PDA

View Full Version : Dying on full throttle



rockr
12th June 2007, 21:38
just got a pocket bike of trade me , took it for its second ride tonight and when the throttle is fully opened it dies and bogs down , not to much , but when ya back of the throttle a bit it pulls away and the revs go up. is this a lack of fuel??? or air??????

breakaway
12th June 2007, 22:49
Checked your spark plugs?

rockr
13th June 2007, 16:47
thanks for your reply
na i havent, thought it would be ok considering the bike has probly done less than 1km but i shall check it tonight or replace it , what the best replacment for the factory fitted item??

it just starts to bog down from about 3/4throttle and if ya open it up it gets worse , but pulls away when ya back of .

SHELRACING
13th June 2007, 17:30
thanks for your reply
na i havent, thought it would be ok considering the bike has probly done less than 1km but i shall check it tonight or replace it , what the best replacment for the factory fitted item??

it just starts to bog down from about 3/4throttle and if ya open it up it gets worse , but pulls away when ya back of .


If you bought a chinese pocketbike you will need to check everything. All the bolts, nuts, wheel bearings, chain, spark plug, carby etc. It could be the accelerator cable is the wrong length, or adjusted incorrectly. The carby could be blocked by a sliver of plastic from the fuel tank. We were told to put a petrol filter on for the first two full fuel tanks. The fuel line maybe too small to the carb. Have you got the correct fuel mix, running in the bike should be at 25 to 1, then 50 to 1 after that?
Its a matter of trying everything that anyone on here suggests, then hope something works.
Good Luck.

mdooher
13th June 2007, 17:40
perhaps the mixture is a little lean, can you adjust that on pocket bike?

Had the same thing on a bigger bike All I did was lift the needle 1 stop but I freely admit to knowing nothing about these things I just followed the advice of an expert

Gadgit
13th June 2007, 17:55
Be lack of fuel.... If it was going good the first time then it will be a blockage in the main jet Common with these bikes as shelracing pointed out.. if it has allways run like this the move the main jet needle adjustment clip down a few knoctes as mdooher surgested

rockr
13th June 2007, 18:25
cheers guys , yeah the first thing i did was cleaned out the fuel tank and checked that it had a fuel filter, which it has , then replaced alot of bolts with stainless steel ones and checked everything else was tight, i have not had the carb apart yet , will do that tonight. so i move the clip down on the jet??? no idea what this will look like but im an engineer so should be able to figure it out when i get in there, any help would be appreciated , cheers guys.

98tls
13th June 2007, 18:44
Yep gotta agree...........its sounds like its flooding itself.........if the plug was whiskered it wouldnt just bog down it would be real jerky so will hedge a bet on the carb being the problem.......good luck.

breakaway
13th June 2007, 19:08
Usually dying under high revs is a sign of fouled plugs.

(I think. I'm sure its plug related though.)

zooter
13th June 2007, 20:34
sounds from the symptoms that your midrange is too rich so I'd be lowering the needle (raising the clip) and staying off full throttle until the speed gets up.

I've never set eyes on a pocketbike but the others seem to be describing a flatslide carb with a needle that goes down into the main jet. The needle controls the midrange by virtue of it progessively opening up the main jet as the throttle slide is raised. The needle is suspended and retained in the slide by the clip. You may have to wiggle the needle to get the clip clear of the recess in the slide.

Cayman911
14th June 2007, 07:22
i dont know if its what you mean, but i sorta ad the same problem, when i reved it a bit it started lagging power and then rev'ed again and same thing over and over again. i didnt know what was wrong so i just replaced the whole engine. since the original was a chinese piece of sh*t anyways

rockr
15th June 2007, 16:38
sounds like ya got the same bike as mine going by ya profile , i got a pod filter for mine and a new spark plug, and im going to adjust the main jet when the parts get here and its all back together so ill let ya know how it goes , ya probly got an engine with nothing major wrong with it

Cayman911
15th June 2007, 16:52
yea then with my new engine came shitloads moer trouble as you can see in the thread under yours lol. im just gonna buy a proper motorbike. pocket bikes are trouble, the mroe you fix the more it stuffs up

rockr
17th June 2007, 18:31
ended up opening the needle two clicks on the clip to stop it dieing under full throttle, but after its been open for a few seconds it just goes all cranky and ya gotta back of a bit before it comes on song again. im gonna try some fresh fuel as the fuel i used to mix up the fuel for it was some for my lawnmower which has been sitting for a few months. any one tried mixing with av gas 50/50???? (and 2 stroke oil)?????

