I have two MC21s (an R and an SE) that have been languishing in my rented garage for the past 15 years. The time has come to get them back up & running again and then sell one (or maybe both) of them.

I don't have the appetite (or location) to do this myself, so I'm looking for a specialist who can do it for me. I'll stick them in a van but don't really want to travel more than 50-100 miles. I'm in Berks / Surrey area.

Having sat so long, they will need at a minimum carbs cleaned and rebuilt and fluids changed. Any other essential jobs you guys would recommend after sitting so long?

Both bikes also repeatedly suffered from fried PGMs / inoperative power valves. This was a common problem when I was last active in the NSR community 20-odd years ago, but there didn't seem to be a consensus on fix. I remember something about voltage regulators causing power spikes to the PGM?? I presume there is now a well-known fix? Can someone point me towards a link with fix / explanation please? I want to put that fix on both bikes. They both used to seize a lot too, which is somewhat annoying on what were basically stockish bikes.

I think I have a couple of spare (possibly fried) PGM-IIIs in a box too.

Can anyone suggestion a localish specialist please?

Thanks!

Spa motorcycles in Cheltenham have very good 2 stroke experience. GT Engineering in Plymouth are the most knowledgeable for NSRs
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Why do things simply when you can complicate them

Raine wrote:
https://www.rhrmotorcycles.co.uk/

Can anyone suggestion a localish specialist please?

Thanks!

Raine wrote:
Both bikes also repeatedly suffered from fried PGMs / inoperative power valves. This was a common problem when I was last active in the NSR community 20-odd years ago, but there didn't seem to be a consensus on fix. I remember something about voltage regulators causing power spikes to the PGM?? I presume there is now a well-known fix? Can someone point me towards a link with fix / explanation please? I want to put that fix on both bikes. They both used to seize a lot too, which is somewhat annoying on what were basically stockish bikes.

Wow! There's a name I've not seen for a long time!

PGM-III failure was almost always nailed down to poor RC Valve maintenance and adjustment. Since pressing this at every available opportunity over the years, blown PGM's (on the RC Valve side of things) have become virtually non-existent, except for the odd noob that's not heard of the past problems.

As for seizing, it certainly shouldn't be a common problem if set up correctly. The problem is there were (still aren't) any stock settings for a delimited NSR, and "somewhat stockish" is rather telling. Pretty much every bike we set up over the years, that wasn't bone stock, varied slightly. Also, as soon as one does seize, and gets a replated barrel, invariably the plater skims the top off the barrel to clean it up, and that can spell disaster for some motors that are already on the limit.

You won't find a more qualified company for NSR250 work in the UK than Performance Engineering in Plymouth. There are some spectacularly good RS250R techs in the UK, but for NSRs specifically, you won't do better than GTPE. They often have a van heading in your direction, so could possibly even collect the bike(s) depending on timing & convenience, so worth giving them a call and asking.
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Andy.
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Hey guys,

Thanks very much for your replies. Sorry for my late reply.

Good to hear about Performance Engineering, and that they often send vans out to collect bikes - that could save me a 400-mile round trip in a rented van myself! I will give them a call. I guess they will know what to do about the power valves / PGM issue too.

Andy - it's been so long since I spent any time on my NSRs that I basically can't remember what's been changed on them, but I do know that I always kept my powervalves meticulously clean after the first couple of fried PGMs, but then still had the "powervalves stopped working" issue appear after that. I think I remember having to replace voltage regs (not 100% sure), and definitely replaced PGMs a couple of times. So, when the powervalves stop working, do you have to replace both the PGM and voltage reg at the same time? Can PGMs be rebuilt these days?

Changes on the bikes - I think the R is totally stock apart from an M-Max box and maybe a free-flowing air filter (or perhaps NO air filter). The SE had been tracked or possibly raced before I bought it, so not sure, but I think it might have a wire-splice derestriction. I put Jha pipes on, and also free-flow or no air filter. Nothing else I think. On that basis, would you suggest that I need either / both bikes rejetted or else set up somehow?


Last edited by Raine on Mon Feb 03, 2020 7:54 am; edited 1 time in total

Cleaning the RC Valves is only half of the story, correct adjustment and well conditioned cables makes up the other half. ANY resistance against the servo operation can be enough to kill the PGM, so even slightly sticky cables, or just one of the four cables being too tight, can cause failure. However, since working to this mantra, we've not had a failed PGM ourselves for well over a decade, which can't just be down to coincidence in my personal opinion.

Reg/rec's are a strange one. We rarely hear about problems with them these days, but were, as you say, an issue back in the day for some reason. Indeed, I had one fail myself, although I believe that was linked more to a damaged stator than individual component failure.

It's impossible to say what setting your MC21s require, without seeing/running them. Every motor is different. We've seen delimited but otherwise "mostly stock" NSRs that have taken both richer, and leaner, main jets.
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Andy.
NSR-WORLD.COM

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