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Hoping to bring my old DT 360 back from the dead

04 Oct 2020 22:03 04 Oct 2020 22:06 by Jack. Reason: Edited to add pics
Jack
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Hoping to bring my old DT 360 back from the dead #1
My 74 DT 360 has been patiently waiting for me to bring it back to life for almost 30 years. After the engine started making some scary noises I decided to try and rebuild it, even though I had little knowledge of how to do that. But to make a long story short, after I took the top off and found the rod was pretty sloppy and the piston looked like it was way past it's prime I thought I'd better check into parts availability and prices before going any further. So a trip to the local Yamaha dealer only to find out that some of the parts on my list were obsolete and couldn't be had at any price. So disgusted and demoralized I just rolled her into the shed along with a box of parts I had already removed and there she's sat for all these years.

A few days ago I finally pulled it out of the shed, along with the box of parts and brought it all up to the shop. The engine is now sitting on my work bench. My reward for letting it sit all those years with the the top/sidecovers, etc. removed is rust. Hoping I can clean that up and it won't be a problem.

Although the rod and what I can see of the crank is rusty, it spins freely enough, feels smooth actually, which is pretty surprising to me. Anyway, I'm going to try to rebuild it. Maybe a bit wiser now than I was thirty years ago and definitely a lot more patient so hopefully I can pull it off this time. But any help/advice I can get here will sure be appreciated.

Tomorrow I'm going to make a puller and hopefully split the case.so I can see how bad everything looks down there.

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05 Oct 2020 07:26
darinm
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Hoping to bring my old DT 360 back from the dead #2
Sometimes the rougher the beginning the most interesting the story and rewarding the final running machine. Will be great to flow the progress for one that's been sitting so long.

1972 Yamaha CT2 175
1972 Suzuki TS 185 Sierra
2016 Yamaha WR250R
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05 Oct 2020 08:43
msavitt
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Hoping to bring my old DT 360 back from the dead #3
Cool project!
There are enough parts on eBay to get her running!
Impossible to place an ROI for the fun and satisfaction zipping around on this vintage bike will bring!
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05 Oct 2020 15:23
Jack
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Hoping to bring my old DT 360 back from the dead #4
After a couple of false starts I got the case split. The gears were surprisingly rust free and everything else down there looks to be in pretty decent shape considering everything. From my research it looks like pistons, gaskets, and rods are still available so maybe my only real obstacle will be finding a good crank and then a good machinist to mate it to a new rod.

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05 Oct 2020 15:59
MarkT
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Hoping to bring my old DT 360 back from the dead #5
What's wrong with your existing crank? Doesn't look too bad in picture.

1963 YG1-T, 1965 MG1-T, Allstate 250, 1970 CT1b, 1971 R5, 1973 AT3MX, 1974 TS400L, 1975 RD350, 1976 DT175C, 1976 Husqvarna 250CR, 1981 DT175G, 1988 DT50, 1990 "Super" DT50, 1991 RT180, 2017 XT250
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05 Oct 2020 16:36
Jack
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Hoping to bring my old DT 360 back from the dead #6

MarkT wrote: What's wrong with your existing crank? Doesn't look too bad in picture.


Axial play at both ends of con rod is over specs, especially on small end. I'm just assuming that's due to crank wear. Am I assuming too much? I have no way (that I know of ) to take the crank apart to inspect the bearing area to verify my assumption. Service manual doesn't go into this.

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05 Oct 2020 16:48
Pedalcrazy
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Hoping to bring my old DT 360 back from the dead #7
I sent my crank to Crankworks in Arizona for dismantling, new crank pin, thrust washers and bearing. They balanced it and put a weld on each end to hold it solid. The welds hold it tight from any slight turning and getting out of balance. They also welded up and machined down the oil seal surface on the stator side where it had rust pits. I highly recommend them. The work for me was on my DT400. Should be able to Google them...I think that was the spelling? They have a long list of crank and gear services on their website.

1978 DT400E
1976 DT400C
1973 RT3
1971 RT1B
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05 Oct 2020 17:16
Jack
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Hoping to bring my old DT 360 back from the dead #8
Thank you. I do appreciate the information. I didn't even know the crank pin was replaceable. From what I see on their website it looks like all of that would cost about 300 plus what ever parts I needed, which will likely be a new crankpin and bearing. And the piston and rod which I guess I supply and send along with the crank? Can I use my old wrist pin if it's in good shape or should I go with a new one? And am I forgetting anything?

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05 Oct 2020 17:47
Pedalcrazy
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Hoping to bring my old DT 360 back from the dead #9
You can just send them what you have and they have some kits that might be cheaper and be all inclusive. They will go over whatever you send them and make recommendations of if they can save you money or find something you missed....Maybe a crack or something. I agree not cheap though...but highly respected...at least by me. When I rebuild a top end I figure a new wrist pin, upper bearing, clips and piston/rings. There are, as you have found, tolerances that can be measured and then determine the exact parts you want to replace. I tend to put all new parts in my bikes because I only want to have them apart once! It seems my crank repairs were in the $300 range too. Some would say you could buy another parts motor and take a chance on more used parts instead of sending the crank away. Either way, I hope you get it back on the road.

1978 DT400E
1976 DT400C
1973 RT3
1971 RT1B
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05 Oct 2020 18:00
MarkT
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Hoping to bring my old DT 360 back from the dead #10
I've had good luck with Mr. Crankshaft.

Bill Bune is another place that comes highly recommended by many.

Big end pin should always be replaced with rod.

1963 YG1-T, 1965 MG1-T, Allstate 250, 1970 CT1b, 1971 R5, 1973 AT3MX, 1974 TS400L, 1975 RD350, 1976 DT175C, 1976 Husqvarna 250CR, 1981 DT175G, 1988 DT50, 1990 "Super" DT50, 1991 RT180, 2017 XT250
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