My raptor 80 (sort of) engine issue
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Thread: My raptor 80 (sort of) engine issue

  1. #1
    Stock, ready to MOD YFM80moto4's Avatar
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    My raptor 80 (sort of) engine issue

    Hello everyone!

    I have a bit of a unique situation. I am currently building a 1988 yfm80 moto4, which has the same motor as a raptor 80, but I'll go into more depth about my build later. It's been rebuilt from the ground up with all raptor 80 parts. My question is: when I give it gas just from idle, it wants to cut out at lower rpms but if I'm able to keep the throttle in a certain spot it will slowly climb in rpm and then hit a certain rpm and rev amazing all the way to redline. As the rpms drop, if I give it gas to rev again, it wants to bog or cut out. So in order to have power it has to be in higher rpms. I can't figure it out. It sounds to me like a carb issue.

    Let me list what I'm working with:

    Raptor 80 carb with 15 pilot jet and 85 main jet. Custom intake with 35mm cone filter. All electronics are from Raptor 80 including the cdi box which is a procom. 48mm wiesco piston, vesrah valves with new valve springs.

    Spark is good, and I know it's getting fuel. Valves are in spec and compression is good. It starts and idles like a boss and higher rpm sounds awesome. Just can't figure out why at lower rpm it wants to bog. Almost like I have to wait for the motor to catch up to the throttle position. Anyway thank you in advance for any advice!

  2. #2
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    I had this similar problem when I opened up my Raptor 50. It was getting too much gas(jetted to rich). We had to ease into the throttle to take off. If you just pegged it, it would die. I don't know much about the 80 but that's my experience.

    Coop we miss you brother..

  3. #3
    Stock, ready to MOD YFM80moto4's Avatar
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    Sorry I haven't updated since my last issue. I haven't been able to figure it out due to now a random no spark issue. It started and ran one night and the next day it doesn't get spark. I don't understand haha. I tested the pick up cool and it was below spec. Installed a new Yamaha one and same issue. It will get spark the first crank and then nothing. I dug a little deeper and noticed the pick up coils test perfect not installed. But when connected to the harness they are below spec. Before it was a custom harness I made but since then I installed a raptor 80 harness and I'm still getting the same issue. The only thing I haven't changed is the stator and flywheel. Both are different part numbers from the raptor 80 but in theory that shouldn't matter right? It started before so why would it not now?

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