back firing in the exhaust

[alex_in_az]

The Panterra has started doing this on long decelerations from high speed. I just changed from the massive airbox and high mounted pipe to a UNI airfilter and a low mount cafe style exhaust. timing has not been messed with and the plug color looks OK. The exhaust may be leaking at the joint to the head. what could cause the back firing?

[pchitti]

Lean condition when not on the throttle. Pilot is a little low is my guess. More knowledgeable people will confirm or denounce my idea shortly.

[Weldangrind]

That's exactly my theory.

[katoranger]

Would not hurt to replace that gasket at the head too, but I would same they are correct.

[pchitti]

Good point Katoranger, easy way to test that is spray some starter fluid on the connections between head/carb mount and carb/carb mount. If the engine responds in anyway to the extra fuel, you have a air leak and need to replace the gasket. Usually a o-ring style gasket.

[pchitti]

Rereading.... You meant on the exhaust side... lol

[SpudRider]

If the exhaust is leaking at the connection to the cylinder head, it will definitely cause a backfire. Does your bike use a copper gasket to seal the exhaust header to the cylinder head? If so, you should always install a new gasket any time you remove, and re-install the exhaust header.

[alex_in_az]

Originally Posted by SpudRider

If the exhaust is leaking at the connection to the cylinder head, it will definitely cause a backfire. Does your bike use a copper gasket to seal the exhaust header to the cylinder head? If so, you should always install a new gasket any time you remove, and re-install the exhaust header.

I have a copper xl185 gasket in there, I should probably have not re-used it. thanks, this is most likely the problem

[katoranger]

I would get a new one and start from there.

[SpudRider]

Originally Posted by alex_in_az

I have a copper xl185 gasket in there, I should probably have not re-used it. thanks, this is most likely the problem

I agree. I think you are wise to remove the old copper gasket, and install a new one. Besides ordering the gasket from a Honda dealer, you can also purchase the copper gasket on eBay.

http://www.ebay.com/itm/Honda-XL185S...d0f3f0&vxp=mtr

[alchemysa]

Originally Posted by pchitti

Lean condition when not on the throttle. Pilot is a little low is my guess. More knowledgeable people will confirm or denounce my idea shortly.

It could now be too lean or too rich due to you changing the air flow. Both can cause backfires. If this is the cause its easily tested, and fixed, by turning the mixture screw a 1/4 turn either way and seeing if the backfiring increases or decreases.

[culcune]

Originally Posted by SpudRider

I agree. I think you are wise to remove the old copper gasket, and install a new one. Besides ordering the gasket from a Honda dealer, you can also purchase the copper gasket on eBay.

http://www.ebay.com/itm/Honda-XL185S...d0f3f0&vxp=mtr

Just ordered one, but was having a little trouble accessing ebay earlier, so had also called the local Honda dealer who is also ordering one, too (about $5 a well like ebay)

I was riding on Friday, and right near my work, I heard my exhaust suddenly get louder. I could definitely hear a 'leak' on idle and twisting the throttle. The entire ride home, I noticed it was louder, a little quicker, but also kind of missing at or near full throttle.

I let it cool for a while at home, and noticed that the bottom bolt was a little loose, so tightened it up. Loud leak was still there. Found this thread again, tried to order, called the Honda dealer, as my story above goes.

Out of curiosity, I unbolted the pipe and noticed that there is a rubber seal, but no gasket, and part of it seemed to have blown out, hence the louder exhaust and leak.

So, my question is, the gasket is a universal fit? I never knew my old TMEC was 'missing' a gasket, so it was louder and got louder, even after the pipe was welded on, over time. I wish I knew it needed a proper gasket.

[SpudRider]

Both my Honda XR650L and Honda CRF250X use a copper crush gasket under the exhaust header. My Zong employs a clone of a Yamaha engine, and it uses a different exhaust header gasket, which is not crushed, and can be reused.

[culcune]

I should have asked 'universal' in the sense that my 200 engine is kind of related to a Honda, like Alex-in-AZ's 125. I'll have 2 to 'play' with if I ever had to take off the exhaust later in life.

[SpudRider]

I initially inquired about the copper gasket because I suspected the Hondoid bikes might employ them. However, I don't own a Hondoid bike, so I really don't know if the copper gasket is 'universally' employed. Perhaps other Hondoid owners will chime in, and help us reach a consensus.