Something i have to ask guys!i heard rumors that mc18s barrels and heads can be fitted to the mc21 without modifications and work normally!is that true?i am asking cause i cant find used mc21 barrel which i need but i can find tons of barels and motors from mc18!of cource i mean that i must change everything both barrels and heads.
Something i have to ask guys!i heard rumors that mc18s barrels and heads can be fitted to the mc21 without modifications and work normally!
Yes they can, but go for 1988s , rumour has it that the early cylinders were more powerfull as they were made before the restrictive japanese mc laws passed in 1989 _________________ Poul
"If Life Gets Boring, Risk It!"
MC21SE, KISS box
MC21SP, HRC box, racing loom
If you use the heads in the original configuration, i.e. an MC18 top head the top, and a bottom head on the bottom, the standard MC21/28 hoses will fit!!
I used an MC18 cylinder on my '21 for a couple of weeks on the bottom, with an MC18 top head, and it mated right up to the HRC style hose without any modification! _________________ Andy.
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On my MC21, my top cylinder seized and I only then discovered I'd been running a MC18 cylinder as I had to get another top too when I changed the cylinder.
I didn't change anything else. _________________ Poul
"If Life Gets Boring, Risk It!"
MC21SE, KISS box
MC21SP, HRC box, racing loom
Use an MC21/MC28 piston though - it's not a must, but it's preferential over the MC18 piston. I got away with it, but I wouldn't do it again unless I had to. _________________ Andy.
NSR-WORLD.COM
Please keep all responses to Forum posts on the Forum so that others may benefit.
Please DO NOT PM me for technical advice. My time is precious, and you will probably receive a faster response on the Forum anyway.
So the rumors are true...thanks guys for sorting it out and for tips andy! ill do it cause cant find barrel and cant wait anymore!matt i dont think that the mc18 barrels will be so aggresive compared with the 300 barrels you will prepare for me one day........................
Just to add to Andy's comments, the 21/28 pistons are preferred as they're more robust with better lubrication qualities.
Agressive 300? The last tuned one I built was for Paul and he's scared to ride it The first shakedown was going reasonably ok, revving to 13,500 and lifting the wheel easily in 3rd, but I got a little too carried away with the jetting and we got some detonation , so ended up a tad rich just to keep it cool and running.
It'll now rev nicely to 12,500+ and will take full throttle from 2000rpm without a hiccup, right up to full volume.
I'm still building mine. Typical! Why do my bikes always take ten times as long to build? The latest mod was to fit the bigger reed valves from the '92 NF5. Lots of hacking with the chisel, but they're in there snugly now.
I've got a new head design I want to try which should give me more top end power but it looks like I'll need to buy my own CNC lathe to get the job done, and that's not gonna happen this week.
Got a nice lightweight F3 box to throw in it and I've lightened several components in the hope of more mojo. I've modified the R cover to blank off the waterpump and will be running an electric waterpump 'cos that pump must sap at least half a pony.
Oh, and those nice guys at Wiseco made me some specials so hopefully they'll handle the strain.
Electrics are a mix and match of MC21, NF5 and F3.
My software estimates 90+hp at the wheel. We shall see.
If it goes above 90 then I'll switch to alcohol and go for the big 100hp.
Maybe I should eat less cheese before bed......it's giving me funny dreams.
No you re not dreaming everybody here knows who is MATT! i believe in you!you have my respect cause you have shown true LOVE for this bike!so we are waiting the MATT PATERSON'S 300extreme modified kit..........................................................................................OR MAYBE 350???????????whow! i think i should go to bed.......
need to buy my own CNC lathe to get the job done, and that's not gonna happen this week.
Maybe Matt should sell shares to be able to buy his CNC lathe. 50£ now, for a rebate of 100£ on the 80++ kit _________________ Poul
"If Life Gets Boring, Risk It!"
MC21SE, KISS box
MC21SP, HRC box, racing loom
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The first shakedown was going reasonably ok, revving to 13,500 and lifting the wheel easily in 3rd, but I got a little too carried away with the jetting and we got some detonation 
, so ended up a tad rich just to keep it cool and running.