Choke is pulling itself in & needs throttle to start

[DevelopedBug]

Hi folks, I've just picked up a lovely NC35 but could do with some help as I'm not used to these things!

It all seems to be in good nick, but it won't start unless I give it just a little smidge of throttle while the starter cranks - which from what I've been reading is a bad thing?

Also when I first got it, it was really reluctant to idle, however I quickly noticed that with the choke fully out, and the engine running it slowly feeds itself back in over 30 seconds or so - kind of like it's being sucked closed by a vacuum or something? It coincides with the dodgy idle and eventual stalling. I have to manually hold the choke on for a minute or two to get it warm, and then can feed it in a bit at a time while it stabilises, after that it's fine, it idles sweetly at 1400rpm. Any idea why my bike has decided it's got an automatic choke?!!!!

It's a standard bike, only thing it's had done is have a Scorpion can fitted as far as I'm aware.

Thanks for any pointers!

Dan

[slowsport]

Welcome!

i don't know enough to give advice about the throttle, but there is a rubber boot screwed into the choke pull(located on the base of the choke on the top side of the fairing), if you tighten that it will be harder for the pull to fall back in

[DevelopedBug]

OK, thanks slowsport, I'll have a look for that boot tonight.

Could anyone else shed any light on the requirement to hold the throttle open to get it to fire?

[Neosophist]

Carbs might not be quite spot on, on a well setup engine throttle will usually stop the bike from running..

Dont' forget the bike is going to be knocking on for 20 and many people may have owned it and tried to do 'performance' mods and played around with things.

If the bikes running ok then you can go with the golden rule.. if it isn't broke don't fix it, could be a side-effect of the way its been setup.

However, If your worried take it to a dyno operater and get a run done and have them check bhp as well as fuel ratio (don't worry too much about the fuel ratio), also if you've ridden bikes for a whil you should be able to feel if its not quite crisp. (bear in mind 20 year old carb bike isn't going to run like a modern EFI bike)

but if it's down a lot on power and the fuelling is waaaaaay off then you need the carbs setting up properly.

Theres guides on here how to do it but see how the bike runs before you rip it apart :-) (plenty of people will be able to help).

[DevelopedBug]

OK thanks for the replies guys - much appreciated.

I nipped the nut under the choke up about 1/8th turn and it's sorted the creeping out, so top marks to slowsport!

I hear what you're saying Neosophist, the old girl could have potentially had a lot of grubby hands fiddling with her as there are 5 registered keepers on the V5, and I do wonder with having the Scorpion can fitted if someone has had a play with the jets as well? Carbs really aren't my thing, to date I've only played with fuel injection, and that been associated to a turbo and 4 wheel drive, so I don't mind getting my hands oily, but it looks like I need to brush up on my mid 90's bike knowledge; particularly carbs....

Does anyone know what a C+S kit is? There's one listed on an old sales invoice I got with it.

[hardnutdvd]

C&S = chain and sprocket

[Neosophist]

Cammo has wrote up and excellent carb guide with pictures in it thats a sticky thread (top of the list) in the workshop section.. have a read through that to familiarise yourself with the carbs.

NC35 carbs are similar to the 30 ones but a few differences (jet sizes / float heights) but we can fill you in on these.

Not a difficult job if you take your time and dont rush.. give youself best part of a day first time messing to have enough time to get it done!