Right gona upset the cart here! i know the Tyga kit is a nice set up and works well, in fact its on my wish list, but i sat down and had a cup of tea in someones work shop today (im not saying just yet as i wana see what you guys think) got onto the topic of big bores, i told him about the 300cc kit and he said yup should be good but why not go for a 380cc!!!!!!!! WHAT!!! he pulled out a set of barrles (not NSR) that he's made up (well made to fit) for a friend with a 21 they slap straight on apperantly and he has the pistons as well! there not complete yet but he hopes to have them done soon! what do you guys think has it been done before is it possiable we could go 380cc? lets forget about the crank for a second and thnk about the 380cc, Can it be done?...........................imagine a 380cc v twin!!!!

Sounds awesome, but I'd like to see the insurance quote first!
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MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball

mick at total traction has been working with a customer on a very large big bore on a aprilla rs 250
lots of torque but not big horse power was a while back when we last spoke about it may be worth giving him a call
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Half the strokes, twice the fun

The NSR clutch and tranny is only good, even tweaked, to about 75hp max. If he is going to do it, he needs to run the F3 tranny and clutch.
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Paul Herr
'88 FZR4/GSXR/YZF Frankenbike
MY BIKE PICS

There are 2 options, using either Malossi or Athena barrels. The Athena kit could give around 410cc (Matt?), but has no powervalves... The Malossi I think is the 380cc solution.

Both are interesting!
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NSR300R - Why did i ever have a 250...

Having ridden Steve's 300 (running the PWK39s) I have to say I'm not blown away. Don't get me wrong, it is very quick, similarly quick to his F3 '18 and I wasn't thrashing it. But that's the point, it's not worth thrashing it, you get no result, it pulls the same at 9000rpm as it does at 13000 (pretty well really), it's more like a slightly lighter version of my RVF400 with no engine braking, no V4 wail and a really early red line. Why would I want that? I've got one of them already and it doesn't go wrong.

The NSR was designed to be a 250, all the ignition etc was designed to be a 250, the pipes were designed to be a 250 and when you get them up into the mid 60's hp where they should be they're the best bikes I've ever ridden.
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The NSR was designed to be a 250, all the ignition etc was designed to be a 250, the pipes were designed to be a 250 and when you get them up into the mid 60's hp where they should be they're the best bikes I've ever ridden.

I guess you have never ridden a 2mm overbore NSR then...
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Paul Herr
'88 FZR4/GSXR/YZF Frankenbike
MY BIKE PICS

That's what I'm saying, it's nothing at all to do with power, let me guess, this 2mm overbore makes a chunk more midrange and about 2 bhp at the top? If it was I'd just buy a 600, Wayne's '05 R6 ran 114bhp on the dyno with just a can, it just revved and revved for ever and made more torque at 5000 rpm than any NSR will ever make, NO 250 is ever going to get near it on the road, he shot past Steve and I whenever he fancied it even though he was 2 up.
But it doesn't matter how fast my 250 is or isn't as a bike for sunny summer blasts or track day fun it's in another league.
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fontyyy,

right as usual. have you ridden one????? I am running a 2mm overbore and have ridden a well tuned 21 back to back. 2 bhp?? actually, it makes 71bhp and has a minor improvement on the mid-range but alot more on the top. ask racer38 or professor jim what they think about the bike.

scott

That's where you're wrong Fontyyy... I know, hard to believe!! But my 300 makes 11bhp more at the top, at pretty much the same rpm, as my 28SP did with the same inlet mods and pipes...

An NSR making 70 odd though I admit would feel soooo crisp, I understand fully where you're coming from!
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NSR300R - Why did i ever have a 250...

Are these 380 and 410 monsters over bored or over sleved cylinders from a smaller machine or designed for the displacement? I know we do a lot of work on banshee's (or RZ 350 for the road only guys) and the biggest problem with big over bores is as the cylinders get bigger the transferes get smaller. Pretty self defeating! your almost better to run stock displacement and run it to the moon! Thats why I love my 300 because Honda designed the port layout for 300cc's. But hey you know theres no replacement for displacement!!!
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1995 A kit TZ 250
1994 Rothmans NSR 300sp SOLD
1998 RM 250 freestyle/motorcross
1998 Meathanol burning CR 500 AF super retard/motorcross/sand dunes/play bike

They're designed for the specific displacement... So all their port timing and sizes should be good, but the crankcase volume I imagine would start to become a bit of a mismatch... Not sure what I'm talking about when in comes to that kind of detail though!!
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NSR300R - Why did i ever have a 250...

Does anyone have more detail on the cylinders that would be used to make these 250's into 380-410cc's? This would be perfect for a sand drag project im working on! Right now im just running the 250 vtwin in my trx250r quad frame and it runs pretty good but it would really shock some banshee owners if I were playing in the same cc range. Are the cylinders mentioned here easily available to the U.S. and were they designed for about the same stroke as the nsr's? Are they a single exhaust port or bridged like the nsr or do they have the auxilary exhaust ports? Maybe if someone could give even a little better description of the bikes these cylinders come from, then I could possibly track down some more info myself. Thanks
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Alex

i dont want to say to much just now, shops / people always get slagged if it goes wrong, i think its great they are even trying!!!!!

Anyway, if he gets it running the barrels i understand are from a popular 125 that (im not techy) have been machined to fit and bored out!!!! overall size looks big inside and out, they do have power valves so!!!!

The only reason i liked this project is the thought of have a big v twin 2 stroke!!!! feck power, if she runs and kick out reliable 75hp thats cool!!!

maxim wrote:An NSR making 70 odd though I admit would feel soooo crisp

How's that F3 coming Steve?? Matt mentioned one a while back made 73 on normal fuel....as does Keith's '28 I believe.
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Please do not PM me technical questions, if you can't find it on the Forum start a thread