Problems jetting - Page 3

I've just disassembled my bike to clean the carb, I've not done this before so I may have made a school boy error when reassembling ie: jets not set up correctly or whatever.

Anyways, stripped it, took the "head" part off, soaked both pieces in white spirit for 5-10 mins, got bored and reassembled, started it up and it wouldn't idle, if I let go of the throttle, it would cut out.

I thought this is probably normal as the engine is running off white spirit partially now..so decided to give it a good blast to clean it all out, took it for a 15 minute ride including about 7-8 mins of max speed (55mph).

Got it back and it's still not idling right.


Say if I'm doing 55mph, I let go of the throttle then reapply it only 25% of the way, it won't put any fuel through and does nothing to the engine response, I have to almost twist it all the way for it to recognise it.

If I'd accelerate to 15 mph, it'd have some flat spots on the build up and again if I let go of the throttle, I'd have to apply quite some revs to make it register (but not as many, only about 25% of the way this time because im going slower)

I've tried adjusting the idle speed control and it doesn't matter if I run it 100% one way, 100% the other, 50%, 60, 70 etc.

Is this just the white spirit interferring or have I made a school boy error when reassembling?

Come to think of it, when putting the "head" of the carb back with the rest of the carb (2 screw attachments), I'm not 100% sure I tightened them up properly...

Probably the cause of this?

Any help would be really great because as I said I haven't done it before but I like to learn by putting things into practice.

Thanks :good:

 

Re: Flat spots after carb cleaning..

hi, im not an expert but white spirit? lol, does nt sound good to me like, i cleaned mine the other day with carb cleaner and was ok. again no expert but mabye the spirite has done something to the carb?

 

Re: Flat spots after carb cleaning..

could easily have done, began to strip it down again today but it's proving difficult as a 8mm bolt on the carb is:
1- difficult to get at
2- slightly rounded

so I tried taking it off further down, got 3 bolts off, 1 is:
1- very difficult to get at
2- slightly rounded

>_< wish I never bothered for the sake of cleaning the carb now, gonna upload pics and hopefully you guys will help me solve it, cheers

 

Re: Flat spots after carb cleaning..

ah shit thats all ya need rounding off shit i hate that

 

Re: Flat spots after carb cleaning..

that's one of the problems with having an older bike, bolts get rusted and rounded..

 

Re: Flat spots after carb cleaning..

unable to get pics up but my dad reckons the idle jet needs replacing as it could be nakkered since I played with it...apparently they're only a few quid

 

Re: Flat spots after carb cleaning..

You should clean a carb with petrol, white spirit may corrode the rubber seals on the carb.

You've put it back together wrongly one way or another, strip it and rebuild again but make sure you do it properly.

If still no joy, get a new carb fitted and dont touch it.

 

Re: Flat spots after carb cleaning..

bertie i think i need to clean my carb again proberly. whats the best way i have got carb cleaner

 

Re: Flat spots after carb cleaning..

I've took it off and looked at it and it's still not going properly so either I've:
1- interferred with a jet(s)
2- broke a jet(s)

 

Re: Flat spots after carb cleaning..

Could possibly be that you need to have a tweak with your pilot screw? Some people think the pilot controls idle only when it does affect idle yes, but also plays role in transition to midrange, not sure how much you've turned the pilot screw by and not too sure on how many turns you need to turn it lol but I know that turning the air screw clockwise reduces the airflow and turning it anti clockwise increases the airflow :nerd:

 

Re: Flat spots after carb cleaning..

a jet is a piece of brass that screws into place with a calibrated hole through the middle,
its not really possible to interfere with one or break one, unless its blocked or you drill out the hole to a bigger size, or damage the thread somehow, meaning it wont screw into place...

The most likely cause of a flat spot is having the wrong size jet fitted (too lean or rich)
or the mixture screw is not set up correctly...

people have a habit, ive found of taking things off, looking at them and declaring them to look ok, when really they dont know what they are looking for

 

Re: Flat spots after carb cleaning..

I did unscrew a few jets to inspect the quality of them, I screwed them back in but perhaps by interferring I messed something up?

will have another look today

 

Re: Flat spots after carb cleaning..

:cheers: That is me! lol
They are the correct jets, they are from some Honda (but same in my engine), 70cc jets, they was working before. I'll take some pictures today and try to upload if possible but yesterday my USB cable to upload pictures was being annoying and not working properly

 

Re: Flat spots after carb cleaning..

Most likely yes mate. If they make a haynes manual for your specific bike, it might be worth investing in one (if you already haven't) and seeing if it tells you the amount of turns out, to give you a better idea of how to work from. Or if you know anyone with the same bike, asking them perhaps.

Have turned the pilot screw all the way in do you know? If it is turned all the way in, I'd give it 2 full turns anti clockwise, and then see how the bike runs, and then from that, you can work from there really :grin:

 

Re: Flat spots after carb cleaning..

ive got a speedfight 2 100cc and what should the revs be at? like should it be really low as if its going to knock off or should it be turned up to were the wheels are just going to turn? whts the best for my bike

 

Re: Flat spots after carb cleaning..

They do not make a Haynes manual for my bike, the closest I think they make is "chinese/taiwan scooters" or something of that sort, which is obviously nothing specific so pretty much useless.

The idle screw is meant to be 2.5 turns isn't it? or 1.5? Either way, I could sit there changing the idle screw all day and it's still not running correctly.

What does the pilot jet look like please? Pictures would help a lot, thank you!

 

Re: Flat spots after carb cleaning..

the middle, I think it's 1.5 or 2.5 turns from fully in and it's about there, of coarse if it's running too lean/rich, you can always adjust accordingly

 

Re: Flat spots after carb cleaning..

No it's not the idle jet I mean, it's the pilot screw. You have a pilot jet which is based inside the carb and the pilot screw on the outside of the carb.

Here's a little acknowledgement on carburettors.. http://www.justkdx.dirtrider.net/printcarbtuning.html

Here's what the pilot screw looks like http://www.google.co.uk/imgres?imgu...3&ndsp=8&ved=1t:429,r:5,s:26&biw=1024&bih=497


http://www.freewebs.com/dominantmonkeyracing/Carb 003.jpg .... the far left gold screw, that's where the pilot screw is situated, I think anyways :glare: lol

 

Re: Flat spots after carb cleaning..

Thanks for the reply.

Yesterday I took the exhaust off for ease-of-access purposes, snapped a bolt that was holding the zorst on, today when refitting the zorst, snapped a manifold bolt.

>_< old bikes = rusty bolts =

So depressed, can't even be bothered to continue today, it's windy and crap outside

Thanks Rhysss

 

Re: Flat spots after carb cleaning..

Gotta do it sometime aint ya mate, the sooner the better! And get some nice new shiny bolts for her, make her feel appreicated

No problem mate