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DT400 rebore advice

  • NickM
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DT400 rebore advice was created by NickM

Well, I eventually got my bike running for the first time since buying it:) but it sounded bad:( It ran fairly well but lots of piston slap. Took it apart and the bore and piston is trashed. So, my question is, what's the biggest oversize I can go to??
It's got a Weisco .080 oversize piston which is 2mm over already and the bore measures 87.1mm.
Some pics.

Last edit: 08 Aug 2019 06:13 by NickM.
08 Aug 2019 06:11 #1

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Replied by NickM on topic DT400 rebore advice

I think i've found the answer looking through old posts. It's bad news! Biggest oversize I can find is +1.5. Weisco used to sell a +2 which isn't available any more and it's what I have anyway.
It's looking like another cylinder. Any advice appreciated.
08 Aug 2019 06:38 #2

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Replied by monel12 on topic DT400 rebore advice

Enduronut (Dave Sigle) bored a jug 1.5 over and sold me a Wisco piston, after I seized my 4th over. You might contact him.
1971 RT 1B
1971 RT 1B
1970 RT 1
1970 RT 1
1969 CT 1
1971 DT 1
1974 100MX
2016 BMW F700 GS
1982 Yamaha Towny
1971 CT 1
1975 DT400
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08 Aug 2019 07:46 #3

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Replied by Gr8uncleal on topic DT400 rebore advice

Nick

Engineering type stuff isn't really my bag (if indeed anything is!) and I wouldn't even consider questioning your conclusion over the state of the barrel and piston. All I would say is that there have been a number of posts here stating that it is usual for Wiseco pistons to be noisy when the engine is cold. Something to do with clearances when re-bored. But as I say, most people know more than me on this!

Alan
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Last edit: 09 Aug 2019 05:40 by Gr8uncleal. Reason: typo
08 Aug 2019 07:47 #4

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  • RT325
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Replied by RT325 on topic DT400 rebore advice

YZ490 starts at 87mm & goes to 89 in wiseco or probably 88mm in genuine piston kits. Need to consider pin size & gudgeon height etc but might be worth chasing up. I have a 4th over 465 kit on trademe but i'd guess that's only 86mm but i think in theory i could have bored my 465 to 490 so i could measure this piston [where did i hide it lol] so far as pin size & other things if ya want as will relate to a 490 kit.
www.trademe.co.nz/Browse/Listing.aspx?id=2257839629
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08 Aug 2019 16:02 #5

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Replied by bluntz465 on topic DT400 rebore advice

Check here also
wossnerpistons.com/
Call them,sometimes have stuff unlisted
1957 Cushman Eagle 1969 Honda 90 ATC 1969 Honda CB250
1973 Yamaha AT3 1974 Kawasaki KH440 1974 Honda XR75
1975 Suzuki TS75 1975 Kawasaki GreenStreak 90 1975 Suzuki GT550
1975 Suzuki TS250 1976 Suzuki GT550 1976 Indian Chief
1976 Yamaha YZ80 1978 Yamaha IT175 1980 Suzuki GS550
1982 Yamaha IT465J
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Last edit: 08 Aug 2019 16:26 by bluntz465.
08 Aug 2019 16:23 #6

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Replied by NickM on topic DT400 rebore advice

Thanks for the advice everybody, much apreciated.

After all the research it has to be a replacement cylinder. There's no option for any piston sizes bigger than +2mm (8th over)

RT325, that all sounds a bit deep for me (port timing, jetting etc) but I apreciate the pointer.
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09 Aug 2019 05:14 #7

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Replied by liferbiker on topic DT400 rebore advice

Maybe LA Sleeve has your 400 sleeve still, they have sleeves for days! But, not mine! Your's is newer than my ol 73 gyt cylinder with a +2mm as well. Mine is usable (barely). Your's looks pretty hashed! a conversation paperweight maybe? Unless someone here has one try LA Sleeve, EBay may get you one like I got, usable, but not 2nd over as advertised. (it was stamped that, but that was 1.5mm ago)!
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09 Aug 2019 23:57 #8

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Replied by liferbiker on topic DT400 rebore advice

I wish there were somewhere that had piston specs, I mean real specs like compression heights (pin location), skirt & "window" specs, rod lengths, etc. A trick we used in 2.4 911 motors (for racing ,time trials or hot street) was to use 2.2 pistons as w/longer rod of 2.4 pin height in 2.2 yeilded 10.5 compression in a smog de tuned 8.2 of 2.4. (bore the same) This infromation in vehicle "tech books", pin heights, skirts, cam profiles, etc. baisically they are blueprints. Anyone have this type info? With stuff getting scarce, it'd be nice if some other part could be used.
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10 Aug 2019 00:20 #9

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Replied by RT325 on topic DT400 rebore advice


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