Gilera 50cc misfire

[Paivi]

The son of a friend of mine is having probs with his Gilera 50cc.

Can anybody offer any suggestions as to what could be wrong with the scoot?

[DOS]

To be honest I don.t know much about scooters and will check tomorrow
for a manual for it.
Is the choke a manual one or is it auto.It could be that the choke is
sticking on partly.

Paddy.

[Phil_P]

Sounds like it's running lean, which could be the result of the aftermarket exhaust. Obviously, being fuel injected it becomes more involved to sort out fuelling. If you can get hold of a standard exhaust to try it may be worthwhile. In the meantime, do a plug chop and have a look at the plug colour. Get the bike up to full chat under load, uphill is good, then hit the kill switch, and let the throttle shut. Pull over and whip the plug out and check the colour. It should be a nice pale brown colour.
____________________
It is not enough to win, others must fail.
Moto Guzzi 1100 Sport Injection '96

[djrichieb]

Some automatic scooters do not have a kill switch so if you can not use a kill switch just turn the key off.

If it idles and rev's ok on the stand could it not be the belt or rollers? Or variator?
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Rides: Honda CB400 SF (ART can) - Citroen Saxo 1.1i SX

[baldy]

it probably runs fine on the choke as it is richening the mixture, i suspect that the sports exhaust is the problem.
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One day i will rule the world, just not today.

[pax]

[GeorgeCBR]

Ive heard that F.I scoots dont react to sports exhausts, or any other kind of tuning other than derestriction... It might be a good bet to source a standard exhaust... But this is just from what i've heard. When you fit a performance exhaust on a carbed bike, its common to up jet the carb to suit, now if the E.C.U hasnt been remapped to let more fuel in/change the mixture, this could well be your problem.
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|| Ride - Kawasaki Z1000 & Honda Bali 50 || Theory - Passed || Practical - Passed ||

Previous || Suzuki Bandit 600N - Honda CBR 125 - Gilera Runner 50

[pax]

[GeorgeCBR]

Suppose i didnt take that in to account. That's me out of ideas anyway.
____________________
|| Ride - Kawasaki Z1000 & Honda Bali 50 || Theory - Passed || Practical - Passed ||

Previous || Suzuki Bandit 600N - Honda CBR 125 - Gilera Runner 50

[pax]

[GeorgeCBR]

Not a problem, the F.I scoots seem to have no end of problems when people simply put bolt on's on, and completely forget about fuelling, hence my reply. Good luck with it all
____________________
|| Ride - Kawasaki Z1000 & Honda Bali 50 || Theory - Passed || Practical - Passed ||

Previous || Suzuki Bandit 600N - Honda CBR 125 - Gilera Runner 50

[prawny1]

often scooter rollers can wear leaving flatspots on them what this can do is stop the variator pulleys from returning to there rest/lowratio position properly and makes the scooter feel underpowered and run iffy (think trying to ride your manual bike in the higher gears all the time it will feel crap at low speeds then will pick up as road speed increases)

Being a 50 it may not have the power to accelerate at lower speeds with the pulleys in high ratio position
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hellkat wrote:

Some people are only alive cos its against the law to kill them.

[Phil_P]

The symptom of the dead temp gauge is quite interesting. If the problem with the gauge is with the sensor AND if the ecu uses the same sensor to derive it's engine temperature date, then your guess that it might be at the root of the problem is possibly valid. I would like to see a circuit diagram of the bike to try and figure out if this is a possibility.

The amount of fuel that the ecu tells the injectors to 'squirt' is certainly temperature dependent.
____________________
It is not enough to win, others must fail.
Moto Guzzi 1100 Sport Injection '96

[cheekythomas]

If it was a sensor issue surely the garage will have checked for that as being a Fi purejet engine, it has a fault code system so will be flashing a fault code at them as soon as they plugged the diagnostic box in.

It needs to be looked at by someone who knows the machines, as first checks before bolting any bits to the purejet engine is..

A=check for faultcodes on the ECU

B=check fuel pressure is 8.0Bar at tickover

C=check air pressure is at 5.5Bar at tickover

D=make sure the 2 figures stay approx 2.5Bar different as the rpms are altered.

