hi guys, new on here :)

i have a starting issue from cold, full choke but wont start without a tiny blip on the throttle and then it needs a blip to get it to rev up on the choke. same if you then halve the choke it will need a blip to settle it or the revs will drop.the only way to get it to start without touching the throttle is to adjust idle upto 2.5k when warm and then it will sart on the button????

also around 7-8k and 10-11k the bike seems to hesitate slightly in any gear, worse under heavy acceleration.

ive checked the airfilter, cleaned carbs, checked plugs, float hieght but cant seem to get rid of it.

it has 115 main jets in all carbs and 35 pilot jet. i checked the jet sizes with david silver spares and they said some of the nc24's had 4 of the same main jets rather than 112 and 115 jets.

i dont know much at all about carbs,and didnt want to touch the pilot screws due to not wanting to make it worse. but could these be the cause?when the i had the carbs off i checked that the butterflies all opened the same and the rear two are open slightly more than the front? checked it using a small drill blank.

the bike is a 1987 vfr 400 v4 17500 on the clock

hope someone can help

cheers dave

What is the stock pilot screw setting so i have a reference to check it against?

i also get a smell of petrol when sitting in traffic?

cheers dave

NC24's had 115's, if you take out the emulsion tubes that the jets sit in, you'll find the rears have an extra hole in them, make sure there not mixed up.

NC21's has 112's

How did you check / set the float heights?

If it's smelling of petrol either the carbs or tanks leaking. It could be that you have a float bowl pin thats not sealing properly.

Well, if you want to adjust the pilot screws just record how far each one was screwed out by screwing it in until it just seats.

Correct settings are 2.25 - 2.5 turns out.

hi,

thanks for the reply. i checked the float heights as specified in my mates nc30 manual so they are just resting on the spring loaded floatpin but not compressing it.

i havent got any leaks on the carbs or drains, and ive just replaced tank so that is all ok. could pilot screw settings cause this?or is that me clutching at false hope??

i will check settings tonight if i get a chance, failing that ill have the carbs off and check the emulsion tubes are correct.

any other ideas?

cheers dave

pilot screws will just cause a crap / no idle in extreme cases and make it very hesitant to pick up (although slow pick up is normal on a cold engine)

Did you increase the float height? (lower fuel bowl level)
or
Did you decrease the float height? (increase fuel bowl level)

hi

I didnt need to adjust float height, it was 6.8 as specified in the back of the nc30 haynes.

i did check the pilot screws last night, they were all out just over 2turns so seems about right

the hesitations throughout the rev range are when the bike is hot or cold, dont rev it hard when its cold only up to 6k.

the plugs looked ok but would it be worth changing them anyway, they were new last year according to the seller and dont look very old?

anouther thing is when you do get past the hesitation at 10-11k it takes off till the redline in any gear except top of course???

is so do you know the correct plug number for the bike?
cheers dave

I had a similar problem with my nc24, it seamed to rev in like slow motion (by the time you got to full throttle the rev counter was only at about 6000rpm!) turned out to be one of the carb float seats, it hadnt seated properly!

Took it out and tightened it down and it runs nice again now.

christ044 wrote:I had a similar problem with my nc24, it seamed to rev in like slow motion (by the time you got to full throttle the rev counter was only at about 6000rpm!) turned out to be one of the carb float seats, it hadnt seated properly!

Took it out and tightened it down and it runs nice again now.

hi, thanks for the reply. yeah my bike revs quick,slow, quick, slow.. lol nightmare! just stripped the carbs again to ive them a blow out with an airline!didnt have one when did it before!

Neosophist wrote:NC24's had 115's, if you take out the emulsion tubes that the jets sit in, you'll find the rears have an extra hole in them, make sure there not mixed up.

ive just stripped the carbs and check the tubes, there was a 4 hole and a 5 hole tube in the front carbs and same in the rear. im hoping this is the prob, could that cause some of what im describing?

when i stripped them before i bagged each carb up as i took it apart, didnt realise the emulsion tubes were different front and rear, whoever done it before must have done it.

fingers crossed

cheers dave

Hehe oops...

The 5 holes go in cylinders #1 / #3 (Rears) as this slightly richens the mixture as they get hotter than the front two.

Give it a try and see how you get on.

If its got standard gearing and healthy it should pull to the redline in 6th.

Neosophist wrote:Hehe oops...

The 5 holes go in cylinders #1 / #3 (Rears) as this slightly richens the mixture as they get hotter than the front two.

Give it a try and see how you get on.

If its got standard gearing and healthy it should pull to the redline in 6th.

The flat spots are gone!!!! as the emulsion tubes were mixed up so was running rich on one front cylinder and lean on a rear.pulls like a train now!!!!

well happy thanks Neosophist you are my hero


only thing is it still wont start properly unless tickover is turned up to 2k when warm turn it down to correct setting when warm and it wont start and tick over when cold choke or no choke,if you dont give throttle it wants to conk out?? donesnt hold a smooth idle keeps fluctuating?

could this mean my carbs need balancing??



any ideas cheers dave