Crf230f cylinder in an X31?

Yeg.chrisc · 06-10-2020, 12:30 PM

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 · 06-10-2020, 02:50 PM

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

**JerryHawk250** · 06-10-2020, 03:07 PM

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

**JerryHawk250** · 06-10-2020, 03:19 PM

The CRF230F Big Bore kits and cams will also work on these engines. https://www.ebay.com/itm/Athena-67mm...2228ab027919bc

Yeg.chrisc · 06-11-2020, 11:24 AM

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** · 06-11-2020, 11:30 AM

Quote:

Originally Posted by 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??

They are meant for a 65.5mm bore. I don't remember the exact measurement but the piston is slightly smaller.

Yeg.chrisc · 06-11-2020, 01:47 PM

Mine is like 64.98mm.

**JerryHawk250** · 06-11-2020, 02:28 PM

Quote:

Originally Posted by Yeg.chrisc

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 · 06-11-2020, 05:51 PM

Yea the cylinder is 65.5 top, bottom and middle.

**JerryHawk250** · 06-11-2020, 05:54 PM

Quote:

Originally Posted by Yeg.chrisc

Yea the cylinder is 65.5 top, bottom and middle.

So yeah that piston is worn out at 64.98mm.

humanbeing · 06-11-2020, 10:24 PM

From CRF230F shop manual:

Measure at the gauge point w/ correct tool & not as these http://www.chinapartsdepot.com/shopp...exd.asp?id=771 clowns as possible

===
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 ...

Yeg.chrisc · 06-11-2020, 10:52 PM

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** · 06-12-2020, 08:40 AM

Quote:

Originally Posted by 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.

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:/...91965565636000

franque · 06-12-2020, 11:00 AM

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** · 06-12-2020, 11:05 AM

Quote:

Originally Posted by 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.

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

06-10-2020, 12:30 PM	#1
Yeg.chrisc Join Date: May 2020 Location: Calgary Posts: 16	Crf230f cylinder in an X31? 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.
	0

06-10-2020, 03:07 PM	#3
JerryHawk250 Moderator Join Date: Oct 2016 Location: Houma, La. Posts: 11,734	I recently installed the CRF230F Wiseco 11:1 piston on my X22R 250. It's a 65.5mm bore with 15mm pin. __________________ 2024 Linhai 300 ATV 4x4 2023 Lifan Lycan 250 Chopper 2023 Venom Evader 2022 Lifan KPX250 2020 Kawasaki Vulcan S (Sold) 2004 Honda ST 1300 2016 Black Hawk 250 (sold) Keihin PE30 carb,125 main,38 slow.Pod filter,ported & decked head 10:1 CR,Direct Ignition Coil,15/40Sprockets,NGK DPR8EIX-9,De-Cat,Dual Oil Cooler,Digital Cluster 2016 Cazador180 XL 2014 Coolster150 JerryHawk250.com My YouTube Channel
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06-10-2020, 03:19 PM	#4
JerryHawk250 Moderator Join Date: Oct 2016 Location: Houma, La. Posts: 11,734	The CRF230F Big Bore kits and cams will also work on these engines. https://www.ebay.com/itm/Athena-67mm...2228ab027919bc __________________ 2024 Linhai 300 ATV 4x4 2023 Lifan Lycan 250 Chopper 2023 Venom Evader 2022 Lifan KPX250 2020 Kawasaki Vulcan S (Sold) 2004 Honda ST 1300 2016 Black Hawk 250 (sold) Keihin PE30 carb,125 main,38 slow.Pod filter,ported & decked head 10:1 CR,Direct Ignition Coil,15/40Sprockets,NGK DPR8EIX-9,De-Cat,Dual Oil Cooler,Digital Cluster 2016 Cazador180 XL 2014 Coolster150 JerryHawk250.com My YouTube Channel
	0

06-11-2020, 10:24 PM	#11
humanbeing Join Date: Mar 2008 Posts: 2,436	From CRF230F shop manual: Measure at the gauge point w/ correct tool & not as these http://www.chinapartsdepot.com/shopp...exd.asp?id=771 clowns as possible === 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 ... __________________ Last edited by humanbeing; 06-11-2020 at 10:54 PM.
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06-10-2020, 02:50 PM	#2
franque Join Date: Nov 2017 Location: Marseille, France -> Conakry, Guinea Posts: 1,481	Yep, it should work. You'd be the first on here to do it though, so make sure that you document it!
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06-11-2020, 11:24 AM	#5
Yeg.chrisc Join Date: May 2020 Location: Calgary Posts: 16	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??
	0

06-11-2020, 01:47 PM	#7
Yeg.chrisc Join Date: May 2020 Location: Calgary Posts: 16	Mine is like 64.98mm.
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06-11-2020, 05:51 PM	#9
Yeg.chrisc Join Date: May 2020 Location: Calgary Posts: 16	Yea the cylinder is 65.5 top, bottom and middle.
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06-11-2020, 10:52 PM	#12
Yeg.chrisc Join Date: May 2020 Location: Calgary Posts: 16	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.
	0

06-12-2020, 11:00 AM	#14
franque Join Date: Nov 2017 Location: Marseille, France -> Conakry, Guinea Posts: 1,481	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.
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