Speedfight has died after one days use :/

Hello guys, basically was riding my speedfight 50cc home from school when all of a sudden it completely cut out, as if someone had just switched the ignition off. Was quite flustered at the time as I was trying to get out of the way of traffic so I pulled over, left it half an hour and tried to restart it.... NOTHING. After a 5 mile walk home I managed to get it to start outside my front door (pisstake!!) however at first it only started with WOT but sounded as if it was idling. All of a sudden it picked up and back wheel span up so i left it for a couple mins and proceeded to go for a spin round the block. It would barley hit 20mph and then once again it died. It not will not start at all. Every 2 or 3 kicks it makes a squeeking noise that sounds like its coming from the cylinder area (will attach a video) https://www.dropbox.com/s/d00royxwu8ouyis/20160505_164704.mp4?dl=0

I have checked and i am getting a nice blue spark (have tried 2 plugs)
Compression seems okay, however has not been checked with a tester
Fuel tap is operating correctly
Carb has been rebuilt so no blocked jets or sticky floats.

STILL WONT START, hope someone can help me :/
Many thanks

 

Sounds like it has seized, the 'squeak' is a dead giveaway. If you have plenty of oil in the oil tank, then either the oil line has a blockage or an airlock, or the jetting is wrong causing the mixture to run weak, leading to a seizure. Has the bike been modded with a sports exhaust or air filter and if so, was the bike re-jetted to correct the fuel/air mixture? Please tell me that you dodn't run it out of 2-stroke oil...

 

The bike has been modded, its got a Leo Vince ZX exhaust and a Malossi E5 open air filter. Was upjetted to 80 and is being run premix using 50:1

 

80 is maybe too low a jet for that setup and your oil premix is too weak. Peugeots use approx. 33:1 (3%) from the oil pump which is still a tad on the low side and they prefer to run more like 25:1 premix (4%) to run well. My TKR2 runs an 82 main jet, with the needle set in the bottom groove to richen the mid-range a bit. My bike has a sports air filter and a Yasuni Z exhaust and although I am still on the oil pump, I add 1% to the fuel when I fill up. It's always best to over-jet then test the bike before jetting down. I'd rather have a smoky exhaust than a seized engine and an extra 1% of oil won't weaken the fuel mixture too much.

I'm afraid that you are looking at a new piston and barrel kit. At least they aren't too expensive on the Bay of E's.

 

Literally just ordered a new piston and barrel kit. As ive just bought another 50 kit can i use my old head?
Have you listened to the video? Worried my ped's never gonna run again need it for school and work
As for my premix ratio, once its all fitted ill switch over to 25:1 and see how that runs. What jet size do you recommend that i use?
Also what needle position shall i use?, as mine is on the middle clip at the moment.

 

Get yourself a jet kit that runs from 72 (the stock jet) to about 90. Set the needle on the lower clip to raise it and make the mid-range a little richer. Start at an 88 or 86 jet and if the bike 'bogs down' on take-off, jet down one size and try again. When the bike just about stops 'bogging down', take it out for a spin, get up to cruising speed and cut the ignition. Check the colour of the ceramic insulator of the plug and if it's grey to brown, you are just about right at the top end and try lowering the needle one notch. If the plug insulator is very dark brown to black in colour, it's too rich - jet down another size, reset the needle to the bottom groove and try again.

The bike will pick up noticeably when the mixture is getting close to correct. If it flies at the top end but is flat in the mid-range, then adjust the needle position again and re-check.

No two bikes are exactly the same and it's a bit of trial and error. Your optimum jet size should be between 82 and 86 I reckon. Different kits jet from different starting points and they usually go in steps of 4, so an 88 will step down to an 84. Some go from a 78 to an 82 jet, so check the jet sizes that are available in the kit before you buy. Your jets are M6 thread, so watch that you don't buy an M5 threaded kit.

Yes, you can use the old head with the new barrel kit.

 

Thanks for your help Merlin, ive just ordered a pack of jets. Could only get 74-96 though.
I bought them anyway as i figured im deffo not gonna be using a 74 jet

 

Erm, no.

So, with that kit, start at 90 and the bike should definitely bog down. Drop to an 86 jet, needle in the bottom groove and note the difference, You should be able to feel and hear it. try adjusting the needle up one notch and see if that makes a difference. To do this properly, then try the 86 jet with the needle in the top groove before dropping to an 82 jet. This will be useful experience for you, as to how your bike behaves with fuel mixture changes. Remember to start at the bottom groove every time you jet down.

You will most likely end up with an 86 or an 82 jet with a needle groove adjustment of some sort for the mid-range.

 

Thanks ever so much for your help. Hopefully my 50 bore will turn up tomorrow and i will get the bike started, as the sound in that video is definitely not healthy

 

On the topic of noise, an engine with a weak mixture will sound very metallic and 'tinny' with a pronounced 'WAAAA!!!' sound. A bike with the correct mixture will sound softer and will have more of a 'burble' to it.

You'll probably find that the top bearing has had it and it may prove to be a challenge to get the piston pin out. Patience and WD-40 are your friends and don't hammer it or you risk bending the con rod.

 

What exactly is the squeak in my video? My first though was piston rings against the bore?

 

It's more likely to be the needle roller bearings that go between the piston and the con rod, the pin goes through it - it will be as dry as a bone. There's a little bearing race in there and your new piston and barrel kit will come with a new top bearing and pin. Slather it in 2-stroke before you fit it, to ensure that it starts up lubricated.

One thing to watch. The piston has 'cut outs' each side of where the piston pin goes through. Make sure than when you fit the circlips that the open ends of the circlips don't face these cut outs, set the open ends at 45 degrees where they face solid metal. If you don't to this, you risk the circlip coming out and getting jammed in one of the transfer ports. Note the position of the old circlips before you remove them and a photograph on a mobile phone helps a lot for reference when you come to re-assemble.

 

Okay, ill remember to take lots of photos. Also I have just looked and my kit does not come with a conrod bearing or pin, should it have? Ill PM you a link the kit ive just ordered

 

You have the pin but you need the top end bearing.

 

Fitted my new 50 kit today and was a bitch to start, finally got it started (would only start WOT) and then could drop to about 1/2 throttle to burn off all the 2 stroke in the bore. Bike would not idle at all, managed to get it restarted after an insane amount of kicks (once again only started WOT) and it was barley revving, all of a sudden it picked up and was okay, ran it at half throttle and took it for a spin, shit acceleration and dies after 2 mind use. After walking it home it started again (once again WOT) and the revv rate seemed to 'pulsate' if you know what I mean? Low revvs then it picked up and then lowered again and then died. Now it will not start no matter what I do

Extremely lost with this need and just need is sorted ASAP

 

OK, so what size jet is in the bike now? If you are still on the original jet you are risking another seizure.

 

Not sure what jet is in it atm as I'm using the one that came in it however I've switched over to 25:1 and used a couple of gloves over the air filter to restrict airflow and risk another seizure due to too much air in the mixture

 

What colour is the plug insulator (the ceramic part)?

 

Old plug was all gunked up so I fitted a new one, and after running it (if you can even call it that) the plug was a powdery brown colour, bit like hot chocolate powder

 

I am at a total loss...