I have found someone selling some HRC chambers/pipes for an MC21. Basically my question is, will the MC21 HRC chambers/pipes fit my MC28? Or will it be likely that I will have to cut the fairings? (I really don't want to cut the fairings).

Cheers
Tom

The fairing will be fine (they're the same*), the problem you might have is a l/h pipe designed to just clear an mc21 swingarm will foul an mc28 swingarm.

*leave it Andy, Matt, Steve and anyone else who just likes contradicting me, they're near enough the same for the purpose of this post
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Last edited by fontyyy on Tue Dec 29, 2009 7:50 pm; edited 1 time in total

Bugger, so I guess thats a no go. I'm almost tempted to buy them and store them for when i buy a 21

I can definitely confirm the GP style (both on the throttle side) does not have swingarm clearance, so it will not fit.

The side by side style may fit, but buy at your own (hopefully not) peril.

If they're real HRC they'll be side by side and if they're HRC for an mc21 (i.e. made before 1993) they'll almost certainly not fit an mc28 without some tweaking.

But I'd still buy them; as it's the l/h pipe that will be causing the issue (the r/h pipe will obviously fit) it's only going to need a bit of heat to bend the stinger out of the way of the swingarm and then bring it back in line so the can doesn't poke out at a silly angle.
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So tomorrow I'm probably going to do the airbox lid mod, and possibly grind out the horrible exhaust restriction. After these two mods, and installing the MC21 flywheel, will I need to tune the carbs? Will I risk running the engine lean if I don't tune the carbs?

Yes. Anything you do to improve the flow through the engine will risk siezing it, so you need to use a bigger main jet so that the carb can provide more fuel to match the greater airflow.

We can't give you figures as every engine is different, and the only way to do it is by trial and error. Have a read of the main part of the site looking at the engine tuning section...
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Thanks for your post Dave. Have had a look at that page, and from what I've read you can't adjust the factory MJ (you must always install new MJs)? I don't have any experience messing around with carbs so I guess I should leave this to a professional.

You're doing most of the stuff Tyga did here, jetting is mentioned there, have a read here as well.
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I have decided that I will just leave it until I move back down south (where I usually live), and get it dyno tuned / rejetted when i fit aftermarket chambers/pipes.

Something a bit more sinister now! I decided to take the bike out today and see how it performed under WOT in 4th and 5th gear. Both times it would rev nicely until about 9-9.5k, and it just wouldn't rev above about 10k. So I decided to take a look at one of the plugs and this is what I saw:



The end of the silencers are quite black and sticky too:



The bike has recently had a rebuild, is running 95 octane fuel, and TTS oil. It's used mostly at sea level, average temp during the days is probably about 20-25 degrees and around 70-80% humidity.

From my limited knowledge I think it's running way too rich.

Thanks in advance for the help.

Tom

Major_Tom wrote:
From my limited knowledge I think it's running way too rich.

They all run rich as standard... no manufacturer is going to let a 2-stroke out of the showroom lean, or even close!!

With a stocker the "secret" is to keep the plugs clean by not dawdling about on it, changing them and cleaning the air filter regularly, and by making sure it's not over-oiled by a poorly set injector pump.

Regardless of what anyone tells you, and regardless of the stick some of us get from the deniers for telling the truth, 1/2 measures on an MC28 simply aren't worth the effort. To get anything near the performance of any other model you have to go the whole hog... pipes, jet kit, HRC card, airbox, etc. Grinding washers out of the headers will give you all of about nothing except maybe some rpm, and the airbox is ultra restrictive. Nothing else is even worth considering until you fix the lemon of the PGM-IV though.
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You can't tell me the plug is supposed to look like that. Surely.

Depends how you ride it. Like Andy says they're very rich std.

When was the last time you cleaned/changed those plugs? Or the airfilter? The service schedule is every 6 months/5000km for both items

Andy, my Rothmans didn't go too badly at either the Llandow TD or on our rideout and it certainly went a lot better than a stocker.
I fitted the stock '28 pipes when I first built it and rode it for about 3 miles. Absolute garbage, I had to stop to laugh at how bad it was.

It really depends what you want, the difference you can make on a '28 without swapping the PGM or running an HRC card is quite a lot, about 17bhp or just over 40%.
That's worth having, it's 2/3's or all you're going to get without taking the motor apart no matter what PGM you fit.

And way over 3/4's of that's in the pipes, most of it's caused by those washers and that's "free" to fix.

Basically a '28 with it's pipes opened up and the airbox modified is enough to keep up with other 60ish bhp 250's and 400's and they're fast enough to keep up on most vaguely sensible rideouts or with average trackdayers.
A stock '28 is not.
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Personally I don't believe that graph. I think it's an enthusiastic reading... and I'm not the only one.

However you look at it, an MC28 on a standard PGM-IV is crap, full stop.

Someone once said to me, "I'd never want ride another NSR that pumped out under 65hp!", and at the time I was like everyone else in thinking 60-ish hp was fine. Live with 65+ for a few miles and you'll never look back. <65 for a road bike depresses me too now! Sub 60hp... may as well have an RGV, at least they're cheap!

It's not the numbers so much, it's the way it makes them! Sure, some 28's seem to rev like mad, but by all accounts they feel "hollow".
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Run any NSR around lightly and the plugs will soon turn black and nastie.

I would'nt bother with half measures either with a '28. Mind I wouldn't bother with a '28 at all anyway.

Get a set of good pipes on it, HRC jet kit, do the air box, wire splice and you'll be up there with a stock '18
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If I have to take the carbs off once more...