Ignition advance key and carb adjusting - SV650.org

17-08-05, 01:39 PM

I've been having a look at the dyno readout on JHS Racing's site after they fitted the new Woodruff key, and I was wondering if shimming the carb needle might fatten up the mixture in the middle to produce a smoother torque curve.

I can see the new key boosts the torque between 2.5k - 4k, where I spend most of my time riding, but it flattens out again until about 6000. Is it fairly straightforward.....?

No, thought not

Sid Squid · 17-08-05, 04:08 PM

Shimming the needles is only really applicable to US bikes, as they don't have grooved needles the same as we do. The idea being that the US bikes will be harder to fool about with as their emissions laws are stricter and include regulations as to what can be adjusted as well as what the adjustments end up giving.

If you want to try alternate needle positions, you may well find that lifting by one groove helps a little, it's hard to be prescriptive as different bikes and different pipe/filter combinations respond differently.

johnnyrod · 18-08-05, 11:20 AM

No point altering the fuelling if you have the stock can and air filter. If you chop them in for more free-flowing jobs you really need to upjet as shimming only richens the midrange but leaves the top end lean (not good). Proper set-up is done on a dyno though.

18-08-05, 12:27 PM

Surely with the slide all the way up the fuel mixture wouldn't alter?

17-08-05, 01:39 PM	#1
Fuzz Guest Posts: n/a	Ignition advance key and carb adjusting I've been having a look at the dyno readout on JHS Racing's site after they fitted the new Woodruff key, and I was wondering if shimming the carb needle might fatten up the mixture in the middle to produce a smoother torque curve. I can see the new key boosts the torque between 2.5k - 4k, where I spend most of my time riding, but it flattens out again until about 6000. Is it fairly straightforward.....? No, thought not

17-08-05, 04:08 PM	#2
Sid Squid No, I don't lend tools. Mega Poster Join Date: Jul 2003 Location: Skunk Works, Nth London Posts: 8,680	Shimming the needles is only really applicable to US bikes, as they don't have grooved needles the same as we do. The idea being that the US bikes will be harder to fool about with as their emissions laws are stricter and include regulations as to what can be adjusted as well as what the adjustments end up giving. If you want to try alternate needle positions, you may well find that lifting by one groove helps a little, it's hard to be prescriptive as different bikes and different pipe/filter combinations respond differently. __________________ If an SV650 has a flat tyre in the forest and no-one is there to blow it up, how long will it be 'til someone posts that the reg/rec is duff and the world will end unless a CBR unit is fitted? A little bit of knowledge = a dangerous thing. "a deathless anthem of nuclear-strength romantic angst"

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18-08-05, 11:20 AM	#3
johnnyrod Member Mega Poster Join Date: Jul 2003 Location: Doncaster, oop norf Posts: 2,128	No point altering the fuelling if you have the stock can and air filter. If you chop them in for more free-flowing jobs you really need to upjet as shimming only richens the midrange but leaves the top end lean (not good). Proper set-up is done on a dyno though.

18-08-05, 12:27 PM	#4
Fuzz Guest Posts: n/a	Surely with the slide all the way up the fuel mixture wouldn't alter?