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Post by scrambler on Oct 19, 2016 0:35:42 GMT -5
Dear All, I start this thread since finally I got to the point when I had some time to dismantle the engine of my `73 TX that I bought a while ago and had a couple of post about it here and there on this forum. The engine is a stock, unmodified engine having around 35k miles in it, I believe. It was equipped with an oil cooler and a huge automotive oil filter, so I assumed the engine should not have any serious issues.. Well, to err is human.. So, here are some pics about the disassembly. I forgot to mention that the reason why I took it apart is that it`s not working and has low compression (by feel, I`ve never measured). I think it hasn`t been running for decades, so I was also driven by curiosity of what i will find inside the engine of the worst nightmare in Yamaha`s history. Here is how she looked before the disassembly. Seems quite intact, from far though. Oil filter with huge capacity compared to the original.
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Post by scrambler on Oct 19, 2016 0:39:00 GMT -5
Is it possible to upload multiple pics here? More than 3, I mean? Electronic ignition from the seventies:
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Post by scrambler on Oct 19, 2016 0:44:51 GMT -5
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Post by scrambler on Oct 19, 2016 0:46:42 GMT -5
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Post by scrambler on Oct 19, 2016 0:51:12 GMT -5
Rings seem not that bad. One is stuck, maybe the reason for the low compression.
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Post by scrambler on Oct 19, 2016 0:54:49 GMT -5
THe conrod bearing is scratched. Perhaps the huge filter didn`t do its job? The conrod looks really bad. Any idea how to fix this? To be continued...
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Post by farmrjohn on Oct 19, 2016 12:45:30 GMT -5
Thanks for the pics. Interesting conversion for the oil filter. I found a used original oil cooler on eBay and used flex hose on either side of the cylinder bases for the supply lines. That allows use of the stock air box since the hoses run under it. Looking forward to updates!
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Post by scrambler on Oct 19, 2016 16:36:00 GMT -5
Thanks for the pics. Interesting conversion for the oil filter. I found a used original oil cooler on eBay and used flex hose on either side of the cylinder bases for the supply lines. That allows use of the stock air box since the hoses run under it. Looking forward to updates! Yep, the filter is quite interesting indeed, it may have come off from a big truck or tank, probably it also functioned as a cooler, it`s so large.. But unfortunately it has to go. I saw a small size filter attached on the rear side of the engine, in front of the swing arm somewhere, I`m planning to build something similar. I came across an original cooler on ebay as well, I should have bought it, it`s very rare...
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Post by don73tx750 on Oct 20, 2016 6:48:51 GMT -5
That looks like a standard Ford oil filter. An extra qt. of oil in the system can't hurt. Regarding the conrod small end, I'd clean it out with some solvent and a gray fine scotchbrite pad and check the piston pin fit. The FSM should list a tolerance. Partzilla shows the pins still available, but they've lied to me before lol. I've had luck getting piston rings unstuck with my HF ultrasonic cleaner using parts solvent. Looks like you're having fun, keep us posted.
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Post by scrambler on Oct 20, 2016 22:02:43 GMT -5
I got the rods soaked in carb cleaner, see if that helps. Here are a couple of new pics about the progress. Centrifugal timing advancer is off. Silicone vs engine oil: although they used up about half of a tube, finally it collapsed under the pressure. No question I will have to do the modification of the oil passages to depressurize the cavity behind this cover. It`s not really visible on the picture, but the journal has some scratch marks. Under the clutch cover all seems fine.
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Post by scrambler on Oct 20, 2016 22:13:32 GMT -5
Deep in the transmission something is not ok.. Sump off: no way of adjustment, looks intact though.
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Post by scrambler on Oct 20, 2016 22:17:43 GMT -5
This guy is also interested in getting some insight into the transmission:
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Post by farmrjohn on Oct 20, 2016 22:50:34 GMT -5
Centrifugal timing advancer is off. Silicone vs engine oil: although they used up about half of a tube, finally it collapsed under the pressure. No question I will have to do the modification of the oil passages to depressurize the cavity behind this cover. Would service bulletin 338 apply to this? tx750.proboards.com/thread/70/service-bulletins
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Post by scrambler on Oct 20, 2016 23:13:14 GMT -5
Centrifugal timing advancer is off. Silicone vs engine oil: although they used up about half of a tube, finally it collapsed under the pressure. No question I will have to do the modification of the oil passages to depressurize the cavity behind this cover. Would service bulletin 338 apply to this? tx750.proboards.com/thread/70/service-bulletins FJ, I took a look, I don`t think this was a long-lasting solution at the time. In my understanding this cavity is depressurized in the later models, from `74 probably. I posted a picture about a crankcase like that earlier. In that one the oil is fed into the middle of the main oil gallery, as compared to the early type, where it is fed on the left side of the cavity, like on mine. This latter version sucks, not only because it increases the chance of leaking, but also because the oil first has to fill the cavity before it reaches the main oil gallery and the head supplying pipe.
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Post by scrambler on Oct 20, 2016 23:16:23 GMT -5
If I split the cases I wanna fix tis issue once and for all by modifying the passage like Argo described in his thread.
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