Explosions whilst deaccelerating

**cornepol** · #1 20 Sep 2003

Hi,

Recently my AT started to produce some banging sounds from the exhaust whilst deaccelerating. Normally that only happens when I go downhill and use engine compression to slow down, but now it also happens on level roads...

Ignition timing is not adjustable, so what could it be? Is is harmfull, or should I have something adjusted?

Cheers,
corne

**mattoneill** · #2 21 Sep 2003

Hi Cornepole,

I occasionally get this on my NX650 (single).

In the early days I was a bit concerned but quickly realised it was the exhaust drawing air back in.

I thought it was a problem more common in singles and not twins.

When I asked a mechanic about it, he said it's worth checking for holes in the exhaust system.

Maybe this helps?

Matt

**RichLees** · #3 21 Sep 2003

explosions sounds fun. dynamite or just backfire? I´d check the idle mixture. sounds like its runnning lean as you shut off and fuel is still burning as it goes through the exhaust. could be dirt in the jet or just needs setting properly. start by adjusting the mixture screw (not the idle speed screw!)
1) warm engine thoroughly
2) count number of turns to gently wind screw all the way in (don´t force it cos it´ll break)
3) wind screw in till idle becomes rough
4) wind screw out till idle becomes rough
5) set screw to mid way between these two "positions"
6) re-set idle speed to correct value using idle speed screw

**electric_monk** · #4 22 Sep 2003

Hi Cornepole

I recently had the same problem with my own bike and the problem was that the valve clearances needed adjusted, in fact one of the exhaust valves was sticking. Once re-adjusted the bike ran perfectly.
Hope this helps.

------------------

**wbagwell** · #5 22 Sep 2003

If this has recently started happening, it may be because you have developed an air leak, which is making the bike run lean. Check the manifold between the carb and cylinder to make sure it's not leaking air. When we were kids, we used to spray starting ether on the manifold to see if it was leaking air, but that seems awfully dangerous now. There are kits you can buy to test for leaks - ask your local shop.

Also, check that yor exhaust headers aren't coming loose from the cylinder head.

**electric_monk** · #6 22 Sep 2003

hearing talk of air leaks reminded me of the other time this problem occurred. If you have a scottoiler fitted check that the vacumn connection to the rear cylinder is not dislodged.

------------------