Lexmoto Street 125 (2012) engine trouble

[Punkforareaso...]

Hi guys! This is my first post on BCF so bare with me! I have a Lexmoto Street 125 (I know I know, "chinese bikes are rubbish" etc ).

I have had it since last October and when I purchased the bike engine wise, all was okay! It has been running absolutely fine since purchase (other than the few problems the previous owner forgot to mention regarding the shoddy wiring for the brake light and ill fitting hub on the rear wheel!)

I have done a few modifications; I put an after market exhaust on it (a stubby megaphone) this caused a big loss of power which led me to replacing the air box with a performance air filter, re-jetting the carb, and putting on an engine breath filter ( Replacing the pipe that used to go into the air box from the engine ) to get it back to normal running order, but sounding much better!

Bike has been running perfectly since these modifications where made, even changed the back sprocket to one with more teeth to give me a bit more acceleration at the price of some top end speed (very useful being in and around London all the time!)

BUT here is the issue! Yesterday while I was riding back from university, The engine just started sputtering out all of a sudden and the completely stopped, so I rolled to the side of the road and spent about half an hour trying to get it to start again, with and without choke, even tried bump starting it but to no avail! Eventually it came back to life and i was able to complete the journey home. Later on that evening I encountered this problem a further 3 times on a longer journey, engine definitely warmed up plenty, full tank of petrol, Spark nicely brown and HT lead only 2 months old and seems fine! At a complete loss as to what the problem could be and was wondering if anyone else had encountered similar problems and if so, what steps you took to solve it?

Sorry for the mini novel but thought it best to provide as much info as possible!

[Rogerborg]

That sounds like fuel starvation.

Could be:

Stuck float - give the carb a whack with something rubbery, woodeny or meaty. It wouldn't hurt to drain your float bowl as well to remove any crud that's in there. But since it recovered by itself, I'd lean more towards what's behind door number 2...

Vacuum in the tank. Air has to get in to replace the fuel that's coming out. Fuel tap off, detach hose from carb, put in a jar. Tap on, check the rate of flow. Pop the fuel cap open and see if it increases. If it does (or just on general principles) give your cap a good clean and see if you can clear any breather hole or valve.
____________________
Biking is 1/20th as dangerous as horse riding.
GONE: HN125-8, LF-250B, GPz 305, GPZ 500S, Burgman 400 // RIDING: F650GS (800 twin), Royal Enfield Bullet Electra 500 AVL, Ninja 250R because racebike

[Evil Hans]

Everything he said, plus if you've got a fuel filter make sure it's not blocked with crap.
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Triumph Sprint ST 1050. And it's Red.

[Punkforareaso...]

Cheers guys, I did give it a whack and The flow did increase when I opened the fuel cap! so I gave that a clean and gave it a ride and seems okay for now, will check the float when I have some daylight tomorrow!

[Rogerborg]

I should mention that both my Chinese HN and Indian Enfield vent(ed) the tanks thoroughly by dint of the caps not sealing tightly. You may be suffering from decent build quality.
____________________
Biking is 1/20th as dangerous as horse riding.
GONE: HN125-8, LF-250B, GPz 305, GPZ 500S, Burgman 400 // RIDING: F650GS (800 twin), Royal Enfield Bullet Electra 500 AVL, Ninja 250R because racebike