NS400R / CBR250R

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ian wright
Posts: 155
Joined: Sun Oct 02, 2005 8:16 pm
Location: huddersfield

NS400R / CBR250R

Post by ian wright »

I've recently started building a CBR250R MC19 which I plan to fit a CR barreled NS motor in. I chose this chassis as it has more room for everything as the original bike is an in line 4 cylinder 4 stroke (more room between the frame spars), more room for the carbs and a bigger airbox than standard and much roomier than an RGV or Aprilia RS250. The chassis is nearer the size of the 250 2 strokes but smaller than it's 400 brother the CBR400R


Work done so far -

Original CBR side engine mounts cut off the frame, new alloy top brackets made to fit bolt on a cradle to support the engine.
Made new rear top engine mount.
Replaced original forks, brakes and front wheel with NC30 parts.
Fitted CBR250RR rear wheel to match the front (will be replaced with a 5 inch wide wheel at a later date).
Modified original rear sub frame and fitted Honda RS250 race seat.
Petrol tank has had the lower half cut off and capped to make way for the rear seat exiting pipe.
Home made rearsets using original CBR hangers.

I plan to build the motor, build custom made exhausts for the bike and get the bike running and set up making decent power before spending more time and money on uprating the chassis parts and bodywork.

As well as the CR barrels I plan to fit uprated gears and crank to the engine and also a double cored radiator to take care of cooling.

Target power 90bhp
Target weight 130kg ( wet )
Target finish date April 2012 ! ( LOL )

Cheers Ian
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Mananon
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Re: NS400R / CBR250R

Post by Mananon »

Hi Ian,
Was the 250 frame just an easy buy or a considered one?
I'm wondering how it will cope with the stress.
A couple of guys have gone for the RGV route, like Bloodnut, and of course there's the RC30 based NC431V I'm sure you've seen.
I'm favouring going the NC30 route myself as the V4 motor is also very small and, being a V4, it has parallel frame spars and is designed to route an exhaust out the back.
It's also available as a 1989 so meets post classic racing regs here. I have an 89 NC30 in roadrace trim so I know there are plenty of off the shelf mods and kits to get the handling up to modern spec.
I see the NS forum has gone pretty quiet but please don't think no-one is watching.
I'll be paying very close attention.
Best regards and good luck.
Duncan

fredie
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Joined: Thu Jun 28, 2007 1:32 pm
Location: sydney australia

Re: NS400R / CBR250R

Post by fredie »

very nice concept . i have the same plan project . cbr250rr very common down here . great frames i think . how about a different swing arm . whats the ideas :P

Mananon
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Re: NS400R / CBR250R

Post by Mananon »

Again Fredie, I know they are common but thin frame spars, not meant for anything like the potential power and torque possible to input.
The NC30 is close to the RC30 in design and is known to be able to handle 90+RWHP with new shocks and forks, hence my inclination to go that way. Common does not mean best in this I feel.
Even with the NC30 chassis I think the single sided swing arm is heavy compared to a more usual design and I will look at replacing it to save weight. Weight on a track bike is everything, including me, helmet, leathers etc.
That said, there are some benefits to a SSSA when one considers exhaust routing.
My intent is to go frame up, with attention to everything, regardless of the time it takes.
For example, I want to use a stock, 1 ring piston, but want to go over 400cc, so I'm thinking 1mm over titanium con rods. I think (with very carfull ballance and cryo) the box and crank can take it but would prefer to over stroke than over bore.
I'd like PV's too but need to do much more research.
Maybe port injection?
Needless to say, this is going to take years, but I'm an engineer and am well used to a slow, methodical approach.
Cost of course, is the telling factor.

Duncan

ian wright
Posts: 155
Joined: Sun Oct 02, 2005 8:16 pm
Location: huddersfield

Re: NS400R / CBR250R

Post by ian wright »

Hi Duncan,

The frame choice was a considered one as I had looked at the RGV which actually has narrower frame spars than the CBR250, the RGV's are also closer together and only just has enough room for the 3 carbs of the NS. The CBR frame is also stronger around the headstock than the RGV as the original engines mounts hung down to support the weight of the much heavier original engine,this is where I have welded the new engine cradle top mounts to. The rear top engine mounting bracket is bolted directly to the original middle frame casting as was the original engine and the lower cradle is fixed to the same.

I also considered going the Aprilia RS250 chassis route but the frame spars like the RGV are very close together, I have a friend with one who said to me he would never choose the RS again if he was to do a frame swap as squeezing everything in was a nightmare and made the bike difficult to work on.

The NC30 also needs a frame cradle of some discription making like the CBR, whether it be a loop or plating of some sort to the frame and there is less room than on the NC to route the rear pipe than ther is on the CBR.

I'd be happy to put a 120bhp motor in the frame if it was possible to squeeze that out of the motor which I'm sure would be safer than putting an 140bhp RG500 motor in a RGV or RS chassis with big chunks of the frame side spars cut out to squeeze the over sized motor in as I've seen on numerous RG500 / RD500 specials.

