Crf230f cylinder in an X31?

[Yeg.chrisc]

I'm having a hell of a time finding top end parts for my X31.
ZA169FMM, more like a 65mm bore with 15mm pin.
It looks like the valves are the same dimensions as the crf230, so I ordered seals from Honda already.

[franque]

Yep, it should work. You'd be the first on here to do it though, so make sure that you document it!

[JerryHawk250]

I recently installed the CRF230F Wiseco 11:1 piston on my X22R 250. It's a 65.5mm bore with 15mm pin.

[JerryHawk250]

The CRF230F Big Bore kits and cams will also work on these engines. https://www.ebay.com/itm/Athena-67mm-Big-Bore-Piston-Cylinder-Engine-Kit-Easy-Install-P400210100054/324049743062?fits=Model%3ACRF230F&epid=239059982&_trkparms=ispr%3D1&hash=item4b72deacd6:g:s-AAAOSwSsheWYKX&enc=AQAEAAACcIQvEcHUrT7nmUC3yY5qbPyaBN1nJEDYW8Myyp sJPgXKKoZA2iqbHzAEKToApxCqvYuMZJb8Ht31sA%2FWhcEpms S%2FTiPXFI1B1PSpm53qJEuW1lzPlmazVvo6zwb9W1b6HGzSbw VT5RmJWcl9grE1A2y%2BE1Xzace6JgfBa9kWBROcTkyUbjxIsu cndZ%2FyA5rkxxNPugGK34GFsHH4sYfYgLP9jV1cS7%2BW3VAR JyUpTL4Wgpghp2%2FNRFdH9xz5B1EqdZMKKLikW0Ws%2FJcD50 tR9FuFET9RtkIZ4mzmtw1WbIXkPn%2BM9RpAohrF7Q0f1Wau1j dVyTAofa7jR0KSfI1HIpydQYFxHdTYaR4jPwYU1cuW3iqP6Gv3 zqcbH4WLINZD3KYMY6rngWUqilS3UZvztR0CXxeJjHL%2F2EEh PFXtRDAa4%2BAGLUYh9XquUWE5oYpJYtvlzab5T6iFLFWxF8YD 2%2FllGw5JZjtLRfDQ3zixAeg5GwFWIwOWaEVtGONdBRIz8SQn 1fMGxiSVmup%2BVOFZ%2Fi%2BfI1P4yIEiPQPZWmTCVV68yQoX i8BHmOCGk0nXlL3MBs28Fpl36D2dYwOg%2FT8WmFb9GZnsvTjh jGvGAoH1GcOo7ozq5ZYKR5haGb8p2Szr1iiv8xsdGznJg%2Fb4 Sq%2Fbgm%2BkfzaIyix1t6luZIFAAWrak3QGbSVuSULcoH%2BO 4fbctO0mQgUH1knpzU1YNtHLm23S2hzSR%2BtabLV%2BYGXrtk phS1txm7pbUDqs44BVzYgmsZl5eaMjBtA9ETOkcwz96RUWH%2B 2j%2BuerqhuGKsHYvWcfnntSnpEPhi2fqP0SbB94og%3D%3D&checksum=324049743062bfaa8f8139644b77b82228ab02791 9bc

[Yeg.chrisc]

I see a bunch of pistons sold as 65.5mm of, do you guys think it means they are actually 65.5mm of or they are meant to for a 65.5mm cylinder??

[JerryHawk250]

I see a bunch of pistons sold as 65.5mm of, do you guys think it means they are actually 65.5mm of or they are meant to for a 65.5mm cylinder??
They are meant for a 65.5mm bore. I don't remember the exact measurement but the piston is slightly smaller.

[Yeg.chrisc]

Mine is like 64.98mm.

[JerryHawk250]

Mine is like 64.98mm.

Stock piston on a 65.5mm cylinder would be around 65.49-65.47mm. Service limit is 56.40mm.

Did you measure the bore of the cylinder?

[Yeg.chrisc]

Yea the cylinder is 65.5 top, bottom and middle.

[JerryHawk250]

Yea the cylinder is 65.5 top, bottom and middle. So yeah that piston is worn out at 64.98mm.

[humanbeing]

From CRF230F shop manual:
https://i.postimg.cc/mz0WsFfZ/crf230F.gif (https://postimg.cc/mz0WsFfZ)
Measure at the gauge point w/ correct tool & not as these http://www.chinapartsdepot.com/shopping/shopexd.asp?id=771 clowns as possible
https://www.youtube.com/watch?v=u-6tUWAXo-0
===
The average Chinese Joe will just put another 67 BBK https://item.taobao.com/item.htm?id=617131505511 when worn.
Anway the standard 65.5 chonda nowadays is using [0.8/0.8/2.8]. Why such 2.8 oil rings cuz there's history reason https://motorcycle.sh.cn/thread-17320800-1-1.html (Change to destop mode if via from mobile device) Suzuki F10A (& copycats) 2.8 really works unlike the bike specfic thin rings they failed to copy ...
http://img.alicdn.com/imgextra/i4/389662530/O1CN0198jMHd1UYmdvXmVLY_!!389662530.jpg

[Yeg.chrisc]

Yea, 0.52mm clearance is double what it needs to be.
I have a new piston coming. Bore seems alright. Once I get the new valve seals and piston installed and the bike running, I'm going to order a crf230 big bore kit whick I think is about 67mm, and they come with a domed piston. But I just want to get back riding asap.

[JerryHawk250]

Yea, 0.52mm clearance is double what it needs to be.
I have a new piston coming. Bore seems alright. Once I get the new valve seals and piston installed and the bike running, I'm going to order a crf230 big bore kit whick I think is about 67mm, and they come with a domed piston. But I just want to get back riding asap.
Check the cylinder for roundness. If the piston is worn that much cylinder could be worn too. Also you want to hone the cylinder so the the new rings will seat.
Here's a link to the CRF230F shop manual. https://www.google.com/url?q=https://www.dropbox.com/s/gxu4xf2i3v1ln0g/CRF230F_ServiceManual_2003-2013.pdf?dl%3D0&sa=D&ust=1591965565636000

[franque]

How old is this bike? A piston that worn out would likely not run in the engine, I've never seen one wear out a whole half mm. The piston/cylinder would look pretty gnarly if it was that much worn out.

[JerryHawk250]

How old is this bike? A piston that worn out would likely not run in the engine, I've never seen one wear out a whole half mm. The piston/cylinder would look pretty gnarly if it was that much worn out.

I was thinking the same thing. A new cylinder and piston would be the way to go. Might as well do the BBK.