Knackered zxr 400 race engine overhaul

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rigsby
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Knackered zxr 400 race engine overhaul

Post by rigsby » Mon Jan 07, 2019 7:19 pm

Hi,
i am not new to this forum because i race an nc30 so i am usually on the v4 section. I have just bought a race zxr 400 off ebay and have been well and truly stitched up. I paid 1500 for it as it was advertised as tuned i.e kent cams . lightened crank , bdk ram air etc, cosmetic a bit rough but looked ok, the owner fired it up and all seemed ok although he was using a auxillary car battery/ booster. I handed the money over and left, that was about a month ago and yesterday was the first time iv had a proper look so stripped bodywork off etc. I tried to get it running but it wouldn't catch i then decided to woft easy start into the bell mouths and it finally fired this is when i noticed a serious problem there was exhaust gases been ejected from the crank case breather so iv diagnosed a serious piston ring issue and poor compression been the reason it wont fire easily, when viewing the extra cranking amps from the car battery probably helped get the thing fired up.
So now i have to strip the engine and at best replace rings i was told its 0.50 mm oversize so getting rings is my next issue also someone told me that zzr 400 rings fit and are probably easier to source, what i need to know will standard size zzr 400 rings fit the 0.50 oversize zxr pistons or do i need to source zzr 400 0.50 mm oversize pistons if that makes sense.
Any help advise greatly appreciated.

Bloody ebay srtikes again :oops:

rigsby
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Re: Knackered zxr 400 race engine overhaul

Post by rigsby » Mon Jan 07, 2019 7:22 pm

Sorry i meant to say do i need to get zzr 400 0.50mm oversize rings to fit the zxr 400 0.50mm oversized pistons

moforockband
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Re: Knackered zxr 400 race engine overhaul

Post by moforockband » Fri Feb 01, 2019 10:24 am

Although it does sound like rings, compression check it to definitely diagnose the problem. Around 150 psi on each pot. ZXR oversize stuff is rare, but is around if you hunt for it.
Don't be worried about contacting the guy you bought it off if you want to return it and start again. I'd be firm but nice, you have been stitched!
Thye little 400's can be a pita for top ends, you could buy a set of zzr400 oversize and measure them against whats fitted, just be mindful of getting the right size end gap, and the correct fit in the ring lands. Also check what material they are made from, so that they can be safely run at 15000 rpm in a steel bore.
Otherwise you'll be back at square 1!

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ChowderV4
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Re: Knackered zxr 400 race engine overhaul

Post by ChowderV4 » Fri Feb 01, 2019 2:35 pm

Stock Zzr pistons are 57.5mm and the zxr oversize are 57.5. So just order stock zzr 400 rings and you'll be sorted


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