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My exhaust is 'popping?'


dan.porter15
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Hello.

Please forgive me if I aren't using correct terms and if this is posted in the wrong place, I'm new to motorcycling and these forums :)

So I recently replaced my head gasket on my bike, and was told I needed some exhaust paste, so I visited my local garage and they supplied me with some high temperature exhaust paste. When I got home I fitted the new gasket and put the paste on and went out on it the next day.

All was well until I rode half way down a main road I got to about 55mph and I lost revs (I'm not sure if that is the correct term), which made my bike slow down and a loud pop or bang out the exhaust. I pulled over, waited a bit and set off to my destination and everything was fine as I took it slow.

Unfortunately due to wet weather conditions, as I arrived at my destination and set off again to go for lunch I slipped and my bike crashed and the bike needed a new chain and sprockets but that's a different story.

Anyway I picked up my bike from my garage yesterday, I set off and forgot about this problem altogether as it has been two weeks. The same thing happened again as I got down the road, the loud bang and my bike slowed down. I managed to get it home and I've had a think and I thought I may have put too much paste on my head gasket so I had another look, took the gasket out and sort of cleaned out all the silicon type gunk that was in there. Put the exhaust back on and rode down the road at a high speed. The exact same thing happened.

Has anybody got any ideas? Could some of this paste have gotten into the exhaust somehow? The exhaust is a new exhaust too and it never had this problem at high speeds before. It never happened before I put the paste on. I have a Sinnis Max 125 which I am told is a cheap version of a GS 125 as parts are interchangeable.

Sorry if some of it didn't make any sense and I'd be happy to assist with any part that didn't make sense. Thanks in advance!

-Dan :)

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Welcome to TMBF Dan......pop over to the Newbies section and introduce yourself to the guys when you can..... 8-)


I think you're talking about the exhaust header gasket......which normally shouldn't need any exhaust paste..... :wink:

The bang is unburnt fuel in the exhaust igniting.......so the problem is more about why you're getting unburnt fuel there......which is most likely due to a loss of spark for a bit. Could be a bad spark plug or coil breaking down under load......I'd be changing the plug first and see where you go from there...... :wink:

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Hi Tango!

Thanks alot! I went and put a post in the newbies section :)

I will buy a new spark plug tonight and hopefully should get here soon, was looking at the one I have listed below, would this one be okay?

http://www.chinesemotorcyclepartsonline ... GK4549.php

In the meantime, could I simply clean my spark plug and see if that helps the situation?

Thanks for your reply! :)

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Dunno mate......seems that most parts suppliers are saying NGK CR8E plug for your bike......but that one is a CR7......you may need to pull the plug that's on your bike and check the number on it to be sure...... :shock:

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I had a similar problem on a 250 twin. One exhaust started poping when one o the exhaust studs snapped. Apparently, the air drawing in through the gap was enough to alter the temperature of the dribble of fuel in the exhaust to cause it to ignite. Didn't make any noticable difference with the revs though. Maybe worth a look. Did you put a new copper gasket on the header when you fitted it (from the engine to the pipe)?

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Hello! :)

I pulled the spark plug and I took it to my local garage, they've ordered a new one and it should be here in the afternoon, I'll give that a go thanks! :)

And am I right in thinking the exhaust studs are the two allen bolts where the exhaust meets the engine?

Thanks for your help!

-Dan

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Oh thanks!

One of these bolts needed tightening a bit more, I just didn't want to over tighten them. I've tightened them as much as possible and I'll give it a go when I (eventually) get this spark plug I'm waiting on haha!

Yes I did put a new copper gasket on it when I got my new exhaust and before making this post I did in fact try another gasket and still had no luck.

Thanks for your help! :)

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Hi:) I put in the new spark plug, and like I said in the other post tightened up those bolts, and when I took it out I got up 30mph and the exact same thing happened :/

Could really do with my bike tomorrow morning as I have things planned, any other ideas?

Thanks in advance!:)

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Are your head bolts tightend down correctly, it sounds like the head gasket is leaking air that could be your popping noise too,


If its not compressed the gasket enough then at the higer rpms its could be forcing air between the block and head

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If the problem only happens when you are going faster I wonder if it's fuel starvation?....blocked fuel tank breather or clogged fuel filter? Try running it down the road again and when it stops open the filler cap and see if you can hear a hiss of air being drawn in......if so, it could be a blocked tank breather..... :wink:

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What an abosolute muppet I am, I've kept checking back here for a reply only to notice now that there is a second page, *facepalm*

Haha, sorry for the late reply :wink:

So as a little test I tried my old exhaust back on, and I ran it down the road, and I had no noise, which was great.

However, I could still feel like bike sort of jolting whenever I got to about 7000RPM and I couldn't go any faster, and as the bike was jolting due to instinct it forced me to slow down as it felt unsafe.

I will try opening the filler cap and listening next time I take it out which will be after I've finished another job first, thanks for your help :)


P.S yet again sorry for the late reply

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I had no noise, which was great.


I listened a bit closer and you can hear a popping/bang noise, it's because the baffles are bad on the exhaust and the noise of that covers up the banging. Which means the old exhaust didn't do any difference, and also as I got off the bike I noticed an almost screeching high pitched noise but I couldn't identify which part of the bike it was coming from, could that be anything?

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is the bike water cooled and if so is there any coolant in it.once engine is off then nothing should be making high pitched noise unless its the fuel tank gasping air into itself when you turn it off and can hear the noise open petrol cap quickly and see if you hear it breath and the noise stops

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The bike is not water cooled. I went down the road on it today, and I opened the cap and I could not hear anything at all. I did this when I got too my desination and when I got home and I couldn't hear anything either time.


The high pitched noise was from my old exhaust, which was only used to see if the exhaust was making the noise. Let's forget I mentioned that :wink:


Thanks for your replies:)

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