Fooked bearings?

[tatters]

The awful humming noise from my KR1-S engine has returned and is now much louder and l thinks that it has nothing to with the cooling system as before. Me and my old man reckon that it’s coming either from the main bearings/ magneto/ balancer shaft area. So last night l took the balancer shaft out all looks fine apart from some small amounts of magnetic metal underneath on of the bearing each side of the shaft also this bearing is not a pressed fit and moves/sides off the shaft (no wear on shaft ) which l think shouldn’t be right could this cause the loud humming noise?




Symptoms:


No noise at all at tick over or below 3,000 revs or after 7,000 revs

Noise can only really be heard on the throttle after-burn

Comes from the left hand side of the engine






Any Suggestions, very Grateful for any
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Past:NRG50,AF1125(x2),NSR125RR,ZZR250,CX500,VFR400,KR1S,ZZR600(x2),CB400N,YZF1000(x2),KH125,Z200,FX400R,CBR954RR(x2)GPZ500S,GT550,VFR750F(x2),RD350N,XR650R,CBR600F,CB250,KDX250,YZF750R,CRM250,400EXC,KLR650,TTR600RE,DR350S,R100GSPD,RGV250,VMAX1200,DL650,KZ750 Present:G650XC,C12,CRF450X,1190ADV

[sickpup]

Sounds like the small ends but could be any bearing really. Strip the engine and find out.

[Robby]

I like this guy. He has a proper 2 stroke man response.

[tatters]

l don,t think its the small end bearings beacuse they were re-placed at the 1st re-build 2,000 miles ago and small end bearing noise is ushally heard at tick over, were l have no noise.
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Past:NRG50,AF1125(x2),NSR125RR,ZZR250,CX500,VFR400,KR1S,ZZR600(x2),CB400N,YZF1000(x2),KH125,Z200,FX400R,CBR954RR(x2)GPZ500S,GT550,VFR750F(x2),RD350N,XR650R,CBR600F,CB250,KDX250,YZF750R,CRM250,400EXC,KLR650,TTR600RE,DR350S,R100GSPD,RGV250,VMAX1200,DL650,KZ750 Present:G650XC,C12,CRF450X,1190ADV

[sickpup]

[catgate]

Heavy rumbling low down in the engine on "over run" is usually a good (or perhaps bad) sign of worn main bearings (perhaps balance shafts too, I am not sure about that) because the "load" on them, whilst under load, keeps them from waving about in their locating "holes" (often called bearings).
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"Always remember you're unique, just like everyone else."

[Kickstart]

Hi

Main bearings have normally whinned when they have been on their way out on me. Suspect they could rumble is badly worn, but (assuming it comes from the engine not the gearbox) then I would be a bit more suspicious of a big end bearing starting to fail.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[sickpup]

And if it's not the small ends your gonna have to strip it anyway so why wait, strip the fucker.

[catgate]