As the title says, I've just fitted 112 dyno jets to my carbs after having them cleaned and I was wondering how have people that have already done this, how many turns do you adjust the air screw by?

I currently have mine set at 2.5 turns

Cheers
Andy

any ideas?

Im not a techie type, but what i would do is set all screws at standard turns, then one by one i would turn them in until the revs start to die then out until they started to rise and set them in the centre.

I've got a similar set up on my NC23 and I'm running with the airscrews about 2 turns out. It seems to run fine (although there is room for improvement) and the plugs are a decent colour but really it really needs setting up on a dyno.

Have you changed the air filter? I've cut out the paper elements and replaced them with foam.

CB1pod70 wrote:I've got a similar set up on my NC23 and I'm running with the airscrews about 2 turns out. It seems to run fine (although there is room for improvement) and the plugs are a decent colour but really it really needs setting up on a dyno.

Have you changed the air filter? I've cut out the paper elements and replaced them with foam.

Cool, yeah changed the air filter a coupe of months back so still pretty clean. I have seen the foam filters but I wasn't too sure about them to be honest. Any Good?

I'm just talking to RJS Superbikes now who are based at Mallory Park (just up the road from me) and they charge £40 for a dyno run, then however much for the time it takes to get it set-up up correctly. I might just have a dyno run and see where it's at and make some tweaks based on that.

So the bike is back together, jets fitted, air screws at 2.5 turns... and it bogs out really bad.

I checked the choke cable earlier as I could only pull it out a fraction compared to before i stripped it all down and the choke seemed to be out a little. So I've adjusted the cable and it seems to be the same as before now, but won't know until test ride number 2 later.

If this doesn't resolve the issue has anyone else got any ideas of what it could be??? The bike pulled really well before? Could the standard air filter be restricting it?

Cheers
Andy

You have probably checked, but float heights may have a bearing and stopping fuel. Another wild guess if your using softer fuel pipes than standard creating a vaccum.

I had the carbs off again last night... Checked them and everything was fine. I haven't balanced the carbs since having the bike, how hard is this to do?

Then I think it's a case of setting up the pilot screws one by one.


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You don't adjust the pilot screws to balance the carbs, it's the screws on the sprung throttle linkages between the carbs that you need to adjust. You will need a set of vacuum gauges to do this however. Balancing the carbs mainly affects how smooth the bike idles and the low speed performance so is unlikely to be your issue here.

Are you coming to Cadwell this weekend? I could do it for you there.

CB1pod70 wrote:You don't adjust the pilot screws to balance the carbs, it's the screws on the sprung throttle linkages between the carbs that you need to adjust. You will need a set of vacuum gauges to do this however. Balancing the carbs mainly affects how smooth the bike idles and the low speed performance so is unlikely to be your issue here.

Are you coming to Cadwell this weekend? I could do it for you there.

I was getting a little confused with it all and after a good read of the Haynes and a talk with GF all is good.

GF broke it down nice and simple and explained what each screw or jet does at certain rev ranges.

So the pilot screw - up to around 2000 rpm (tick over)
Pilot Jet - 2000rpm to 8000rpm
Main Jets - 8,000rpm+ but I prefer the the explanation from GF, "when the bike is singing"

The bogging down was the CDI putting the bike into limp mode, this has now been resolved.

Bike ticks over nice, pulls well till the higher rev range but the bike needs to go on a dyno to get the AF ratio set-up properly to cure this.

So all in all, pretty happy at the moment.