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MX360 overbore pistons

  • diesel digger
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MX360 overbore pistons was created by diesel digger

Hi everybody. I have a 74 MX360 barrel bored out to 81.5mm that I would like to put on my 74 DT360. Having trouble finding a piston for it. First off, will a rt-3 piston work at all? does it need a little massaging to fit or is it completely unsuitable? I remember reading somewhere about piston ring locator pins being in the wrong place, but that might have been IT pistons. Can't remember. Would like to stick with a 2 ring piston if possible but will use a single ring if that's all that will work. Thanks, Brad
18 Nov 2019 06:30 #1

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Replied by mdscott on topic MX360 overbore pistons

I have a DT360, only pistons available are OEM, a few on this forum still have factory pistons.

Diesel Digger, are you a heavy machine operator?
Thanks Mark
Roseville, Ca.

'03 ST1300
'75 Norton
'73 CB500K
'81 Honda CT110
'87 PW50
'64 McClane Edger
'02 Honda XR70R
18 Nov 2019 08:34 #2

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Replied by RT325 on topic MX360 overbore pistons

Genuine Yam only go to 81 or 4th over but aftermarket should still be out there. I run a 2X5 YZ400F 1979 only kit in my 360. Well sold it sometime ago & haven't heard it exploded lol. Are 82mm std if you're stuck & they need about 5mm off the skirt to be safe at bdc as get close to the wheels but in saying that i didn't remember to shorten the one on the bike i sold--worried now uhh. Head may need the edge taken out enough to clear but minimal amount. Anyway--was just a thought & another option. They are a two ring piston with the big cutaway. I'm talking an RT2 but same horse in respect of how it'll work on a later shape motor. Enduronut's the man though & take his advice first.

Just another thought & remembering my muckups in history--i had an 85mm YZ400 D or E piston kit given to me back when i had an RT2MX top end on my RT2 to Scramble/MX. Took cylinder to the machine shop & they ran about an hour later & said hey mate the fins fell off--bugger. Raced around there in despair & alloy had shown up around the transfers & still had about half a mm to go to finish. Wasn't a good day--another not good day--had lots of those.
Last edit: 18 Nov 2019 14:08 by RT325.
18 Nov 2019 13:53 #3

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  • diesel digger
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Replied by diesel digger on topic MX360 overbore pistons

Thanks everybody I appreciate it. What I need to know is whether a 1.50 mm over bore Piston from an RT-2 will fit a 1974 MX360a cylinder with an 81.5mm finished bore. Pin size and height. Crown height. Skirt length, cutaway. Ring pin locations etc. Thanks, Brad.
Last edit: 18 Nov 2019 17:20 by diesel digger. Reason: Needed more info
18 Nov 2019 17:12 #4

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  • Rhylbert57@gmail.com
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Replied by Rhylbert57@gmail.com on topic MX360 overbore pistons

Brad,do you still have 82mm piston,if so would you sell it to me,how much.   Thanks rob
22 Aug 2023 03:19 #5

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Replied by RacerClam on topic MX360 overbore pistons

 -Try calling Athens Sport cycle  , He had some Wiseco pistons made for the 360 I bought one a while back

Rich
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23 Aug 2023 15:13 #6

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Replied by turbodan on topic MX360 overbore pistons

I like the wiseco 639m piston. Available up to 82mm. It is 3mm taller from the center of the wristpin to the edge of the crown. Requires a spacer or allows you to pop the piston up above the deck at TDC and take the opportunity to adjust port timing and entry angles as well as the squish band.
25 Sep 2023 19:40 #7

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Replied by RT325 on topic MX360 overbore pistons

Or use an 82mm 2X5 YZ400F "79 kit with about 5mm of the skirt base or gets close to the flywheels a BDC. Just slide the pin through old & new together to get a comparison of the skirt length. Not easy to find those kits nowdays as were one year only long stroke small bore 400.
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26 Sep 2023 00:41 #8

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