Honda cr125 crank eater?

Branham96
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Branham96
Edited Date/Time 4/4/2013 8:32pm
I have a honda HPP valve style engine that has a recurring issue. The lower rod bearing has went out on me twice. Any ideas on what I'm doin wrong. I've had a couple of these engines and have never had this issue before. I had an 01 cr125 that I rode for 3 years on the same crank. Any help/advice is appreciated, thanks in advance!
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motosicko
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motosicko 4/3/2013 3:47pm
4/3/2013 3:47pm
Stop mixing sand in your pre-mix! Just kidding, kind of: Check your air boot for a good seal. Even the tiniest leak will suck sand & fine dirt in and mix with your fuel/oil pre-mix and end up in the bottom end. Check the whole route from the air filter to case for any air leaks that would lean out mixture.
xnationalwrench 4/3/2013 4:33pm
4/3/2013 4:33pm
When rebuilding the crankshaft are you lubing the big end bearing? If you replaced the crankshaft assembly is it orginal equipment or aftermarket? How are you breaking the engine in?
project racer 4/3/2013 5:16pm
4/3/2013 5:16pm
If you run it hard, maybe go to a richer oil mixture in the fuel. Bearings like oil.
Branham96
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Branham96 4/4/2013 2:31pm
4/4/2013 2:31pm
Thanks for the suggestions, I'm pulling the engine out tonight to rebuild for the 3rd time, I'm definetly getting better at it! I don't think I have any airleaks but will surely double check. The first time I rebuilt I used a wiseco bottom end kit, second time I used the hotrods kit. I heard the wisecos had some issues so the first crank I chalked it up to that being my issue. The only lube I used during assembly was some 2 stroke oil,maybe that wasn't enough? I've always ran my bikes 32:1 should I richen it
up? Thanks again!

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slipdog
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slipdog 4/4/2013 4:33pm
4/4/2013 4:33pm
Chinese cranks?
xnationalwrench 4/4/2013 5:23pm
4/4/2013 5:23pm Edited Date/Time 4/4/2013 5:26pm
Branham96 wrote:
Thanks for the suggestions, I'm pulling the engine out tonight to rebuild for the 3rd time, I'm definetly getting better at it! I don't think I...
Thanks for the suggestions, I'm pulling the engine out tonight to rebuild for the 3rd time, I'm definetly getting better at it! I don't think I have any airleaks but will surely double check. The first time I rebuilt I used a wiseco bottom end kit, second time I used the hotrods kit. I heard the wisecos had some issues so the first crank I chalked it up to that being my issue. The only lube I used during assembly was some 2 stroke oil,maybe that wasn't enough? I've always ran my bikes 32:1 should I richen it
up? Thanks again!
So you are installing a new crankshaft each time rather than a rod kit? What brand 2 stroke oil are you using? 32:1 is usually a good mixture. I make up the engine myself.mixture of 2 stroke oil with some anti seize when assembling How are you breaking the engine in? Is the big end bearing (needle bearing on the bottom of the rod) that is failing?
Branham96
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Branham96 4/4/2013 6:20pm
4/4/2013 6:20pm
I am going with an oem crank this time around and yes I have been installing whole cranks instead of a rod kit. I have never pressed out just the rod and am intimidated by it to be totally honest, do they need to be balanced after doing just the rod? Also yes it is the lower needle bearing that's been going out on me, that's what I find strange same thing and its always on the second ride after rebuild. I live on a dirt road so I just cruise my road to break it in. I run maxima castor 927 in it. I also changed my avatar to a pic of the bike so you can see what I'm working on. Thanks again!
xnationalwrench 4/4/2013 8:32pm
4/4/2013 8:32pm Edited Date/Time 4/4/2013 8:36pm
It sounds to me your pre-mix is ok at 32:1 You can buy a Rod kit for less than 50% of what a new crankshaft sells for, of course you would need to have a shop install the rod kit. Yes they use a truing stand when they rebuild the crankshaft Unless it was the rod not finished properly (at the big end bearing) it sounds lke you need to take it very easy on break-in. Make sure you use your 2 stroke pre-mix oil and lube all the bearing (top end bearing, big end bearing and even the main bearing the crankshaft rides on). You might foul a spark plug at first but it is better to be safe than sorry.

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