces the inner race hard back and binds the bearing. That's cause for a replacement engine. It's rare but tolerances can gang up to cause it.

Well Downunder,
The picture does not show that washer.
But I looked at the parts list and it's under one part number as drive washer & cone.
The engine is the Tower Hobby PRO 46 BB ABC ENGINE.
The engine was very tight until I put some oil into the cylinder.
I put the prop on and it's very loose and gets very tight when the piston is near TDC so I guess i'm OK?

Looks to me that everything is OK on your Tower Hobbies PRO46.

start it up and bench test it, none of us will really know till you do that and tell us the result, good luck and happy landings

Jeremy

Whirley Bird...you'll be fine with it then. What I think you're feeling and worried about is the just the pinch of the piston near TDC. But with an ABC (and particularly a new one) it's not a good idea to turn them over slowly, give the prop a good fast flick to get the piston over the top. Because the piston is an interference fit in the liner the oil gets squeezed out if turned slowly and then you're down to metal to metal. Use some castor in the fuel because it resists being squeezed out much better than synthetics.

The same goes for plain bearing engines: if you turn them slowly with the plug installed so there is compression, the oil will get squeezed out from between the bushing and the crankshaft...don't do that...

Okay, here's the skinny on why new engines are "squeaky tight" at TDC:

ABC engines have no ring to seal the gap between the piston and liner. They rely on precision machining to provide as tight a fit between the piston and liner as possible.

Piston liners are actually tapered, wider at the bottom, and narrower at the top. This is because the top of the liner gets much hotter while the engine is running, and expands more than the bottom of the liner. When the engine reaches proper operating temperature, the cylinder liner has expanded to the point where the sides are now perfectly parallel.

You do NOT want to turn the engine over by hand until it "loosens up." That's a bad thing to do. All you're doing is wedging the piston into the liner and wearing the bejeezus out of both. The best thing to do is get the engine running and warmed up as quickly as possible. Hand starting new ABC engines is darned near impossible, so you will do well to borrow someone's electric starter for the first few starts if you don't own one.

You do not want to run the engine blubbering rich. It won't get hot enough to expand the liner, and the same thing will happen as if you turned the engine over by hand. Tune the engine for maximum RPM, then richen it down to blubbering rich, then lean it back out until it just starts to run smootly.

Whoever told you to turn the engine over by hand until it loosens up at Tower should be fired immediately.

Hi mkirsch,
I usually remove most text from a long post to save the server disk space but I left yours because of the valid info.
I'm getting back into R/C and many things have changed.
I never recall having an engine that was so tight.
This one was tight even and the bottom of the stroke so I called Tower hobbies and they told me to add more oil and turn it by hand until it starts to loosen up.
I did that with no glow plug installed.
Then I got my electric starter and held a rag over the top and it spun like it was free.
It seems OK now and I have not run it yet.
With the glow plug installed I do hear that little squeak at the top.when I try to turn it by hand.
I have nice free loose rotation now excep t when i'm getting close to TDC.
But it goes with no problem with the electric start.
BTW,
Is this the engine that has the bad rep for developing air leaks around the carb?
Thanks to you and the others for the nice educational postings for us newbies getting back into this great hobby

Ok, it may be a bit over the top, but I even used a heat gun on a couple of really tight ABC engines to loosen them up a little before starting them the first time... Just heating the head a little seemed to do the trick, they started just fine by hand after doing that...

Anyone done this too?

Some of the Tower Pro 46 engines have had air leaks around the carb somewhere.

Jim

Go ahead and break the engine in. By what you are telling us it sounds ok. Break in the engine by the manufacturers instructions. I have one of these engines and after breakin you couldn't ask for a sweeter running engine. My air leak sealed off after using about a gallon or two of fuel with castor in it. The only thing that the air leak affects is the engine turning off. Thats all. Avoid idle bar glowplugs with this engine they mess up the throttle transition. OS A3, OS #8, and Tower Power Plug work best. Good luck.

Sport10

.I'm not sure if I understand.
I was told that a different gasket was needed.
If you have a leak I assume that it will get worse with age?
I appreciate the info but i'd rather run my engine with no air leaks.
Wouldn't it be better to just correct the problem?
1-2 gallons of fuel is a lot.
I have 6 of each plug you listed.
Thanks for the post