NC35 track bike dieing at end of session

[[STU]]

HI all,
Ive had my NC35 track bike for about 4 months now and have done 3 track days.
The bike seems to perform beautifully for the entire day, with the exception that at the end of each session when i come into the pits, As soon as the bike revs drop to pit lane speed the bike struggles to stay running unless im continually revving it. As soon as i stop it dies.
It doesn't appear to effect it for the next session and starts up without drama and idles easily. I thought that perhaps the plugs might get fouled easily at the end of a session after working hard. but after inspection that doesn't appear to be the case.. Would overheating cause this behavior?
The bike:
*hrc ram air tray,fuel tap and rear ride height shims
*braided lines front and rear
*front and rear suspension re-sprung and re-valved
*new battery,brake pads,chain and sprockets(520 pitch)
*new racetune full exhaust system (im assuming it has been tuned accordingly but not sure to what extent)

I dont know if the carb is stock or not or if the jets have been changed/modified.

Any thoughts would be appreciated.
thanks.

[superlite]

It's definitely carb/airbox related.

Are you running NC35 or NC30 carbs? You say you're running an HRC air tray, but are you running open carbs/filter/airbox lid, etc with it?

And after that, what main jets/pilot jets/needles/settings are your carbs running?

Sounds like it may be running rich to me.

[Cammo]

*new racetune full exhaust system (im assuming it has been tuned accordingly but not sure to what extent)

Don't assume anything!

Any previous owner can bugger up the jetting no end...

The only way to tell what you're running is to take the carbs off and open them up. A necessity to solve an issue like this unfortunately.

Would overheating cause this behavior?

It could possibly (but unlikely) how hot is it getting?? Are you still running the standard fuel tap setup?

[[STU]]

Thanks for the replies guys,
sorry i omitted a couple of things you have pointed out.
Im pretty sure they are NC35 carbs, no filter (all open).
Its running the HRC fuel tap.
It doesnt appear to be too hot.... Certainly the bike is hot and there is some overflow into the bottle but nothing i would consider abnormal. I have flushed the radiator but doesnt seem to be the issue.

Hmm, i was really hoping not to have to take the carbs off. but maybe i have no choice

[montsta56]

I use'd to have a similar issue with my race bike an I put it down to heat soaking into the carb's because they sit in the V, Early RC30 superbikes used to run Air ducts to keep the area in side the V cooler to try an over come this> May be off the mark but it's food for thought.

[[STU]]

I use'd to have a similar issue with my race bike an I put it down to heat soaking into the carb's because they sit in the V, Early RC30 superbikes used to run Air ducts to keep the area in side the V cooler to try an over come this> May be off the mark but it's food for thought.

hmm. thanks. thats interesting. The last few track days have had air temps of 37 C and 42 C so im hoping that maybe heat maybe the problem. I have another track day for May so it will be interesting to see if the cooler temps help the problem a bit.

[montsta56]

Yeah I think it may well be the issue your having. Mine is fine at the start of a race but if you have to come in an line up on the dumpy grid again for a red flag or some thing it can be a pain
I'm not sure how they ended up solving this issue with the later V4's. Maybe a heat shield like a V8 runs??

[superlite]

I'm not convinced that heat is the issue - but would definitely contribute to poorly set-up carbs. I run in hot (Australian) temps with open carbs and don't have any issues. I think you need to get the carbs off and check the settings.

[CMSMJ1]

The HRC tray is used for shelding the carbs from the motor rather than "rma air" as people think. If you don't have a tray, then you could always try one!

[superlite]

The HRC tray is used for shelding the carbs from the motor rather than "rma air" as people think. If you don't have a tray, then you could always try one!

True that. Let it be known to all that a bit of plastic does not equal ram air! Stu does have an HRC tray though.

It's interesting, as I only run the front half of the HRC air tray - so there is nothing covering the 'V' of the engine. Basically my set-up just acts like a scoop under the headstock to deliver air to the carbs. HRC released them this way for the NC21 (for some reason?). Runs a treat in hot and cold. And makes carb removal/installation a lot easier too