flyby50

Hello, i have a .50 sx which seems to be almost new and the bearings are perfect, i removed the back cover and realized it had circular lines on it, i wish i could send a picture but i have not figured it out yet, maybe someone could send one-- normal lines, or problem lines, i would like to know what causes this and if slight circles are ok, thanks for your help.. [sm=72_72.gif]

Flyboy Dave

My Feedback: (21)

....those lines are made by the connecting rod rubbing on the backplate....

....perfectly normal.

FBD.

w8ye

My Feedback: (16)

You would think that the marks would form a perfect circle but it amounts to an eccentric swirl

flyby50

Thanks guys for your help, i guess the design keeps the rod in place, it seems like this would throw metal in the engine, what if the light lines become deeper groves- i'm wondering what parts would be wore out to cause this, thanks again, fly by 50

downunder

The backplate keeps the rod from moving back off the crankpin so it comes in sliding contact with the backplate. This is all nicely covered in oil though so very little wear occurs. The swirl pattern comes from the rod moving around a path that isn't concentric with the crankshaft.

flyby50

Thanks for the reply, sounds like a guy who runs his engines very lean might end up with deeper lines than a safe run, flyby50....

djlyon

Buy yourself a new backplate, then don't use an electric starter anymore. Use a chicken stick. Then note how much less if any swirl marks appear on the back plate. You also might want to check to see if the crankshaft is seated all the way forward in the rear bearing.

Denis

flyby50

Thanks for the info, very easy on the electric starter-- if any-- seems like what your saying is very little lubrication while you are cranking away, i never thought of that, when you stop learning -- ITS OVER !!! Thanks...[sm=thumbup.gif]

Flypaper 2

When using an electric starter, the load is on the front brg, not the backplate.

djlyon

Quite true especially if every thing is properly assembled, but the bearing does have end play and the crankshaft can slip inside the collet (spelling) over time reducing the clearance between the crank pin and backplate and the pressure of an electric starter and you can start to have contact.

Denis

estradajae

Take it easy with the starter, I think when an engine is properly primed and averything is ok, it tooks a fraction of second to get it started...

by the way, I have always marks in the backplate, it's quite common and nothing to worry about.

Jorge

flyby50

Thanks for all the help guys, i thought maybe the engine had some problems, -- Is there a section on how to make Ohio weather warmer...[sm=frown.gif] flyby50....

Flypaper 2

I'll take some of that too Nuff of this stuff.