Hi guys
I am finally ready to derestrict my MC21. At present it is full std with exception of a set of cans on std chambers

What i will be doing is the GPS splice, and the PGM splice. From what i've read these 2 mods alone, do not require any carb rejetting

Next on the list was to cut the air box (to copy the TYGA version)
From what ive read, this DOES require re jetting. Info i've gathered from this site and the TYGA site say that going larger in the main jet alone is enough to keep the bike safe to ride without running lean.
Obviously this requires testing to get the right jet for my bike.
What i want to know is, what is the std jet size, and what is a good starting point (ie what size jet is common for a MC21 with these mods)
Im in AUST. Comming into summer. Bike is street ridden. I was thinking 142 or 145. I dont really want to change every jet and have the thing right on the edge. Just want it to run safe and make best use of the above mods, without it running lean.
Any info would be appreciated.
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Winning isn't everything, but loosing isn't anything

I got the same set up, cut airbox, stock pipes and splice . 145 mains and 42 jets. Running premix.

Hmmmm. Ok. Thanks your info. 145 mains with premix. I might try a smaller size as im going to keep the injection set up.
Cheers
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Winning isn't everything, but loosing isn't anything

If you blow it up, you'll kick yourself!

No way of getting to a dyno?
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MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball

You can blow them up pretty comprehensively on a dyno... allegedly!
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Andy.
NSR-WORLD.COM

Please keep all responses to Forum posts on the Forum so that others may benefit.

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Heh heh, but at least it's the tuner / operators fault, and they have to pay for the rebuild!
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MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball

Not if hes got any sence, 2 strokes are run at the owners risk. Never had any trouble with one mind.
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If I have to take the carbs off once more...

Im not sure what the tuners are like over in the UK, but over here, i wouldn't trust a workshop with a car, little lone a 2 stroke bike !!!

I have found a nice bit of highway where i can do some plug chops
And i have access to an AFM measuring device, i was just looking for some first hand info on a safe starting point.

Judging by your comments Dave, you think going leaner than a 145 main is a bad idea ?
_________________
Winning isn't everything, but loosing isn't anything

Well we usually refrian from giving jetting advice, as every single bike is different. Mine ran fine on Mains up near 190 with only a few mods, others run better with mains only a size or two up from stock.

There's so many things which can affect the jetting, and getting it wrong is such a pain in the bum!

Still, we all had to learn sometime, so as long as you're aware of what to look for on a plug chop, and go about it sensibly, then I'm sure you'll be fine.

I certainly wouldn't start leaner than 145. It might cost you a few quid buying a selection of jets, but I guarantee it'll be cheaper thana new piston and a replate...
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MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball

80XAR wrote:Im not sure what the tuners are like over in the UK, but over here, i wouldn't trust a workshop with a car, little lone a 2 stroke bike !!!

I have found a nice bit of highway where i can do some plug chops
And i have access to an AFM measuring device, i was just looking for some first hand info on a safe starting point.

Judging by your comments Dave, you think going leaner than a 145 main is a bad idea ?

I had some trouble looking for a mechanic as well, as they guy I had planned to use moved down to Sydney. After a while I heard about a guy over in Springwood, Tony Bogaart. He's doing the tuning on mine as we speak, and has previously done a bit of work on some friends' nsrs with good feedback. When I dropped my bike off he had a custom framed race bike powered by an rz500 motor up on the dyno, and he seems to like the two strokes.

If tuning it yourself doesn't work out I can give you his contact info.
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If I have to take the carbs off once...

Cheers guys. Appreciate the help. I understand you being reluctant to recomend something that could potentially hand grenade a motor

I have had a bad run with mechs. So i am reluctant to trust anyone.

Plug chop - The closer to white it is, the leaner it is ?
Caramel Tan colour is on the money ? SHould the plug accually be wet, or completley dry ?

So the wire splice doesn't require any re jetting ? If not, is it best to do the splice then tackle the air box, or air box first then splice
_________________
Winning isn't everything, but loosing isn't anything

I'd go with the splice first, as it gives you a little more aggressive acceleration and releases the top end. One you're happy the motor is running well like that, then do the next mod.

White plugs means the motor is about to expire - or has!

Tan is good, and black is safe as houses, but you'll feel it's running woolly if they're black.

Wet plugs can cause a misfire, and is an indication that the plug is not burning all the fuel - possibly ignition problems.
_________________
MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball