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CG125 big bore 150cc kit

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  • CG125 big bore 150cc kit

    Has anyone tried to fit one of these kits to a ‘proper’ CG engine, not a Chinese copy? I have a 1991 Brazilian built and have come across a couple of eBay kits that claim to fit Honda engines. I know the pin is the right size at 15mm, but a bit concerned if the crankcase mouth will fit.

    Any my info would be great. The link to the kit is Honda CG125 OHV push rod type engine 150cc Big Bore Kit Straight Fit

  • #2
    I had a look at the kits and they did not include cylinder heads only barrels and pistons, dont you also need to upgrade carb and ports? It might be worth joining a couple of forums for specific questions re model, I'm a member of other forums. I like that your looking to do more than just change the styling of the bike.

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    • #3
      Thanks for the input, I was planning to change the change the jet in the carb for a bigger one, but may look at a bigger carb. I’m going to polish the exhaust ports on the head while it’s off. May just take the plunge and hope it all fits, if it means I can get to 70mph I’d be happy although I may need to put my feet down to stop

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      • #4
        If the Thai/Chinese CG150 had the same carbs as the CG125 you might not need bigger carbs you need a chinese CG friend.

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        • #5
          The head on the CG has basically the same inlet and exhaust tract as the XR200 so I would advice against doing anything major to them. If you must, then only match up the joint between the inlet manifold and the head, smooth out the area where the valve seats fit in the head and smooth the surface of the exhaust tract. Do not make either tract bigger, you may gain a tiny little bit of top end but the torque and mid range power will fall flat on it's face.

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          • #6
            So assuming the kit fits I may get away with a light polish and a bigger main jet to hopefully balance out the 25cc, k&n and exhaust. I still don’t know if it will fit but the seller assured me it will. We’ll see

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            • #7
              I presume the kit will be a Chinese or similar affair, there is nothing much wrong with them apart from you can't treat them like genuine Japanese stuff. If you run them in properly like things used to be done and take a bit more care with them they are ok. The jetting should be the same as a 125 with a K+N and pipe and will depend more on the quality of the filter and pipe.
              Polishing and porting ? As I said, I wouldn't really bother. I raced a 125 (not over bored ) and got it up to 16 bhp on the dyno when stock gave 10 out of a good engine. I, got it up to 14 bhp with a cam, pipe, carb and good ignition, tidying up around the valve seats helped a little after that but a full port job lost mid range for a tiny increase at the top end.
              Put it together properly, get the jetting, valve timing/tappet gap, ignition timing etc spot on and enjoy the extra mid range umph.
              Basically, get the power out of it that the designer put in on the drawing board before you go looking for more.

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              • #8
                There's a CG200 engine for sale on ebay ://www.ebay.co.uk/itm/Viertakt-Motor-CG200-Jaguar-200-Shineray-164FML-Chinamotor-Motorrad-200ccm-Honda/253391654614?hash=item3aff51ced6:g:iQsAAOSw-xVaLTIg

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                • #9
                  Kit is on order so will update once it arrives, I’ll put some pics up when I get it.

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                  • #10
                    Been a while, but after an engine strip I can confirm the kit does fit, the crankcase opening was 1mm too small. Not worth the engineering to get it to fit so back to the drawing board

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                    • #11
                      I have fitted 3 150cc big bore kits to 1980’s CG125’s (one was actually a CG110 and did require the crankcase mouth opening up, did it with a dremel). This kit will fit a CG125 without machining the crankcase for sure as the liner has been skimmed so it will fit in the crankcase opening. The big bore kit makes a big difference to performance. Definitely recommend.
                      Cheap motorcycle cylinder kit, Buy Quality cylinder kit directly from China motorcycle cylinder Suppliers: ZJ125 CG125 Upgrade Modified To ZJ150 CG150 62MM Motorcycle Cylinder Kits With Piston And 15MM Pin

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                      • #12
                        Hey there, i actually need some similar help. I have a CG150 and was looking forward to upgrade it to 200 or better. Anyone can help me on this?
                        thanks

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                        • #13
                          Originally posted by andrewww View Post
                          I have fitted 3 150cc big bore kits to 1980’s CG125’s (one was actually a CG110 and did require the crankcase mouth opening up, did it with a dremel). This kit will fit a CG125 without machining the crankcase for sure as the liner has been skimmed so it will fit in the crankcase opening. The big bore kit makes a big difference to performance. Definitely recommend.
                          Interesting. Any write up or pics of the process?

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                          • #14
                            What sort of performance gain are we talking?

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