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Message started by seve321 on 04/13/18 at 19:53:48

Title: decel bogging noise
Post by seve321 on 04/13/18 at 19:53:48

My bike one day just started to make a lot of noise and backfiring. I have 155 main jet and a 52.5 pilot jet. I've had this set up for a while and never had all the noise before. I've messed with the air/fuel mixture screw and the pilot jet and I can't get it to let up. Also I noticed the owner before me cut the spring for the little diaphragm near the air/fuel mix screw (I don't what its called). Not sure if that affected it much. do I need to change the jets? Btw I'm at about 650 elevation.

Title: Re: decel bogging noise
Post by Dave on 04/13/18 at 20:02:09

It could be an air leak....have you check to see if the carb manifold is cracked and the bolts are tight? As the rubber ages, sometimes they crack and create an air leak.

Title: Re: decel bogging noise
Post by DragBikeMike on 04/13/18 at 23:17:58

It might also be that the little diaphragm that you mentioned has failed. Do a thorough visual inspection. Hold it up to a light and see if there are any holes or tears. That diaphragm is part of a system intended to surpress the afterfire that you describe.

Title: Re: decel bogging noise
Post by batman on 04/14/18 at 08:18:52

DBM,is right the TEV valve adds extra fuel when the throttle is closed. you should also check the tiny passage that sits behind the little "arm" on the diaphragm ,this is the place the vacuum comes from to open the valve it could be plugged. after firing can also be cause be air leaks in the exhaust.

Title: Re: decel bogging noise
Post by seve321 on 04/14/18 at 12:02:04

To check for sure leaks should I use soapy water and look for bubbles or is there another method?

Title: Re: decel bogging noise
Post by Dave on 04/14/18 at 13:02:12

With a warm engine idling.....take an unlit propane torch around the intake manifold, and listen for any change in idle speed.

Title: Re: decel bogging noise
Post by wordet11 on 04/14/18 at 16:14:34

Could also be a failing petcock. When the stock petcock started to wear out on mine it did this same thing. The bike was running lean but the carb wasn't the issue. The petcock was restricting fuel flow.

Title: Re: decel bogging noise
Post by seve321 on 04/14/18 at 18:53:54

I checked the diaphragm and it looks like it has a little damage but it didn't look like any tears all the way through. I'll be checking for an air leak next.

Title: Re: decel bogging noise
Post by Dave on 04/15/18 at 03:36:50

46706370262724150 wrote:

I checked the diaphragm and it looks like it has a little damage but it didn't look like any tears all the way through. I'll be checking for an air leak next.

If the diaphragm is stiff...it may be too stiff to work. I had to replace one of these diaphragms in a carb not long ago - rubber parts don't last forever.