Project bike: 1986 Honda CR125R

Jmmx
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Jmmx 4/26/2017 3:15pm
4/26/2017 3:15pm
Hi, what does it go like? I sold you that Hrc cylinder

John.
JMX82
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JMX82 4/26/2017 11:24pm
4/26/2017 11:24pm
I haven't had much time to work on the bike lately. I tried to start it after motorcycle exhibition but carb was flooding and I haven't had time to look in to that. I also have to get rear shock rebuilt, replace linkage bearings, replace rear sprocket and get leaking radiator fixed before it's ready to be ridden.
atsz350
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atsz350 6/28/2017 3:01am
6/28/2017 3:01am
JMX82 wrote:
She is a roller now :) [img]https://p.vitalmx.com/photos/forums/2017/03/05/179814/s1200_DSC_0597.jpg[/img] Nice new Pirelli rear tire [img]https://p.vitalmx.com/photos/forums/2017/03/05/179815/s1200_DSC_0598.jpg[/img] New shock mudguard [img]https://p.vitalmx.com/photos/forums/2017/03/05/179821/s1200_DSC_0592.jpg[/img] Shock reservoir mounted proberly [img]https://p.vitalmx.com/photos/forums/2017/03/05/179827/s1200_DSC_0599.jpg[/img]
She is a roller now Smile


Nice new Pirelli rear tire



New shock mudguard



Shock reservoir mounted proberly



Hello,
Could you tell me where did you buy that splash guard please?
Thanks, Attila
JMX82
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JMX82 6/28/2017 4:46am
6/28/2017 4:46am
Shock mud guard is brand new part for 1990 CR125. They are still pretty easy to find. I bought it from local Honda dealer and it is perfect fit for -86 model

The Shop

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atsz350
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atsz350 6/28/2017 5:10am
6/28/2017 5:10am
Thank you!
Congrats for your restore and build!
Any news since then?
JMX82
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JMX82 6/28/2017 6:31am
6/28/2017 6:31am
Project is still on hold at the moment. I haven't had time to work on the bike lately. I hope I can get some work done on my summer vacation
JMX82
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JMX82 8/14/2017 10:59pm
8/14/2017 10:59pm
Finally I have made some progress with the bike. I got another shock from Ebay and got my rear shock rebuilt using best parts from both shocks



I also changed linkage bearings







JMX82
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JMX82 8/15/2017 3:29am
8/15/2017 3:29am
I was also able to score slightly used HRC piston for the bike from Japan







1
Badman250f 9/1/2017 2:09pm
9/1/2017 2:09pm
is a 1986 cr125 right hand crank case the same as a 1986
Badman250f 9/1/2017 2:10pm
9/1/2017 2:10pm
sorry is a 1986 cr125 right hand crank case the same as a 1985
JMX82
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JMX82 9/2/2017 2:31am
9/2/2017 2:31am
Badman250f wrote:
sorry is a 1986 cr125 right hand crank case the same as a 1985
I think there are differences because they have different part numbers. -85 part number is 11100-KA3-760 and -86 part number is 11340-KS6-000. They might still be interchangeable but i'm not sure about that. I think water pump is bit different in -85 and -86.

Badman250f 9/2/2017 6:16am
9/2/2017 6:16am
so a 1985 cr125 right hand crankcase will marry up perfect and work with my 1986 left case
Smed
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Smed 9/3/2017 12:57am
9/3/2017 12:57am
This is a top build, well done, I like the way you refurbished some parts instead of just putting on new bits, Any updates on how it runs?, I am interested in the top end, I think it may be an RS125 road race top end going on the coolant outlets on the head, 84-85 RS125 used basically the same motor.
Smed
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Smed 9/3/2017 1:06am
9/3/2017 1:06am
I would have thought the Omara bike has a HRC top end, this looks more like production where the coolant outlets are


l
NorCal 50+
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NorCal 50+ 9/3/2017 11:47am
9/3/2017 11:47am
I am thinking of finding one of these. I had it new in '86- one of the best bikes I ever owned- a "magic bike" as far as handling, unless my memory has just gotten rosier over the years.
JMX82
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JMX82 9/3/2017 11:32pm
9/3/2017 11:32pm Edited Date/Time 9/3/2017 11:33pm
Smed wrote:
This is a top build, well done, I like the way you refurbished some parts instead of just putting on new bits, Any updates on how...
This is a top build, well done, I like the way you refurbished some parts instead of just putting on new bits, Any updates on how it runs?, I am interested in the top end, I think it may be an RS125 road race top end going on the coolant outlets on the head, 84-85 RS125 used basically the same motor.
I think you are right about RS125 cylinder. My cylinder looks quite similar than the 1986 RS125 cylinder.





I got the bike running for a while but after some test rides around the yard it suddenly lost spark. I tried with different spark plug and ignition coil with no luck. I think problem might be faulty stator coil.

At least the bike looks pretty...





1
Smed
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Smed 9/4/2017 12:33am
9/4/2017 12:33am
Yes the bike looks great, I am very interested in how it runs, If it is an RS cylinder you would think it would be ported for top end & very hard to keep on the power, Of course the pipe also contributes to power delivery, Please keep us informed
JMX82
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JMX82 11/12/2017 10:00am
11/12/2017 10:00am Edited Date/Time 11/12/2017 10:02am
Finally I got electrical gremlins sorted out and the bike is running great. I had to replace both stator coils,CDI unit and sort out the wiring before it started to work properly.

