Friday, October 1, 2010

Honda Rincon 680

Today I have a 2007 Honda Rincon 680 in the shop.  This is supposed to be one of Honda's biggest and best ATV's.  It has a big fuel injected engine, independent suspension, and an automatic transmission.  The transmission is an actual automatic with a fluid torque converter and computer controlled solenoid shift valves.  It is just like a mini automotive transmission.  I can't imagine what it must have cost to engineer that thing!

The engine on this model is kind of odd.  The basic Hondas use a simple air cooled engine with pushrod operated valves and a cam down low in the block.  Other manufacturers high performance machines have overhead chain driven cams that operate the valves or rocker arms directly.  One the Rincon Honda decided to put a chain driven cam halfway up the cylinder and use short pushrods to move the rocker arms. It's not an "overhead" cam, it's an "along side" cam?  I guess they had to have a cool chain driven cam but just couldn't give up their traditional pushrods?

This particular machine was in my shop about 18 months ago.  Back then the machine had around 2000 miles.  The problem was that it would start and run fine at idle, but when you revved it up it just would not go.  It acted like it couldn't breath.  I checked everything out and discovered that the lobes on the cam had wore down so far that the valves hardly opened.  Everything else checked out ok.  I eventually came to the uneasy conclusion that the cam shaft must have been defective (not heat treated properly?) and it simply wore out.  I replaced the cam and everything worked fine.

Now the machine has around 4000 miles on it and it is running the same way.  I have not tore the motor apart yet, but at this point I am assuming that the cam is bad again.  Before I open up the motor I figured I should check the oil pressure.  The only place that you can access the oil system is at a small bolt with a sealing washer under it.  You are supposed to use your Honda factory authorized pressure tester with a banjo bolt fitting on it to connect to this port.

I don't have the Honda pressure tester tool so I had to improvise.  I had a few odd banjo fittings that I have collected from other machines, but they are all to big.  I made a banjo fitting out of a left over scrap of HDPE.  I also had to drill out a standard bolt to turn it into a "banjo" bolt.  In the photo you can see these two items next to a manufactured banjo fitting that is just a little bit to big.  The homemade fitting worked great, but the 1/4" hose that I stuck on the hose barb with no clamp blew off.  Turns out the machine has lots of oil pressure and a good pump.  It made a big mess in the few seconds that it took for me to turn the thing off.

Does anybody have an idea why this machine is wearing out cam shafts?

No comments:

Post a Comment