Fungus
Part of things
Posts: 960
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Go straight to page 2 for the new plans and parts, all of this engine swap stuff isnt happening Ages ago I recall reading that a CB250rs single engine has the same mounting points as the small honda 4t's like the cg125 / cb125. I want to try something different, and install one of these in my 1978 CG125 k1. I can make some brackets if necassary, and also I will be strengthening the frame, as I am a pretty decent welder. I will also upgrade the wheels, brakes and suspension, probably to those from a larger honda bikes of the same time period because I want it to look pretty ''authentic'' aswell. So can anyone clarafy this and tell me whether this engine will fit with little work? Any other info about these engines would be great. Thanks
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Last Edit: Dec 1, 2010 21:25:41 GMT by Fungus
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Fungus
Part of things
Posts: 960
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Also, yes i am aware that i could just buy a 250, but I'm doing this to see what can be done to this bike, not just to have a 250 if you see where I'm coming from.
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93fxdl
Posted a lot
Enter your message here...
Posts: 2,000
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cant help directly but a popular conversion when those bikes were common was an xl/ft 500 engine into an rs 250 so if the 250 fits into the cg then there is a chance the 500 will ttfn glenn
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not a hope... I've owned both, there is a huge size difference between the 250RS and a CG125 engine I tried once to get an RS250 mill into an XL185s (same size as the CG/CB engine) and it didn't go in at all.
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To get a standard A40 this low, you'd have to dig a hole to put it in
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Fungus
Part of things
Posts: 960
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curse word. Any other engine ideas?
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Fungus
Part of things
Posts: 960
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This filter's pretty cool
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Fungus
Part of things
Posts: 960
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I was thinking about a cd/cb 175 engine, but theres really isnt that much of a size increase so i don't really know if its worth it
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Steve
Posted a lot
Making progress in small, easy to handle chunks of awesome
Posts: 2,028
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CG125 K1Steve
@sleeperviva
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Again tho, the 175 engine is still bigger in physical size so prob wont go into a standard 125 frame :-(
Steve
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will
Posted a lot
Posts: 4,023
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CG125 K1will
@familybanger
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cg's upjetted with a k+n style filter should see a decent power increase anyhow. Cut down the pipe megaphone style, stick a tooth or 2 on the back cog for some semi serious fun round town Mind you I'd not do anything to drastic with a 78 model. Good year to be born that was
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hmm, he's updated the page alot since i last looked, bit less on alternative superchargers now, just search "smog pump supercharger" and you'll get loads
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ye the 175s should fit in. i think they are just cd 125s just a wee bit bored. n i managed a cd 125 in mine just need to modify the bottom and top bracket a little bit and it slots in with a bit of push and shove and knuckle skin on the engine
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Mar 11, 2010 12:57:55 GMT
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I've stuck a CMX 250 engine in my CA 125 and when i did it i was told they engine is the same as the CB engine. All i had to do is use the engine top mount from the 250 as the other mounts all lined up. I went on britchopper.com and asked and they helped a lot.
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Mar 11, 2010 15:32:47 GMT
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a cmx250 is a twin, nothing to do with a cg125 or a cb250rs
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Mar 11, 2010 20:21:50 GMT
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^^ yup. CMX 250 is a development of the CM200/CB125T engine. Fits a CB125T or 125 rebel easy enough, but not the single cyl bikes i e CB100/CB125S/CG125/XL125/XL185 which are all roughly interchangeable. I say roughly, because there is always something to do (often the top mount..) and the wiring/genny type varies quite a bit. CB250RS is a big single, most closely related to the XL/XT250 range. Nothing else road bike fits them, and they don't fit anything else (unlike the 250N superdream.. all the mid twins (CB250C/CB250N/deluxe/CB400/450) are interchangable (and the CB350 almost fits)
As an aside, the old CB400/4 engine is a straight bolt into a CB250G5 because honda used the same frame. I'm aware that that is useless info unless you have a dead G5 and a 400/4 engine but it is true.
PS, I've had a *lot* of hondas, lol
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To get a standard A40 this low, you'd have to dig a hole to put it in
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Fungus
Part of things
Posts: 960
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Mar 23, 2010 18:48:02 GMT
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Thanks guys, that saved me alot of money (i thought it would fit, and waws planning on getting one! :L) So, i think ill stck to tuning the ol' 125. I'm currently makiing a new megaphone exhaust with some specs i found on a tuning site, so it should be nice and torquey What is a safe commpression ratio for the 125, and whats the best way to go about increasing it? Base gasket or head gasket? thanks
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Mar 23, 2010 19:44:47 GMT
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I had a cb125 to 11.5:1 by head skimming and piston choice (some are flat, some peaked) which went like hell but used to blow the centre out of spark plugs.
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To get a standard A40 this low, you'd have to dig a hole to put it in
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Fungus
Part of things
Posts: 960
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Mar 23, 2010 20:05:40 GMT
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Wow! that must have been a pain :L Did you have to use high octane fuel with 11.5:1?
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Mar 23, 2010 20:25:02 GMT
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avgas
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To get a standard A40 this low, you'd have to dig a hole to put it in
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Mar 23, 2010 20:56:53 GMT
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Last Edit: Mar 23, 2010 20:57:35 GMT by TerraRoot
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