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Makotosun

1968 DT1 rebuild/rejuvenation

  • nhsteve
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Replied by nhsteve on topic 1968 DT1 rebuild/rejuvenation

Teardown continues. Magneto situation on it's way to being solved. Solution will be either later crank assembly bits to accommodate a later mag, or an earlier mag assembly.
Cases came apart without trouble. I was concerned about a couple of rusted screws but they cooperated. It was quite a mess inside. Most of that liquid is penetrating oil.

I am curious about the apparent punch or drill marks on the flywheel cheeks near the rod. Never seen anything like that before, almost look like a punch made them. Also some blue on the rod, kind of unusual. But things were pretty dry, and the injection was not hooked up.

Any thoughts on those 2 points?
25 Nov 2020 10:37 #11

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Replied by nhsteve on topic 1968 DT1 rebuild/rejuvenation

Main bearings removed this morning; using heat and a bearing drift they came out easy enough. My desire is to clean the cases with my soda blaster if I can get it working again, or have them (water) vapor blasted by a man nearby. To do that I will want to extract the bearings to avoid damage to them, although replacement is probably the way I will eventually roll. I have found that sometimes it costs more to save something than if I had just put new bits in (provided they can be found!).

So, on to a thorough cleaning then.

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25 Nov 2020 10:48 #12

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Replied by nhsteve on topic 1968 DT1 rebuild/rejuvenation

Probably not a lot of progress that can actually be shown, but I have spent a fair bit of time researching things, as there are some differences in this 'early girl' that don't really jump out.

The first was the flywheel mag. I started a thread in the "parts wanted ", and SWM apparently has a '68 flywheel that looks very good. I have PM'd him about that. Before that showed up, however, I grabbed a later year flywheel, stator plate assembly, and even a crankshaft assembly, that I can use. I have sent those items and the meters to DEET to work his magic. Those will will all take 2-3 months to come back.

I have also started purchasing the bearings, seals, and other bits that will be needed for reassembly. Having a funny issue with one transmission bearing, which is on another thread in the "general" section. I'm sure all those problems will be resolved.

Today I am posting up a photo of the two crank assemblies I have, the '68 should be on the left, and you can see that there is a definite length difference in the snout, as well as an increase in the size of the threaded portion (that was indicated by MarkT or Enduronut in the magneto thread search.

The picture of the 4 mounting bolts show, just, yup, they are mounting bolts. But I do not think the locknuts used are the type used on later years, maybe? When I was reassembling the 360A, I don't recall seeing this type of locknut. So wondering if these are "'68 specific" or maybe they were changed by a previous owner? Also, the top bolt is an early 8mm diameter, not 10mm. My parts book shows there was a changeup at one point. (I actually have a 10mm bolt, and am wondering if I should use that, or leave the 8mm......:Coffee :Coffee ) Other differences I have spotted so far are the dipstick is alloy, not rubber, and the drain plug has a larger head on it than I've seen, and is almost counter-bored.

As my soda blaster is being balky, I am sending the case halves, covers, and cylinder/head off for vapor blasting this week.

'Till next time, be well! :Buds

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10 Dec 2020 11:47 #13

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Replied by shyted on topic 1968 DT1 rebuild/rejuvenation

I don't know about the AT of that year but i have nuts of that type on my RT1B (71) and DT3 (73)
So they could be Yamaha but i couldn't say for certain.
Finding them if they are would be another story ,well at least here in the UK.
11 Dec 2020 02:06 #14

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Replied by nhsteve on topic 1968 DT1 rebuild/rejuvenation

Interesting problem with the carburetor last night/today, in that after removing the float bowl screws, I could not budge the float bowl to remove it. I was able to remove the main jet holder at the bottom, and fed WD-40 into the cavity that way and from above via the nozzle. I put the main jet holder back and filled the cavity from above and let it set overnight. This morning I was able by working the float bowl back and forth to get it to start to loosen up by wiggling it. The fix seemed to come when I took a piece of gas line and put it over the nozzle, and gently fed some air pressure from above, wiggling the bowl at the same time (that was kind of a dance). In the end, it came off. I think soaking overnight helped.

I had not come across the little caps on the top of the float shafts before, only seen pictures. The clips were pretty tight but I was able to remove easily enough with some gentle persuasion.

The carb/parts as well as cases, cylinder, & head are shipped off to be vapor blasted. I'll post up the results when they come back.

Carb ick:

11 Dec 2020 14:05 #15

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Replied by Mothersbaugh on topic 1968 DT1 rebuild/rejuvenation

Looks like it's filled with miniature barnacles. Wow.
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11 Dec 2020 14:08 #16

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Replied by nhsteve on topic 1968 DT1 rebuild/rejuvenation

Got the bits back from the vapor blaster. Things have cleaned up quite a bit. I am having problems coming up with the proper bearings for one application but I "hope" that a resolution is on it's way to me. The difference between clean and dirty is remarkable. Removing the dirt reveals the damage done by the water and time to the cases. I note especially areas at the bottom of the case halves that appear to have eroded away some. I am hoping that a good bead of Yamabond will still seal there, otherwise I will have to do something to build that area back up.

Any thoughts on that?

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29 Dec 2020 09:52 #17

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Replied by nhsteve on topic 1968 DT1 rebuild/rejuvenation

Barnacles are gone at least!

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29 Dec 2020 09:55 #18

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Replied by Midlife Motor on topic 1968 DT1 rebuild/rejuvenation

I think it will hold tight with the Yamabond4. It looks like engine case halves I put together a few years ago and so far no leaks.
It's better to remain silent and be considered a fool than to speak and remove all doubt.
29 Dec 2020 12:23 #19

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Replied by Dirtboy on topic 1968 DT1 rebuild/rejuvenation

You're making great progress!

Last edit: 29 Dec 2020 14:02 by Dirtboy.
29 Dec 2020 14:02 #20

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