Hi All
For many years I have owned a NSR250 MC18 R5K. Some years back I had an issue with it and started to strip it down for a rebuild unfortunately all that turned out at fault was on of the cables to the front cyclinder. Upon inspection of the engine and bores I noticed a crack between the ports and sadly my rebuild had stopped there due to money and time. However a few years on I wish to get it back on the road. However I am unsure on the route to take.

Rebuild to Standard and get the bores replated
or second option would be to buy one of the big bore kits.

Can you guys offer any advice thank you.

There are companies then will repair and replate. http://www.poetonaptec.co.uk/ are one

I've read mixed views on 300 kits. Some have commented that the bottom end needs to be in good condition and also its not a straight forward bolt on power increase as with 4 strokes.

I've always been happy with the performance of my standard MC18, which put out 56bhp on the last dyno. That results in a fair acceleration / top speed and is still reasonably reliable, for a 2 stroke
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Why do things simply when you can complicate them

Cheers Rob

Think I will keep it fairly standard I think.

Is the R5K easy to convert to a dry clutch as I always liked the sound of dry clutches.

Hello Kris, and welcome to NSR-WORLD.

Dead easy to convert the R5K to a dry clutch. Make sure you get a complete setup though, including the primary gear for the crank. All the parts are technically interchangeable, but make life easy on yourself and get a complete R6K, MC21SE/SP, or MC28SE/SP dry transmission setup and swap it all over.

As for the motor, it's no secret that I am a firm proponent of the purity of a 250, and a well built one is a match (so far) for any 300 we've ever tested. On the plus side of the 300 kit though, you do get brand new components.

If there is a crack between the transfer port and the exhaust port, or a crack across the exhaust port itself, it will almost invariably crack again even after a weld/replate. While I am NOT simply saying to ignore it, I will say that we've run plenty of cracked barrels with no ill effects, even on the NSR500Vs. You'll ultimately need to judge for yourself what you are happy to proceed with, but if you do go for a repair/replate, I suggest you pull the barrel(s) off again after a couple of thousand Kms and take a look... I virtually guarantee they will have cracked again.
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Andy.
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Hi Andy

Thank you for your advice that is very helpful. So any NSR250 engine with a dry clutch is compatible that certainly helps matters atleast if I get an almost complete engine I should have everything I need.

Think I will have to dig the barrels out and get a few pics up for people to see then hopefully put the engine back together.

Of course, the R6K is the easiest swap, but obviously the hardest to find parts for as there were the fewest made.

You may need to fiddle around with pushrods and "top-hat" lifter ball bearings to get the actuation correct, and may need to swap around the selector detent depending on the transmission used. It should be apparent when you have all the parts in front of you and compare them. It's pretty simple though.
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Andy.
NSR-WORLD.COM

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Quick question I got my wheels out the garage today and the sides as cracking in places so I need two new tyre. question is which one

What tyres they using on the MC18

I seen people mention using the rear wheel form a MC21 is this correct.

Would the complete rear arm swap over?

Does the MC21 engine a direct fit into an MC18 if I use existing mc18 loom etc.?

I have recently seen 2 new mc18 barrels on Jauce.com. The price is about £850 though
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Why do things simply when you can complicate them

NSRMADKRIS wrote:
Does the MC21 engine a direct fit into an MC18 if I use existing mc18 loom etc.?

A bare MC21 motor will fit directly into an MC18 frame.

You will of course need to identify the neutral pin on the MC21 G.P.S. to wire into the MC18 harness, and play around with things like the stator/flywheel/pickup coils to make sure everything matches the MC18 systems. The external dimensions and mounting points of the engine cases are identical though.
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Andy.
NSR-WORLD.COM

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