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Hey! My name is Kyler. So recently my bike overheated like 3 times, then finally one day it quit on me. After draining the oil, it turns out there's shredded metal everywhere. So I tore it all down. Now I'm not sure whats the problem. So far all that I found is the little rectangular reed valve was missing 1 out of 2 screws, and around that area down there is where I found the most of the shredded metal. also, I'm not sure if its a problem but the actual shaft on the crank has the slightest bit of play. Mainly I just don't know what to replace so please help! I don't want to put it all back together and not replace the main prob. Thanks in advance!

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Also, I was thinking it was the crank bearing. But after checking them, I'm not sure that's the case. The special roller bearing, (When viewing from the back of motor, left side.) feels ok, but I'm not sure how smooth it should be.

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Shredded metal in any significant amount is no good.  You didn't say how large the shavings were or how much, or which oil reservoir had shavings but I'm assuming there's a decent Amount in the engine oil.  IMO, anything more than the equivalent of a pinch or two of small powder-like shavings would alarm me. Bad crank bearing usually shows copper shavings in oil filter but not always. In any case, check cylinder condition, and if it's OK, clean the hell out of everything and replace what you can afford to since its already torn down. I'm anal, but I'd be replacing crank bearings and seals, crank, piston and connecting rod bearings and anything else those shavings got to. I'd be doing a complete rebuild.

There should be 0 up and down play on connecting rod parts. Side to side, a little is fine. When shredded metal makes its way around at 8000+rpm it can do a lot of damage quickly. Even if things seem ok, there's no telling how much excessive wear those shavings caused. And you'll never get them all out of any existing bearings. Separate oil reservoirs on crf models so clutch contamination of engine oil is unlikely, but that crank seal may be bad now. May have sucked in that missing screw and shredded it, but that point is moot. Shredded metal causes more shredded metal causes more, and so on.  Time for a rebuild.  My two cents for what it's worth. 

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Yeah, I'm thinking I'll do what you said and just clean it all down and replace whatever looks like it needs replacing. And thanks! Appreciate any help I get. Truly I believe it would be a good idea to get a rebuild kit but I also don't think I could afford to be spending that much on my bike.

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if the piston and cylinder aren't scored you can probably reuse them, that would leave you needing a crank and lower end bearings, and gasket set.  selling for <500 USD on denniskirk.  I wouldn't be putting any of the lower end parts back in, its just going to cause more problems down the road.  Save for a while if you have to, and do it right, or it will cost you more in the long run.  Easier said than done, I know, but that lower end connecting rod bearing, and your crank/countershaft bearings absolutely need replaced, without compromise IMO.  Much cheaper than a full blown rebuild, but only you can see the damage and make that judgement call.   FWIW, all those bearings should turn freely and not bind AT ALL.  if they resist at all, get them outta there.

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You mention a "reed valve" but your board name is CRF450R.  4-strokes don't have reed valves but 2-strokes don't have engine oil.  So may the teeniest little bit of detail as to what your bike is would be useful?

IF this is a 2-stroke then the oil only lubricates the transmission and clutch and thus any metal shavings in the oil can only come from the transmission or clutch.  However a missing reed valve screw isn't exactly good as it can only get into the crank case and bounce around in there.

IF this is a 4-stroke then I don't understand the comment about a missing screw from the reed valve.

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The crf450r does have a reed valve although it's completely different than a 2 stroke, it's there as a one way valve for oil and pressure in the crankcase.  Take pictures of the metal and cut the filter open.  Is the metal magnetic?  All bearings should turn smooth as silk.  Like others have said we need pictures.  Also how did you come to the conclusion that the bike overheated, was it leaking coolant, low on power, seize or just feel hot?  Does the connecting rod have play?

Edited by 96motorhead

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When you say 'it quit on me' I am assuming you mean it locked up on you.  If it rattled and then locked up, then it must be rebuilt.  If it simply stalled and wont start, then that's a different issue entirely.  If you post pictures of your oil filter, and the metal shavings with something for size reference (penny, fingertip, etc), and answer some of the questions others have asked, we can paint a pretty accurate picture of what youre dealing with, then we can help you decide which direction to head. 

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The debris can collect on the crank trigger pick up soldier points and ground to the flywheel killing the ignition. You need to find that second screw, or find the pieces of it. With that much crap in the oil, I'd pay very close attention to the oil pressure by pass and the oil passages in the stator cover. Not to mention the oil pump cavity in the case. It may be ok, but ya gotta look. And you may want to replace the oil pick up unless you patiently clean it like it was going to be surgically implanted into your body. It doesn't clean out as easy as you think.

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Ok, So I am gonna finally get going and do full engine rebuild. I'm ordering the parts today and will be working on it sometime this week when I don't have work. But please stay tuned because I will prob. need some help during the rebuild. And thanks ya'll for your help so far.

 

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4 hours ago, kylercrf450r said:

Ok, So I am gonna finally get going and do full engine rebuild. I'm ordering the parts today and will be working on it sometime this week when I don't have work. But please stay tuned because I will prob. need some help during the rebuild. And thanks ya'll for your help so far.

 

Good to hear.  It sucks but that's the right thing to do.  Take your time, don't rush it, and use a torque wrench!  Invest in the shop manual too, it will go step-by-step with pictures and tips.  Online theyre cheap, you can have it right on your phone in the shop with you.

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7 hours ago, kylercrf450r said:

Ok, So I am gonna finally get going and do full engine rebuild. I'm ordering the parts today and will be working on it sometime this week when I don't have work. But please stay tuned because I will prob. need some help during the rebuild. And thanks ya'll for your help so far.

 

You can order gaskets and all that, but until you've got it open, you dont really know what you need to replace. Just sayin. I never order parts until I've seen the carnage.

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