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| CR125 crank and rod in MR175 engine https://vintagedirtbikeforums.alp-sys.com/viewtopic.php?f=21&t=911 |
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| Author: | mdlafferty [ Sun Feb 12, 2006 9:19 am ] |
| Post subject: | CR125 crank and rod in MR175 engine |
I plan to put a 76 MR175 engine in my 75 CR125. Will the 75 CR125 crankshaft fit into the 76 MR175 engine? I want to be able to bolt on the CR's ignition rotor so I can keep the CR's CDI ignition. The crank "wheels" ("cheeks") are a different shape. Maybe they need to have a different balance to match the greater weight of the MR175 piston so the engine doesn't vibrate. Has anyone done this? Advice appreciated, thanks. Mark |
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| Author: | Elsinorestuff [ Thu Feb 16, 2006 10:14 pm ] |
| Post subject: | |
The CR125 crank has different size rod bearings on both ends so it will not go in the MR175 motor. I think you can space the ignition on the MR175 crank so you can use the CR125 type ignition. I want to try the opposite mod by using two MR175 crank halfs with a 1981 CR125 rod kit which should mount to the MR175 crank without mods. Don't know how much vibration the MR175 crank will cause though. |
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| Author: | Thor [ Sat Feb 18, 2006 6:12 pm ] |
| Post subject: | |
Hi! I have done both mods, and it is not to complicated at all. The CR125 CDI ignition will work just fine on the MR175 crank, (stroke is the same as a 125) and will give you a little quicker throttle response. If you are going to put the MR175 carnk into a CR125 bottom end, you need to machine the cases ot accomodate the slightly larger crank weights. It is not to tough do this, it is only a millimeter or two. They all use the same main bearings, so no worries there. If want a real screamer with a bit more power, the MR175/CR125 transmission is a great setup. Good luck! |
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| Author: | mdlafferty [ Tue Mar 14, 2006 5:19 pm ] |
| Post subject: | |
Thanks. The CR125 rotor and stator bolted right on. Easy!! The CR125 ignition cover fit on too. |
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