Moped Dangerously Slow
Discussion
I have just bought a ’98 Yamaha 50cc Two Stroke that is dangerously slow going up any sort of hill. It reaches 45 on the flat (even with the variator restriction), but will slow to under 20 on even a moderate gradient. Following a very helpful online guide I have now removed the variator ring, and looked for the exhaust restriction on the Leo Vince Touring, but there was no restriction. Anyway the engine still bogs down after the initial acceleration, in fact it has the opposite of the very sharp 2 stroke acceleration I was used to with my previous ’96 Piaggio. I can perhaps get a hardly noticeable increase in power if I use a little (manual) choke. What should I check/change/adjust next?
One suggestion I have read is to lighten the variator rollers, another is to check the main jet. Any thoughts?
One suggestion I have read is to lighten the variator rollers, another is to check the main jet. Any thoughts?
OP - are you generously proportioned per chance?
All this effort to extract extra 'performance' is futile. Why on earth are you dicking about with a 50cc scooter anyway? Surely an afternoon of your time and £100 is worth it for a 125cc machine, if you simply need to get around?
f
k me, I thought it was only 16yr olds who rode 50cc scooters.
All this effort to extract extra 'performance' is futile. Why on earth are you dicking about with a 50cc scooter anyway? Surely an afternoon of your time and £100 is worth it for a 125cc machine, if you simply need to get around?
f
k me, I thought it was only 16yr olds who rode 50cc scooters.GreatPretender said:
OP - are you generously proportioned per chance?
All this effort to extract extra 'performance' is futile. Why on earth are you dicking about with a 50cc scooter anyway?
No, I'm 60kg.All this effort to extract extra 'performance' is futile. Why on earth are you dicking about with a 50cc scooter anyway?
I've had a CBT certificate a couple of times, but it always expires before I get round to doing the full test, so I am riding on a Full Car licence only.
julian64 said:
If the answers are better and no problem then I thing its mixture, otherwise its timing.
Is it not far more likely to be utterly shagged and in need of a piston/rings/rebore? If it is a 50 and will make 45mph under some circumstances, then someone has already done the derestricting work, otherwise it would stop dead at 30 (50kph) whether up hill or down dale.Check the rear pulley unit. They have a 'kick down' mechanism for when load is high - the main spring might be broken or the slides gunked up.
What are the surfaces of the pulleys like? Totally smooth? Belt in good nick?
Also have a look at the plug see what it's like.
Pic for clarity,
If you alter the weight of the rollers then the rear spring will need altering too as the balance will be off. Imagine in your car if you set off and went through all 5 gears before you got to 25 mph that's like having heavy rollers - ie it takes a low rpm to fling the rollers out wards (high gear) if you tried to get to 100 mph in 1st and 2nd then that's like having light rollers you'll be revving the tits off it but not going fast enough ie you need 15k rpm to throw the rollers out and the bike only does 9k rpm. Of course you can temper the characteristics by putting a harder spring in the rear so it needs more force (rpm) for the rollers to overcome it. I.e, like staying in gear for a bit longer in your car.
What are the surfaces of the pulleys like? Totally smooth? Belt in good nick?
Also have a look at the plug see what it's like.
Pic for clarity,
If you alter the weight of the rollers then the rear spring will need altering too as the balance will be off. Imagine in your car if you set off and went through all 5 gears before you got to 25 mph that's like having heavy rollers - ie it takes a low rpm to fling the rollers out wards (high gear) if you tried to get to 100 mph in 1st and 2nd then that's like having light rollers you'll be revving the tits off it but not going fast enough ie you need 15k rpm to throw the rollers out and the bike only does 9k rpm. Of course you can temper the characteristics by putting a harder spring in the rear so it needs more force (rpm) for the rollers to overcome it. I.e, like staying in gear for a bit longer in your car.
Edited by MajorProblem on Monday 18th August 15:12
MajorProblem said:
Check the rear pulley unit. They have a 'kick down' mechanism for when load is high - the main spring might be broken or the slides gunked up.
