Manuals & Measurements

[roger_scotty]

Yanmar manuals are among the best quality that I have seen as far as detailed instructions and illustrations. However, it is common for them to make errors in their conversion of metric to inch measurements.
Yanmar published several technical bulletins trying to straighten this out, but only muddied the waters.

If you are ordering rod and main bearings you should be warned that it is particularly difficult to interpret their measurement scheme. Sometimes they list a journal bearing as .25 US or US .25. What they are trying to say is that these are the equivalent of .010" undersize. Probably they got tangled up because a quarter of a millimeter is about .010". Where I have checked, the metric measurements seem to be correct. You should always double check their conversions to the inch system.

Here's another type of error: I was just looking at the specs for head flatness. (Page 20-05-11 in my 336 manual). They quote .03 to .1 mm and then follow this up by saying that it is .012 to .040 inches. The metric measurement is correct.....but if you do the arithmetic you'll find that their conversion to inches is too large by tenfold.

 

[clifst2310]

Roger the same problems seem to exist in the YM276 manual. I just had my 2310 head shaved, and took the page with the measurements to the machinist so he had the correct specs and he told me the milimeter measurment didn't convert to the inch as the book said. He did the conversion and shaved the head .005. I have the book on CD from www.classicmanuals.net. The cd has the 276 service, 135-155 service and 2210 parts manuals on it. I bought it off ebay for $20. Was a deal because my brother has a 1300. It is also handy to print out a page or two to work on the tractor and throw it away after, if it gets all greasy. I did print out the whole book just in case. It's also got a JD650-750 operators manual.

 

[roger_scotty]

Yes, the measurement errors exist in all the Yanmar manuals that I've looked at. I haven't looked at any of the aftermarket ones to see if they copied the information or checked it. The mistakes are pretty obvious to any machinist or mechanic because they just don't make sense.
A head is shaved so that the gasket will compress evenly. However much it takes to do that is what is necessary. Your machinist did it just right. Yanmar implies that the gasket can accomodate a .004" bow, but they prefer to keep it to .001". Usually when a head is shaved the grinding or milling machine will easily hold closer than a thou. in flatness. So its just a matter of cutting till less than .004" bow remains and hoping that the compression ratio and valve clearance is OK.