RZ/RD 350 & Misc. 2-Stroke Tech BBS

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PostPosted: Fri Oct 20, 2017 12:38 pm 
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I am now about to give up and go get the grinder! I am weighing whether get an acetylene torch and heat the crap out it and risk the seals or get the grinder cut the flywheel into peaces. What would be the worst. Djizzzz I am out things to try now. Defeated...


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PostPosted: Fri Oct 20, 2017 7:15 pm 
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I had to cut one of mine off about 8 years ago. I used heat + extreme cold and boiling water and special potions and even prayed to the bike gods and all sorts and no, it wouldnt budge. Grinding was tough and meant the crank needed an new outer web as well. I dont recommend it.

The next hard work one I had I tried heat, penetrating oil, freezing and I always use a good puller. But nothing. I took it to my mates garage and he used a 1000ft/lbs gun on the tool (dont hold the tool with anything), I told him 'either get it off or break the tool... I dont care' and it still took 20 secs of serious banging to free it, but it did come off. I saved the crank and the taper was perfect, threads too. The flywheel looks ok too and the stator looks awful covered in oil and even after all the messing about it tests ok.

So, before you resort to a grinder, go to a car or truck workshop and ask someone there to try their biggest rattle gun on it.

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PostPosted: Sat Oct 21, 2017 2:09 pm 
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Ok. I will give it a final try with a new puller and an airtool then. The last puller I got was tougher then the previous ones in that the center bolt was thicker dia. But it then tore the outer threads instead. The threads of the flywheel is still intact though.

Another idea? Has anyone split the cases and put the crank (stator has to go with it) and flywheel in a hydraulic press? Could it work?


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PostPosted: Sat Oct 21, 2017 7:18 pm 
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The problem with splitting the cases idea is that unless the stator is fitted with the OEM bolts, or an actual hex head bolt, you will really struggle to get the 3 bolts out. It is possible to do it, I did that. pressing might work you know, else if youve given up on the flywheel and stator anyway why not just get a crank guy to split the left web off and chuck the lot in the bin anyway?

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PostPosted: Sun Oct 29, 2017 2:31 pm 
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Got it off!
Cut into pieces and split the hub. 7 Dremel cutting disks and some patience. No damage to the axle.

Stator to be sent off or replaced - haven't really decided yet. Two of the windings found clearly overheated.

How can I now check the integrity of the crank seal?
-I am a little worried it could have suffered from heat applied to the flywheel at my first attempts.

Also, what can I apply to the conical faces of the flywheel and shaft to ensure this never ever happens again?

Image

Image

Thanks
Kjell


Last edited by kjellz on Sat Nov 18, 2017 7:01 pm, edited 1 time in total.

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PostPosted: Sun Oct 29, 2017 10:53 pm 
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You can coat the new shaft with moly grease and then wipe it off. It will stay on at a molecular level.

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PostPosted: Mon Oct 30, 2017 4:06 am 
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pressure test your motor for the seal.


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PostPosted: Mon Oct 30, 2017 9:24 am 
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I would not use any type of grease on the flywheel. If you are that worried about it becoming stuck again try some powdered graphite. If you don't have that, just use pencil lead.

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PostPosted: Mon Oct 30, 2017 11:22 am 
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Put nothing on the taper when you install it.
Before you install the rotor permanently, lap the taper with valve grinding compound.

Check the main seals by doing a leak down test.
When was the last time this motor was run?
Unless you know the history of the motor my suggestion would be new rings, seals/gaskets and bearings all round.


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PostPosted: Mon Oct 30, 2017 11:47 am 
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Having rethought this, I agree with bitzz. Nothing is what Yamaha did at the factory. Since you will be using a different flywheel, lapping compound is a good way to get the tapers to match. If I were to offer an opinion, I suspect some prior owner probably put something on the taper which is why you couldn't get it off to start.

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PostPosted: Tue Oct 31, 2017 7:17 am 
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Regarding the taper. After pulling the flywheel off I expected to see rust or other old gunk causing it to stick. But nothing was seen. Just clean smooth metal surfaces!

Makes me wonder if overtightening could be the main cause here?
- But tightening is limited to what the threads of the center nut can transfer without failing so I have no idea if that is relistic.

Thanks again for all your valuable inputs.

Kjell


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PostPosted: Tue Oct 31, 2017 8:39 am 
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remember the stator passes electricity through the taper, Ive had then arc weld themselves, tho thats not the case here.

Defo lap the parts with grinding paste, I always do that now.

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PostPosted: Thu Jan 18, 2018 8:57 am 
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bitzz wrote:

Check the main seals by doing a leak down test.
When was the last time this motor was run?
Unless you know the history of the motor my suggestion would be new rings, seals/gaskets and bearings all round.


I made an attempt at a leak down test. All I got was air hissing out the exhaust of the other cylinder (I could hear and feel the air flowing with my fingers). That does not promise well for the center labyrinth sea!!l . But what can I expect here; is this center seal actually as tight as the outer seals when good/new? The outer crank seal was fine and showed no leaking even with 10-ish psi pressire was maintained.

Or is there something else I should be aware of here?


Regards
Kjell


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PostPosted: Thu Jan 18, 2018 3:11 pm 
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The center "seal" does not actually seal static pressure as its a labyrinth.
You need to plug BOTH cylinders for a leak test and even then most YPVS engines will leak at the PV seals or bearing surfaces.

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PostPosted: Thu Jan 18, 2018 3:23 pm 
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Ok thanks Martin.
I will try that before I go any further.
-So it will be the centre bearings that usually triggers a centre re-build then?


Regards
Kjell


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