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NSR to NS400 carb. mod


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Binka

 
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NSR to NS400 carb. mod

Fri Dec 30, 2005 1:50 pm » Post: #1 » Download Post

Have we anyone out there who has used 3 x NSR34mm's in place of the stock (pea shooter) sized carbs on the NS400R ?

Any issues to be aware of or things I need to know before I start massing the parts ?

Thanks.
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Andy
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Fri Dec 30, 2005 1:58 pm » Post: #2 » Download Post

Bill Limb built up a bank of three NSR carbs for an NS I believe, and I think Dave "Elegy" Reynolds was going to do the same, but he's not been around on here for a couple of months.

Try a PM to Matt Grant too.
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mat grant

 
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Fri Dec 30, 2005 2:57 pm » Post: #3 » Download Post

Hi, I have done this conversion on an NS engine in an RGV frame, only just ran it for the first time a few days ago after a *GRRR* problem with broken 500cc barrels.

Anyway you need two sets of NSR carbs, I used MC21, and 1 set of NS carbs to use the brackets etc.

The biggest problem is you have to bore out the NS carb to reed rubbers to allow the NSR carbs to fit. I got a company in Reading to do it for me, cost about £40.

The choke is different, the throttle drum off the NS400 also has to be used, and on mine I had to file it down in one place (or a bracket or something) to get it to open to full throttle. Somewhere on the NS400 forum there is a post about it.

I have no airbox, will have ramair filters due to space constraints, and I went for 192 jets in the front, and 195 in the rear - this wasn't done scientifically - just a guess to give me a safe starting point. I've not ridden it yet.

Hope this helps... Laughing

Cheers, Mat.
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Clarkie

 
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Fri Dec 30, 2005 4:02 pm » Post: #4 » Download Post

I'm curious about this one.
The JHA NS carbs are simply bored out stockers.
Not sure where the gain is over this and a triple set off an NSR?
Certainly unsure about the gain vs. ££ equation?
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mat grant

 
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Fri Dec 30, 2005 4:47 pm » Post: #5 » Download Post

Hi,

The NSR carb swap cost me £20 for a second pair of NSR MC21 carbs, £40 for the work to the rubbers plus about maybe 2 to 3 hours of cleaning and fiddling, plus about £10 in new main jets. Someone with the right sized pillar drill could probably save the rubber work.

How much are the JHA NS carbs?

Mat.
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Binka

 
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Fri Dec 30, 2005 4:50 pm » Post: #6 » Download Post

Cheers for that, Matt..
I'll start sourcing parts then.

I've got some carbs being bored so it might be a good idea to get some NSR250 carbs opened up a tad.

Thanks again.
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mat grant

 
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Fri Dec 30, 2005 5:15 pm » Post: #7 » Download Post

Hi,

I've got one NSR carb left over, but it's promised to Steve Moore off the RGV forum, he's building an NS/RGV as well.

One other thing I forgot to mention is you have to drill the fuel pipe area out of one NSR carb to make it the 'middle' one.

Mat.
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Matt@TYGA
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Sat Dec 31, 2005 8:35 am » Post: #8 » Download Post

Interesting thread.

I recently bored a set of NS400 carbs for a mate, but haven't got around to putting them back together yet. Got to get Andy's carbs put back together first or I'll be in trouble. Shhhh.......don't tell Andy Exclamation

I thought about the MC21 carbs being used instead but seeing as matey wasn't too bothered I never looked too deeply into modifying the carb insulators. The NS carbs are tiny by comparison.

I got the job basically because this guy had seen the Jha conversion and had asked for details. Just bored out stock new carbs was the answer so nothing fancy, and seeing as he had three sets of carbs he donated on to the cause.

Let us all know how it goes with the 21 carbs. Gotta be better than those piddly little standard things.

Anyone thought of making, or done a big bore 400?
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mat grant

 
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Sat Dec 31, 2005 10:39 am » Post: #9 » Download Post

Hi,

I 'had' a set of Terry Shepherd 500 conversion barrels and pistons to go on the NS/RGV, but they got broken by a courier.

A few guys on the NS400 forum have got 500 conversions. The only dyno chart I've seen was 70 bhp - Although someone told me they had a dyno trace for 90.2 bhp, but I haven't actually seen it.

Mat.
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nsr.wayne
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Sat Dec 31, 2005 12:07 pm » Post: #10 » Download Post

Binka,Apex have 2 mc21 carbs for sale they want £60,Mat Grant has 1 so there go theres 3 for you Wink
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Clarkie

 
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Sat Dec 31, 2005 12:21 pm » Post: #11 » Download Post

Matt
500V3?
Yeah - where have you been? Laughing
Mine has your RSW bodywork on it.
Engine is in an RVF frame.
ETA ......Spring.[please]
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Binka

 
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Sun Jan 01, 2006 11:50 am » Post: #12 » Download Post

nsr.wayne wrote:Binka,Apex have 2 mc21 carbs for sale they want £60,Mat Grant has 1 so there go theres 3 for you Wink


Cheers for that chap - I have a source for carbs and I'll be asking him to check availability soon (ahem).

The stock NS carb seems a waste of time to use as a starting point so the NSR carb is the default.
As in all strokers and having spent a lot of time looking at the NS400 engine, it is as usual on strokers, all down to getting extra induction volume and then getting the pipes right to get the gas out.

I'm not going for the 500cc conversion, the extra piston weight can't be worth much bearing in mind there are 3 pistons but I am going to have some pipes made just for the engine.

90 at the wheel should be easily reachable with a 400 motor provided the stock pipes are binned and the motor is reworked from the gearbox up.
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Clarkie

 
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Sun Jan 01, 2006 11:54 am » Post: #13 » Download Post

Binka
90brake?
Really?
You'll need CR barrels or similar for that. Is that your plan?
That's a wheezy old porting map the stockers have got in there!
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Binka

 
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Sun Jan 01, 2006 12:06 pm » Post: #14 » Download Post

Well, I can hope Razz

It needs a total rework in the porting, bin the ATACs and it needs a lot of crank case work.
The pipes are just so hopeless and, as asked, the carbs are pathetic.

If it makes 90 then hey, great. If she falls over and makes 75 -that's ok too... it's all good fun.
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mat grant

 
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Mon Jan 02, 2006 7:32 pm » Post: #15 » Download Post

Hi,

I'm not an expert but I can't see why 90bhp isn't achievable from an NS with big bore, porting, carbs pipes etc.

Someone posted a Shepherd NS500 on the NS400 forum which had 70bhp, but even 80s 125s can be made 30bhp - so you only need to match that to get 90 from the NS.

I think it's got to be down to the lack of numbers of people tuning the NS. ie if someone like Mark Dent got hold of one, and did all the development work...

I *nearly* did the conversion to 2 CR barrels on the NS, but it was too much work versus the 500. I'm now planning a really daft barrel swap, plus stroke enlargement, not sure if it will be feasible yet, but if it comes off it will be good.

Happy new year!

Mat.
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