CBR 125 engine upgrade?

w0SS

w0SS

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I'm looking to upgrade my 125 with the Athena Big Bore kit + Power Commander

Does anyone know of a mechanic who has experience doing this? Or could recommend one who would be willing & reliable? I'm in the east end of Toronto

thanks!
 
Be very careful here. It is very likely that insurance is not available for the bike you are looking at building. If you don't bother telling the insurance company and are in a crash bad enough for them to bother investigating, they may not pay. IMHO you are way further ahead to move to a 250, you will get a big (relatively) power bump and valid insurance.

If you are not using this on the road, ignore my previous comments and good luck on building your bike.

As far as affordable labour, in no particular order, Rosey Toes (Ted), frekeyguy, kneedragger88, and stunters inc (johnnyp636) come up often.
 
I've been in those engines a few times; it's a simple job to do the top end on those. BUT ... The one Athena kit that I know of, which was installed a couple years ago (not by me), eventually blew up catastrophically after about 7000 km. The piston broke around the base of the oil control ring groove, which led to the con-rod punching through the cases and turning the whole engine into shrapnel - it "done blowed up real good". Heard of head gasket leakage issues, too. I know how to do it ... easy job ... but NO WARRANTY. I'm not even sure I want to have anything to do with it.

If you can source a complete CBR150-EFI engine from Thailand, including the ECU, it'll go right in, and then you are dealing with Honda OEM reliability - and the bottom end of that engine is properly matched to the top end, i.e. indestructible. Notably, the CBR150 engine has a 1mm larger diameter wrist pin - which is why you need the complete engine, not just the top end. I know someone who has done a CBR150 retrofit, too. The CBR150 engine is not only bigger displacement but also DOHC, 4 valves per cylinder, central spark plug, etc.

There is much more discussion on these matters on the CBR125 forums.
 
GreyGhost, thanks for the list of mechanics!

Brian, hmm sounds like the 150 engine is the way to go. I've heard others warn of potential danger of installing the non OEM Athena kit and your example of one blowing up makes me think it's not worth it.

Do you know where I'd get a 150 honda engine from though? I'll try searching the 125 forums as well for more info
 
w0SS said:
GreyGhost, thanks for the list of mechanics!

Brian, hmm sounds like the 150 engine is the way to go. I've heard others warn of potential danger of installing the non OEM Athena kit and your example of one blowing up makes me think it's not worth it.

Do you know where I'd get a 150 honda engine from though? I'll try searching the 125 forums as well for more info
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PM CBR250 on that forum, he did the 150cc install on his old 125.
 
GreyGhost said:
It is very likely that insurance is not available for the bike you are looking at building. If you don't bother telling the insurance company and are in a crash bad enough for them to bother investigating, they may not pay.
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Unless you're installing a turbocharger on your bike, insurance companies aren't going to bother looking for engine mods. Many owners install 1200cc cylinder kits in their Harley 883s and I've never heard anyone get nailed by insurance for it.
 
jonpurdy said:
Serious question. Why not buy a 250?
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I borrowed a friends Ninja 250 for my M2 exit course and test at Humber. Other than it being carburated, I enjoyed riding it a lot and knowing what I do now, probably should have bought that as my first bike.


The 125 is still a fun commuter bike though. I've also put in a bit of effort customizing it, so I guess i'm a bit attached and don't want to let it go just yet :p


I figure my best option is to see if I can get a bit more power to hold me off for a year or two until I eventually upgrade to something 600cc+.


I've been looking at the CBR F4's but I can't afford the $3500-4500 cost of a used one as well as the insurance increase at the moment...currently paying $30 a month. I got a quote for a 600fi and it was about $80 a month
 
w0SS said:
I've been looking at the CBR F4's but I can't afford the $3500-4500 cost of a used one as well as the insurance increase at the moment...currently paying $30 a month. I got a quote for a 600fi and it was about $80 a month
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$80 a month you call it expensive for a 600? omfg! which insurance company SF? with or without car? your age? please PM me I need yours!!
 
