Instructables

Honda rebel 125 upgrads honda cb125tdc engine rebuild with some mods

Picture of honda rebel 125 upgrads honda cb125tdc engine rebuild with some mods
with this step by step im going to tell you how to upgrade the rebel engine from its standard 11 hp to about 19 to 25 hp 

this is not as simple as putting a big bore kit on it 

i will tell you what you need and what thing to upgrade on the engine 

this will go into depth how the engine works 

i only know what i know by hours of research on this engine and wondering why there is no performance parts available for it

please note the there isnt a 180 crank that will fit the cmx250 as the 250 has a 53mm stroke and the cb crank im using only has a 41mm stroke however saying that this is one way you can make a crank that will work but it will be impossible to get the crank aligned properly without specialist equipment 

if you have any questions on doing this project im always hear to help 
 
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Step 1: Why i desided to upgrade my rebel

i went to a bike meet and got talking to a couple that knew these engine and they told me that i could get twice the power out of my bike by changing a few thing so then when i got home i had a look on ebay for different bikes that had the same engine and i found that the rebel had the same crank casing as the cm125 cb125 cd185 cmx250 cd200 and a few more so then i looked up the stats for each engine and notice that out of them all the cb125 t engine had the most power to cc 
so i had a look at different engine components and noticed the internals for the cb125 engine where a bit different in there layout 

the cb125 engine had the so called 180 deg crank
where as the rebel engine had the 360 deg crank


hobbit5901 year ago
Great idea on the cam bearings, but where did you source them?
I've an old CB125TDC thats needing a top end rebuild and these should be a bit more reliable than the originals
rebel diy (author)  hobbit5901 year ago
hi there you can get them online from
http://simplybearings.co.uk/shop/advanced_search_result.php?sort=2a&search_in_description=0&keywords=RNA4902&x=-282&y=-239

but i got mine from a local bearing shop there a bit pricey but my engine runs allot smother
rebel diy (author)  rebel diy1 year ago
the bearing size is
id 20 mm
od 28mm
width 13mm

rebel diy (author) 1 year ago
i probably wont be able to get all part numbers but i can put the parts that i got off ebay item numbers
and i can convert the price to usd no problem
DIMyself751 year ago
Will you please update with all part numbers, I have a Rebel that needs the motor rebuilt anyway so this looks like a great time to do this. Also if you have prices in US dollars that would be helpful, Thanks