flat spot / jetting

[lee.pb]

Are you running dynojet jets?

I'd still say 110 is too lean for a full system like that quill...have you any dyno sheets?

no have nothing at all along them lines, quill say there is no need for rejetting on that system and th eowner is a mate.
carbs came on the bike so assume they hadn't been played with.

[alexwitham]

110 will definately be too lean mate.

[Cammo]

carbs came on the bike so assume they hadn't been played with.

They all seem to have been mucked around with at some stage, at least all the carbs I see have.

[Cammo]

i'm a little confused about the air hole location?

Realsitically it's not wise to just use some of the nc30 hrc carb setup parts, the setup was designed to be run with all the parts/settings. You can get replica parts from Rick Oliver. What you can't get is the hrc velocity stacks, and you'll need to do some mods to get the carbs to work without them.

You can cut down the standard stacks nicely and easily to improve top end power a little, but they don't have the function of the hrc stacks.

The standard air jet opening is what's causing your running problems when you have no filter. This took me personally ages to clue onto until some members posted the technical workings of carburetors on the old forum, and many people made the mistake of trying to remove the filter/airbox and expecting the bike to run properly prior to this information.

The hrc velocity stacks are designed to restrict the carb air jets by shrouding them:




I think you have 2 options to get the bike running properly:


1. Restrict the air jets if you want to run with no filter. The hrc stacks are very hard to get now, but you can restrict them in other ways which is just as effective. An easy way is to tap the air jet hole to take standard carb brass pilot jets, and then drill these to the required size (2mm). This is just restricting the air jet opening to 2mm (standard is about 4mm I think).

Without the air jets restricted and no filter (your current setup) you'll need to run 160+ size main jets, and it will probably have a big midrange hole that you might be able to ride around. This is what your bike is doing now but the main jets are so small that it won't even rev through this midrange hole. The engine can't handle the change from needle to massive main jet fuel requirements.

The answer to get around this is simple - restrict the air jets. With the air jets restricted you'll need 138-150 sized main jets (depending on the size you restrict the air jets to - start with richest jets first and work down) and it will rev cleanly all the way through even when the jetting is out a bit*.

If you decide to restrict the air jets to use the hrc setup, you'd be best off getting the rest of the hrc replica parts:
- needles (Rick Oliver replicas or possibly NC24 [8ZC] needles)
- emulsion tubes (Rick Oliver replicas - although it is possible to mod standard ones to hrc spec)
- pilot jets (standard keihin parts)
- main jets (standard keihin parts)
- hrc fuel tap mod and fuel line coupling so you can disconnect fuel easily

The hrc setup will give more slightly more power over a well dialled standard type carb setup (the open carb setup pretty much uses all the air it can get without resorting to low levels of forced induction like ramair), and gives quite a much stronger throttle response which is nice. And it sounds agro!



2. Install a standard filter (not aftermarket!), and set the carbs up to suit. They might need anything from 120-128 main jets depending on what standard air filter flaps/shrouds it's running. If you can see exactly what induction parts it has then you can get the jetting nearly right without much testing.


Whichever you decide it will be a joy on the track when it runs properly!



*Off topic, but I see that many ram air setups have the air jet holes blocked entirely. This effectively lowers the main jet needs even further (probably in the range of 132-136 size). You could block the air jet entirely with the hrc setup, but I chose to go with the recommended honda nc30 hrc setup. Some flow through the air jet is desirable apparently as it helps emulsify the fuel in the tubes. No seat of the pants data to verify this!

[lee.pb]

cheers dataracer for the great responce, spoke to rick oliver last night about the issue or should i say issue's.
his responce was if your not looking for every little bit of power then resort back to want you know works and easy to set up.

1. replace hrc airbox with standard box but with snorkle removed.
2. modify standard filter to take less restrictive foam.
3. replace main jets with 120's and add a set of rick's needles.

everything should be fine then, seems like running no air filter can be a right pain in the arse without lots of time and effort.
sounds like a plan to me, dont fancy being on another track day doing 1 lap in first gear again.
going to go down the route of rick's but going to added the carb scoop just to draw in cool air, and i hav just ordered one.

hopefully will have uut done over the weekend if all bits turn up, then it will be a blast down the road sorry track...... to check it all out.

keep you all informed.

[Cammo]

everything should be fine then, seems like running no air filter can be a right pain in the arse

Yes.

going to go down the route of rick's but going to added the carb scoop just to draw in cool air, and i have just ordered one.

Forget the air tray, it will change the jetting requirements and could cause more trouble than good.

[lee.pb]

email sent to rick oliver for the carb internals and there's a standard airbox on its way too.
hopefully everything should be spot on this time, look out oulton park 30 march 2010.
cheers all again

will keep you all informed on the progress.

[Neosophist]

email sent to rick oliver for the carb internals and there's a standard airbox on its way too.
hopefully everything should be spot on this time, look out oulton park 30 march 2010.
cheers all again

will keep you all informed on the progress.

Dataracers right about that carb scoop.. will throw your jetting out :/

[Indiana Jones]

is it possible to get the hrc velocity stacks from the uk?

Not really, but you can restrict them in other ways. If you tap the air jets to take a allen head bolt you can then just drill this out to the required size (2mm).

Blatant show off pic of my setup:

Hi,
Hitting the dyno on Tuesday,just wondering about the 2 pipes that I see in your photo,they come from each bank of carbs.
On my carbs,they just vent into fresh air,yours are connected into something?
They are the black pipes running by the left rear carb top.

[ChowderV4]

just noticed something said about the standard air box with standard snorkle.

my airbox is missing the snorkle, will this cause any set up issues or is it not a big deal.

sorry for stealing the thread a lil