I did some heat cycles for the engine and added hour meter to the bike today. The jetting need some fine tuning but other than that bike works great.






https://youtu.be/kD-FThIl_ts?ecver=2" width="640" height="360


Pit Row

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JMX82
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JMX82 3/7/2018 7:14am
3/7/2018 7:14am Edited Date/Time 3/7/2018 7:40am
It has been a while for my last update but finally I managed to get proper exhaust brackets CNC machined from aluminum. I made 3D models myself and my friend at Botnia CNC did all the machining work. New brackets where perfect fit for my exhaust pipe and much better looking than the previous ones that I had made by hand.


Front bracket 3D model


Rear bracket 3D model


Finished parts


I also found right size silicon hose from Ebay to seal the exhaust joint properly



Here are the new parts mounted to my bike










I still haven't been able sort out why the engine is running rough on full throttle. I don't if it is caused by jetting ATAC valve or something else. It's still winter here in Finland so I just have to wait for all the snow to melt before I can do more testing to sort out the problem
JMX82
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JMX82 4/19/2018 9:18am
4/19/2018 9:18am
Finally I bit the bullet and got new number plates for the from www.jkracinguk.com





The spring has finally arrived here in Finland so I took the bike out for quick photoshoot

















I have now tried various jets and needles and the bike is still cutting in full throttle. That had led me to suspect that running problems are caused by ATAC valve not closing or ignition coil. Ignition coil is only ignition part that I haven't replaced in the electrical system
3
RABnasty
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RABnasty 4/19/2018 11:51am
4/19/2018 11:51am
Awesome build man thank you for sharing!
FiZ
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FiZ 4/22/2018 11:18am
4/22/2018 11:18am
nice build!
Mixon848
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Mixon848 6/23/2019 12:34am
6/23/2019 12:34am
Update?
JMX82
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JMX82 6/23/2019 11:19am
6/23/2019 11:19am Edited Date/Time 6/23/2019 11:25am
It has been really slow progress with the bike due to limited time I have had working on the bike but I got it running fairly well now. I found that what was causing engine running badly was a worn out crankshaft bushing which leaked transmission oil to motor and made finding good jetting impossible. Luckily I found good used bushing from France trough eBay and after I replaced that bike started running better.

I also got new ignition cover and missing chain adjust retainer trough eBay for the bike.







This is how she is looking today



I took her for a little test ride one week ago. I still have to work to do with jetting and squish clearance is way too big now so I need to set that right.








Mixon848
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Mixon848 6/23/2019 1:35pm
6/23/2019 1:35pm
Thank you for the update. I had been wondering how it all came along. I am glad that you got the issue of how it was running sorted out. I really enjoyed this build and was sending positive vibes and positive energy throughout. Bike sounds good in that video.

Once again thank you for the update. And you should be very proud of your build. Positive energy from Northern California.
1
JMX82
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JMX82 7/2/2019 11:41am
7/2/2019 11:41am
Did some jetting changes yesterday and some test rides on the road. I also measured squish clearance and it's 1.1 mm which is spot so no need to change that like I initially tough.

https://youtu.be/K3Vymrm-Dl4
Karpuha174 9/17/2019 8:56am
9/17/2019 8:56am Edited Date/Time 9/18/2019 11:54am
Hi everyone) I'm new here) I was lucky to find 125 1986 in relatively good condition the original) Partially restored, but I want a fully working motorcycle)
https://www.instagram.com/p/B2e0xyUipNE/
A thousand questions)))
  what to do with open metal parts? (plating zinc, plating chrome, knitting needles, star, bolts) to avoid further corrosion ...
  Aluminum Coating?
In general, a lot of questions, few answers)
There is not much experience))) But there is a great desire ....
Guys, share the links, who bought what for the bike) I will be very grateful)))
And yes, the bike is disassembled, I can take measurements, if someone helps, I will be glad)))
JMX82
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JMX82 9/20/2019 11:06am
9/20/2019 11:06am
I have made quite progress how the bike lately. I turns out that the ignition had too much advance that it wouldn't allow it rev till the end. Once I got that figured out and retarded the ignition the bike is complete different beast now. I also replaced stock silencer with brand new one from DEP and replaced stock 34mm carb with a 36mm version.







I also took the bike with me to Classic scramble event in Old Erkylä GP track at Hyvinkää. The event was super fun although at that point the bike wasn't running as goods as it's running now. The suspension is still too soft so I have to do something about that.








3
JMX82
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JMX82 11/12/2020 3:30am
11/12/2020 3:30am
Made some updates for the bike

Piston was replaced with brand new VHM RS125 piston:



Stock reed petals where replaced with Boyesen ones:



Overly soft stock suspension was replaced with fully rebuilt Showa front forks from -88 CR250 and WP rear shock from -86 CR250:



Chance1216
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Chance1216 11/12/2020 7:01am
11/12/2020 7:01am
JMX82 wrote:
Made some updates for the bike Piston was replaced with brand new VHM RS125 piston: [img]https://p.vitalmx.com/photos/forums/2020/11/12/458766/s1200_IMG_20200930_202620.jpg[/img] [img]https://p.vitalmx.com/photos/forums/2020/11/12/458767/s1200_IMG_20200930_203804.jpg[/img] Stock reed petals where replaced with Boyesen ones: [img]https://p.vitalmx.com/photos/forums/2020/11/12/458768/s1200_IMG_20200930_200317.jpg[/img]...
Made some updates for the bike

Piston was replaced with brand new VHM RS125 piston:



Stock reed petals where replaced with Boyesen ones:



Overly soft stock suspension was replaced with fully rebuilt Showa front forks from -88 CR250 and WP rear shock from -86 CR250:



Red Hondas with blue seats. One of the cleanest looking bikes to this day. Your bike looks great man.
3

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