My friend's Pitty is having this problem...hes bummed out about it, help us?

[ThisGuy]

He started his bike up last night and it was fine...He changed his gas from regular to premium and now it does this...It idles but constantly bogs in and out (no cutoff)...His carb is spotless, no blocked jets...What could it be? Valves? I dont think it is since all he did was change his gas....He took his carb apart 3 times and cleaned it with cleaner but the problem was still there.

 

[bulldog93]

Check the fuel pet**** and filter (if fitted). They might be blocked.

 

[ThisGuy]

Check the fuel pet**** and filter (if fitted). They might be blocked.

I told him what you said to do, and he said that his tank is brand new and it checked it today and it looked fine and so did the air filter

 

[bulldog93]

Is he cracking the throttle or opening normally?

Changing the fuel wouldn't cause anything like this. Has he done anything else to the bike since? Only other thing I can guess is the spark plugs on its way out but that's happens pretty quick.

 

[rotn50]

Maybe a batch of bad fuel, as in water in the fuel, drop a cup of methylated spirits in the tank and this will evaporate the water if there is any, and it won't hurt anything on your bike.

 

[ThisGuy]

Maybe a batch of bad fuel, as in water in the fuel, drop a cup of methylated spirits in the tank and this will evaporate the water if there is any, and it won't hurt anything on your bike.

I'll let him know. And he does not do anything to the throttle he starts it lets it idle, and it runs bus down a bit then the rpm gets back up and it repeats like that. He just bought that engine(Lifan 125 manual) he did no engine upgrades to it. Bike wasn't doing this before but now it does

 

[rotn50]

Do the fuel thing or run some other fuel just to try, still sounds like a fuel prob.

 

[GooseMan]

Could it change the mixture maybe, being more explosive so might be running rich or something, just my guess what do ya think.

Also how does it run when you open the throttle and close it slowly.