could any one provide me would some advice as my MC28 PGMIV would not rev pass 10,000RPM. It revs really strong and clean all the way up to but as soon as it gets to 10 it seems like there is a rev limiter set.
I have just cleaned out the float bowls and fixed a pinched o ring seal.
I have checked and rechecked all the fittings and connectors on the bike and i can't for the live of me find anything obvious.

Please help.

Is the jetting clean in the high range? A rich setting could stop it from revving.

Or, if non resistor plugs are fitted they can cause a problem with the MC28 at high revs.

I have recently experienced the same problem, revs clean all the way up to around 9-10000 rpm then it dies. If it is in lower gears, the engine can usually rev past the problem. If it was aproblem with the plugs, would it just break down altogether at 9000rpm?

Does it do it everytime you venture into the high rev range? Does it cut suddenly or more like it's out of gas? I've been getting the same thing sporadically usually in high gears. Will just quit like it ran out of gas, clutch in will rev then it seems fine again til next time. Checked everything too. Spark? Fuel? Other?

Have you had the tank off recently? Kinked fuel pipe can sometimes cause this.
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MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball

Will certainly have a look, just in case

Hi all,

I have removed the tank and airbox to check for anything obvious, unfortunately there was not anything that was obvious.
The symptoms are as follows:

1 Will rev up to 9800- 9900 then it feels like a rev limiter is activated, there is a sudden dip in power delivery and it surges.

2 This problem occurs in every gear

3 If it does get pass the 10,000 rpm mark it is very slow in reaching 12000 red line.

I have since checked and reset the RC valves to the factory setting as they were equally out on both barrells.

I have replaced the plugs (BR9EIX Iridium) prior to the first track day and also have covered 350 ks since.
I did check the state of the plugs and the were wet and sooty, although I am not a professional tuner it tells me that the it is running rich.
Further investigation into the jetting revealed the main jet are 152 on cyl 1 and 150 on cyl 2. When compared to the factory settings listed on this site they are bigger.


Could this contribute to the problem?

Cheers

I am going to put the old plugs back in (BR9ECM) for this fault finding mission. If it is the plugs then great!, problem solved.

If it is not then,"Back to the drawing Board"

I will post my results as I go, and it is interesting to note that my MC28 is not the only one with this issue.

Those jet sizes do seem quite high if your bike is standard. Has any tuning work been done?
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MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball

Hi Dave,

I thought that the jet sizes were on the large size. As far as tuning work goes I am unsure as I had not taken any of the cyls off.
It still has standard expansion chambers and carbs and still is limited to 180 ish km/h

As for the 10,000 rpm problem, I reset the RC valves to factory settings and to rev through to the 12000 rpm redline. That is the good news!!!!!!!!!!

Now the bad news, it does not pull from the mid rpm range as well as it did prior to the adjustment.
I think that the large mains could contribute to this.

The next logical step is to disassemble and clean both RC valve assemblies and re lube the cables and reset as per the instructions. Will ask around to see who is a 2 stroke guru that can rejett and retune the bike.

This is not starting another MC28 bashing, but is any standard MC28 going to pull strongly above 10K? My full power but otherwise standard 21SP peaks around 11K, runs onto 12K downhill / tailwind but no hard power. If your heavier than an average Japanese rider and even one tooth overgeared, 40 BHP is never going to pull hard past 10K, particularly in higher gears. is it???
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Rich
MC21 Track Bike / RS250 NF5 'Spencer', NX5 'Cadalora' & NXA 'Aoyama' / RS500 / Two Brothers Racing RC30

Rich, they pull fine and right round to flat out in top (stock '28 gearing is 44/15 so that's only about 115mph for 11,500rpm in top), just with no real gusto.

If it's running stock pipes and a stock airbox it's almost certainly a stock motor which someone has tried to jet to run better with the powervalves set wrongly.

Billy's '21 was exactly the same, stock motor, stock pipes, stock airbox, massive mainjets, 42 slows and the power valves lined up with the TPS plugged in.
I'd check the power jets are still in place, check the slows are 38's and swap the main jets back to stock (140's).
Then take it for a spin, I'd know straight away if I was going in the right direction, a stock '28 is almost unbelieveably smooth and tractable.

Note this is what I'd do, I might be wrong....

And this is walking right on the edge of discussing jetting in General so I'll leave it at that.
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Please do not PM me technical questions, if you can't find it on the Forum start a thread

Thanks for your advice Fontyyy,

Will head down that direction with the jetting, and will post the results.

Cheers.

Just got my MC28 today and it's doing the same thing too except mine seems to rev limit at 9,000 rpm. The bike is completely stock, starts fine and idles beautifully. Pulls well but then hits 9,000 rpm and it won't go any higher, so it feels like I only have half a bike. Checked power valve operation and it seems they open quite low (4000 rpm ish). I feel it is probably a fuel issue, but I don't know much about NSRs so am open to suggestions.

Cheers
Tom

Major Tom: Have you checked what they recommended above?