Mystery Yanmar problem

[countryboi]

Hello all, got a real mystery here with my old Yanmar 1700, hoping someone may recognize my problem! Here's some backround;

Old 1700, runs good. Replaced the clutch, pressure plate and throwout bearing about three years ago. (what a job!) Anyway, was mowing with a new to me Bushhog finish mower. She was in some heavy grass and started "lugging" and before I could react, everything stopped. Engine was still running, but mower stopped, clutch was still out. ???? Ok, I figured the clutch let go.
Tore her down again and the clutch looked ok. Pressure plate showed no obvious signs of problem. Throwout bearing appeared as new, springs looked ok, even the connector for the drive shaft to transmission shaft looked so-so, but blah, blah. Well, I broke down and ordered a new connector, pressure plate and clutch. Installed everything, fired it up, and it will not move. Here's the kicker; if you grab the transmission shaft and turn it by hand, the gears inside move, PTO moves, even the wheels turn. You can grab the drive shaft and turn the engine. But when you bolt it all back up, start it, it will not move.
Without pulling the top of the tranny, just removeing the dipstick, I can turn the shaft and see the gears move. Nothing seems "out of whack". Yet connected to the engine, she won't move.
Now, some of you may be saying "BS!!" and I agree, I don't get it. I've talked to two Yanmar guys where I get my parts, and they're stummped. Anyone got any ideas?? I'm going home tonite to recheck everything to see if there's something stupid I may have missed. Believe me, I'm Homer Simpson when it comes to missing simple stuff, but this has got me.....

Will appreciate all suggestions and will do my best to check them out and let you know what I find!!

 

[winston1]

Welcome aboard. :welcome:

Are the splines good on both ends of #12? Yanmar Tractor Parts: CLUTCH

Are the splnes good on #1 and #35 shafts here? Also the #2 coupler between those two shafts? http://www.hoyetractor.com/mm5/merchant.mvc?Screen=CTGY&Store_Code=HTE&Category_Code=YM1700TRANSIN

 

[deepNdirt]

Have you check to see if it slipped out of gear? the lever that changes it from high to low range, After some age and wear Some models have been known to knock themselves out of gear when under a load, sending the lever into the neutral position,

 

[winston1]

Have you check to see if it slipped out of gear? the lever that changes it from high to low range, After some age and wear Some models have been known to knock themselves out of gear when under a load, sending the lever into the neutral position,

I've been wrong many times and probably am again but I am thinking the pto would turn regardless of whether range shift was in or out of gear.

 

[Car Doc]

Sure seems like its pointing to the splined coupler in the bellhousing? But I can only imagine its just not engaged for some reason once you put the 2 half's back together?

 

[countryboi]

Welcome aboard. :welcome:

Are the splines good on both ends of #12? Yanmar Tractor Parts: CLUTCH

Are the splnes good on #1 and #35 shafts here? Also the #2 coupler between those two shafts? Yanmar Tractor Parts: TRANSMISSION_INTERNAL

Sorry it took so long to get back to you, I'm on the road......splines are fine!

 

[winston1]

If splines are good on all three shafts, couplers are good, clutch is good, then I think you are missing something somewhere.

You stated you could turn the transmission shaft by hand and see the gears move through the dipstick hole. If you then put it back together and the engine won't turn it so you can see it through the dipstick hole then that indicates the problem is in the bell housing/clutch, coupler area, not in the transmission.

 

[Car Doc]

The clutch staying disengaged is logically thinking. I would think as long as he has ran it he would notice a different "feel" to it though especially after another replacement. I have been in these spots where I am positive something is perfect and move on around to my tail and start the spinning cycle. Ive done it many many times only to wake up and see it right in front of me d'oh.

Like I mentioned it may well be in the assembly of the 2 halfs where something is not right.... like a snap ring etc missing on the input to the trany letting the coupler move back as the halfs come together......elifino that would take a measurement from block to the front of the tranny etc to know for sure..

 

[chriswheeler]

Not exactly clear from the description of the problem what's not working. Sounds like the transmission turns free, does the engine start in natural ?? Is the brush hog disconnected ?? Reason I'm asking, ran into a odd problem with my YM 3000. Turns out Yanmar uses the bell housing for part of the frame on these. My 3000 had the guts and HP to keep turning after 4 or so of the 8 bell housing bolts had broken. When I removed the flywheel to replace the clutch, I found the bolt heads had been scraping the back side of the fly wheel for quite some time. Broken bolt heads were almost ground to a powder. I think a indicator that this might be the case could be that the engine is hard to crank or locked up. Was easy to fix, removed the bolt stubs, installed heli-coil inserts in all threaded holes and new bolts. Also noticed that something similar had happened with my JD 950 at one point as a brace was installed between the engine and the bell housing. Could be a design fault that happens when something on the 3 point places more stress on the bell housing than the factory engineered it for. There have been some reports of broken bell housings from folks using a 3 point backhoe attachment on some of these for what looks like the same reason. Just a thought here, it sure could be one of the drive lines or couplings as well. But note that when ever doing a clutch replacement on these, it's wise to remove the fly wheel and check the bell housing bolts, could save some trouble down the road,
Chris

 

[Leejohn]

I'm just going to bring this up because I seen it and had to fix it. The guy said his engine was running funny. It was a mercury OB inline 6 cyl and when I started it I seen the flywheel move up. Come to find out the crankshaft was broken at the top counter weight and the engine didn't run all that bad.
I guess what I'm trying to say is make sure the flywheel is good and tight with no side movement or in and out. Hope that's not it.