Afternoon

Bought a Lexx Exhaust. Installed and now the bike is backfiring or popping like 2 milliseconds after letting off throttle.

I put stock exhaust back on and all seems fine. No popping or back firing.

It seems I need to figure out if this is considered back firing or popping as the issues for each are separate and the trouble shooting is a bit different?

I am thinking it is an issue with a leak in the header possibly? Or is the bike running rich now? Adjusting the idle RPM screw doesn't seem to help anything.

Stock bike with crank case delete and emissions block off delete. Air box is not opened up and has stock jetting. Checked air filter and it is on with a very good seal. Checked air box to carb connection and it is a also a good seal. The exhaust has the spark arrestor installed.

When I installed the exhaust I never put the clamp on that clamps the header and exhaust piece together that is utilized on the stock header/exhuast. The exhaust piece is different and smaller and sit further back but appeared a good enough seal.

Video of the problem below.

http://youtu.be/sYgHAM3CZSU?hd=1

Some help from fellow Honda X owners is muchly appreciated. I really want to ride with this new exhaust but not if I have issues like this.

Edited by mobgma, 07 May 2012 - 01:45 PM.

PS - There is about a half tank of old gas in there from October of 2011 as it sat through winter. Could this be the issue? I have no issue getting rid of the gas that is in there if this could be the problem but I do not want to get rid of premium 91 or 93 fuel if it just simply is not required.

I am willing to answer questions as necessary or as I know them. The bike is actually a Canadian model 2011 (just a rebranded 09?).

Thanks

Edited by mobgma, 07 May 2012 - 01:50 PM.

To be clear the bike ran great with no decel popping or backfiring.

The only time it pops is when turning the bike off after riding a small pop ensues.

You can't decrease back pressure without changing the jetting.

You are now lean.

Adjust your fuel screw for max idle with hot engine. If it is not near 1.5 turns out, it is the wrong size.
It will probably need to be 2+ turns out, meaning you need a richer jet.

But, you should re-jet anyway, as the stock jetting is extremely lean.

www.jdjetting.com

Sigh... I was hoping it wouldn't come to jetting...

From all the threads I have read it just seems like a black art and that so many people have had issues with jetting after they dive into it. I am worried that this will be me.

mobgma, on 07 May 2012 - 02:34 PM, said:

Hardly a black art.

You change your exhaust, remove the airbox snorkle, and use these jets:

Main 165
Pilot 45
Needle NCVS 3rd clip
Leak 50
Adjust fuel screw for highest idle

All other jets stay the same

Edited by Krannie, 07 May 2012 - 03:34 PM.

I just bought a JD Jetting kit it's more then buying the jets but the instructions are clear and easy to follow.

Took header off and put a new gasket in place of the old one.

No more popping or back fire during decel.

You will still like the bike better if you rejet.

Popping on deceleration is a lean pilot or fuel screw adjustment.  My 450 likes a 48 pilot, yours may differ, but more than 2.5 turns out on fuel screw to get rid of problem means richer pilot jet.

P.S. Don't be afraid of jetting changes!

I'm afraid of jetting, and I've rebuilt my top end! Is this what you mean by the jd jetting kit? http://www.ebay.com....=item3a742816dc

I reckon my bike is running rich as when its cold, say around 8 - 10 oC, my 2006 CRF 450X starts without a choke. I dont know what its currently got hiding inside of it.

If I buy this kit, is this all I need or do I need needles as well?

http://www.thumperta...0x-faq-central/

I needed to re-jet my 450X and took Krannies advice.  The bike now runs like it should (thanks Krannie!).  Don't be afraid of jet changes, JD kits come with clear instructions and it's not nearly as complicated as you may think.  I would recommend getting a service manual and studying the carburetor in exploded view to familiarize yourself with the parts before you jump in though.

JD Jetting has excellent support. I had issues backfiring and running hot even after trying almost every main jet it came with. I called and talked to them and described the issue. They said I was likely compensating for the needle clip in the wrong position even though I followed the directions for my altitude. My bike was running lean because of intake mods and aftermarket exhaust. I took their advice and have not had a problem since.