Loss in power

[MichaelC]

I recently had an engine rebuild on my 2003 Peugeot Speedfight 2 50cc, and ever since i've noticed the bike has been severely lacking in power, struggling for even 15mph come the slightest hill.

Upgrades go as follow:
Derestricted Exhaust (Brand Unknown - previous owner put it on)
Malossi Variator kit
7g Malossi rollers

Standard carb, standard airbox

Use to pull 50mph on flat and an easy 45 come a big hill, now struggles for 40 on flat and struggling for 15 on the slightest hill

Any ideas as what the issue could be or how to regain some power?
Thanks!

[Teflon-Mike]

Oh-Kay... if it was so wonderfully fast 'before'... why did it 'need' a rebuild?

(Sane) People don't often pull working, let alone working well engines to pieces just for the heck of it.

Prompt's suggestion that the 'before' wasn't just before it was rebuilt, but before it had problem that begged the rebuild... so what problem suggested it need a rebuild?

Prompts two further suggestions:
1) whatever the problem that begged a rebuild, hasn't been fixed by rebuild.
2) rebuild is likely cause of new problems

Who did the rebuild?
Exactly what have they done in that rebuild?

I can take a shagged engine to bits and 'rebuild' it.... without having the cylinder re-bored, fitting new piston rings, replacing worn out bearings, and using all new gaskets, its the same heap of crap I had to start with, likely even more leaky and loose, and even less likely to work properly!

That's where I would start, looking for the problemS, and what might cause THEM, its unlikely to be one single problem by now....

But; before even that, I would look at the fact it's a moped, and one probably older than its rider, that has likely had 17 16 year old owners all looking for illegal speed, thrashing the knackers off it when it works, loath to spend a penny on basic essential maintenance, and more intent on 'upgrades' to make it even more illegally fast than it should be, if they ever get the spanners out to work on it, most likely when it's stopped working.... list of go-fast pink-power-band goodies sort of supports that notion... a-n-d would make me ponder, whether the thing was even worth fixing before I went any further.....

It's not a particularly valuable machine. How much a set of gaskets; how much a rebore and piston rings; how much just likely parts would it take just to have a look at what might be wrong, would it be before it was cheaper to buy another, working, legal, reliable moped? And that's without adding paid-for mechanic time, at £50 an hour or so.... that would suggest that if it took more than a day of work-shop time, the thing is and was likely long ago, beyond 'economical' repair, and cheaper to buy another than even try fix this one.....

Undoubtedly not what you want to hear; BUT, that's the reality; this is a moto-bike not grand-theft-auto; there's no magic cheat codes to get you into the upgrade store; takes real money, real time and real effort, JUST to make the thing work, and to keep it working, let alone find 'up-grades' to make it work laughably 'better'....

So start at the beginning.... that 'Rebuild' is the most likely suspect... likely to have made problems not solved them. So why did any-one think it was a good idea? What problems did it have to beg the rebuild, and was the rebuild done even remotely like properly?
____________________
My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?'

[Ste]

I agree with Teffers.

[MichaelC]

It was a full engine rebuild, it was done by a professional bike mechanic.

It had an engine rebuild as the main bearings were shot, so he recommended a full engine rebuild, it was bogging down and not running right before (however still able to pull 50 when running well)

Everything on it is new (engine wise)

I do suspect that something is still wrong with it since the engine rebuild as like I said it is severely lacking in power.

[Ste]

Go back to the garage and ask them to have a look as it's a lot slower since they worked on it.

[Teflon-Mike]

If the main bearings were shot, then the crank would wobble.
That play in the crank would tend to knock out the crancase seals.
Without crank case seals sealing, on a 2T, engine wouln't run too good, let alone well enough to exeed stipu;lated moped limits by amount claimed...
And why are main bearings 'shot'? There's two of them, one on either end of the crank, natural wear and tear could wear them out, but so too would the single doubly loaded bigend bearing, and that would beg a new crank or the crank properly reconditioned, pressed apart, bearings replaced, pressed back together, reballenged and jig set; usually more expensive than a brand new crank if available. And that is without considering the state of the cylinder bore, piston and rings, that would likely also be as or more worn or bludgered from oil starvation.

My spidey senses are on full bullchit alert....

A proffessional mechanic is also just that; a man who is paid to do the work; doesn't mean he does the work well.

I would expect a new crank to be around £7o, a new piston, rings and barel, or good rebore, to be around £7o, full gasket set, probably around £3o, new outer crank bearings, £2o, crank seals, £15, and so on and so on... a full engine rebuild would take me, probably a day, so at least £2oo of workshop time; and give you a bill in the order of £4oo to £5oo IF I were to do a 'full' and propper engine rebuild.... heck, just the labour is £2oo odd quids worth without any bits.......

I ask again... HAS this thing REALLY had a full and proipper engine rebuild, by a genuine, knws what they are about paid for mechanic?

If so.... there still lies the most likely suspect.. take it back to them and argue over your running in procedure... if not? That still likely bill to do a realo pukka rebuild.... properly... and put right anything this supposed proffessional has put wrong or missed along the way.... and how much be bike worth? How much to buy something running properly and not old enoughj to have its own licence?

Your call.
____________________
My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?'

[AshWebster]

50cc.....

upgrades....

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Honda cg125 J reg peice of shit ---> CB650F ---> 2016 CBR600RR
Ford KA ---> 93' MR2 ---> 94'MR2 ---> 98' Subaru WRX STI Ver 3 (track car)

[Tony12345]

If this 50cc is a 2stroke engine then the piston head and cylinder head needs de cokeing. I had a 50cc mz simpson. It had a top speed of 40mph. After a few months the speed would drop down to 35 then 30mph. I removed the head and descaled & polished the piston head and head. This restored the power. I agreed with a garage that serviced these bikes that the engine didn't get hot enough to burn off the carbon. We couldn't use a hotter plug, the max we could use was a 7, any thing higher would have damaged the engine.

[u33db]

[u33db]

P.S i think they were still selling speedfights right up to 2014 so its probably not fair to scare the lad into thinking its not worth repairing.