IamCornholio
17th June 2007, 22:39
ended up opening the needle two clicks on the clip to stop it dieing under full throttle, but after its been open for a few seconds it just goes all cranky and ya gotta back of a bit before it comes on song again. im gonna try some fresh fuel as the fuel i used to mix up the fuel for it was some for my lawnmower which has been sitting for a few months. any one tried mixing with av gas 50/50???? (and 2 stroke oil)?????


The reason that your bike speeds up when you let off the throttle some is because your main jet in the carb is too big causing the bike to run pig-rich at WOT. If you have not recently changed to a bigger jet to cause this it could very well be that airfilter is clogged up and causing this 'overrich' condition. Clean your airfilter and make sure you are using the correct jet.

The needle that you adjusted the clip on only really affects the mixture between 1/4 and 3/4 throttle and will have very little (if any) effect on how the bike runs at full throttle (WOT)...

You will not notice any real gains by using av gas. My bike has a nice engine in it running a true, corrected compression ratio of 15:1 and I need nothing more than 93 octane, pump gas for it to run fine. :scooter:

I have always run the Klotz (80%synthetic - 20%castor based) in our engines at a 40:1 ratio and have had no issues. :yes:


IamCornholio :Punk:

rockr
18th June 2007, 16:45
it is a standard jet and a brand new air filter, so what adjusts the mixture at full throttle??

Drew
18th June 2007, 17:09
it is a standard jet and a brand new air filter, so what adjusts the mixture at full throttle??

Nothing, the volume and velocity of air rushing over the top of the jet, sucks fuel up and into the combustion chamber.

IamCornholio
18th June 2007, 17:24
it is a standard jet and a brand new air filter, so what adjusts the mixture at full throttle??

The only 'part' that will adjust the mixture at WOT is the actual jet itself. :yes:

3/4 to full throttle is where this part comes into play...

As the stock jet is a size .64 in most stock carbs, I would suggest trying this one out to begin with.

A jet 'kit' is good to have...

Jet kits are readily available for these bikes and cheap as well if you look around first. If that is not possible at this time, make sure your airfilter is flowing as good as possible as a poorly flowing filter is similar to having the choke on a slight bit and will cause a 'rich' condition at all rpms...


The needle is of most concern between 1/4 and 3/4 throttle...

The actual slide itself controls your air/fuel mixture from between 1/8 to 1/2 throttle (mostly between 1/8 and 1/4).

You CAN control the air/fuel mix (at idle and down low) with the slide via. the size of the 'cutaway'... :scooter:

A larger 'cutaway' will give you a leaner mix while a smaller one will make things richer. You DO NOT want to grind your slide so much that you don't have at least the front half of the slide remaining... When it is closed, You should NOT be able to see through it. You want to try to maintain the same bevel as before and you want to go 'slowly' and check it often. Grind 1mm and give it a check...


You do NOT need to grind your slide here friend...

I only posted that for other members who may wish to 'tweak' this... :innocent:



IamCornholio

newmanz
19th June 2007, 11:35
Cheap engines tend to give problems, it really is luck of the draw.

1# Leaky crank case seals, bike dies when engine reaches running temperature and the compression starts escaping..remedy, try tighten up your engine bolts..worse case ... buy a better engine.

2# Fuel .... sparkplug fouled, fuel filter is rubbish, fuel pipe is bent, blockage in your tanks fuel hole. (poke a nail down it or drill bit and open it up a little bit more...... carburetor is poor quality (buy an OEM carburetor)..

3# Air filter standard horrible black box (bad design... remove and drill about 6 small holes in the back, this will open it up and allow better air supply at full throttle)

4# Faulty CDI/Coil pack ... probably not this but symptoms when it starts to die will include problems like this.

5# Fault engine kill switch ... common problem, check the connections and spray some brake cleaner into the switch, easy to upgrade to the kill switch type 2 model, is bigger and a proper switch.