Engine Trouble Accelerates on start up

Gwarbs

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1:46 PM
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Dec 18, 2022
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When i release the clutch the engine runs but will then rev and start accelerating straight away, feels like its at 10 -15ish mph with no throttle input. The throttle also seems like it isnt doing anything and when i slow down the engine bogs down and stalls (cant get it to idle) if i clutch in whilst its running it starts to redline.

Any help would be greatly appreciated, thanks
 
Air leak or the carb slide is stuck open partially. That would explain why the throttle seems to do nothing at all. Take off the air filter and see if you can spot the carb slide is up or down. If up you may have it turned slightly and caught on a little guide pin that is supposed to keep the slide from rotating. It isn't too hard to get it snagged on that little thing when putting it back together.
 
Thanks for replies,
I can't do the brake cleaner check since I can't get it to sit still and don't feel like going evel knievel to test 😂
I've checked the carb and the choke moves freely inside the carb with the lever with decent friction, throttle also pulls spring in a few mm but I've noticed there isn't an O ring sitting between the inlet pipe and carb mounting point and it's just metal on metal sealed with a hose clamp ("speed" carb, came with cheapest kit on amazon £89) is this likely the issue ? Could I try to seal it with some electrical tape ? If not what is suggested.

Thanks in advance
 
When you are off the throttle the barrel should be almost fully closed. The piston should be near the bottom. When you fully twist the throttle then the barrel should be fully open. It should move a lot more than a few mm.
 
there isn't an O ring sitting between the inlet pipe and carb mounting point
Take the carby to your local autoparts store and have them find you a Viton O ring to fit that receptacle...Viton material is gas and oil resistant and shouldn't swell up and disintergrate on you...I have seen and heard of enough cases here that this tends to solve the air leak problems in many cases...At least it's a good place to start off with...lol.
 
Thanks for replies,
I can't do the brake cleaner check since I can't get it to sit still and don't feel like going evel knievel to test 😂
I've checked the carb and the choke moves freely inside the carb with the lever with decent friction, throttle also pulls spring in a few mm but I've noticed there isn't an O ring sitting between the inlet pipe and carb mounting point and it's just metal on metal sealed with a hose clamp ("speed" carb, came with cheapest kit on amazon £89) is this likely the issue ? Could I try to seal it with some electrical tape ? If not what is suggested.

Thanks in advance
I never said the choke. I said the throttle slide, aka piston.
 
Thanks for replies,
I can't do the brake cleaner check since I can't get it to sit still and don't feel like going evel knievel to test 😂
I've checked the carb and the choke moves freely inside the carb with the lever with decent friction, throttle also pulls spring in a few mm but I've noticed there isn't an O ring sitting between the inlet pipe and carb mounting point and it's just metal on metal sealed with a hose clamp ("speed" carb, came with cheapest kit on amazon £89) is this likely the issue ? Could I try to seal it with some electrical tape ? If not what is suggested.

Thanks in advance
Your best option is a o ring but if you are using the stock intake I found that white lithium grease will also work. If you use grease then you need to remove the carb, put grease on the intake where it meets the carb, then reinstall you carb. I let mine sit for a few hours but I don’t know if it made a difference or not.
 
Just realised the throttle slider was in the wrong way inside the carb, wasn't inline with the guide pin (throttle was open all the time) it now idles and throttle works.

Apologies for my stupidity everyone So grateful for the advice wouldn't have thought this was the issue on my own.
When your other post said it moved a couple mm that is what I suspected was the issue. Glad you got it figured out. These things are fun to tinker with and fixing a problem feels good
 
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