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I have a 150cc Chinese dirt bike. About a month ago it started to bog a lot. It could only start on choke, so I took apart the carburetor, cleaned it and put it back together. The problem still there. It doesn't need to start on choke anymore. The bog is pretty bad with constant backfire and it will not idle (like at all).

The bike doesn't sound the same at all. It becomes really hot really fast and shuts down when I let the gas go. When I try to ride its like it has hiccups. Like there's large pockets of air in the engine. I tried playing with the mixture screws on the carb, but it makes no difference literally.

If I slowly turn on the choke it almost goes back to normal, but backfires badly and shuts off. After that the only way to start is to push start with the choke off and it's back to the insane bog and backfire. There's a small smoke leak from the connection of the silencer and the exhaust connection, but I don't think that's the problem.

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  • Have you checked the air filter? Has it had a service recently? – Solar Mike Sep 22 '18 at 13:03
  • I tried to remove the air filter but its been siliconed into the fitting. – MohammEd Arbaz Sep 22 '18 at 13:52
  • But i dont think the air filter can cause such backfire and overheating – MohammEd Arbaz Sep 22 '18 at 13:53
  • I think the former owner might have serviced the air filter – MohammEd Arbaz Sep 22 '18 at 13:53
  • If i cud post a video it cud really show the condition of the bike – MohammEd Arbaz Sep 22 '18 at 13:54
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Your problem is a fueling problem, as in it's not getting enough fuel. This is the reason for the bike getting hot when you do run it (running lean will cause it to run hot). This leads right back to the carburetor.

You can try one of three things (or all three, if it suits you):

  1. Try to clean and/or rebuild the carburetor again. I'd say this would most likely fulfill Einstein's theory of insanity (ie: doing the same thing over again expecting different results).
  2. Running a heavy concentration of carb cleaner (like SeaFoam or BG44K) through your carb. This may clean up the issue. This is a long shot, but worth a try before moving on.
  3. Replace the carburetor. This is most likely your best bet, will save you the most time, and be the easiest to accomplish.

More than likely you got a batch of bad fuel or it sat too long or whatever. The carb no longer wants to function correctly, so your best bet is to replace it. It will take care of it quickly without a lot of muss/fuss.

I doubt at this point you could blame the air filter, as it would only help to make the air/fuel richer, though it wouldn't help with running at higher speed.

  • Do you think it might be a problem with the engine maybe the timing chain ? – MohammEd Arbaz Sep 22 '18 at 17:07
  • I cleaned the carb several times i even used seafoam but the problem persists. It had a hard time starting but after cleaning the carb the bike starts but has the hardest time ideling – MohammEd Arbaz Sep 22 '18 at 17:09
  • Its like the bike has the worst case of the hicups – MohammEd Arbaz Sep 22 '18 at 17:09
  • Everything you're saying is pointing to a fuel issue to me. You may just find out how much a new carb is for the thing and see if it's worth it to just replace it, but that's going to be up to you. – Pᴀᴜʟsᴛᴇʀ2 Sep 22 '18 at 17:19
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    There is a fuel filter on the supply line or screen on the fuel shut off valve that may be clogged. Replace the filter or remove the valve from the tank and clean it. – Moab Sep 22 '18 at 18:50

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