Rough spots in rev range when cold (EFI) - FIXED

[Easy-X]

Hey guys,

Long time lurker on these forums but I'd really appreciate some advice. Give me a moment while I don my flame-retardant jump suit...

I have a Keeway Superlight 125 and yes, I know how well you guys love cheap Chinese bikes Anyhoo, I bought it nice and cheap and have almost got it back to good running order but I still have one minor annoyance.

From cold it starts perfectly but once I get around the 3000 rpm mark it bogs a little bit. Get over 5000 and it's fine. Takes about 5 mins to warm up and then it's great through the entire rev range. (Note, this is the engine under load, it's not noticeable when in neutral.)

TBH it's not a major problem as the first mile of my commute is all 20mph suburban rat runs anyway so by the time I can get to its cruising speed of <cough> 30mph the engine's fine!

Sensible things I have done:

Cleaned the air box, replaced the filter and checked for leaks
Replaced the spark plug, gap'd to manufacturer's spec
Oil change, 10W40 Castrol racing oil (racing?! wtf was I thinking!)
Adjusted the path of the throttle cable (previous route was a little "sticky")
Replaced the handlebar throttle (again, original didn't turn as smoothly as i would like)
Checked ECU for errors (none logged)

Sensible things I haven't yet got around to:

Check the valve gaps (where are my feeler gauges? I had them for the spark plug...)
Check the throttle is *actually* turning smoothly after sorting the other throttle/cable issues
Replacing the fuel filter (haven't actually found it on the parts diagram)
Do a data log of whatever the ECU can give my Torque app

Insane things I haven't considered doing:

Strip down the throttle body (my mechanic mate said leave it alone)
Pull the fuel injector and examine/clean/replace (seems extreme)
Piled a load of so-called "injector cleaner" into the tank

So, suggestions other than "buy a Yamaha" would be appreciated
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Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter

[Nobby the Bastard]

How did you check for air leaks? The traditional way is to spray wd40 round the rubbers and see if the engine speed changes.

Oh, and don't buy an FZR thou unless you own shares in esso.
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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

[Easy-X]

TBH I only did a close visual inspection when I had it out to clean but thanks for the WD40 tip, I shall add that to the check list.

Hehe, I'm already expecting to change the oil a lot. I got this to learn on and, so far it's been - how shall we say - as entertaining as expected
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Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter

[Robby]

So it runs a bit rough in some parts of the rev range when cold, and its fine when hot. It's a fuel injected bike, and you don't have an FI error light on the dash.

That would suggest its just the EFI map, and just a feature of the bike.

[stevo as b4]

As above its a feature of the bike/ECU mapping and probably basic sensor inputs and feedback information. A non issue if your aware of it and warm the bike up a bit.

Try running an old two stroke if you think you have poor running when cold. Then you'll appreciate how good your EFI Chinq runs in comparison.

[Easy-X]

Yeah, I'm probably shooting for the moon. I've taken it from a wreck back to a near perfect example of an admittedly cr*p bike.

I'll probably just run a data log and see if anything makes sense: just 'cos there are no ECU errors doesn't mean one of the sensors isn't iffy.

On the other hand, how easy is it to examine or modify the maps?
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Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter

[stevo as b4]

You want to re-map the ECU on a 10bhp air cooled 125 Chinese engine? You'll never get access to the map anyway, and it'd need a bodged on piggy back module like a power commander that's not designed for the bike. It'd be a world of wiring diagrams if you could even make it work with the ECU and you'll never be able to make a performance or economy gain from doing so.

Think you need a new hobby or something else to occupy your mind and time tbh!

[Baffler186]

Doesn't sound like much of an issue to me, given that you've already checked most stuff. My only advice is to not waste money on expensive oil when you change it. I put the Castrol racing in my 125 once, it ran quieter for about 2 days and then same as usual. In fact it actually didn't start quite so well as cheapo Asda 10w40 oil.
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Current: 2009 SV650 S, 1990 Kawasaki GT550
Previous: 2009 CBF125, 1998 GSF600, 2004 FZ6 Fazer, 1978 CB400a Hondamatic

[linuxyeti]

If it was doing this even when warmed up, i would have said look at the TPS, but, I think it's just a case of letting the bike warm up.
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Beware what photos you upload, or link to on here, especially if you have family members on them

[Easy-X]

Dammit! I've been sold a lie: EFI is meant to be sooooo much better than carb, especially when it comes to cold starts
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Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter

[Robby]

It is. You just happen to have the cheapest, shittest EFI imaginable.

The problem is not EFI, the problem is Chinese bike.

[linuxyeti]

Nothing wrong with chinese bikes, if looked after. At least they don't keep randomly cutting out, usually when slowing down off slip roads or roundabouts, which my Triump America hada very good habit of doing !!

The weather has been pretty nippy, so, just let the bike warm up for a minute or 2, leave it ticking over whilst you put your helmet & gloves on. Read up on quite a few efi bikes stalling etc, can't remember which forum it was now though that suggested allowing an efi engine to warm up, and that seems to pretty much completely cure the issue.

Pretty sure that came from a Yamaha forum.
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Beware what photos you upload, or link to on here, especially if you have family members on them

[WD Forte]

Check the battery
the Lexmoto Urban I worked on had efi and was a bit rough when cold but after I got the guy to fit a decent battery it got better.
I reckon as it came with weeny cheap as shit battery with low CCA
and performance, that it took a while recover from cold starts and this affected the EFI
A Yuasa battery made a big difference
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bikers smell of wee

[Easy-X]

Interesting... last time I checked the battery it was 13.something volts so I assumed that would be okay.

I have a new one kicking about (that I just use for testing bulbs!) I might swap it over this weekend if the bike hasn't blown away in the gales
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Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter

[EazyDuz]

Throw in some Redex for the sake of £2
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To shreds you say? Tss tss tss

[Easy-X]

Does that stuff *really* do anything or is it just snake oil?
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Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter

[P.]

[jaffa90]

[Easy-X]

[jaffa90]

[talkToTheHat]

Hold on, your problem is "Bike has a bit of a hiccup at 3000 rpm when it's cold, but is fine over that" ???

Now, maybe I'm an old fashioned sourpuss here, but every bike I've owend warned me not to take it over 4000 rpm until warm and were varius kinds of unridable untill they'd had 30 seconds to 2 mins on choke warming up and none of them got the beans untill they responded normally to the throttle with the choke off.

Cars don't run smooth cold either. You're not advised to sit idling to warm up any more becasue emissions, but seriously, just because you have EFI cleverness doesn't mean it's a good idea to thrash the nuts off the bike before its warm.
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Bandit. does. everything.

[Easy-X]

[Easy-X]

For reference: 80% better just from having the correct valve clearances.
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Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter

[Tankie]

There you go!
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Always learning, everyday is a school day