Sorry but I have had a quick search and I am still confused as to derestriction of my MC28SP, splices, HRC cards etc etc.

I thought I just had to change the exhausts - the main tuning restriction, and have the wire splice to get a healthy 55 BHP or so. What does the wire splice do?

Do I loose the digital display with a wire splice???

Do I have to make any further electronic changes to optimise the bike. I don't want to tune the bike any further than fitting race exhausts, ie. compression, porting, ignition etc will all be left as standard.

Am I wrong to expect ~55BHP from a standard engine with a race exhaust?

The previous owner said the bike was ~57BHP but had no supporting evidence. The bike will pull well past where the speedo stops at 180 KPH and I reckon I've had it up to ~195-200 KPH so it must be >45BHP right?

http://www.tyga-performance.com/pages/mc28wiresplice.php

your speedo will turn into a temp gauge which will mean the fitting of a digital bicycle speedo (or if you are fontyyy nothing), and you will loose the oil light and neutral light.

the pipes are restrictive on the 28 but i beleive to get anywhere near the 57 figure you will need to deristrict and modify the airbox, most of the modded NSRs (pipes, airbox,wire splice) hit around 63BHP it is unusual to see above this with out going to the extremes that you mentioned porting ETC.
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Certainly I still have a working speedo, and neutral indicator on the digi-dash, not sure about an oil light. So this would indicate that the wire splice has not been done - right?

In which case, does this mean that my '28 will be limited to the 45BHP you mention monkey? Regardless of the M Max pipes? And the previous owner was talking bollox when he said it was making ~57BHP?

yes mate that right it still has the electronic restriction.
sorry but i dont know the answer to your second question, my 21 when it was restricted would start to tail off in 5th and there would be virtually no power in 6th so fitting pipes i dont believe would have made any difference as the restriction came in at about 90MPH and wont let you go past 115MPH but i dont know if its the same on the 28.
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The wire splice does nothing without an HRC card.
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well there you go....i thought the HRC card did ther same as fitting the 21 flywheel.

so how do you deristrict a 28 without a HRC card?
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the power of the '28 is resticted in 2 main places;

a, in th exhausts, the headers have tiny inlets, fixed with race pipes
b, in the pgm4/card, the timing is retarded more than a std '21, fixed with the HRC card and wiresplice, cheap workaround involves the '21 flywheel.

also general consensus is the airbox is quite restrictive.

There is no plain splice (i.e. just a wiring mod) like on the '21 as the restiction is actually in the card, the '28 splice is to allow the running of the HRC card without the HRC loom, running the loom means losing all road gear, lights, indicators the lot.

Wheather a 28 running the '21 flywheel has a top end speed restriction or a gear related power tail off (like the '21) I don't know.
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Beat me to it fonty. I dont notice any power tail off at top end (I have been clocked at over 120mph - but my speedo was disconnected at the time ). I seem to remember Jamie saying that the clock stops at 180kmh but the bike keeps pulling, mine revs right out in 6th.

Here is the my post before this edit:-

You should be able to get near the 57 bhp quite easily without any fancy wire splice or HRC card. You just need new pipes and an MC21 flywheel. Maybe the airbox mod and re-jet, however mine is making reasonable power (around 55)without the airbox mod and the rejet.

http://www.tyga-performance.com/pages/MC28.php

Tyga got 58.5 without any wiresplice at all. I have a HRC card for mine but I dont like the idea of cutting the loom so I went the MC21 flywheel route instead, it certainly made a difference. You also keep all the standard warning lights and speedo which can only be a good thing. I also have JHA exhausts.

Sorry - I must be fick or somefing...to recap:

My '28 zings along nicely up to 11,500rpm or so - as high as I've let it rev in top, this equates to ~190-200KPH, though not exactly sure as the digi speedo stops at 180 KPH. So no speed restriction.

My '28 has fully functioning clocks etc. so the splice has not been done - RIGHT?

Running original Card Key.

Under this state what is the max power I could expect?

It sounds like claimed 57 BHP is not possible, UNLESS it has a MC21 flywheel (which I don't know) - I'm e-mailing the previous owner to see if he can tell me anything.

I guess it depends on your gearing. At what revs do you hit 180 kmh in top? and how much further does it rev?

Yes correct, this is what I was saying to Tom H the other day. Both 28's I've hadm have started out restricted and then I've full powered both. On standard 15/44 gearing, both would hit the redline in 6th, at an indicated 180kph... I changed both to 15/40, as I prefer this gearing on the road, and to my surprise, they would both still pull 12000rpm in top. I would say that the restriction is initially also in the gearing too.

I remember grinding out the exhaust headers on the standard pipes... Nightmare! This was unfortunately before Tyga, so I ended up putting a 21 pipe on one side and the ground out 28 pipe on the chain side, jetting to suit and Gibson cans... Sounded great! It was a bit too much to get a pair of Jha's for a grand!

The second one also cam with a great pair of Harc-Pro's, which were without a doubt the loudest pipes I've ever heard on a road 2-stroke!
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Don't know what cogs are on it - though I keep meaning to check as I got some spare ones with the bike.

180kph ~ 11,000 rpm.

At the moment it is doing almost exactly 10mph / 1,000rpm. ie. In 6th gear 112 kph on the speedo = 7,000rpm = 70 mph. I quite like it though like that as then I just read the tacho for speed in top gear - 7,000rpm = 70mph .

I thought if it was restricted then it would stop pulling at a given speed - 112.5mph or 180 kph ?

As mine keeps going I thought it wasn't restrcited.

I saw 188KM on my 28 before it was de-restricted. I never noticed the tail off I've heard about in the upper gears.
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Colin NSR wrote:My '28 has fully functioning clocks etc. so the splice has not been done - RIGHT?

Running original Card Key.

That's right, you lose the oil light and neutral warnings (actually they are always there but you still lose their function) with the splice as it involves shorting those leads to earth but there is no reason to do the splice other than to allow the HRC card to function, the card does not work with a standard unspliced loom and the splice has no effect with the normal card other than to render the low oil and neutral indicators useless.

Then if you run the HRC card itself (contrary to popular belief the normal card still works) you lose everything except the main (speedo) display which is now a big temp gauge.

I am presuming here but I guess the HRC card advances the timing to the same sort of setting as the HRC '21 part #30490-NKD-840 does.

That there is no speed restiction or gear related tail off would make sense, it doesn't need it, 40odd bhp (which is all a standard '28 makes) would barely reach the 113mph the restriction is supposed to be. That and the standard '28 gearing is only doing about 115mph flat out anyway, mine was showing 117mph on a push bike speedo at well past 12000 rpm in 6th when it "nipped up".

So;

The cheapest '28 derestriction is just pipes (or a Dremel and a lot of patience on the '28 pipes), maybe a modded airbox and some bigger main jets, you might see mid 50's bhp.

Option 2 is the '21 flywheel and the above, Tyga got 57 bhp like this.

The "proper" way is pipes, airbox mod, HRC card and jetting to suit. Mine made 60.7 with ease at the dyno day and probably a couple more running a modded lid (I ran an open airbox at the dyno day) and slightly leaner jetting.

Then maybe the HRC head conversion, reeds, stuffers etc.....
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Last edited by fontyyy on Mon Jan 30, 2006 10:55 pm; edited 1 time in total

fontyyy wrote:

Then if you run the HRC card itself (contrary to popular belief the normal card still works) you lose everything except the main (speedo) display which is now a big temp gauge.

If it's anything like the 2 I had Fontyyy, the standard card made them run like pigs once the mod had been carried out... Useful for MOT's though!
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