E=do a compression test to make sure its not a issue with the piston, which reminds me, what oil are you using as the FI motor needs specific oil, not any old 2 stroke from halfords.

But in main reply to the temp gauge issue, then yes the signal from the temperature sender unit screwed into the head goes direct to the ECU at terminal 9. Without that the ECU has no way of knowing what temperature the bike is so will revert to a base setting which will make it run like a pig. So thats certainly the first thing to do... but the fact the dealer hasnt makes me think it needs to go somewhere better as they clearly dont know the system.

Assuming youve been using the right oil so the engine should be ok, the only other common fault on these engines is water emulsion issues in the fuel injector body, which is easy to see by taking it out and looking into the pressure regulator, if its clean all is good, if its full of milky substance then it needs cleaning. The air compressor is also a common problem if the diaphragm splits.

[Phil_P]

Where on a scoot will there be air at a pressure of eight bar? That's 100 psi! Atmospheric pressure is 1 bar (give or take a few millibars) and in the inlet manifold, the pressure will be LESS than 1 bar. 0.8 bar I could understand.
____________________
It is not enough to win, others must fail.
Moto Guzzi 1100 Sport Injection '96

[cheekythomas]

(i got the 8 and 5.5 wrong way round, now edited.... but 0.8bar pressure and the engine wouldnt run at all... wouldnt even fire)

Infront of the rear wheel running off the crankshaft is a compressor unit that pumps air into the fuel metering head at 5.5bar and increases with rpms.

(now added piccy from workshop manual )


https://img176.imageshack.us/img176/5/51089190mq7.jpg

[cheekythomas]

Youve obviously not played with one of these beasts then...

Without getting into the major technical stuff, it basically has a fuel metering head with built in pressure regulator that keeps the fuel to air pressure within approx 2.5bar of each other. It uses a fuel injector that doesnt spray into the engine, just into a chamber that houses the air injector, which also fires and provides the engines air/fuel supply.

(imagine holding a airline blowing into a inlet manifold, and then mist some fuel into the air flow so that the air drags the fuel in with it, and thats basically the system in a crude form.)

[Phil_P]

Ah well, what do I know, even after reading that excerpt however, I'm completely baffled as to what that 8 bar of air pressure actually does!

I can only assume it is a crude form of supercharging.
____________________
It is not enough to win, others must fail.
Moto Guzzi 1100 Sport Injection '96

[cheekythomas]

And i thought i could remember from the training course about the air hitting 8bar.... and here it is... it gets to about 8bar when switched off so its ready for the restart.

https://img138.imageshack.us/img138/176/44642146it9.jpg

[cheekythomas]

[Phil_P]

I understand the principal now. seems like an awful lot of trouble to go to to do what atmospheric pressure does on most 'normally aspirated' bikes. Each to their own I suppose, no doubt it's sold loads of scoots.
____________________
It is not enough to win, others must fail.
Moto Guzzi 1100 Sport Injection '96

[cheekythomas]

It was done to show how much the 2 stroke emissions could be controlled... and that there was no need to kill the 2stroke off.

Its a good system and used by a few companys now, but its costly to make, and to tool up for.

[davidlewtas16]

my runner has a problem where it keeps cutting out when i rev it can any of you help me

[cheekythomas]

As per your main post. More info is needed before any advise can be offered.

Age of machine, type of machine, type of fueling (carb or purejet), has it started all of a sudden or got worse, bike standard or had race exhausts etc fitted... give us some info and we will see what we think

[warped one]

i had the same problem with my derbi senda when i had it. It would sit on idle for as long as you like but when you ride off down the road about 200m later the engine would cut out. I would have the head off and have a look at the barrel. 2 strokes with alterations are a bitch for this because the oil pump usually cannot keep up with the engine, my advice is don't try and ride it anymore until you have had the head off and looked at the barrel and piston.
If it has 'ceased' then it will be a new piston, rings and a rebore.
With alot of time in the garage rebuilding it.
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amnesia - Never in the history of usernames has one been more accurate. Warped indeed. You sir are a fecking oddball.