K301 undersized rod

Alvy · #1 07-29-2012, 01:43 AM

Hello all.

I have started the tear down of my K301 due to a loud knock in the engine under any kind of load. Previous owner installed new piston/rod for unknown reason but I think I'm finding out why. I found knock to be excessive play in rod to crank clearance and looks like stock rod was used. Measuring rod journal on crank is 1.489 at the smallest dimension/slight damage to journal in small area and minimum wear spec I have found is 1.499 so I'm wondering what my options are? I've read that a .010 undersized rod is available but it seems I'm already at .010 under wear spec. so will getting the undersized rod work? I've also seen that there is a .020" under rod available in rebuild kits on Flea bay that's extra on top of the cost of the kit but this seems like it might work as well. I cant find a new or used crank so mine will have to be repaired I guess or left as is and hope the undersized rod (s) will work? I'm assuming that I should take the crank out and bring it to my local machine shop to see what they have to grind it down to? I don't have much experience in this so any advice would be appreciated.

Thanks

mrcubcadet · #2 07-29-2012, 03:45 PM

Any pictures of the damage? If it is minimal, you might be able to lightly sand on it with sand paper.

If you are having issues finding a crank, put a wanted ad on here..Or contact one of the sponsors. I'm sure someone has an extra crank.

Matt G. · #3 07-29-2012, 07:00 PM

If the journal is at 1.499", it is 0.001" worn, not 0.010", so it should clean up at 0.010" under unless it is badly scored. You'll need to have the crank turned undersize at a machine shop.

Alvy · #4 07-29-2012, 08:07 PM

Quote:

Originally Posted by Matt G.

If the journal is at 1.499", it is 0.001" worn, not 0.010", so it should clean up at 0.010" under unless it is badly scored. You'll need to have the crank turned undersize at a machine shop.

I stated that the journal is 1.489 which is .010 under already. So does that mean I need to get the .020 under rod? The Damage seems quite minimal enough (not gouged) that I can polish it out but I'm afraid it's out of round and will need to be ground?

Thanks for the replies. Looks like its coming all the way apart.

mrcubcadet · #5 07-29-2012, 08:56 PM

Mic it in 4 different places and see if it's out of round that way.

I've had some pretty bad cranks, that sandpaper has taken care of. As long as there is no jagged parts sticking above the surface of the crank, the lines/grooves will actually help lubricate it.

Matt G. · #6 07-29-2012, 09:02 PM

I read that about 4 times and thought I saw 1.499. I must be awfully tired. I think only 0.001" wear is allowed, so you'll either need to have the crank built up and turned back to standard size, or get it turned 0.020" under and either use the aftermarket rod or have a new OEM rod machined for a bearing insert.

'Lines and grooves' are not going to help lubricate a new rod, they'll tear it up. The bearing surface area is reduced and the rod will be worn to match. They are machined smooth from the factory for a reason.