bigger carb more speed were do i get

[speed demon]

8) my mate on his rs has a bigger carb on is rs 125 and its all standard apart from the carb and it f*cking batters my bike in acceleration is it possible to get a bigger carb for the nsr 34mm or higher if so were from and what changes will need to be made to accomadate this carb thanks for your answer

[Dan]

the RS should beat u n e way

[craigT19]

mallosi do a larger carb for the nsr not shur how much it is but theres pics of in on there web site,

dont forget a standard rs will beat the nsr hands down anyway, it has a tuned engine:) but thats why they have a bad rep for reliability
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Bikes owned :- 2001 nsr125, 1999 zx6r, 2006 yzf-r1, 2009 xmax 250, 2012 yzf-r1, 2015 MT-07
Current bike : - 2016 MT-10
BCF member pops. sadly missed 1945-2003

[Stevo]

The big carb if set up right might give you a small powerboost at high revs, but it wont be much, if the rest of the motor is std. if you have a 28mm carb then going to a 34mm will make a difference, but expect to loose your midrange completely, and you probably wont be able to use full throttle without bogging until at least 4-5k rpm. The bigger carb will almost certainely mean binning the airbox and having to run with a large K&N clamp on type filter. This will mean alot of time and effort needs to be spent on jetting to get it running properly without flatspots etc. The gain in power that you might see on a dyno could be misleading, as changing the filter will probably have more effect on power than the bigger carb itself will. I wouldent expect more than 1-2hp gain at the most, and as i said drivability will suffer. If you really wanna smoke your m8's RS125 then id say that the best way is to have a 160cc big bore kit fitted like Polini/malossi, as if its done properly then it should remain as reliable as std, and you dont have to tell anyone that your NSR is 160cc's right?

[Kickstart]

Hi

I think the Malossi kit is just a 30mm carb, but not sure.

The problems you will have with the larger carb are increased fuel consumption (the extra power doesnt come free), needing a new air filter (although you might be able to force the old airbox onto the new carb), and needing someway of opening the throttle fully. The RS uses a small round box in the throttle cable to gear up the cable (so you pull the cable 10mm, and the other end of the cable moves 12mm, or so), but this gives you a heavier throttle. Also the carb rubber (the rubber piece that the carb slots into, which bolts to the engine) will almost certainly not accept a 34mm carb. On the Aprilia it is easy as the RS was sold with a 34mm carb, so you just by the other carb rubber.

As to power, the old AF1 managed 22hp with a 28mm carb. The RS125 with a 34mm carb managed 28.5hp (PB road test figures). How much of that is due to the carb, and how much is due to improved exhaust and porting I am not sure. I would guess that about half that power difference is due to the carb.

A bigger carb will give plenty more power, and I would say all through the rev range. However, if you open the carb too far at particular revs then you will be making less power.

All the best

Keith

[Stevo]

Hi Keith yeah id agree with what you say, but id still expect low end power to fall with the bigger carb, as the airspeed would be lower through it at low revs, than the std carb. I remember reading about someone having an RG500 tuned with the target to reach the claimed crank 95bhp at the rear wheel. They tried bigger 36mm carbs, but the motor would not hold a steady load on the dyno nor accept full throttle below 5k rpm. They then found that the power increase they had found had little to do with the big carbs, but the fact that the airbox and intake ducting had been removed, and it was the increased airflow that was responsible for most of the power gained, rarther than the big carbs, which actually made the bike run worse for the most part. Having said all this, i have heard that the modern large bore flat slide carbs like those used on MX bikes (Keihin PWK/ Mikuni TMX) are very good at responding to the throttle even at low speeds, as they seem to promote a higher airspeed through the carb at all times when compared to a normal roundslide carb.

[Kickstart]

Hi

I agree that you wont manage to pull full throttle. Thats why most big bikes use CV carbs, which only open as much as the airflow want them to, except for some of the homologation specials where the extra power of a slide carb was important.

The VHSB Dellorto 34mm carb used on Aprilias is a flat slide carb

The old Rotax 127 engine used in the 1987 model AF1 was also available for kart racing. In kart race spec it ran on a 38mm carb

All the best

Keith

[Ropehead]

A stock bike with a turbo will piss all over any bike nomatter how much u have spent on induction kits, race exhausts, new reeds BLA BLA BLA.
Just stick a turbo on ya bike. Get A HOLSET one!!

OHH but it might blow up..... well it would go shit fast before it did!!

[Kickstart]

Hi

Anyone ever heard of a 2 stroke running with a turbo? Would certainly screw up normal 2 stroke tuning, and given the need to fill the crankcases then transfer the fuel / air to the cylinder I doubt it would give any usefull power increase.

Now a nitrous oxide kit could give amusing results, if you have a large piston budget!

All the best

Keith

[Guest]

most gains come from pipe , after that is porting and head work , carb dont yield much with stock setting ,so unless you got everything else done i would not recomand a bigger carb ,the manifold and rear carb from 88 to 89 rgv 250 or rg125(fun) fits into nsr , they are 32 to 34mm depending on year ,or fit 39mm from cr125 motocross ,all found from breaker , problem is the original box must be scraped which increase the noise plus you must spend lotsa time jetting ,another option is to bore the original carb to 31mm

[Hunter]

Does anyone have any ideas about the size of the jet an RK comes with? Usually is this number etched on the jet itself?

Thanks

[uglykidjoe]

check out this deristriction kit for an rs on at the mo

https://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=1746961192

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get in ma belly.

[Swede]

Keith Walker, I have the malossi 180cc kit, whitch jetting should I have for that cylinder? 150? 160? Or what?

[Kickstart]

Hi

If Malossi cannot tell you, jet it as rich as you think it might need to be and then do plug chops and work down

All the best

Keith