YZF125r Cylinder

[Pete.]

I just had cause to look at the cylinder of one of these. I was surprised to see that the piston runs directly on the plain alloy barrel casting - no coating, nothing. I've seen nitrided alloy barrels and that coating is harder than coffin nails - can't even touch it with a normal cylinder hone, have to use a diamond hone.

This has really surprised me, I wonder when they will start to suffer from worn-out barrels? Are any other bikes the same?
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a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[Kickstart]

Hi

Would expect a soft alloy barrel to wear out in no time at all.

All the best

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

[Paulington]

Fairly soon I'd wager.

Pretty incredulous considering they charge £4100 for the plastic fantastic monstrosities! .
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"Four wheels move the body, two wheels move the soul."
Current Vehicles: '89 Kawasaki KDX200, '99 Yamaha XV535, '00 Honda ST1100 Pan-European, '08 Suzuki GSX-R1000, '08 Mitsubishi Lancer GS4 2.0 TDCi, '15 BMW 1 Series 116d Sport Turbo.
CBT: 27/08/08. Theory: 04/09/09. Module 1: 16/09/09. Module 2: 01/10/09.

[P.]

[Paulington]

[Pete.]

[Kickstart]

[Pete.]

Standard '09 engine never been opened before. A foreign object got sucked into the inlet and wedged under an inlet valve, which then suffered a piston-strike and got bent, so I stripped off the top-end. Inspecting the barrel I noticed a couple of very shallow dints in the wall so I put a 3-legged hone in it for about 5 seconds to knock-off any high spots. Marks are still there but very slight so I don't think they are going to be an issue. So long as it runs and doesn't smoke the guy's not going to care really.
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[P.]

[Frost]

So is it actually a case of alloy barrel vs steel rings?

Maybe its some new alloy which is harder than normal? maybe there is some fancy oil system in there to keep the whole thing lubricated to hell?

[TUG]

[Pete.]

[Frost]

Yeah, maybe the barrel used to be plated?

[Pete.]

The bike has done well over 20k miles but this is the second engine. the original engine ate itself at 18k miles from having the skirt fail on the fancy forged piston

Nickel-plated barrels are harder than hell. You'll often still see the original honing marks on them after 20k miles of use. In comparison to a nikasil barrel, the walls of this one are soft as butter.
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[Pete.]

I did wonder if the piston was coated, but as Keith said the rings would still wear the barrel - I'll fetch some pics of the piston and barrel tomorrow.
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[Carvel]

[stonesie]

[Pete.]