Read about the camshaft mod on the 125 forum, for around the same cost (with new efi unit) of the Athena kit you get a reliable upgrade which gives you a little more power without sacrificing reliability. I'm one of the riders with that mod and have over 25k km on it with no issues. Brian is another rider with similar distance on it.
 
elton_t said:
$80 a month you call it expensive for a 600? omfg! which insurance company SF? with or without car? your age? please PM me I need yours!!
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I never said it was expensive, I just said I couldn't afford it ;p

I have car, renters and motorcycle insurance with SF. I'm 27
 
derailleur said:
Read about the camshaft mod on the 125 forum, for around the same cost (with new efi unit) of the Athena kit you get a reliable upgrade which gives you a little more power without sacrificing reliability. I'm one of the riders with that mod and have over 25k km on it with no issues. Brian is another rider with similar distance on it.
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I haven't been on the 125 forum for a while, but I do remember a thread about the camshaft mod. I think a lot of people were complaining about it...build quality or installation troubles? From aseanmoto right?
 
As long as you understand that YOU are the final QC inspector for that camshaft, and take care of any and all issues that may be found, it's fine. I put 27,000 km on that camshaft before recently selling the bike ... now Wheelieboy will carry onwards with it - and I just put another one of those camshafts in the 2011 cbr125 that I bought recently. Installing that camshaft takes an hour or two (more on 2011 ... bodywork is a much bigger PITA on that bike) and the engine doesn't even have to come out of the bike. Aseanmoto is where those camshafts are coming from.

Recommended fuel injection controller www.electronicjetkit.com - I have this in mine - now that we are FINALLY able to get adjustable fuel injection on these bikes, no more resistor mod, and they run much better through the whole rev range. PowerCommander will work also, it just costs more. I don't have a map for a PowerCommander but could take a fair crack at it based on how I have the EJK controller set up.

Stock exhaust recommended. Everything aftermarket that I've seen for these bikes, has a header pipe far too large in diameter for the engine. Aftermarket exhaust plus that camshaft will kill your midrange.
 
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I spoke to CBR250r on the 125 forum (he did the 150cc engine swap) and it looks like the cost of doing that is way too high for me.

Brian, where are you located? Would you be willing to install the camshaft?
 
If your mindset is that you wanna upgrade this bike to keep it exciting for another year or two, you're not gonna get the desired result out of it... in my opinion.

You know you're gonna upgrade to a 600, and nothing you do to that 125 will bridge the gap. Ride it until you can afford a 600... which will come sooner if you spend less money modding your WEE-BR.
 
mmmnaked said:
If your mindset is that you wanna upgrade this bike to keep it exciting for another year or two, you're not gonna get the desired result out of it... in my opinion.

You know you're gonna upgrade to a 600, and nothing you do to that 125 will bridge the gap. Ride it until you can afford a 600... which will come sooner if you spend less money modding your WEE-BR.
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+10

This was my thinking exactly (except the "WEE-BR" comment - c'mon - don't make fun of the guy's bike! :rolleyes:)

Sounds like you're enjoying a good ride. Get tons of miles and experience under your belt, and then buy what you really want.

I'm going to sound like a dad right now, but: if you tuck away the money you would have spent on your upgrade now, then you'll have that plus interest when you buy your 600+, and then you'll REALLY appreciate the difference.
 
w0SS said:
The 125 is still a fun commuter bike though. I've also put in a bit of effort customizing it, so I guess i'm a bit attached and don't want to let it go just yet :p
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i agree, u will kinda miss it.......but once u feel the power of another bike, u will let go.

i had cbr125 before....up for sale recently, hehe...
 
FYI, a cbr125 with a few carefully chosen things done to it is a silly fun bike, and the parts we are talking about here are very cheap. Total cost of the upgrade being discussed, parts and labour all in, should be around $500. If that's what the OP wants to do, so be it.

The argument "just buy a bigger bike" can be used to argue against modifications to ANY bike. Don't bother putting an exhaust on your 600, just buy a 1000. It is the exact same situation. If what you want is a 600 with an exhaust, then get a 600 and put an exhaust on it. If what you want is a 125 with a wee bit more poke than standard, then do that. Only the OP can make that call. Let him make it.
 
chin.r said:
i agree, u will kinda miss it.......but once u feel the power of another bike, u will let go.
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Then you might even go back when you realize how much fun the 125 is ;)
 
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