Afternoon all,

After owning a Aprilia rs 250 that’s been nothing but a ruddy headache since day 1 I’ve resided to the fact I now want to go the Honda route. I appreciate these old 2 smokers can be fickle beasts though.

So I’m looking at a mc21 for sale at the moment in track form which is how I’d probably keep it. My question is… what’s parts availability like generally, any good uk stockists that can be recommended?
I want to enjoy it, expecting issues/maintenance I just wanna be a step ahead.

Ps if anyone has a bike for sale drop me a pm

Cheers

Ross

Pps

Any noob buying advice or what to watch out for mucho appreciated

Hi Ross
Welcome to the forum. I always recommend a search through the posts, as there have been many similar discussions.

I would say once you have an NSR running well, it's pretty reliable for a 2 stroke. You can get a view of parts availability from cmsnl.com. Fortunately new cranks are available at the moment
_________________
Why do things simply when you can complicate them

Hello Ross, and welcome to NSR-WORLD.

First off, as Rob says, once prepped and set up properly, it's possibly [probably] the most reliable of the 250 two-strokes.

The MC21 has three main areas of weakness. In order of severity:

1. PGM-III fragility: Generally solved by routine maintenance of the RC Valves and cables.
   
   Drag on the servo caused by carbon build-up on the valves, or because of corroded cables, can cause the components on the PGM-III circuit board to burn out. It's been a hugely less prevalent problem since we started preaching it almost religiously about it on here, but still something to look out for.
   
   If the PGM-III does burn out, it can usually be repaired, or there's an Ignitech available, but I am reliably informed the ignition map is very basic compared to that of the PGM-III.
   
   
2. Crankshaft centre seal failure: Failure initially prolonged by only using ethanol free fuels in the UK, which is getting increasingly difficult to do. Cannot ultimately be prevented, in my experience.
   
   Shell V-Power, ESSO Ultimate (not in the Devon & Cornwall), and Tesco Momentum are all classed E5, however they are generally ethanol free. This continually changes though, so do more research in your area. In our opinion/experience, ethanol in the fuel causes the integrated seal on the labyrinth type centre main beaing to fail more prematurely than would normally be expected. Before the introduction of ethanol in fuels, we'd see 15-20 year old bikes with 25,000-30,000km on the clocks without issues. In the last 10-15 years though, lifespan has been dramatically shortened. (This affects 1989-1997 models, but doesn't seem to be a problem with 1987-1988 bikes with the separate centre seal.)
   
   Crankshafts can normally be rebuilt, but they are classed by Honda as a consumable item, and should really be considered as such while new items are still available. No rebuild parts are officially available, but GT Performance Engineering will do the best job in the UK if the crank passes their assessment (£25 non-returnable fee if it fails assessment). The cost of a rebuild is not far off the cost of a genuine new replacement though, and with a new crank, obviously everything is new, not just the main bearings!
   
   
3. Crankshaft main bearing lubrication: If you have 1992 or later cases (MC21 or MC28), this is less of an issue.
   
   Honda added an additional feed gallery in the crankcases, and an updated 2T oil pump. It's not a mod that can be done to early cases, and you cannot retro-fit the later 2T pump, so if you have 90/91 (and some 1992) cases, you just have to live with it. It's not a major problem, but it was an issue Honda saw fit to deal with.

Don't let any of the above put you off though. It's really "worst case scenario", but forewarned is forearmed, as they say.

All service parts can be ordered from Honda UK if you quote part numbers, GT Performance Engineering in Devon, TYGA Performance, or as Rob says, CMSNL easily enough.

Personally, I can't stress enough the use of genuine parts. In the interests of longevity, don't be tempted to try and use aftermarket consumables. For example, we've had to turn Mitaka pistons down in the lathe before because they interfered with a crankshaft, and have seen some aftermarket base gaskets "crush" more than OEM Honda ones, which can be catastrophic in some cases, where motors are run close to the limit. (The NSR is extremely sensitive to compression changes... which really isn't necessary anyway.)
_________________
Andy.
NSR-WORLD.COM

Please keep all responses to Forum posts on the Forum so that others may benefit.

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

Check us out on Facebook! Please "like" our page!