This bike has me really frustrated

Its a 1990 UK NC30 done only 7000 miles Its supposedly had the dynojet treatment I have the sheets that show this the standard exhaust has been modified to an absorbsion type it has 124/126 jets 35 pilots and a K&N filter in a standard airbox

The bike stood for 15 years I have cleaned the carbs thoroughly twice even the brass jets were starting to corrode they were the most filthy carbs I have ever seenIts starts easily and but wont rev past 5 or 6 thousand unless you put the choke full on then you get to 10 thou then when you roll it of it back fires as though its weak I rode it to the MOT place with great difficulty it would not go over 40 ! I did not try the choke in case it flooded and I had to walk home

any Ideas



In the cleaning I have lost a float valve filter does anyone know where I can get one ?

If things dont iprove the best solution will be a week in the local Chronicle that should cure it

Make sure you have the carbs in the rubbers properly, and that they aren't cracked or perished. Sounds to me like it's drawing air in from somewhere and running lean, hence you needing to use full choke to get it to run properly.

the easy answer is to stop riding in a dangerous state and spend a few hours putting the carbs back to std setting as it sounds fooked.

Have a read of Cammo's carb guide, follow it and you will get a bike that works..

There is nothing wrong with the carb settings I have the Dyno printout that shows the improvement over the standard settings

There are no air leaks or perished inlet rubbers the carbs have been cleaned twice very thouroughly and have now been ultrasonically cleaned

I have read the article on carburation very good it is too

It has new plugs and a brilliant spark you would swear the was an air leak but I cant find one

i had a problem where mine wouldnt go above 40, unfortunly it happened on the a1 and i had to ride on the hard shoulder for 30 miles until it died completly, the problem was the regulator/rectifier the wires had come completly out from some one elses boj job atempt of fixing a faulty unit, it could be electrical damaged wires or corroded terminals

if the carbs were that bad, i suspect they are done for.
either send them off for ultrasonic cleaning, or simply change them for another set, and transfer your slides and jets over.
if the carbs are troublesome, less stress to simply change them

I fixed my carbs up from cammo's thread and worked a treat until it started running like a bag of nails and wouldn't pull, the vacuum tume had cracked and so had the main fuel pipe, on the bike it didn't show any signs of leaking as the crack was on the inside bend radius.
I would listen to advice above and don't rely on a bit of paper as you don't understand it's history by the sounds of it.

Thats the frustrating bit I know the place where it was dyno tested and that it did 500 faultless miles a week later around the IOM and then was stored in a dry garage for the last 15 years

is it a new dyno print out? Or one from 15yrs ago?

You don't mention what exhaust you have fitted, is it the same one as was fitted when the tubing work was done? To be running those size jets it must be a pretty fruity exhaust.

I would do what has been suggested and either get a known working set of carbs or return these to standard settings then work from there. You have checked the electrical system I take it seeing as you've stripped the carbs twice now.