150cc big bore kit for CG125 on eBay

[davidzweig]

I'm planning to travel the back-roads of Eastern Europe in the summer on my '94 CG125. My girlfriend wants to come, so a little extra power wouldn't hurt for going up hills. Size wise the bike is alright for the two of us, we weigh about 135kg together, and would pack light. If we could hold a comfortable 50mph, that would be alright. The bike has a front disc brake.

I have a full license and my last bike was an XT600, so not riding a CG because I'm on L plates or something.

I found this on eBay:

https://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=151039342017&ssPageName=ADME:X:RTQ:GB:1123

Title reads 'Motorcycle Big Bore Barrel & Piston Kit For Honda CG125 1978-2008 NOT ES Models'

From reading online, I thought the maximum capacity possible on the CG125 without machining the crankcase is 140cc ish? Seller confirms it's for a CG125, not a Chinese copy. Could it be?

150cc is a 20% boost in cc's, so I guess that would mean an almost 20% extra torque, given that some volumetric efficiency would be lost. Would the bottom end cope alright, or would it significantly shorten the life of the bearings etc.? I guess the bottom end is mostly shared with other engines, some of which produce a bit more torque..

[Copycat73]

2 up on a bored-out 125 around Europe... good luck wit that one..
getting break down cover will be an interesting challenge aswell.
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[clancy]

As above really, probably not the best idea and probably won't get as good gains as youd expect. It will possibly just become less reliable as apposed to large enough gains to make it worth while, especially with massive distances

If your not restricted to what you drive howcome you don't take a more capable bike ? Esspecialy if your going two up
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[moonzoomer]

The CG comes standard @150cc in some countries in the world due to the low octane fuel they use usually called a "Titan", a friend runs a 150cc conversion with no problems though the head is not a perfect match due to the increase in the bore.
https://www.novidadediaria.com.br/wp-content/gallery/cg-150-sport-2012/cg-150-sport-2012-10.jpg

[davidzweig]

Thought people would wonder why this bike..

Pluses:
-I rebuilt it from the frame up and know every screw and wire on it.
-Easy and cheap to find/scavenge parts pretty much anywhere if needed
-Light, decent clearance, robust: can handle bad roads
-Very good on fuel
-Big enough for the two of us
-Already has a luggage rack and a pair of well-fitting panniers.
-Has upgraded suspension, brakes, 12V socket and an HID headlight.

Minuses
-Oil changes are quite frequent.
-Unsuitable for motorways.. well, maybe can just keep up with the trucks, in which case alright.
-Not a lot of torque, have to use the gearbox to maintain speed.
-Worried about keeping up with traffic on inclines.
-Seems a bit vibey, got a new pair of compound grips and some bar-ends, will see if that helps..

The big bore kit would help quite a bit. Can anyone say if it is likely to fit?

[Rogerborg]

Hmm. Well, they're very specific about what it does and doesn't fit, which is reassuring.

I can recall a couple of folk who have fitted 150cc kits to their Chinese copyengines, and IIRC their opinion was that it helped a little bit on inclines but didn't give significantly more speed. I don't know anyone who's run one for an extended period of time, but I can't see any problems with it as that engine is run as a 150 in half the world anyway.
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[Clutchy]

I honestly don't think it will make much noticeable difference at all...

Other than possible mechanical issues?



But then again I've never understood why anyone would want to such a long trip on a tiny bike which is so slow


Each to their own, I wish you good luck
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[hmmmnz]

they run the 150s in thailand and india, most of asia, i can say for a fact that they do have a bit more balls than the 125, atleast over there they do, the asians never seem to have a problem with the 150 motors and carry stupid loads on them,
go for it i say, make sure you rejet to suit though
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[cb1rocket]

As one poster said, you need a matching head to suit the bigger barrel. So get the head and barrel together
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[dangerousdave]

[Alpha-9]

100cc makes about 10bhp
150cc will make about 15bhp

right?
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[dangerousdave]

[davidzweig]

The bike is not ideal.. something with 20-40 Hp would be better, whilst still being a simple bike. But I'm not sure I'll have money to buy a solid one for the summer.

Any idea where to get a jet for the carb? It's the accelerator-pump type one. Maybe a Honda part for high-altitude? Thanks for the help..

[bladerunner]

Most bike shops will have jets in stock or try Allens carbs online...or eBay! It's deffo a tiring bike to ride with vibes and high revs not to mention the dreaded head wind dropping your speed to 40 mph if gusty but it should be possible if a bit crazy! I'd be tempted to fit an led rear light as you'll be poping a few of them with that distance and maybe try a tooth bigger front sprocket to make use of the extra torque. I would deffo be buying a heavy duty o ring chain and sprocket kit with a spare split link given the weight and distance your planning on doing and tools for road side repairs and servicing/ tire repair which for a cg won't need much! Don't forget to keep us posted with your progress if you do do it!
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[Tench]

Whether it will fit or not depends on your engine, the original japaneese manufactured engines did not have a large enough crankcase mouth the accept the skirt of the 150cc barrel, if it is a Brazilian one it should fit.

[davidzweig]

The engine has 20,000 miles, runs very well, doesn't smoke, but I don't know the history. Would it likely worth changing the valve seals and grinding the valves into the seats, whilst the head is off? Can it be done without a valve clamp tool?

For the jets I suppose I will wait until the new piston/barrel is on. From reading online I might have to go down one size on the main jet.

Bike already has a 15T front sprocket, instead of the regular 14T.

[stevo as b4]

I'd have possibly gone for a simple but more than useable 500 twin like the air cooled Suzuki GS500E. Maybe it wouldn't be as cool or as much of an adventure as flogging the CG there and back though?

probably not practical, but if you both had a CG125 each for the trip, then you would be making about 1000times more sense for a good choice of simple rugged bike x2, so that you can share/swap parts and need the same tyres, tubes, and tools etc.

[Irn-Bru]

Personally I would want my other half to be safe, don't know why you'd want to risk her life 2 up on a commuter 125.
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[i2ico]

Go without the bore up kit!

CG is a a CG, great little bike, reliable, good MPG.

Itll make for a fun experience.
Good luck and hava a safe journey

CG for life
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