Areox 50 LC power problem after derestricting

[jbmk]

Hello

I've recently purchased a Yamaha Aerox 2013 50cc, liquid cooled, with 500 miles on the clock. I've removed the restrictor in the variator, increased the jet size from a 60 to 68, and fitted a LeoVince ZX exhaust (which included fititng the LeoVince rollers and clutch springs). The bike comfortably cruie at 50mph but won't go any faster, I believe due to an RPM limiter and I'm quite happy with the restriction. However, the bike goes on to develop power problems.

After about ten minutes of riding, the engine will lose power and refuse to accelarate. Typically, the bike won't go faster than 30mph. I think it's temperature related because on a cool (5oC) morning the problem is less evidence - I guess due to cooler air passing over the bike and less traffic hence less stopping.

I've tried putting a little copper grease on the variator spindle in the event the variator was sticking, but this hasn't resolved the issue.

I've checked the coolant level and it's a little below 'max' on the bottle but does not seem 'low'.

I've taken the air filter back off and inspected the pipes going into the carb and can not see any kinks. I changed the carb jet by taking the float valve off the bottom of the carb so the carb was never removed, merely opened.

Does anyone have any ideas of what else I can do before I take it to a garage?

Thanks

[rennie]

hello and welcome

please say hello in the newbies section and put your location in your profile

Are you over 16? do you have the correct licence to ride an unrestricted bike?

Is your insurance valid for derestricted?

[eastanglianbiker]

i wont give advice on the problems on this bike even tho fairly easily solved as it is a 50cc moped with maximum design speed of 30mph and as it seems fine at 30 according to the op t hen there is no problem

[jbmk]

About two decades over 16 with CBT! And the bike isn't designed for a max speed of 30mph - it's restricted on import to 30mph. I think it would be helpful to simply not respond if you don't wish to help... I appreciate you may not want to, and that's fine.

[Stu]

I think you need to look at things from their point of view

We get plenty of young lads with this sort of question which if they derestrict their bike invalidates their insurance as they aren't riding in accordance with their licence

Which all contributes to continuing rising insurance and crap like that

Couple that with the risk of them speeding down the road above the speed limit and killing someone or themselves and we as a forum could have a problem on our hands

Its ok saying your over 16 and have a full licence but how do we know that?

[Joeman]

About two decades over 16 with CBT! And the bike isn't designed for a max speed of 30mph - it's restricted on import to 30mph. I think it would be helpful to simply not respond if you don't wish to help... I appreciate you may not want to, and that's fine.

 

Regardless of how it was built, it's type approval for the uk is as a restricted 50cc moped. If you derestrict it then becomes a motorbike and no longer type approved for the roads. Probably then requires an IVA and new registration as a Motorbike not a moped.

[jbmk]

I think it's perfectly reasonable for someone to be interested in how 50cc bikes work. The question is quite clear, and it didn't include any query on insurance/CBT/etc. So if this thread is to be useful, then useful responses would be much appreciated. Yet another debate on whether a 15 year old destricts a bike is not useful (I can google many of them), particularly given the law is quite clear on who is to blame (ie not someone on a forum).

The responses may include a discussion on jet sizes, or whether the torque spring is man enough, or the quality of the standard Yamaha variator, etc. I'm no expert but I've learnt enough to share some useful advice for beginners to bike modifications/maintenance, and would appreciate anyone's thoughts on typical problems when a 50cc is running at 10,000rpm as designed (and not in a fuel inefficient restricted state).

[Joeman]

Its a two-stroke right?

So 50mph for 10mins, the it slows down. It may be partially seizing.

Turn up the oil pump so it gets a bit more oil.

[jbmk]

Turning up the oil pump: Now that's a great idea, how do I do this? I shall consult the Yamaha service manual but pointers appreciated.

[jbmk]

So various forum postings either say, you can't adjust the oil pump, or you can via turning a cable. I think the best way to confirm this theory is to add a little oil into the petrol and see if the problem eases.

I believe the standard oil pump adds on a ratio of 50:1 (2%), so if the tank capacity is 7litre, I guess I should be pouring about 35ml into the tank to get an overall ratio of 40:1 (2.5%).

I shall try this and report back. Thank you.

[Joeman]

So various forum postings either say, you can't adjust the oil pump, or you can via turning a cable. I think the best way to confirm this theory is to add a little oil into the petrol and see if the problem eases.

I believe the standard oil pump adds on a ratio of 50:1 (2%), so if the tank capacity is 7litre, I guess I should be pouring about 35ml into the tank to get an overall ratio of 40:1 (2.5%).

I shall try this and report back. Thank you.

 

you're clearly not 16. these days, they cant do maths like that!

