cateye engine problem home made scooter please help need advice

[steptoe1111]

hey guys how is everyone i hope this is the right part of the forum .
i have a homemade gas scooter that i whipped one day out of boardem
it has a early cateye pocket bike engine 49cc that i salvaged off hard rubbish years ago now this thing has been getting me around for the last 6 months after the coppers gave me a bright yellow canary on my old falcon and i cant aford to drive so ive been getting around on this it does or was doing 50kph an hour at full WOT wich was mesured with a gps (true no joke)
until i decided to take it for 1 hour long ride wich i held it at WOT the whole way now i am 4 strokeing at about 4 thou rpm where i was geting about 10+ out off it before, i have already replaced the fuel pump diaphram thinking it may have been streched but it made no difference my fuel econamy has gone out the window and i am spitting a fair bit of fuel out tha venturi on the carb i have compreshion checked the cylinder and i am only down by 5 psi after that long ride... is it posible i have worn the rings down? the only other thing i can think of is the coil winding may be breaking up i have already checked for cloged muffler, dead spark plug and compreshion seems fine if any one can give me some ideas on this thing it would be great thanks guys i have included some photos aswell its my 4th build so far and probably my best so far i recently bought a f80 enging kit off ebay and i recon this thing beats it by a mile for performance and quality
here are pics

here is a quick you tube vid off my scooter the build only took about 5 hours
and i am acualy realy blown out at how long this motor has lasted i only expectid it to last about 200k if i was lucky... but 6 months !!! its a great motor
CLIP0002.AVI - YouTube

 

[DaveC]

Hey there I'm thinking you've worn out the cylinder from all the crap thrown into the air intake by the front tire. I'd bet the bottom end bearings are about shot, too. You gotta run something over the carb even if it's an old nylon. If you ever tear that motor down when it's done there will be a sandy oily grit packed into corners inside the bottom end of the motor. Just imagine how much has gone through....

 

[steptoe1111]

yeh thanks mate your probably right ... it was a long ride on the dirt i shoul take a closer look .....in the motor and maybe get some crank bearings with the piston kit but i might try the carb kit first and then work from there ....... i just cant see how the botom ant top end can be screewd when ive only lost 5 psi out of the cly compreshion and looking through the exhaust port it looks preety resonable .... i will post my findings for everyone but is it posible the metering diaphram,float needle or spring in the carb can that where out after something like that a good hard long ride??? i would not have thought so!!! but its not driveing a brushcutter its driveing me 80kg with a 49cc motor at 50 kmh ....i supose you can get dud aftermarkit kits for walbro carbs !! but on a riggy didge pocket bike do they re-kit there carbs after each race????? due what i described above....... whould be interesting to know !

 

[wayne z]

I would just try changing the rings and seals. That's usualy the first thing to wear out sorta quickly on 2 strokes. Bottom end prolly OK.
On that long hard ride and without the cooling shroud, the rings prolly got too hot and lost their tension.
On race bikes they change the rings quite often.
No, the carbs don't wear out quickly no matter how hard you run it.

 

[rustycase]

lol

Yah...really should have an air cleaner!

Nice scooter!
rc