Is this repairable?[What caused it? ]

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https://www.bikechatforums.com/files/aaaaaaaaaaaa.jpg

Hard to see properly but the chips next to the ports are about 2mm deep.

A replacement cylinder is £600 so if it's not repairable the engine is scrap

Thanks
Dave
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DRZ-400sm

[boundy]

I think most mild damage like that is fixable, its the cost that scares the shit out of me, is there any 2T engineering places near you?

[Kickstart]

Hi

Should be pretty easily repaired. They will weld it up and the reshape it properly before replating it.

All the best

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

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Cheers for the reply's ,i was pretty sure it would be beyond repair!

That's cheered me up a bit. Just got to hope it's not too expensive now
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DRZ-400sm

[boundy]

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[stevo as b4]

My KMX200 barrel is damaged about the same as that one. It is definately repairable. I sent BDK and another 2stroke tuning place a pic to look at, and they confirmed that it could be welded and re-nikasil plated again.

Do not let anyone fit an iron or steel liner to a plated cylinder, as at best you will lose alot of performance!

[MaybeGuy]

DT230 didnt last long then?
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Blue_SV650S wrote: it was a sh1te wheelie, but it proves that he can get it up in 3rd and can do angles. In summery, mattsprattuk is a gobby little sh1tebag, dopehead tw4t, but sadly for all of us, he probably isn't THAT full of sh1te!!
Kickstart wrote: Hi I tend to agree with Matt. All the best Keith

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The engine sounded quite rattly since i bought it to be honest but i thought nothing of it until my mate bought one which sounded a lot quiter than mine.
I should have trusted my gut instinct and stripped it then for a look.

Even if i did have to buy a new cylinder,i'd do it but if it's repairable i'll have it back on the road within a couple of weeks
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DRZ-400sm

[Frost]

Welding and reshaping will be fairly cheap. Replating is the bitch! If you can get a liner put in it will save you alot of cash.

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So i took the cylinder over to ard racing today.
He advised me to get the liner fitted because i'll get 4 re-bore's out of that one liner (re-bore is only £20)
In regards to power loss,he say's i wont notice the power loss at all,it would only be slightly noticable on a dyno.

So cost of the liner is £150 (nikasil was only £30 more) then however much wiseco charge me for the new piston & rings.

Not too bad at all considering i thought it was un-fixable

Thanks for the reply's
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DRZ-400sm

[Frost]

Be careful, you will be tempted to buy a piston of an abnormal shape to improve compression etc, its probably not worth it

[Kickstart]

Hi

£150 sounds a pretty high price. Would expect about £100 (plus a bit extra for the welding) for a replate, and about the same for a liner to be made and fitted.

One issue with a liner is that standard rings might well not be compatible with a cast iron.

All the best

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

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Price is a bit higher than a few online company's,but up here ARD Racing are quite well known for doing a good job so i dont mind paying the extra.

Had another bit of luck tonight aswell as i found the little piece of piston ring which caused all the damage it was in the exhaust
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DRZ-400sm

[oldbiker]

For a repair to a single cylinder engine I would go for a liner;

It`s usually quite affordable and cheaper if you can do your own porting.

You then have the option of a few rebores,

If you want to you can bore to a much more common and therefore cheaper piston,

Down side is you may loose a little power,

A cast liner can be used with any type of ring.
but i would go for a modern steel type ring rather than the spun cast iron types,
as the modern wire types are suited to very wide exhaust ports, ie about 70% of the bore.

However if I had a multi cylinder engine and one bore was damaged I would go for welding and a replate so that both barrels had identical cooling and ring to bore friction.

but that`s just what I would do and everybody sees things there own way
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It`s all powerfull white mans magic
https://i897.photobucket.com/albums/ac178/tzrsteve/album%201/035.jpg

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Over a month now and i'm still waiting for the cylinder head back ! The waiting is killing me

So another week or so and i should get this back and i have all the gaskets e.t.c. waiting.
I'm wondering what could have caused this in the first place on a bike which only has 3000 miles I really don't want to put it all back together for it to happen again!

The carb was just setup a few weeks before this happened and it's running perfect according to the plug chop.I usually use normal unleaded but i have used super unleaded a couple of times

I do thrash the bike constantly and with it having no rev counter i tend to rev until the power drops off then change gear,maybe i should stop this? but it's a 2 stroke they loved to be revved don't they?

Any advice would be appreciated
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DRZ-400sm

[chillpill]

piston rings clipping the ports would be what id guess

no they dont love it , high revs aren't ideal for any engine over revving could cause excessive ring wear which is likely to cause this , id fix the tacho and play it safe , you shouldn't feel a noticeable drop in the power till your a fair bit into the red line i would have thought plus reaction times and shit its not worth putting that extra strain on your engine

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[ms51ves3]

The drop in power is in a way the rev limiter, I wouldn't bother getting a rev counter.

The way you warm it up is the way I have always warmed my bikes up, never had any problems.

I think you may have just been unlucky.

[Pete.]

Over-revving causing extra ring wear

Looks like the plating's come off to me on the large patches at least and something has got trapped in there to cause the deep gouge (piec of plating perhaps?).

Send it off to be repaired and re-plated properly and get a good quality piston like wiseco, better yet, find out if you can get over-sized pistons and have it bored to suit that instead of welding.

Put a cheap piston in it and you're asking for more bother.
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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

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[Pete.]

If Wiseco are making a custom piston then have them make it oversize deliberately to accomodate the repair to the barrel.
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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

[stevo as b4]

I don't think overevving caused the problem IMO. It will probably safely rev to 10000rpm, which admittedly will be way past peak power, but my old KMX was fine being revved to the red, even though the power isn't still there.

I'd definately leave any 2t engine on a fast tickover for about 1min before riding, and then 10mins of gentle out of the powerband riding from there before letting it rip.

The area i think you need to look into is lubrication and ignition timing if there is any possibility that it could have changed?

I belive that the reason why my 23'000m KMX engine chunked the piston and snapped the rings was down to top end wear, causing the rings to be loose in the ring grooves, and then fret against the port edges. This went on until the top ring land broke off on the exhaust side. I don't think that this was your problem unless your engine had done similar mileage on original components, but the damage to the bore looked very similar to that shown in your pics.

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