Decal poping

My little brothers crf80f runs great but when deceleration it pops all the way until it stops  or if you give it gas again. its pretty annouing but is it harmful and if so how does it happen and how do i start it?

The usual suspects are an air leak in the exhaust, it's too lean in the pilot circuit or both.  I'm not familiar with that bike but perhaps with a little more information, someone who is can get you pointed in the right direction.   Is the bike completely stock?  Has it always done it or is this something new?

 

Doc  

19 minutes ago, Doc_d said:

The usual suspects are an air leak in the exhaust, it's too lean in the pilot circuit or both.  I'm not familiar with that bike but perhaps with a little more information, someone who is can get you pointed in the right direction.   Is the bike completely stock?  Has it always done it or is this something new?

 

Doc  

The bike is all stock and it has done it for the 2 days that i have had it, if it would be an air leak would it be where the the header meets the engine or where the header meets the muffler i think probobly at the engine because the header and silencer are welded together. I will also adjust the pilot when i get home

Pop on decel is caused by unburnt fuel igniting in the exhaust.

Has you done anything to the bike recently like adding an exhaust?

2 hours ago, CRF James said:

Pop on decel is caused by unburnt fuel igniting in the exhaust.

Has you done anything to the bike recently like adding an exhaust?

i have not everything is stock

 

2 hours ago, CRF James said:

Pop on decel is caused by unburnt fuel igniting in the exhaust.

Has you done anything to the bike recently like adding an exhaust?

wait if that was the case couldn't it be valve issue, and if so how bad would it be

 

Or maybe just running to rich or lean? im not sure.

 

The first this I would suggest then is adjusting your air fuel screw.

12 minutes ago, CRF James said:

The first this I would suggest then is adjusting your air fuel screw.

okay i will do that, Should i start by making it leaner or richer

I'm with Doc on the exhaust leak.  If it's popping that  bad you should be able to hear the leak.....................hold a rag over the end of the exhaust plugging it and listen.  Check the nuts at the cylinder head for tightness.  Next, pull the exhaust and check the flange on the header pipe to make sure it isn't cracked...........and check condition of gasket. 

Old School Al

Edited by Old School Al
1 hour ago, Old School Al said:

I'm with Doc on the exhaust leak.:thumbsup:  If it's popping that  bad you should be able to hear the leak.....................hold a rag over the end of the exhaust plugging it and listen.  Check the nuts at the cylinder head for tightness.  Next, pull the exhaust and check the flange on the header pipe to make sure it isn't cracked...........and check condition of gasket.

Old School Al

okay i will

Great suggestion Hunter

On 11/14/2017 at 1:01 PM, CRF James said:

Great suggestion Hunter

could an air leak in the carb cause the problem

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