Hi, this is a long shot but has anyone got a cylinder to sell (preferably a B), mine let go yesterday and I think it may be beyond repair. The gouge between the ports on the bridge is deep and it’s also taken a couple of chunks off from around the ports too.
I’m not sure what’s repairable as far as cylinders go.
Thanks Chris.

Hi

Selling/buying parts are listed in the NSR classifieds section.

Good luck.

Thanks, I’d already had a look there but couldn’t find one. I’ve sent mine off to see if it can be saved.

You could try DK Spares
You could send it to Aptec or Langcourt for are repair appraisal. If the exhaust bridge is cracked it's likely to fail again
You could buy one from Japan https://www.jauce.com/auction/m1081626965
Anything you buy should be replated and sized with the replacement piston
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Why do things simply when you can complicate them

Langcourt have got it, the port bridge isn’t cracked but it’s got a deep gouge out of it from the piston hitting it and also the port openings have chips out of them.
I’ll wait and see what they say.

Well just to update this post, I’ve finally got the cylinder back and it’s a great job they have done. It’s like new!
I chucked it back together and it’s running again (obviously I rebuilt both cylinders), let’s see if it lasts longer than 2000 miles this time.

Thanks for the update Zeus. Good to hear you got a quality job done. I've sent cylinders away before and they've come back in an awful state altogether. Well wear, hopefully she goes past 2000

Zeus wrote:
Well just to update this post, I’ve finally got the cylinder back and it’s a great job they have done. It’s like new!
I chucked it back together and it’s running again (obviously I rebuilt both cylinders), let’s see if it lasts longer than 2000 miles this time.

Great to hear you're up and running again.

I'm a bit late to this one, but here goes anyway, and I apologise in advance... 😬😬😬

Did you tell Lancourts not to face the top of the barrel under any circumstances? The NSR is extremely susceptible to compression changes. If they skimmed it AT ALL I strongly advise you to measure both barrels and fit the shortest on the top. The lower cylinder is already prone to detonation, and increasing the compression will just make it worse.

If you don't have the measurements for the deck heights, and aren't inclined to pull it apart again to check, just ensure you keep a really keen eye on the jetting/spark plugs; particularly on the lower cylinder. Going a tad richer can help overcome very minor detonation, and use the best (highest octane) fuel you can get. If the barrel measures short, depending on the model (R or SE/SP) you really should consider experimenting with 0.6mm HRC base gaskets and alternative heads to bring it back in line for longevity.
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Andy.
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Cheers prelude/ Andy.
Yes I told them to just repair the cylinder and replate, I read everything I could find on here relating to cylinders beforehand.
When I stripped both cylinders down neither one showed any signs of detonation which pleasantly surprised me. I’ve just got back in from the second heat cycle and it feels lovely and tight (it should do really) . I had the plugs out after the first heat cycle just to check that all was ok and again just now. It always has Esso super in it as well.
The only thing that puzzles me is why it let go in the first place, I’ve been through and checked every thing and it’s all spot on.

Once again this forum has been a huge help and source of knowledge so thanks for taking the time and effort to do it Andy.

Chris.

Andy,

I have a spare mc18 cylinder which has been faced. I’ve seen a video on YouTube where T2Racing use a dial indicator fixed to a bracket which is secured to one of the head studs. Is this to check the piston height at TDC and make sure the correct thickness base gasket is used so that both piston heights are they same? Same squish on both cylinders ? Approximately 1.1~1.2mm ?

sami1 wrote:
Andy,

I have a spare mc18 cylinder which has been faced. I’ve seen a video on YouTube where T2Racing use a dial indicator fixed to a bracket which is secured to one of the head studs. Is this to check the piston height at TDC and make sure the correct thickness base gasket is used so that both piston heights are they same? Same squish on both cylinders ? Approximately 1.1~1.2mm ?

Yeah, I'd guess that's what he's doing.

The OEM Honda [ART] pistons are incredibly good (they also made the RS250R/NSR250/NSR500 pistons for HRC), and we never found any measurable differences in the crown heights, so we always just measure the barrels with vernier calipers.

I'd never use another piston in an NSR! (Someone sent us Mitaka pistons to use in their motor once, and we had to machine them to fit! They hit the crank on BDC!)


_________________
Andy.
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Andy,

I understand you should use corresponding heads with the corresponding cylinders on the mc21/28. Wouldn’t using a 0.6mm gasket change the port timing?

sami1 wrote:
Andy,

I understand you should use corresponding heads with the corresponding cylinders on the mc21/28. Wouldn’t using a 0.6mm gasket change the port timing?

Pedantically, yes, by 0,1mm. If you can measure that difference you need to be building rockets or performing brain surgery, not tinkering with NSR motors! 🤣🤣🤣
_________________
Andy.
NSR-WORLD.COM

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Please DO NOT PM me for technical advice. My time is precious, and you will probably receive a faster response on the Forum anyway.

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