Air movement through carb

[basil_brush]

You'll have to bear with me, I'm a novice with mopeds. Perhaps being a masochist, I acquired a beaten up 2002 Peugeot Speedfight 50cc which I have not yet been able to start. The seller said it needed a new carb but I don't know if that's the only problem. I am rather disheartened to see all the internet comments about these 2 strokes being notoriously bad to start in cold weather...looks like I picked the worst time of year to fix a moped.

It turns over fine with electric start and if I put the coil output near the chassis I get what appears to be a healthy spark about 5-10 mm long. But I have a question about airflow. If I place the palm of my hand over the carb mouth I can feel it sucking against my hand, but I can also feel some blowback pushing against my hand. I confirmed this by holding paper over the carb mouth, I can see the paper pushed out repeated with each cycle. Is this normal for a 2 stroke? I'm making an educated guess it isn't and means the reeds are buggered, am I correct?

[Pete.]

If it's an engine that has reeds they yes that would indicated a problem. The reed block is usually situated after the carb and is normally quite easy to remove.
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a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[Blue_SV650S]

spit-back is not unusual, excessive spitback means there is somethign wrong!!

Deffo get in there and check the reeds.

I assume it won't actually start?

Have you taken the carb apart and checked all jets are clear?
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The purpose of life is to fight maturity.

[basil_brush]

No, I have not got it to start yet. I haven't been that patient with it, but have pressed the starter for about 10 secs for 3-4 times in row, but nothing. There are no worrying sounds while it's turning over. So I'm hoping it's just a fuel input/ignition problem. Of course the cold weather doesn't help - I tried starting it with a hairdryer blowing hot air into the carb but it still wouldn't play.

Earlier this evening I completely disassembled the carb and cleaned everything. I'm leaving the parts on the radiator overnight to dry before I put it together again. I noticed it had a 72 jet, which may need replacing in order to match the derestricted sports exhaust that is fitted.

Tomorrow I plan to take out both the reeds and spark plug for checking.

Unfortunately I'm not experienced enough to know what constitutes excessive spitback. Bear in mind that it's really hard to judge just by feel, but thinking back I'd say the spitback against my palm felt about 25-40% as strong as the suction. This seemed to me like a lot of air to be throwing back.

Still I'll see what the reeds are doing when it turns over, might even take a video of it if I can to show you.

Edit: By the way, jets were definitely clear because I got my hand covered in petrol when I completely choked it with my palm! Still gave it a complete clean anyway because this scooter looks like it been in the wars - even the plastic fan casing is melted and warped on one side, god knows what someone was doing running it that hot! Then again maybe it some accident and not an overheated engine. The nutters who had been working on it before couldn't even fit then panels together neatly, and it's got some very amateur patched wiring at the front, lights and horn all work though. Looks to me like an insurance write off that's been given a shoddy repaint. But as I was looking for the cheapest thing I could find for commuting I can't complain too much, and I don't mind doing some fixup.

[Blue_SV650S]

[joop200789]

if you wana here it run for 2 sec's
drop a thimble full of petrol down the cylinder (where the spark plug screws in) then hit the stater or kick it up

mite help point you towards what's a miss

[ms51ves3]

[Ichy]

I find the easiest way to get a cold bike started is to get the end of the spark plug nice and hot. I use a blow torch but a gas cooker will work fine.

A can of easystart can be useful. It doesn't mention in your profile where your based? Might be someone that can give you hand locally.
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https://www.metacafe.com/watch/1972097/how_to_behave_on_a_forum/

[basil_brush]

[basil_brush]

[basil_brush]

Oh well, this will have to wait a week or so until I get hold of a socket set. The bolts on the reeds are too tight for my tools.

If anyone is in Southampton and could lend me a socket set please let me know, many thanks.

