Carb Air Mixture Screw Coming Loose

Slug · 10-28-2022, 06:23 PM

I have the Nibbi PE28 on my bike and it was running quite fine at 2 turns out since installing and tinkering with it.

Me being a dumdum decided to try 2.5 to get rid of barely noticeable backfire at idle... Now the screw won't stay where I set it at all.

e.g. set to 2 turns out, ride down the road a mile perfectly fine, come to a stop, and it starts bogging badly, screw is now out 4 - 6 turns.

I don't want to use blue loctite because.. well, it's a brass screw and I'll never get it out again.

Anyone else have a similar issue they were able to resolve?

krat · 10-28-2022, 06:38 PM

You have messed up the spring on your idle mixture needle.

Go to a local motorcycle or small engine shop and buy a new one.

Slug · 10-28-2022, 06:48 PM

Thanks. Not sure how that would have happened simply by loosening it half a turn.

Should still be under warranty too since I ordered it on 6 Oct.

Maybe I ought to contact Nibbi about it as well.

severely · 10-28-2022, 07:17 PM

Maybe try stretching the spring slightly. Easy does it as a little is a lot. What is needed is sufficient tension on the mixture screw to prevent the screw from rotating. Good luck. Make sure all the o-rings, washers, etc. are all there.

10-28-2022, 06:23 PM	#1
Slug Join Date: Sep 2019 Posts: 63	Carb Air Mixture Screw Coming Loose I have the Nibbi PE28 on my bike and it was running quite fine at 2 turns out since installing and tinkering with it. Me being a dumdum decided to try 2.5 to get rid of barely noticeable backfire at idle... Now the screw won't stay where I set it at all. e.g. set to 2 turns out, ride down the road a mile perfectly fine, come to a stop, and it starts bogging badly, screw is now out 4 - 6 turns. I don't want to use blue loctite because.. well, it's a brass screw and I'll never get it out again. Anyone else have a similar issue they were able to resolve?
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10-28-2022, 06:38 PM	#2
krat Join Date: Nov 2019 Location: KY Posts: 265	You have messed up the spring on your idle mixture needle. Go to a local motorcycle or small engine shop and buy a new one. __________________ %90 of the Chinese motorbikes ever made are still on the road. The other %10 made it back home.
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10-28-2022, 06:48 PM	#3
Slug Join Date: Sep 2019 Posts: 63	Thanks. Not sure how that would have happened simply by loosening it half a turn. Should still be under warranty too since I ordered it on 6 Oct. Maybe I ought to contact Nibbi about it as well.
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10-28-2022, 07:17 PM	#4
severely Join Date: Oct 2021 Location: odessa MO; donna TX Posts: 152	Maybe try stretching the spring slightly. Easy does it as a little is a lot. What is needed is sufficient tension on the mixture screw to prevent the screw from rotating. Good luck. Make sure all the o-rings, washers, etc. are all there.
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