Peugeot Speedfight 50cc AC two-stroke oil in airbox

[andyjonc]

As the title suggests, after a longish run (5+ miles) there is what looks like a mixture of petrol and oil on the transmission casing. When I check the airbox it is full of this fluid.

This fluid is presumably leaking back out of the carb, can anyone suggest why it is doing this? I expect it is happening at WOT (which the scoot is at most of the time!)

Secondary symptom (may or not not be related) is that it only really runs right at idle or WOT, it is very boggy in between. It has a new carb (scooter specific) purchased from WEMoto if I recall so should be the right one for this scooter. I have drained the float bowl and the fuel is E5 in the tank.

Any suggestions gratefully received, many thanks in advance!

[stinkwheel]

Fuel in the airbox is usually a result of an overflowing float bowl.

Was the running problem there before the carb was replaced? If so, that might suggest that the problem is still there and nothing to do with the carb. If it wasn't, then the new carb probably isn't set up correctly and why did you change it?
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[andyjonc]

Hi StinkWheel, thanks for the swift response!

I changed the carb because the oil inlet port was damaged and I was worried the engine wasn't getting oil correctly. I am confident that it is now, although so is the airbox

What else might caused the bogging do you think? I had to repack the exhaust baffle to get it through MOT as it was too loud apparently. I have not had the engine apart in anyway (yet)

[stinkwheel]

Well, an airbox and filter soaked in 2t oil and/or fuel would probably make it run pretty badly, as would an over-full foat bowl so I'd sort out whatever the issue is that's causing that first off.

I'm also assuming it's not a standard exhaust because it doesn't look like standard ones take packing. I'm also assuming it's a sports exhaust on account of being loud enough to fail an MOT. So it could also be that your new carb isn't set up to run with your exhaust on standard jetting. If it was running correcly with your old carb, I'd probably want to check what the jetting is in that one and compare it to what's in the new one.

As a simple test, you can check what the float height is like. Very easy on that type of carb.

On the picture below, you'll see a black drain hose coming off the bottom of the carb. Replace that with a bit of clear hose and route it so it's bending up 90 degrees and running along the side of the carb. Then open the drain screw which is the slotted screw at the bottom middle of the carb on that picture.

The fuel level in the clear hose will mirror the fuel level in the carburettor. I'm not sure what it should be exactly on your bike but it should definitely be slightly below the flange where the foat bowl attaches to the carb body. If it's above this level, you have a problem with either the floats or the needle valve.

As a slight complication I think your bike has a fuel pump so you might need to run the engine (at idle is fine) to get a correct reading on this test. Just be aware of the risk that hose could piss fuel out when the drain screw is open. Make sure it's secured vertically alongside the carb before you try to run it -loosely attached with a cable tie should be fine.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[andyjonc]

thanks again StinkWheel, very comprehensive instructions which I will carry out at the weekend hopefully. I will let you know results!