Rattle on Overrun - Sanity Check

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Cexley
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Posts: 93
Joined: Wed Oct 14, 2009 4:40 pm
Location: East Sussex

Rattle on Overrun - Sanity Check

Post by Cexley » Thu Dec 12, 2019 11:52 am

Hi All,

My now sorted 1984 KR250A starts, goes and rides fine. However, when riding it hard, I can hear a slight top end rattle on the overrun between gear changes. The bikes has done about 11k and runs spot on. I know the early KR’s had a reputation for catching piston rings in the ports, so is this a sign of impending self distraction?

I can’t decide if it is rings, piston slap or small ends. It’s been there since getting the bike and hasn’t got any worse over the last 1000+ miles, so before I needlessly strip the top end, has any of you KR250 owners experienced this, and if so, is it the infamous ‘normal’ or something I need to address PDQ?!

Meanwhile, all looks clean on the piston skirts when viewed through the exhaust ports. My next step was to do a compression test and borrow a mate’s endoscope to poke into the plug holes to see if there are any other tell tale signs or marks. Hope I’m wrong, but my other water cooled 2 strokes are all mechanical quiet on the overrun. The KR reminds me of my old air cooled 2 strokes....
KR250 Tandem - Love It
KR1 Project - Sold
XT600Z 3AJ Tenere Overlander
TZR250R 3MA Reverse Cylinder - Sold
TZR250R 3XV V-Twin - Road & Track
TDR250 - Road & Track
XTZ850 Super Ten Dakar Sonauto Rep - Sold

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StrokerBoy
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Joined: Thu Jul 27, 2006 9:43 am
Location: Yorkshire
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Re: Rattle on Overrun - Sanity Check

Post by StrokerBoy » Mon Dec 16, 2019 8:02 am

I've not heard a similar noise on mine, but there's a lot more moving parts in a KR engine compared to a normal parallel twin, so they are a bit noisier.

Assuming you've got a spare head gasket, you could strip it if you're worried. I'd probably leave it, but then I'm lazy, and have enough actual known problems on the to-do list without going looking for more... :lol:
Kawasaki KR250 Tandem Twin (x4) & KS-II 80,
Yamaha RD350LC,
Suzuki GSX-R750RK & RB50 Gag.

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