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73 RT360 compression

  • Enduro nut
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Replied by Enduro nut on topic 73 RT360 compression

I believe you are correct Carter. I FINALLY got some time today to dig into her and here is what i found. I see a ton of oil build up just everywhere, crank, piston and the gasket that goes between the head and jug. When i pulled the 4 bolts that hold the jug down they all had oil on them especially the front 2. I show a comparison in the pics. Hopefully tomorrow ill have some time to take the piston off the rod real quick to check it over but for now i thought id give an update and get your guys expert opinions.


  


Last edit: 14 Sep 2021 10:01 by Enduro nut.
14 Sep 2021 10:00 #11

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Replied by Pedalcrazy on topic 73 RT360 compression

Yeah the studs shouldn't come out of the block like that either. Get um cleaned up and dry and use some Loctite on them to re-set them. I torque studs that come out a little more than what the nuts are supposed to be. Hasn't failed me yet.
1978 DT400E
1976 DT400C
1973 RT3
1971 RT1B
1968 DT1 (Project)
14 Sep 2021 15:03 #12

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Replied by Enduro nut on topic 73 RT360 compression

Thats some good advice, it was only 1 that came out. If im not mistake i think i can replace those crank seals without having to split the case? Just need to drill a hole in the seal, find me a screw to go in the hole and my trusty vice grips for yanking.... there somewhere on the bench lol
14 Sep 2021 19:56 #13

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Replied by RT325 on topic 73 RT360 compression

My studs just didn't want to come out but needed them for another set of cases. Did get 3 out but number 4 broke off flush. wasn't a happy day. Not sure i used the others after that as were all feeling like suffering before turning. Used an old style remover that got hold of it at the base so the best place. Think were loctite'd in but don't need to be.
14 Sep 2021 21:33 #14

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Replied by Pedalcrazy on topic 73 RT360 compression

Enduro Nut you are correct about the procedure for replacing crank seals. 
1978 DT400E
1976 DT400C
1973 RT3
1971 RT1B
1968 DT1 (Project)
15 Sep 2021 05:08 #15

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Replied by Enduro nut on topic 73 RT360 compression

So i been shopping around for some crank seals and from what i can tell both sides are different. At least according to the part #. Im curious what you guys would recommend buying? i see i can buy sets on ebay for just under $10 but those are made in china and we all know how great their stuff is. Im not so sure about NOS for fear of dry rot after sitting on the shelf for so long.
15 Sep 2021 20:30 #16

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Replied by shyted on topic 73 RT360 compression

I live in the UK so your access to parts is better than here. You might get seals from Rocky mountain and they might be used on a current model of some description . Put the numbers in their search and see what comes up. Bearing suppliers can supply seals and it's possible you might find something there that's not Chinese. In the end ,as i'm finding here, you might have no other option .Double lip seals are what you need . If you end up using anything that looks round from China, check it out as it's not always the case. You can find stuff in the Japanese market ,i have but you need a go between sometimes to buy and need to spend ex amount.
With regards to the compression readings. When you put oil down the bore, the oil acts as a seal on the rings.
That's why your readings changed after a while. A mate races Karts and only uses a twenty to one ratio with racing oil. Why ? Because he gets higher combustion chamber pressure at high temp.
I would say, new rings going in at least and clean the living daylights out the ring grooves . If the pistons goosed ,it would do no harm to measure the piston to bore clearance (0.045 -0.050 mm ) and if that's okay , de glaze the bore and new piston and rings. When you start the bike use mineral 2 stroke oil. It has a higher zinc content and prevents glazing. Don't leave it idling . at least give it the odd rev . Once it's had a couple of tanks of fuel through then you'll be okay to use any 2 stroke oil.
Then you'll find some thing else to occupy the Yamaha bit of your mind .
Dave
Last edit: 16 Sep 2021 01:13 by shyted.
16 Sep 2021 00:06 #17

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