Found a place that will take standard exhaust split them take restriction out and put them back together for £100. Says he has done this before on one NSR and customer was very happy.

Has anybody had this done is it any good?
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MC21 SP

Bill Limb has seen 66bhp on his MC21 on totally std pipes, how "restricted" do you think they are?
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The only ones that are resticted are the MC28 exhausts.

Guy who offered derestriction (racelines at Derby) says that they have the equivilant of a grill inside them slowing down flow. I was unsure so thought worth asking on here.
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MC21 SP

Here's some sneak shots inside a 21 pipe. There are basically two chambers between the stock outer 'shell' and the inner pipe itself. The chamber around the belly is a glass fibre wadding sandwich to absorb the sound, (only the L/H pipe has the mesh by the way) and the chamber around the baffle cone is open to the gas pulses via a small hole in the stinger. (lower pic...no wadding in this part) I just plated over the mesh and covered over the hole. No idea what racelines would do though.






Having done the work myself, £100 seems a bit steep, though it depends how much he charges for his labour I suppose, but only one pipe has the mesh remember. Though it did take a few hours, not to mention the stench of cutting through/welding sooty pipes

No idea of changes to power yet though, as Andy (being the busiest person I know ) has yet found the time to dyno them compared to a stock set.

(sorry if the pics are too big)

Cracking shots Grommit!

So from what you're saying, there's no actual restriction to the flow of gas then? Just a system to damp down the noise.

No wonder they're so damn heavy...
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martin77 wrote:
No idea of changes to power yet though, as Andy (being the busiest person I know ) has yet found the time to dyno them compared to a stock set.

I tell you - there aren't enough days in the week, let alone hours in the day!
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Nope...no 'restriction' as such, but there's always the point about how much energy the extra chambers absorb, which could be used in the sucking and stuffing. Most tuners claim removing the side baffling has an effect (KR-1's/RGV's/TZR's etc. all have a similar thing) but I've never actually seen any proof.

Andy mate.....there are too many hours in a day for me at the moment



(which is the way I like it)

as i understand the only restrictions on a 2 stroke pipe is the shape of the chamber and the size of the manafold and outlet

As we've seen in the past the std Honda pipes are very good, arguably the best compromise setup of the lot especially for a roadbike. There is no restriction there and any pipe change I've seen always results in some level of mid range loss, it maybe worth it on the track if you're really good but on the road you'd make better progress running std pipes. It wouldn't sound as good though and may feel slower.
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Cheers for the pictures and explanation Martin77.

Fontyyy just out of interested if in your opinion standard pipes are so great why are you running Tyga pipes?
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MC21 SP

Most people run aftermarket pipes as they're lighter, sound better and often look better.

They're also a darn sight cheaper than originals!
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nsr Moggy wrote:Fontyyy just out of interested if in your opinion standard pipes are so great why are you running Tyga pipes?

The '28 pipes are restricted (but that can be easily sorted)
The l/h '21 pipe can't be fitted to a '28.
I like the noise.
The '28 makes a tonne of mid range more than a '21 anyway.
It (the '2 hasn't run well for 8 months, I'm hardly likely to start messing with pipes, jets etc till it's running right again.
And I'm booked in on a quiet trackday in July so it'll have to be done by then anyway.
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I have had this work done but it has been done the other way round to the above pictures so you still end up with the out shell but with inners taken out. Went straight on with no problems although not set jetting right for these yet, still jetted for JHA pipes and this seems rich for these.
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MC21 SP

completed jetting now and I would say there is a significant improvement over standard mid range is all still the same but now revs out quicker at the top end.
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MC21 SP