Pocket bike idles, but doesn't rev under load

[Junkers]

Hey guys and gals, was wondering if anybody could help me as I'm stumped.

I have a 49cc pocket bike and have been having problems since day one. Currently the bike will idle but die if you give it a decent amount of revs under load. I can pick the bike up and rev the nuts of it and it will do that without any hesitation but as soon as it's under load it will die past half throttle or less. The warmer the engine becomes, the less throttle you can give it before it stalls. It doesn't really just die, it sounds as if the engine boggs down then struggles to idle.

I've tried replacing the carb and have already replaced the coil, although I think I may need another. The bike is also a pig to start which I presume will have alot to do with the problem. I removed the reeds yesterday and they seem to be sitting flush with the rubber pads so I don't think it's that either. Can anyone please help?

(Yes I've turned the choke off) I can't return it as I had to replace the starter within the first ten minutes of owning it and I live in christchurch

[98tls]

Fwiw i had a dirt bike once on which the coil shit itself when it got hot with the same response your getting though when cold it went fine in neutral or under load as you say,it only crapped out after a few miles.Wonder if its worth checking that the correct plugs in there,whilst at it i would test the lead as well sometimes its the stupid easy things we overlook.....i know this from my own experiances bugger it.

[Morcs]

Running rich.

My cbr had a similar problem.
http://www.kiwibiker.co.nz/forums/sh...ad.php?t=58146

We tried everything, and It took $1100 of shop bills to eventually find out it was rich as hell in the midrange.

I hope this helps. Find what jet sizes and settings your carb has, and work from there.

[BigAl]

Or not getting enough gas? Presume that you've checked your fuel line.
With the carb bowl off does the fuel stream out. The chinese filters aren't flash.

Presume you've tried a new plug, the original ones are crap. NGK6M from memory, $5 from repco.

What does the plug look like, black or white?

[Junkers]

Checked the gas line, pours like a fountain. I don't think it's running rich as I normally have to twist the throttle to start it and this is the second carb thats behaving exactly the same.

Had a look at the spark plug and that suggests a stoich mix, but has a black semi circular ring on the outer lip. I think it could be the coil producing a piss weak spark, when i turn it over at cranking speed it produces a very small intermittent spark. I'm thinking maybe when the throttle is wide open and the engine is under load at low rpm it "drowns" the little spark or the air becomes to dense for the spark to jump from the electrode. However when the engine isn't under load it flies up into the high rpm perhaps because the there is less air/fuel per cycle. Just my 2 cents anyway.

New coil is on the way. If you guys have any other ideas I'd really like to hear them. Cheers for the help.

[98tls]

Cant help anymore but be sure and post up what the fix was eh.

[daytona 2]

ive had two chinese pocket bikes that have done that...the problem in the end was resolved by turning the fuel switch around that other way...but yes its because that carbs not letting in enough gas for that amount of rev's....if i was you i would buy a delloroto replica carb of trade-me wihch will deffinity fix the problem.

[Coyote]

Same problem happens to mine. I pick it up and it'll run fine until you put it back on the ground. Just takes a warm up and you need to push forward to get moving rather than rely on the bike to get you going from a standstill.

Though mine is second hand and it could have a few problems that I'll eventually fix Though it's been far, far, farrrrr more reliable than my Honda VFR, one of the most reliable bikes around supposedly...

I'm on my phat ride in my profile pic

[FLYMO]

being a 2 smoke no doubt id check the crank seals
maybe even pressurise the crankcase to see if theres a leak somewhere

[racefactory]

sounds like coil or carb to me...

and that carb is a piece of **** get a dellorto rep from newmanz.co.nz or trademe.

and i'd replace that chinese spark plug out in an instant mate... that solved much for me in terms of low end acceration. My b1 replica used to backfire under acceleration from a start and new plug fixed it...

good luck

[Junkers]

Cheers, yeah got a new plug and coil is on it's way. If that doesn't solve my problem then I'll invest in a replica carb.

[Junkers]

Well, got the new coil and plug in there this evening, got the bastard started after several pulls. Started idling, then I picked it up after it had warmed enough so I could take the choke off. Gave it a little gas while it was in the air and the rear wheel started to move so I thought "sweet".. sat it down then got on it, opened the throttle then it started playing it's old tricks again.. #@$!!!

I have a few questions.. What is the gap on the coil/flywheel supposed to be? Can using 95 instead of 91 cause any problems? And last but not least, if the coil layers becomes slightly 'smoothed' by the flywheel.. can this wreck the coil?

[racefactory]

hey mate... let me tell you i a similar problem with my C1 before.

are we talkign about a cag here?

Anyway... on my c1 i had a problem where when i applied the gas under load it started backfiring and would die. i had jsut installed a euro made wrist pin bearing and had put a ton of oil back in there before i sealed the engine up again.

i solved it by A- replacing spark plug..was major fouled. secondly... putting the bike on stand and revving the shiit out the engine for 5 - 6 seconds... managed to burn out the excess oil just sitting there inside. Also mate... i found a ton of unburnt oil and fuel inside the exhaust header which i emptied- check your exhaust header for liquid just pooled in bottom if you been running fat. so basically if youve been running the mixture real fat you could have caused some problems.

If its a cag- i seriously think its just plain crap carb (they suck those cag carbs) with a needle that you wont be able to adjust to fix or quite likely a clogged needle jet thats not getting fuel through... take carb apart and clean... that fixes many problems. also might want to play/clean with your idle jet if the bike dies at REALLY low revs ie the slightest throttle increase.

yeah clean the carb you may have a clogged needle jet or something.

oh and coil gap should be thickness of a business card..

good luck let us know how it goes.

[racefactory]

if not that then maybe this

often the chinese put the fuel filter on the wrong way and it means that your carb will never have enough fuel in the float chamber for high throttle settings, check to see that fuel flows nicely through the filter...

if not that then maybe its a kinked fuel line not giving enough fuel through there.....

one things for sure it all sounds like carb trouble one way or another.

[Junkers]

Sorry for the noob questions, but I don't know the difference between a cag and a daytona etc?

It's just one of those cheap trademe job's, I had the old carb apart and cleaned it all out.. removed the jet etc and blasted it with crc.. still kept playing it's old tricks. I know those carb's are crap, you can tell by just looking at them haha. I don't think it even has a independent idle jet.

The fuel line was kinked and turned solid so I replaced that about a week ago, there is definitely no fuel supply problems.

Now looking at getting one of those Dellorto replica carbs from ebay, fingers crossed. I will pull off the exhaust and see what I can find.. cheers for your help.