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I owned 1978 YAMAHA 175 Enduro (2 stroke) and i had to bore the engine cylinder and now i am using 1.00 piston in it.But i noticed that it's not speeding up above 80,when it reaches 80 it's like engine is turning off because lack off gas, but also rpm is not going higher than 3000, my question is am i experiencing these issues because im using the standard jet? Do i need to expand the jet size as well? Or fault is something else?

  • Welcome to Motor Vehicle Maintenance & Repair! What you're describing could very well be fuel starvation. If so, you'd be going into a very lean burn, which could cause your engine damage. I don't know what size of jets you'd need to go to, but would assume someone else has done what you've done, so they could help you figure it out. But by all means, you really shouldn't be running it anymore until you get the correct jets into the carb or you'll be causing yourself damage to the engine ... quite possibly damage your engine can not be brought back from. – Pᴀᴜʟsᴛᴇʀ2 Aug 28 at 18:25
  • Do a compression test and check against spec for a run in engine. – Richard Abbott Aug 29 at 17:08
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    Be very careful running a 2 stroke engine lean. The fuel also contains the lubricating oil, so if it's lean, it's not just running poorly, the bottom end is starved for lubrication. – Tim Nevins Aug 29 at 19:10
  • I'd also check the if the reed valves are sealing.in the reed block. Cheap enough to replace with new just to be sure. They don't last forever - could be 40+ years old... – SteveRacer Aug 30 at 0:58
  • Richard i did compression test, and it was really good. Thats why i am doubting main jet. – Githendra McShane Aug 30 at 2:47

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