What are the surfaces of the pulleys like? Totally smooth? Belt in good nick?
Also have a look at the plug see what it's like.
Thanks that is really helpful. I didn't check the rear pulley when I derestricted the variator, but the variator was in excellent condition, and the belt seemed new too.What are the surfaces of the pulleys like? Totally smooth? Belt in good nick?
Also have a look at the plug see what it's like.
I ordered some lighter rollers before I read your post, and since they only cost a fiver it won't be a disaster if I remove them again. At the moment it certainly feels like it's 'changed up' to top gear within 30 yards of pulling away from stationary, and it doesn't 'change down' again unless I come to a complete stop.
I will definitely check the rear pulley mechanism for dirt and wear when I fit the new rollers. Thanks again.
Edited by ukkid35 on Monday 18th August 20:48
Back in the Day (is that what they say?) I had a Suzuki Ts50Er which needed a De-choke. So instead, I took it for a week of fun in the Lake district. Downhill it would redline at 60 and uphill I had to get off and feather the clutch, and walk with it.
After getting home (Only took 5 hours to get from Windermere to Liverpool), decoking it, filing the exhaust ports, filling the exhaust with caustic soda for 48 hours, and fitting a new spark plug, and checking the mixture, it would hit 45 mph on the flat, and I didn't have to get off going up hill.
But I solved it by buying an RD350LC
After getting home (Only took 5 hours to get from Windermere to Liverpool), decoking it, filing the exhaust ports, filling the exhaust with caustic soda for 48 hours, and fitting a new spark plug, and checking the mixture, it would hit 45 mph on the flat, and I didn't have to get off going up hill.
But I solved it by buying an RD350LC
<scratches head>
Isn't part of the requirement for Class P - the driving licence class that you're riding under, if you've only got a full car licence - that the bike is <50cc and maximum design speed of 30mph? So derestricting it is going to take it out of Class P and into A1. And you don't have a licence for that.
If you don't like riding something with a maximum speed of 30mph, take your CBT and stick L-plates on a 125.
Isn't part of the requirement for Class P - the driving licence class that you're riding under, if you've only got a full car licence - that the bike is <50cc and maximum design speed of 30mph? So derestricting it is going to take it out of Class P and into A1. And you don't have a licence for that.
If you don't like riding something with a maximum speed of 30mph, take your CBT and stick L-plates on a 125.
TooMany2cvs said:
<scratches head>
Isn't part of the requirement for Class P - the driving licence class that you're riding under, if you've only got a full car licence - that the bike is <50cc and maximum design speed of 30mph? So derestricting it is going to take it out of Class P and into A1. And you don't have a licence for that.
If you don't like riding something with a maximum speed of 30mph, take your CBT and stick L-plates on a 125.
Absolutely right, but unless I'm involved in a fatal RTA then that is likely to be irrelevant.Isn't part of the requirement for Class P - the driving licence class that you're riding under, if you've only got a full car licence - that the bike is <50cc and maximum design speed of 30mph? So derestricting it is going to take it out of Class P and into A1. And you don't have a licence for that.
If you don't like riding something with a maximum speed of 30mph, take your CBT and stick L-plates on a 125.
More to the point, I'm not actually interested in maximizing the top speed, I just want it to be able to go up hills without me having to get off and push.
Edited by ukkid35 on Tuesday 19th August 09:21
ukkid35 said:
Absolutely right, but unless I'm involved in a fatal RTA then that is likely to be irrelevant.
Oh, well, there we go. It's OK to drive/ride something without a licence for it, so long as you don't kill anybody.Why not just buy a 125 - or even a proper bike - and be done with it, then? After all, if having a licence for it is so irrelevant...
TooMany2cvs said:
ukkid35 said:
Absolutely right, but unless I'm involved in a fatal RTA then that is likely to be irrelevant.
Oh, well, there we go. It's OK to drive/ride something without a licence for it, so long as you don't kill anybody.Why not just buy a 125 - or even a proper bike - and be done with it, then? After all, if having a licence for it is so irrelevant...
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