What's scarier still is the guy who I bought the CBR off was putting the CBR engine in what looked like a push bike frame, Mike Hailwood replicas I think they call them, now thats scarey !

Cheers Ian

Mananon
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Re: NS400R / CBR250R

Post by Mananon »

There's a guy at a workshop up the road who's putting a Subaru twin turbo motor in a one off bike and he's used spars cut from various bike frames to make his chassis. It's all hub centre steering and the engineering is great. The welding though? Deary me. Glue and celotape might be stronger I think.
Anyway, as you were saying, the CBR frame is very overengineered for the 250 motor as are most frames from that period.
For my VFR frame I can get more room for the top pipe by using a late model GRXR shock which are much slimmer than stock. For front engine mounts I haven't weighed up wether to go cradle or hangers like on the NC21.
I was speaking to a mate back in the UK the other day about TI rods and he's recomended Carrilo. He's guessing about US$1000 each so they will be way down the track. Gotta crawl before walking, let alone running.

Mark
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Joined: Thu Oct 25, 2001 1:01 am
Location: Up Norf

Re: NS400R / CBR250R

Post by Mark »

Having seen a few NS motors in various frames, I'd say the big advantage with the CBR is the available space to package the carbs and airbox, and as Ian says, space to actually work on the bike.

The VFR frame is effectively just wide enough for a twin cylinder engine, and the RGV and RS obviously use the same twin cylinder engine. The NS engine is a wee bit wider...
Mananon wrote:I was speaking to a mate back in the UK the other day about TI rods and he's recomended Carrilo. He's guessing about US$1000 each so they will be way down the track. Gotta crawl before walking, let alone running.
If you speak to Mr Wright nicely, I'm sure he'll solve your rod problem for you, and charge you less than the price of a single Carrillo rod :wink:
If it ain't broke, fix it 'til it is.

ian wright
Posts: 155
Joined: Sun Oct 02, 2005 8:16 pm
Location: huddersfield

Re: NS400R / CBR250R

Post by ian wright »

It's been a while as working on customers bikes and engines has been slowing progress down but have soted a few things lately.

Work done so far -

Engine -

Bottom end built with recon crank using TZ250 rods
Gearbox with uprated gears
Fireblade clutch

Top end bored to 61mm and tuned (444cc)
Heads bored to 61mm
Reed blocks and rubbers sorted.

I'll be fitting the top end to the engine in the next few weeks and slotting the motor in the rolling chassis.
Pipes, ignition and everything else should be before Christmas.

As the standard 475cc barrels are now making 80bhp I'm moving target power from 90 to 100bhp or else it won't be worth bothering !

Will post some pics when the motors in.

Cheers Ian

luggy
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Re: NS400R / CBR250R

Post by luggy »

now , whose bike and engine was that , must be a very disturbing customer there, dont let anymore get in your way , as we would all appreciate the outcome of this project
:mrgreen:
gravity is an extreme painful thing !

Mark
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Joined: Thu Oct 25, 2001 1:01 am
Location: Up Norf

Re: NS400R / CBR250R

Post by Mark »

luggy wrote:now , whose bike and engine was that , must be a very disturbing customer there, dont let anymore get in your way , as we would all appreciate the outcome of this project
:mrgreen:
Probably best you put a cover over your bike for a while then Luggy :wink:
If it ain't broke, fix it 'til it is.

luggy
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Re: NS400R / CBR250R

Post by luggy »

mark,
if you look very closely at a ns, you will find a Ride by ..... date, otherwise it will go off,
so i am going to ride mine ( and get punished with the parts that wear)
:mrgreen:
gravity is an extreme painful thing !

ian wright
Posts: 155
Joined: Sun Oct 02, 2005 8:16 pm
Location: huddersfield

Re: NS400R / CBR250R

Post by ian wright »

A bit more work's been done on the bike now including :

Marchesini wheels / Ebay
Ducati 999 320mm front discs / Ebay
CBR600RR 2006 front end / Ebay
Tyga NSR250 Suzuka 8hr endurance race fairing / Jap 4 Performance
Honda RS250 / 2010 race seat / Hi Fibre

Another sub frame needs making to fit the seat better, pipes need making, swinging arm top bracing, wiring, clocks mounting, painting & setting up.


The tank is to be modified, it's going to have holes cut in it either side where the tank is recessed for the bars at full lock, the holes will have wire mesh covers to act as primary air filters, the holes will feed cool air into the top of the air box (above a secondry filter to slow the air down) rather than drawing warm air in from the rear cylinder and pipe. The upper vents in the top fairing should aid induction by flowing air upwards towards the vents, can't wait to hear the induction roar / noise !

Hopefully if everything goes okay it should be finished while the sun still shines this year, if it ever decides to come out that is !

Cheers Ian
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colbo
Posts: 4
Joined: Thu Dec 21, 2006 10:49 pm

Re: NS400R / CBR250R

Post by colbo »

apologies to resurrect an old thread, but how did this build turn out?, I'm curious to see how the petrol tank looked after the mods were done

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