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Discussion Starter · #21 ·
I did not keep the engine revs under the recommended limit for the recommended time. I probably broke it in for 50-75miles it went with probably 300miles. But I did not have my oil cooler installed and no ARF read out And was hitting 9k-12k revs. Totally my own fault.
 

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Ime an engine break in should use most of its revs after the first 10 miles or so of varying the revs from low to high, after that just ride it hard through some hills to vary the load and rpms nicely... but yeah if you had no idea of the afrs, that was the culprit. I say ride it hard but 9-12k is really hard 馃槄馃槄 I went with a cheap narrowband afr that taps off of the stock narrowband for $22... just to verify what the ecu sees. Not as accurate as a wideband, but accurate enough to tell me too rich or lean. Is your case ok? Id say 12k rpm is what killed the piston. Dont set limiter above 10k, dont bang 10k all day, and your next bbk will last at least a few thousand 馃ぃ i also am under the impression that a big valve head is also a killer ... makes you want to rev too high haha.
 

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Discussion Starter · #23 ·
I agree, once rings set and are happy.. ride it! Yes I was hoping the finbro ECU would keep it happy enough. But it didn鈥檛.. at least through the paces I was putting it through. I was going to stay long at 143cc just a quick project to see what it was like at that size. And didn鈥檛 feel like splitting cases just yet to do crank. Throw the hot 125cc set up back on it to see if it would start and idle and it did, small knock still there. Just got home from work and getting some other projects out of the way before the engine comes apart.
And yes.. I do have big head on :)
Time to research next kit and additions.. ARacer makes the cart a little pricey. But think it will be worth it if I go bigger than 170cc
 

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I agree, once rings set and are happy.. ride it! Yes I was hoping the finbro ECU would keep it happy enough. But it didn鈥檛.. at least through the paces I was putting it through. I was going to stay long at 143cc just a quick project to see what it was like at that size. And didn鈥檛 feel like splitting cases just yet to do crank. Throw the hot 125cc set up back on it to see if it would start and idle and it did, small knock still there. Just got home from work and getting some other projects out of the way before the engine comes apart.
And yes.. I do have big head on :)
Time to research next kit and additions.. ARacer makes the cart a little pricey. But think it will be worth it if I go bigger than 170cc
I used a finbro ecu before my 186 kit, cheap afr told me it was way too lean for my 186.(hell, even for stock piston and a tb cam) the DHM reflash with the pcx150 injector is a damn hoot... Definitely worth not having to fuck with tuning. Ive tried all sorts of intakes/exhausts/cams and the reflash seems to be able to adjust to all of it no problem. Above 7-8k is where youll really need the fuel for that big valve head, haha. I did have to reflash after i ported my head, soon as i hit 7000 rpm my gauge would go from 12.5 afr to 21 LOL. I would buy an aracer but yeah i agree... costs more than the BBK ffs. DHM or CJR would be able to make a nice tune for the 170 that you wouldnt have to fuck with or worry about. Im running a stock crank, throttle up wheelies at 3-4k rpm should break my crank(i would think it would be more stressful than clutch up) but im convinced its rpm that kills them. My mpgs also went UP after the reflash 馃 good luck 馃
 

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Discussion Starter · #27 ·
Went well, removing engine was fine. Pretty straight forward. Tore it apart to try and see what happened鈥 couldn鈥檛 tell what went first the crank or the piston.. maybe both at same time. My guess is (stock) crank on this one. Ran it above 10k on stock block all the time.

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