395xp oil pump drive gear stripping

[Nathan Harp]

Hi all, I haven't posted here before but I have done a lot of reading. 

My 395xp quit oiling during a milling session. 
Upon inspection I discovered a stripped plastic gear for the oil pump that is driven by the clutch drum. 

This may have originated due to use of veggie oil and improper storage, I replaced the whole oil pump assembly, and also got a new clutch assembly, with bearing. 
At first I thought it was fixed, lots of oil on the bar, proceeded to tune the carb. 
A day or so later I re-visited the carb tuning with a handy engine RPM app on the smart phone.  No issues. 
At one point, I did notice the chain turning at idle and idle adjust and low jet would not solve that.
Another start later and that issue went away?  The oil probably stopped then to.
I did blow out the oil holes to the bar and tank when I had the pump out.
The only washer is between the crank seal and the plastic gear. 
The wear pattern on the failed parts looks like the center of the threaded part of the plastic gear meshes with the piston pinion of the oil pump, looks like they line up correctly.

Decided to work over a couple new ripping chains, and I discovered that the chain would not turn freely, the crank shaft was turning with the clutch drum due to an interference fit of the new plastic pump drive gear. 
I don't think I ordered the wrong part, I bought a set of 4, likely not OEM.

Some research here and around the web.  I sanded the bore of another plastic gear so that it was a slip fit on the crank shaft. 
Ran the saw on a couple slabbing cuts, and noticed no oil again.  Opened it up and had another stripped gear. 

1. stripped gear - original had worked, unsure why it failed maybe oil blockage. 
2. stripped gear - new one was a tight fit on the crank shaft.
3 stripped gear - Modified a new one to slip easily on crank shaft.

I have two more new gears and don't want to repeat this insanity. 
I haven't checked for play in the crank shaft itself yet, will do so today.  The seal looks good and I haven't noticed any play when working with the oil pump and clutch.  I haven't had the other side apart.


Any advice is appreciated.  I plan to check closer that all the parts are right.  The new clutch drum looks a little different like the drive portion was brazed in instead of it all being one piece.  On the new one it looks like a washer welded to the bottom inside of the drum, the old one is flat inside, the thrust area appears the same dimension.  . 

a couple quick questions?
1.  Is the clutch drum supposed to have end play, how much is normal?  It can move side to side a little bit, The clutch comes up tight to the bearing but I can still move the drum in and out, Similar to how the sprocket can move side to side on the drum splines.  This creates some bell ringing.   
  If this is not correct, I can see how the plastic gear might be able to move out and strip. 
 
- I can see how if the bearing was too long, that this might be the case, I will compare later today with original clutch parts and bearing. 
- maybe I need a another washer in there?
- the normal rotational direction should work to suck the plastic gear in toward the case. 
- I put some grease in there on the gears. 

2.  I read somewhere that someone else sanded out the bore of the plastic gear like I proceeded to do.  Is this normal, did I get a bad batch of gears?
 - doing this did allow the chain to move freely without turning over the crank. 
 
- are there any other modifications to the gear or parts that will help it along.
 

3.  Is there a proper break in procedure for a new oil pump or pump gear. 



  Hopefully a simple issue, a little long winded but maybe that will help narrow it down. 


 

[dougand3]

Here is the IPL...http://s30387.gridserver.com/partsDiagrams/Husqvarna%20395.pdf
Shouldn't need more than the 1 washer shown.
And check that you have the proper 503 25 30-01 bearing.

And crankshaft end play...none is best but I've had 1mm on good running, non air leaking saws.
I would guess if crank is moving sideways enough to bugger up the nylon gear to metal gear position, saw would have serious crank bearing dysfunction.

[Nathan Harp]

The end play I was referring to is the movement of the clutch drum itself. I imagine it doesn't move when there is a tensioned chain.  


There is no end play on the crank shaft itself.  rather the clutch drum that carries the sprocket and engages the plastic oil pump drive gear and rides over the bearing.  
The spring loaded part of the clutch contacts a shoulder on the crank shaft solid, all the parts are correct per the diagrams.  

Aftermarket parts needed to be modified to reasonably work, I just worry if it will hold up, or if the what I think is the fix is correct.  I may have caused some of it by adjusting the adjuster incorrectly.    
Comparing the replacement gears to the original, its the same wear pattern, everything appears identical with dial calipers.  Original is black plastic, replacements dark gray, same texture.  

Thanks

[dougand3]

OK, clutch, drum/sprocket, bearing "slop" from AM parts. I can believe it. I had an awful experience with a new Husky 55 3 shoe clutch. Exacting standards just aren't there. 
Maybe the nylon worm gear or metal pump threads are way out of tolerance. Can you get OEM for these parts?

[Nathan Harp]

I will look back at what I got, I think a whole new pump assembly and corresponding drive gears should be available OEM and I may have gotten that right for some of it.  The clutch pieces seem fine.  It would be nice to have a bronze gear?  Either way that won't be happening before my upcoming trip, so my plans to mill up a big shingle oak will have to change.  I don't want to go through the super hot fine dust slow going sawing and ruin bar/chain.  Better to hold off than to figure that out with the logs laying.

Pretty sure my last attempt with those parts was another failure.