Yamaha Jog R - 2005 50CC Moped won't start

[Beizsley]

So, I got my license in February, shortly after my sixteenth. My brother gave me a moped he'd bought off of a friend for only £100 - and it worked perfectly after we replaced the ignition, clutch and unsealed the water pump, which, for whatever reason, had been completely jammed up with a liquid gasket...


Anyway, it ran with absolutely no issues until about two weeks ago... Then it started cutting out for a second while at top speed (or near to) and then carrying on as if nothing happened. It also started bogging pretty badly with absolutely no reason to it. Then it started dying.

On my way to school - and back, which takes about 40 minutes each way, it'd stop once or twice each way... and take about 20 minutes to start again. There isn't a starter motor in there, so it's all kick starting. No amount of kicking would start it, but after about 20 minutes, and, I assume once it had cooled off, it would start up again, like nothing was wrong... And could drive for about 20-30 minutes near top speed before there were any issues again.

But then it died - and just wouldn't start up again. We opened it up, the valve under the manifold (directly attached to the carb) had broken. There were four metal valves on there - and a huge chunk had come out of one, with two of the others past the 1mm maximum distance open.

We patched that up temporarily and it carried on going for a while.




But then it died again.

So far, we've replaced the piston, the cylinder head, the rollers, the carb (we have two - the one that was in there and my brother's old one on his 2009 Jog RR), the spark plug, the coil, the aforementioned valve (with a sports one, 6 valves on it, 3 on either side) and looked at most stuff.

Since replacing all of that, it starts again. If we lift the back wheel off the ground and accelerate, it'll spin real nice - and the cutting out isn't too bad, though it can happen if we drop the acceleration too fast. I can't tell you the speed, as the speedo is on the front wheel, but when the wheel is in the air, it'll sway against me when reaching full speed - and it looks and sounds real good.

However, any weight on it (so if the wheel is on the ground) it will not take off. My dad thinks it may be the rollers, so we'll buy some new ones, but he's a car mechanic and doesn't know as much as he pretends to about mopeds. If you walk the moped and pull the throttle back fully, it'll move with you. Other than that, if the back wheel is on the ground, it's not going to go.

Any other details, I'm happy to provide... I'm just not sure what's relevant here. Thanks in advance for any advice.


We fixed that issue by replacing the clutch with an old spare we had lying around. The clutch pads on our new one only had half of each worn like they'd been used. The other half looked pretty much brand new.

We also replaced the contra spring - it was an old one in there, we replaced it with a new 1500rpm one. It's shorter but much taughter, assume the original was 1000rpm.

I managed to drive it around the car park behind my house once or twice, running better than ever, before it died. Then it started dying after running for a couple of minutes. Now it won't start at all. You can kick it to your heart's contempt, but it doesn't start. If you accelerate while you kick it, it fires, the front light comes on - and it dies instantly.

[Andy_Pagin]

Personally I'd stop chucking good money after bad and get another ped, or better still get a bicycle, sweat it out saving your pennies for those few months left until your seventeenth birthday, then buy a not totally shagged Japanese 125. I know a year seems a lifetime at your age, but really it's worth the wait.
____________________
They're coming to take me away, ho-ho, hee-hee, ha-haaa, hey-hey,
the men in white coats are coming to take me away.
Yamaha Vity -> YBR125 -> FZS600 Fazer -> FZ1-S Fazer

[Beizsley]

[Andy_Pagin]

I know where you're coming from, I took up biking when my train fare hit 200 sobs a month.

How about sourcing a complete new engine? I suspect mechanically sound engines can be found on Ebay or wherever, quick search just now shows a few for a hundred quid. The fact that you found stuff broken off in the engine is seriously bad news. The bikes probably been ragged to death with no servicing.
____________________
They're coming to take me away, ho-ho, hee-hee, ha-haaa, hey-hey,
the men in white coats are coming to take me away.
Yamaha Vity -> YBR125 -> FZS600 Fazer -> FZ1-S Fazer

[lukamon]

sounds like a broken clutch side spring (rear wheel end of transmission, this and rollers work together)

take belt cover off, watch belt as engine running. should be running small circle on the front and nearly on the rim on the back. if it isn't, or immediately moves to the top on the front when you rev, that's your problem.
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killa wrote: Im an ass man myself

[evoboy]

Does the wheel spin fast while the bike is idling on the centre stand?
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Suzuki GT250 x7------- Fazer 600------CB250RS------Aprilia Rally 70----- Bandit 600

APT Motorcycles

[Beizsley]

[MattWadz]

Are the rollers jammed? Are there rollers in it ? It is definitely a transmission Side of things start at the variator work back checking the variator sliders belt face plate clutch assembly and all the clutch springs, have you messed with the torque spring behind the clutch?


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Pitbike x2, Mini Moto x4, China Quad, 02' Suzuki AP50 > 03' MBK Nitro > 86' Suzuki GP100 > 02' Yamaha Jog R > 57' Honda Lead 100 > 95' Piaggio ZIP Rst 50 > 51' Suzuki TS50x > 83' Honda CB125TDE Twin > 51' Yamaha Aerox > 98' Kawasaki KX60 > 89' Yamaha DT50MX > 80's Honda QR50 > 05' CG clone > 125cc China Pitbike > 91' Honda MTX125 RW-L > 09' Peugeot Speedfight 2 LC LR > Lucky MX 140cc > Apache Tomahawk 50 Quad (current = 2010 Yamaha WR125R

[merquis00]

as mentioned ^ , sounds like the clutch bowl or variator - either seized or loose (belt slipping under load)

[Beizsley]

We fixed that issue by replacing the clutch with an old spare we had lying around. The clutch pads on our new one only had half of each worn like they'd been used. The other half looked pretty much brand new on each of the three pads (as in right side on each pad was black, fairly smooth, left side on each pad was white, still had the faint ridges).

We also replaced the contra spring - it was an old one in there, we replaced it with a new 1500rpm one. It's shorter but much taughter, assume the original was 1000rpm.

I managed to drive it around the car park behind my house once or twice, running better than ever, before it died. Then it started dying after running for a couple of minutes (the problem we had before we replaced stuff.) Now it won't start at all. You can kick it to your heart's contempt, but it doesn't start. If you accelerate while you kick it, it fires, the front light comes on - and it dies instantly.

Fuel issue? Or could it be electrical? The carb isn't a new one - we have two available. One is a Dellorto one, one is the original. The dellorto carb is bigger than the original carb, but has a 50's jet in it.

The original carb (which is from my brother's 09 Jog RR, was told it was the same as the one originally on mine) is pretty old, but there's nothing noticeably wrong with it.

The original carb has an automatic choke, but it seemed like it wasn't letting the choke off. The dellorto carb has a manual choke, which didn't have a needle on it. My dad put a needle on it and set up a wire to control it. It came with the moped, worked awesomely, then when the ped broke we swapped the jet from what my brother thought was a 90's jet (which is now in his ped) with his 50's jet... Which he has now. It could be broken its self.

So, should I go for a new carb or try something else first?