9000rpm sluggish under load

[chownsy]

Hi all ,

I have a problem with my bike and its not coils, not HT leads, not exhaust, not battery, not rectifier causing the problem, not radiator, not carbs that I can tell as I have cleaned, balanced and put 115 jets in, not the linking rubbers between carb and engine as these are new with new clamps.

The problem seems to be under load when in any gear and the bike is around 9000rpm to 11000rpm.

I can only think that the issue is the TDI unit.

As some may know this bike is an NC24 but has the following:

NC21 Engine,
NC21 wiring loom
NC21 TDI unit (long one by battery)
NC24 carbs jetted to 115

The spark plugs are new but maybe not gapped right

Another thing is it don't return to idle really fast, it gently returns so that may be okay. (checked for air leaks with brake cleaner and there are none)

I really need to get this on a private road or somewhere to see how she does top end as before I stripped and rebuilt the bike it did the same issue but wouldnt get about 70 very easily (not that I need to, just its how sluggish it felt), now it will get over 70 but has the sluggish hesitation at 9000rpm.

Any help will be appreciated. I was thinking maybe the TDI unit is at fault due to ruling out all other issues but unsure.

Richard

[Cammo]

It sounds to me like it's fuelling related - either running too lean or too rich. Are you running a standard honda air filter? Standard airbox assembly? Does the nc24 use a rubber flap in front of the airbox/under the headstock like the nc30 does?

The 21 and 24 carbs have quite different fuelling setups, however they should be fairly easy to get to work on each engine. A quick dyno run would probably point you in the right direction far more quickly than trial and error with jet sizes.

The revs not dropping to idle speed quickly is usually caused by incorrect pilot screw setting. I'd start by adjusting 1 full turn (360 degrees) in or out, seeing if it's better and then adjusting in smaller increments from there (don't forget to check to see what they're all currently set at first by counting how many turns they take to close so you can get back to your starting point if need be!).

I doubt the cdi would be responsible for your issues, if it's a standard honda unit they either generally work or not at all.

If you put the bike model in the subject heading some resident 21/24 experts will no doubt soon show up for more advice!

[Neosophist]

It sounds to me like it's fuelling related - either running too lean or too rich. Are you running a standard honda air filter? Standard airbox assembly? Does the nc24 use a rubber flap in front of the airbox/under the headstock like the nc30 does?

The 21 and 24 carbs have quite different fuelling setups, however they should be fairly easy to get to work on each engine. A quick dyno run would probably point you in the right direction far more quickly than trial and error with jet sizes.

The revs not dropping to idle speed quickly is usually caused by incorrect pilot screw setting. I'd start by adjusting 1 full turn (360 degrees) in or out, seeing if it's better and then adjusting in smaller increments from there (don't forget to check to see what they're all currently set at first by counting how many turns they take to close so you can get back to your starting point if need be!).

I doubt the cdi would be responsible for your issues, if it's a standard honda unit they either generally work or not at all.

If you put the bike model in the subject heading some resident 21/24 experts will no doubt soon show up for more advice!

If I had to put money somewhere id put it with Cammo on this one, im 99% sure he`s right.

Have you had it dynod and got a reliable fuel air graph.

What needles are in your carbs, what emulsion tubes, what airbox? do you have the correct rubber stacks on the carbs, are the needles in the right way, slide springs?

There are many things that will effect the fuelling.. a good fuel airgraph will show you whats up.. it sounds like its either going lean or rich at the top end.

slow return to idle also points to fuel. are the throttle cables ok, butterflies oening? pilot screws/ balance settings good? sticking throttle slides / needles..

pain to get the carbs off to check so id just dyno it first, get back with an a/f graph and can point you in more of where to look and what to do.