Two stroke won’t Rev out

[Farmingstock]

My son has a Rieju with an AM6 50cc engine if you potter around on it or Rev it stationary it is fine.

However when riding it down the road it kind of cuts out like it’s out of fuel/spark at completely sporadic times, so in first it revs fine till red light, put in second it pulls well till around 8000 then dies and splutters until I let off and the go again but the same thing happens, almost like there’s either a limiter or just not enough fuel.

I am going to try using the choke when it does this to see if it makes a difference with more fuel but any other suggestions?

Thanks

[Nobby the Bastard]

Has he fucked around with the exhuast or the air intake?
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trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Sprint ST 1050

[stinkwheel]

Has it ever run properly since you had it?

First thing to try with any misbehaving 2-stroke is fit a new sparkplug.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Farmingstock]

The air intake I think is standard but the silencer has no insides in it, basically a straight through and First run down the road tbh with it!

Got a new plug to fit tomorrow.

[jaffa90]

"""" the silencer has no insides in it,"""

That`s your first reply.

[Farmingstock]

Jaffa90 ?????

[stinkwheel]

[Farmingstock]

Ahhh yeah

He has only just got it, the bike had been stood for 2 years or so, got it running and everything working etc, only been pottering about as not road legal, but took it down a “private track” and found this issue.

I have ordered a silencer and will try that first followed by a carb clean then see if the issue continues.

[ThunderGuts]

I am no expert on 2 strokes, but from what I recall with model air-craft 2 strokes is they're very sensitive to exhaust back-pressure. If you can get a "stock" silencer, that'd be a good first port of call. At least if the engine is out of tune you know some of the other variables are then controlled. Otherwise you've got lots of variables all over the shop - difficult to make progress.
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TG.

[Easy-X]

First thing you need to work out is whether it's leaning out or bogging down (over-rich) when it wobbles. Stock silencer might help but TBH most of the backpressure work is done in the first half of the exhaust system that acts as a resonance chamber.
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Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter

[A100man]

[Farmingstock]

Took it out again before and it seams to choke up about 30mph but there are another 4 gears to go so can’t see it being limited to that.

Definitely looking like it’s the exhaust!

Whilst riding it the clutch fork in the engine popped up and I lost the clutch also (starting to see why it was so cheap) managed to slot it back in and I think it’s the spring that’s loose so I’ve ordered another one, it’s the AM6 engine.

[stinkwheel]

If you're doing 30mph in second, you're probably hitting the rev limiter.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Farmingstock]

How tight should this be?

[A100man]

[Farmingstock]

Not sure if it should have a nut on it also??

[Robby]

I'm not familiar with this bike, but that looks like a clutch adjuster. I assume some kind of top hat or pushrod goes into the middle of it to disengage the clutch.

If so, I would expect it to have a locknut.

Don't take my word for it though, I haven't ever seen an adjuster like that inside a normal multi-plate wet clutch. It looks like it could allow for about 10mm of total adjustment, for a clutch that should be totally worn out after 5mm of wear.

[jimspeed]

As its a 50cc are you sure its not some kind of 30mph limiter on it ?.
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Hyosung cruise 125(passed test on, sold) Kawasaki el 252 (better than expected but sold on) Kawasaki GPZ500S first "big"bike.(sold) ZZR600 E5..Z750 2007,ER5, currently on a 2008 Enfield bullet electra x and loving it..
,"Alpha-9: Is there any correlation between dyno rod and dyno kits?"

[Farmingstock]

Got a new silencer on it and took it for another run, it’s fine up to 3/4 revs in each gear but as soon as I try to go more than 3/4 it dies until I let off the throttle then it’s fine.

Tried using the choke whilst it was dying and it picked up so I’m guessing the main jet isn’t big enough.

I’ve ultrasonically cleaned the carb, all jets were clear.

It’s got a 78main ATM, I can only get hold of a 100 until next year, so I’m going to try that just to see if my theory is correct.

It starts fine, choke works fine and the throttle and power is fine up to 3/4 throttle so the slow jet, choke jet and needle position should be fine.

Just the main jet for the 3/4-full throttle that needs attention.

[jaffa90]

What top speed are you talking at 3/4 throttle and what colour is the spark plug?

[Farmingstock]

Wasn’t going for a top speed tbh just trying to get it running right, why do you ask?

[Robby]

The jet size should be fine. I would be looking for the following, with the bonus of no parts needed for diagnosis:

1. Air leak. Instead of too little fuel it could be too much air. Logic says this shouldn't be the case because you only have the the problem at full throttle, but logic doesn't always play nice with carbs.

2. Float height wrong.

3. Water in the fuel. Very common on something that has been sitting with E5 or E10 fuel, particularly if it was run on reserve.

[Farmingstock]

Thanks for the info,

I completely drained the fuel and cleaned tank and carb throughout.

Float height is fine after checking.

I have sprayed brake cleaner around carb and no movement in revs so I’m guessing no air leak.

I changed the main jet today and it has definitely cured the issue and it revs out now but it is a bit to rich, I could only find a 100 main which 22 bigger than what It had. Going to try a 90 main when I can get one and hopefully that’s it solved.

Quite quick for a 50cc