[jbmk]

My 30 year old mid-life crisis was a Mini Cooper S, which was too scary to require any kind of modification. Sadly, when it started costing roughly £1/mile (deprecation, tax, insurance, 23mpg to drive 4m to the railway station daily), my missus told me to sell it. I was only allowed to buy a moped after promising that it would be rather less costly to run.

[Mr Fro]

my missus told me to sell it. I was only allowed to buy a moped...

This statement confuses me.

[rennie]

I had to ask the previous questions

Could it be overheating? starved of air?

Will the brakes cope with the extra speed?

[techno]

Just to add I don't know whats wrong but I had an aerox 50 back in 99 derestricted. it was more than fine till speeds above what it said on the speedo and it stopped fine.

Carry on.

[jbmk]

I've not upgraded the brakes but they seem fine. I'm actually more interested in reliably getting to 40-45 than top speed. My commute involves lanes and hills.

I added some oil to the tank and shook the bike a little. I drove 20 miles today and the problem persists, but perhaps to a lesser degree. I've therefore added a little more oil and will thoroughly mix oil in a petrol can when I next need to fill the tank.

With respect to over heating, I've not seen the temperature light come on except during the self-test.

(On the subject of instrumentation: I'm wondering if the speedo will only display up to 50mph, as I was fairly sure the bike got beyond that going down a hill but the speedo doesn't register 51+)

Are there any other areas in which I should be looking? Is it possible the variator isn't man enough, despite it being new? Does it get hot and warp/change during heavy use?

[jbmk]

So after adding a little more oil, the problem does seem to have receeded. But I haven't been running flat out (50mph) for long periods of time, so I will report back after I have a go at this at the weekend. The bike did stall first thing this morning after a minute of riding but I assume it was because the engine was cold and maybe some oil had sank to the bottom of the tank, leaving the petrol a bit rich.

[Joeman]

time to buy an adjustable oil pump...

http://www.pedparts.co.uk/product/500/a ... pump-aerox

[Stu]

adding more oil will cause the plug to foul easier which could explain the stall first thing

[jbmk]

I've taken the bike out for a ride on faster roads and the problem persists, even with additional oil. I do intend to take the spark plug out and check for blackening after adding the extra oil, but given the problem persisted prior to the extra oil then I don't blame the oil.

So a recap of the problem: In normal operation, if I ride at 15mph and fully open the throttle, the engine quickly spins up to some high rpm (I don't have a rev counter, but let's consider it full power) and the bike quickly accelerates. But sometimes, the engine will either barely increase the rpm or won't at all. Typically, if the bike starts going downhill then it persuades the engine to spin up but on the flat, I could have to wait for it to start working again, travelling at 20mph, maybe increasing in speed albeit slowly.

After a 20 minute ride with plenty of 50mph, I tried opening/closing the throttle for a few minutes, ie accelarating from 20mph to 40mph and then letting the bike drop back to 20mph. I couldn't reproduce the problem. I stopped the bike, put it on the stand and opened/closed the throttle, watching the back wheel spin as expected, and couldn't reproduce.

Has anyone got any ideas where I should be looking next given the problem seems quite random?

[jbmk]

Hello,

So the power problem remains and is particularly bad when the bike is cold and the weather is wet. I've read a bunch of forum entries suggesting this indicates the bike is running too lean, but with a .68 jet installed, the bike shop reckon that's right for the bike/exhaust. The problem remains when the bike is warm and I am travelling at low speeds, but the problem isn't happening at top speed, ie when the engine revs pick up (I guess 6,000+).

Any more thoughts?

[Joeman]

Its a strange one!

The needle height is normally adjustable too.

If you think its lean you could try raising the needle up a notch.

Are you sure you dont have any air leaks?

[Mr Fro]

Wot im says!

Popping a couple on shims (1.1mm total) under my needles made a great deal of difference to my mid range.

[Stu]

does the bike have a choke? or is it all auto?

if it has a choke go for a ride and apply a little choke and see what happens if it bogs down its running rich if it picks up its running lean

it may give you some idea of how its fueling

[jbmk]

I've taken out the spark plug and it's a golden brown colour, so I guess that suggests it's not running too rich.

I've taken the air filter off, cleaned the point at which it goes onto the carb, and put it on - no change.

I've put in the original 60 (0.60mm) jet in place of the 68 I have been using since fitting the bigger exhaust and there was a noticable difference upon starting (from cold). I could barely get the engine to increase RPMs, almost as if this was the problem hugely amplified. I put the 68 back in and it has gone back to the original problem.

I've ordered 66 and 70 jets and I will try both and report back!

I did consider adjusting the needle but knowing nothing about how it works, and believing it meant removing the carb (swapping the main jet is easy: two screws, take bottom off carb, hold in float valve with elastic band, change jet), I decided against it.