Help - tuned engine misfire and not revving out,

[Drunkn Munky]

Perhaps the other way around is to ask how a proper ram air sysytem behaves without any airflow? IF the carbs have been modified is it possible that it will only run right with a pressuriesed airbox?

Yes if the carbs have been modded for ram air then yes it will only work with that setup, im not sure what you need to do to the 35 carbs for ram air as i had the 30 carbs and someone else modded them but i know theres various plumbing mods that your need to reverse. What you need is good standard set to compare them with.

Shorts stacks For what its worth i have a set of 35 carbs ive built for the RLR engine and they have short stack, 116 mains, 1mm needle washers and HRC slide springs. its jetted for the TSR system which rumour has it likes big jets but your MHP system shouldnt be far off.

Also im not saying the fuel pump couldnt be made to work but you dont need it for a non ram air setup, NC's are sensitive enough with regards to fueling without adding the problem. I like the idea of having one so it shuts the fuel supply off automatically but im not brave enough to try it Mine is a road bike now and i cant afford it to go up in flames!

[Morespeedvicar]

Hi, have you tried it under load at all, like a quick eerr test anywere? my nc30 wont rev very well when not under load, its a bit rich, but works fine when riding.
Best way to look at mixture is a dyno run or ride it and do a plug chop( bit of a pain to do, but free). You'll banging your head against a wall trying to fix fueling faults by bliping the throttle in your drive, it may just be choked up an need a good thrashing to clear it out!
The Air jets could be blocked up, there a bitch to unblock, micron did my FZR4 and blocked up the air jets(before i got it) took me ages to get it back to how it should be.
Do you know anybody with another NC35 you could borow a standard CDi unit or carbs off?
Cheers
Ian

[spanky]

Thanks Cammo, Vicar and Munky..

I went back out tonight with the intention of putting all the ram air stuff back on (including jets) on the basis that I should stop worrying, there was never anything wrong with it and it'll run perfectly when under load and moving. Then I had another look at the air jets and sure enough, there was a bit of wire poking out of the top of one air bleed jet on each carb which hopefully explains why it wouldn't run properly with standard induction and sensible jetting.

I've pulled the wire out of each jet and stuck it all back together with standard airbox, nozzle, flap and filter. It's a bit late for starting it up now so I'll have a go tomorrow and report back. Either way, I'll take it to Silverstone on saturday along with a box full of the ramair stuff and try both configs out and see if the ramair a) works and b) makes any difference.

Cheers,
James.

[CMSMJ1]

Not sure how I missed this one..

I tried a simlar thinkg a while back - bodged ram air. SOunds like it is leaning out as it gets to main jet and just starving to death. I run 130s on RVF carbs on my road bike and had tried 148/150s on the ram air. I now have no lid on the box and but standard rubber flap - it breathes OK from under the tank.

The carbs just do not like it when they cannot get a steady pool of stable air to suck in. I would be prepared to fit a complete std setup to the bike to get it running as going ona TD wiht a bike tat does not work is a sure fire way to get mightily pissed off.

WHere you at? If you are local to me I'll loan you my carbs and setup off the race bike - properly standard but jetted for a full race system and if you fit them I recon it wil work no worries.

[spanky]

Grrrrrrr.

Found a pic of some carbs on here earlier so thought I'd compare mine before I started it up.

As well as the jet that was blocked with the wire, one of my other jets has been blocked off, only slightly more permanently:



I'm not sure if the original jet has been removed and replaced, or if the hole has just been filled in - I can't see the outline so guessing it's the former. do the brass inserts things pull out or do I need to drill out the filler (if there is any)?

Anyway, I've given up trying to de-Ram air for now and put everything back as it was, including bits of wire down the other jets. I gave it a quick check and if anything it seems worse than when I started, really rich despite tidly jets. I'm hungry and past caring so have given up though.

Plan for saturday is to take it along and use it as a test day....I might swap over to normal airbox and jets on the day and see if it'll run with the blocked one above. I'm also taking my 600rr as backup.

By the way, thanks for the offer of carb loan but I'm down near Watford so a bit of a trek...

dinner time...
James.

[Cammo]

It might be best to get hold of a standard set of carbs mate if you can't get these sorted easily.

[spanky]

So I'm back from sunny Silverstone and guess what....it ran fine. In fact it ran very well. Slight flat spot at 8k but not enough for me to rush to fix it.

While I'm happy it's all good, I feel like a bit of a plum for spending a fortnight trying everything I could think of to fix a problem that wasn't there. Moral of the story (and as morespeedvicar said above) is that blipping the throttle and performance under load are two different things.

One other silver lining - I know a lot more about ram air and keihin carbs than I did a week ago so thanks all...
James.

PS one final question just in case anyone knows the answer - what exactly is each of the four air jets for? I know one of them links to the emulsion tube but not sure which and no idea about the other three.

[Morespeedvicar]

Hi, well pleased it runs ok, three or the air jets will be for the main jet emusion tube, tickover emusion tube and i would think one for the choke, tho its been a while since i've taken me carbs to bits so not 100% sure.
Carbs are picky things to play about with, there never seems to one exact setting for everything unless you leave everything as honda intended.
Cheers
Ian