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Coxn
10-17-2018, 02:57 PM
I had an issue with FWD gear the other day. Just got onto the plane and then the motor ran on with no thrust and then died. I thought maybe something had gone through the prop and damaged the hub or gearbox. It started back up and ran in FWD/REV at low revs. Once home, I stripped the lower end but couldn't find any issues with gears, splines, clutch, or springs.

Maybe the problem is at the other end, but I can't see how the driveshaft connects to the crankshaft. The driveshaft has splines, but according to the parts diagram, there's some sort of driver gear on the end of the crank - and it doesn't look splined. Anyone got a picture or advice on how the crank/drive interact and/or what else might be broken?

racerone
10-17-2018, 03:14 PM
Just have the propeller tested.-----Or put a new one on.----Likely the rubber drive hub inside the propeller failed.----Yes there is a rubber hub.

Coxn
10-17-2018, 03:28 PM
Possible, but unlikely the issue. I can't see much wrong with the hub and I can really torque it without slippage. I'm also hearing a knock/click when the engine is running without the leg.

Looking again at the parts diagram, I'm thinking that driver gear is actually for the oil pump. Is the end of the crankshaft internally splined to take the driveshaft?

racerone
10-17-2018, 03:31 PM
Well, ---I tried to help.----But what do I know.

Coxn
10-17-2018, 03:41 PM
Didn't mean to offend :-) Thanks for the input.

haventaclue
10-18-2018, 05:19 AM
I'm with racerone on this one,spun hub.A bit late,but a line marked across the hub,take her for a spin.It takes a lot of power to turn a spun hub.

fastjeff
10-18-2018, 08:23 AM
Spun hubs are both common and are NOT obvious without testing (marking both sides of the hub and running it).

My $$$ on a spun hub.

Jeff

Coxn
10-18-2018, 11:27 AM
OK, good tips. I'll test the prop with a mark as you suggest. Something definitely knocking up top though. Maybe one of the main bearings is also on it's way out...

racerone
10-18-2018, 11:44 AM
Is there a " flex plate " on top of your flywheel ??----Have you grabbed hold of the flywheel to check for excessive up and down movement of the flywheel ?

Coxn
10-18-2018, 12:37 PM
No flex plate, and yes, I'v checked. Doesn't seem to be any excess play anywhere.

Coxn
10-20-2018, 03:25 PM
Ran this engine yesterday with no leg on. Still the same knocking, so prop issues aside there's obviously something going on in the powerhead. Sounds like rod knock, but I can't find any play when I manually check the pistons through the spark plug hole. The engine also runs fine up to 3000rpm on all three cyls, and there's 115 compression in each. Still can't find any play in the flywheel, but I'll need to get a removal tool to check further. Any other suggestions before I strip this thing down to the crank?

flyingscott
10-21-2018, 12:57 PM
Take the spark plugs out of the motor. Then start at the # 1 piston,bring it to top dead center and start it on its down strk. Send it down about 1/2 way and stop. Now take a wooden dowel through the spark plug hole and push on the piston. If the piston moves and you hear a clunk that is a problem. Repeat with all the pistons.

Coxn
10-21-2018, 01:05 PM
Thanks, already done that. Not much in the way of movement anywhere on the rods. Might be the two main crank bearings I suppose. I'll have to dig deeper.

snookwhaler
10-21-2018, 06:52 PM
Piston slap. Scored cylinder or cylinders. I went through this on mine. Injection pump failed on a 2005 model with low hours too. Started hearing a light knock or tapping. Got worse over time. When we tore the engine apart the top 2 pistons and cylinders were heavily scored. Got lucky and did not damage the crank though. So, just a basic rebuild. You should "scope" your cylinders. Funny thing is that the compression was still over 120 psi across all 3 cyls.

Coxn
10-22-2018, 11:57 AM
Possible I suppose, but it sounds more knock than slap. I'll have to stop procrastinating and rip her apart to find out I guess :-)

racerone
10-22-2018, 12:27 PM
Serial # is ??

Coxn
10-22-2018, 12:56 PM
It's a 95 engine, OG range.