Aprilia rx50 2004 dies after 5 minutes

[paddee]

Hi,
If any one can assist please? I've tried searching, but not finding anything relevant. Unless I've missed some results.

My son's bike is cutting out after 5 minuted riding. Then will not start.

Last night, it cut out after 5 minutes (or so) went out to help him, seemed to start after about 20 minutes.
Nearly made it back home, engine cut out again. (about 5 minutes ride)

I've removed carb, stripped and cleaned.
Checked reeds, cleaned.
Checked head and piston rings, all look good. New gasket set installed.
New spark plug fitted.

Started easily
It idles happily for about 10 - 15 minutes.

Son takes it out for some testing, 5 minutes, it's cut out, non starting.

I have a spark with spark with plug held against cylinder head. Fuel is flowing to card.

He bought it last month, and so far has had minimal riding on bike.
He did ride all way from Bournemouth no issues (about 2 hours)

Paddee

[wheelers]

good luck too you, these are the worst problems!!
sounds like something heating up after time, could be piston growing and semi seizing (insufficient clearance) . on a scoot could be electric choke not cutting off and over fuelling, could be tappet gap closing up, could be cdi overheating.
finally on a fuelling point, low compression ,lack of vacuum or hole / cracking of vacuum pipe not operating fuel tap diaphragm.

cross out any of the above that do not apply, ie 2 or 4 stroke valves. manual or vacuum op tap etc good luck

[paddee]

..some thing over heating, my thoughts indeed.

piston and rings seem ok. But I've not got kit to do a proper pressure test.
manual choke. don't think it's that.
I was thinking spark plug breaking down, but it's only a few weeks old (could be some fault in it though?)
Possibly the 'coil' We did have a plug fall off it last week. Not so simple this time. Maybe inder load, this is heating up and failing? But then when spark plug out of head, it is sparking :(
as it's a 2 stroke, not alot of moving parts.
There's no vacuum pipe from card. Just fuel in, oil in, over flow and throttle cable.

[Wes]

Bit of a long shot, but could the choke be sticking ? This could cause the engine to flood and cut out.

[Hondafan]

when it cuts out is there fuel in the carb at that time?
Don't check it a few minutes later, loosen the screw in the float bowl straight away.

Or

Try opening the filler cap and road testing it to see if the tank breather is blocked up, preventing fuel flow.

[Wes]

Was thinking of the breather hole myself mate, worth checking, good shout.

[paddee]

removed filler cap, still no good. If I remove fuel pipe from bottom of tank, fuel flows plenty.
The float chamber is not so accessible. Take about 10+ mins to get at it. So, the carb is the only thing I can't really check so well.
I've removed, sprayed carb cleaner all through it, and cleaned/dried with compressed air.
I do think it's fuel related though (just my thoughts)
The bike is also so powerless when moving off from stand still. If that is a hint to anything else? Unless all 50's are sluggish to get going from 0mph?

[Hondafan]

A 50 is never going to be quick, It's all relative, really

Have you actually removed the carb from the bike?

Is the exhaust or air filter blocked?

Has the bike had any other work or modifications done to it?

[paddee]

Carb had been removed, dismantled, cleaned and refitted. There was dirt in the Carb.
Air filter not blocked. Will double check exhaust.
I believe it's non standard carb and non standard exhaust.

[Hondafan]

I believe it's non standard carb and non standard exhaust.


That doesn't make things easy.

What carb is it?
Is the jetting right?

Where in Melksham are you?

[paddee]

Forrest area. The bike has worked. But recently seems to be failing.

[napalm]

Not sure if it's cold enough but could it be Carb freezing?

[paddee]

Not sure if it's cold enough but could it be Carb freezing?

It was close to 0° last night. But I'd thought after 10 to 20 would have started again?
It is a water cooled engine, so keeps heat for a while.
Will see if it starts this morning.

[paddee]

That doesn't make things easy.

What carb is it?
Is the jetting right?

Think it's a Dellorto PHBG21
What symptoms should we expect if the jetting is wrong?
Tick over seems fine.
It seems to rev fine.

We know the carb and exhaust has been changed, but no details to what they are exactly.

[wheelers]

right carb? jetted for new exhaust??

[paddee]

I've no idea what size jets we require for filter or exhaust, when the bike is running, it seems to be running fine.
Just tried bike, numerous times, kick start and bump start, nothing! I can hear it sucking air through intake.
Have managed to remove card from manifold, there is fuel in float chamber. but it's not so clear. Quite grey to black.
So, thinking, maybe too much 2T oil getting in there, not sure what stage the oil is mixed into petrol.
Petrol from tank looks clean, but could be getting mixed up, and some 'sludge' from bottom of tank getting into carb.
Or the reeds are failing, and we have oil/petrol mixture coming back into card some how.
Of course, I'm still open to suggestions.

[paddee]

Installed carb.
pipes moved to see text.
Card is now off.

[paddee]

update,
Near emptied fuel tank, it looks clear, even shook tank while emptying.
thought I'd check the 'jets' looks like the middle jet was blocked! I didn't clean this one yesterday. (don't know why I didn't bother with this one)
I've just cleaned all jets and put it all back together, it started, instantly.
Just need to know where the dirt is coming from.
Son is off to refuel now, hope he gets there n back.

[wheelers]

where does he get fuel from?
you could try changing fuel pipes as big problem with ethanol eating rubber pipes.

[wheelers]

http://www.telegraph.co.uk/motoring/classiccars/9108430/The-ethanol-threat-to-classic-cars-and-bikes.html

[paddee]

may have the problem solved ??
Again he came back in about 5 to 10 minutes, bike dead again.
Petrol in float bowl was almost oil like!
The breather tube on idle screw side was connected to a nipple on to of gear box.
When we got bike, there was a tube in same place, but was just a bit too short. So I replaced with longer tube and connected them up.
Thinking crap from here is feeding up the breather tube, back into the bowl, blocking jets, cutting out bike.
He's back out on bike, with no tubes connected for now.
Feed back on this thought please

[Hondafan]

Well?

How did he get on?????

[paddee]

not too bad.
The air filter got soaked, as it's just one of those foam things (don't like em me self)
So bike came to a halt.
Air filter off, runs ok. Got a new 'covered' air filter on order.
I'm thinking we're so close to a fix now.

Thanks so far for all the input.
Will update after his next ride out. Probably tomorrow afternoon.

[db]

There shouldn't be a hose from the carb to the crankcase /gearbox breather, they should both vent onto the floor basically.......I've never heard of a jetting problem letting it run well for x amount of time then stopping it dead.

[paddee]

When bike cut out. The bowl looked to have 'thin'oil.
All vent pipes replaced with new. All vented to floor. Bike is running much better.

[paddee]

He's been out these evening, after school, and still going ok.
Looks to be good.
But I'll replace fuel pipes any way. Not much else to do with it now.

[Conehead]

Well done for getting it sorted.