[basil_brush]

Ok, new info to report. The carb has been off overnight. I was going to put it back on when I noticed that the mounting flange on the carb was bent slightly, creating a pretty big gap between it and the inlet flange, and I doubt any gasket is going to seal that for long, unless it was made from springy material that could fill the gap. I was hoping to rescue this carb, even though the choke appears to be wrecked, but it looks like I better just buy a replacement. I don't know if my carb is the original Peugeot one (it says Gurtner France on it) but it looks almost identical to this one:

https://zjshine.en.ec21.com/HONDA-50_Motorcycle_Carburetor--2481176_2481177.html

Mine just doesn't have that brass pipe at the side of the slide and has a hole for the oil pipe near the carb exit. Maybe Peugeot ones are made in China, or maybe this is just an Asian imitation. Has anyone got a similar unwanted carb? If so, how much do you want for it?

Anyway, there's good news too. I wanted to put some petrol in the inlet and see what happens. First though I turned it over to check it will still pump without the carb, which it doesn't because not enough vacuum in inlet, but I was surprised to find that it chugged and tried to catch. I put the fuel line into the inlet and created some vacuum to pump a bit in there, and it chugged a bit harder, a couple of times it even managed to run for half a second. Yay, I guess there's life in the damn thing yet! I drained the battery to a standstill, so that's back on charge. Kickstart is buggered, doesn't catch most of the time, so probably needs a new cog.

What does it suggest though when the engine doesn't show any signs of life, yet you take the carb off and it suddenly tries to do something? Or is there no connection? Maybe it just hasn't been started for ages and took a long time to wake up again.

Edit: I forgot to mention that I opened the valve on my butane pocket torch and let it have some of that in the inlet. That made it catch well and it ran well for a second on that.

[tutton]

I know this might sound silly but are you getting a good spark,
as if your using a butane torch your heating up, almost igniting it so the plugs doing bugger all.
plug out and earth it on frame or barell and turn it over.
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Past: '05 Peugeot XPS '99 Aprillia RS125 '94 FZR600R
Current: '02 ZX636 A1P '51 CCM R30

[basil_brush]

Yes, that was one of the first things I tested a couple of days ago. If I put the coil output near the chassis I get a spark about 5-10 mm long. Haven't checked the condition of the plug yet...I need to buy a socket set to get it out.

Sorry, I should have clarified, the butane torch was not ignited, I just opened the valve to let the gas out. I figured with it being so chilly the petrol will not vapourise so easily, so I thought butane will guarantee to ignite if there's a spark in there, and indeed it did.

[tutton]

Id be checking the plug before going on,
as youve tested the coil, but not the plug itself.
and ive had plugs that just about cough and splutter but wont start.

Careful using butane in your engine too!
____________________
Past: '05 Peugeot XPS '99 Aprillia RS125 '94 FZR600R
Current: '02 ZX636 A1P '51 CCM R30

[basil_brush]

Well, it was only a very quick test so hopefully no problem. Out of curiosity, what is the danger of butane? I guess it might damage the engine from detonating if it's not very well diluted.

[tutton]

Thats about right, same with when spraying loads of brake cleaner down the carb and turning bike over.
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Past: '05 Peugeot XPS '99 Aprillia RS125 '94 FZR600R
Current: '02 ZX636 A1P '51 CCM R30

[The Artist]

Pressure in crankcase may cause to explode and pop some seals out as I found with nitrous.

[Ichy]

[basil_brush]

Bah, it shows no signs of life again today. Looks like I just got lucky yesterday. Maybe it chugged a bit yesterday because the case was probably full of fumes after turning it over so much a couple of days ago. I'll definitely have to check the condition of the plug.

[Pete.]

If the carb mounting flange is bent you could file it flat and make a gasket to seal it. Make a sandwich-plate from 2mm steel to fit under it so that it doesn't bend again when you tighten it.
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[basil_brush]

Thanks, I hadn't thought of that. I'll try it.

Is the electric choke very useful? The choke is broken in this one. I guess I could just improvise a way (like a syringe for example, or just restrict the air flow with my fingers) to get extra fuel in, couldn't I?