New problem with 1075

[Richard Stoots 17]

Earlier issue was how to hook up choke and throttle.

Finally got it put together with forum help.  Started it up today, seemed hard to turn over but I attributed that to new piston and rings.  It was running but with a loud knock so I have 2 things I think it could be.  Crank and cam shaft off by 1 tooth or rod bearing and crank diameter not matched. My rod bearing is standard and I was told that crank was 1.485 " diameter .

I assumed they were a match, was I wrong?  I will pull motor and open up the bottom to check it out.

Any help or suggestions would be appreciated.

Edited January 26, 2017 by Richard Stoots

[953 nut 51,474]

This chart has all the info you need, definitely not standard.

Kohler Single Cylinder Engine Specs _ Torque Values and Sequences for Fasteners _ Identification & Torque Settings of Most Commonly Used Grades of Bolts (1) (1).html

[Richard Stoots 17]

OK, so if I keep the crank, which size rod do I need?  I don't have the tools to measure crank and rod, I would probably need something with a digital read out, is there such a tool?

[Shynon 7,435]

20 minutes ago, Richard Stoots said:

My rod bearing is standard and I was told that crank was 1.485 " diameter

Crankshaft crankpin is 1.500 new, max out of round is .0005, max wear limit is 1.4990 which is .0010 undersize. So you crank is .0005 smaller than a  .0010 undersize rod. If you have a standard rod you are .0015 larger that your crankpin , which will cause the knock and near future failure. You would need to  find a .0020 under rod, which is available and have the crank turned .0020 undersize.

[Richard Stoots 17]

Found a digital caliper for $20, will post my findings.

[953 nut 51,474]

Be sure to measure in more than one plane ( up/down; across) as the crank will probably be a bit out of round.

[Richard Stoots 17]

Crank is 1.4920 - 1.4855

Rod is 1.4995 - 1.4960   

These were taken from several locations and show the largest to smallest measurements.

Looking at a crank to purchase  1.4995??????

 

Please provide comments?????

Edited January 27, 2017 by Richard Stoots

[oldredrider 2,547]

Richard, the crank could be ground to .020 under to be used with a comparable rod. Turning your crank would cost, I'm guessing, $50+/-. However, I would opt for another crank that is within specs.  The one you have your eye on is within specs. You also will need a new rod to go with the new crank. 

Send me a pm if you want extra help with the rebuild as I'm not far from you. 

Edited January 27, 2017 by oldredrider

[Richard Stoots 17]

Are you saying the rod I have will not work with a std. crank.  I bought it new as a std rod so did I wear it down to where it's not std?  The crank I purchased comes with the original rod that was connected to the crank,  I will measure both before installing.  Will know more next week.

[953 nut 51,474]

Your rod should work with a crank that measures standard. You should pick up some "Plastigage" to check the fitment when you install it. There are lots of Utube videos on how to use it. $ 4.00 well spent.

[oldredrider 2,547]

Your big end rod measurements indicate it's out of round. Showing .004 out of spec. If it were me, I would replace it. 

To add to the above, a worn crank pin can wear out an aluminum rod quickly. The knock you heard puts heavy stress on the weaker parts like the aluminum rod.

[Richard Stoots 17]

I had not torqued the rod cap.  It now checks as a std rod but I will probably replace anyway.  After I get the rod and crank I posted about I will recheck all and post results.

Thanks guys.

[lynnmor 6,762]

Just so you know, a digital caliper is not a great way to measure.  A cheap one should be used for a rough idea only.  An automotive machine shop will use a dial bore gauge or telescope gauges and a good micrometer..  The Plasti-gage mentioned earlier, is a good final check.

[Richard Stoots 17]

OK,  I'll take all parts to shop for accurate measurements next week.  I'll post results.

[Richard Stoots 17]

 

 

Took all to shop, both rods measured out to 1.500, 1 crank was 1.499 and the one with the knock was 1.485 which was the cause of knock.  Put all back together with  1.499 crank and it runs good.    Thank all for your help.

 

Added pictures in Gallery

Edited February 6, 2017 by Richard Stoots