IT 175 silencer cause pinging??

[vmxrider]

Had a ride on the IT at Mount Kembla yesterday, after half a lap or so bike started to ping on some of the up hill sections.
Backed off the timing but not much difference. Pulled the baffle out of the stock silencer and seemed to help a bit, so pulled the whole silencer off and bingo no more pinging and it felt a lot liveler an peakier. Only did a lap cause a bit noisy.
So why would the silencer cause pinging? would of thought it would rob a bit of power but not cause it to ping. 

[John Orchard]

From the little I know about exhausts, restrictions in the exhaust can cause excessive heat build-up in the engine.  Running too long a stinger or too small a diameter stinger can also cause excessive heat build-up in the engine.

One would think an IT fitted with an IT muffler would be at home with the restriction?  I wonder if it's blocked with carbon?

[John Orchard]

I guess it's time to go through all the checks, plug heat range, ignition timing, jetting?  Never fear Super-Loz will be along shortly  :-)

[cyclegod]

What year IT175 are you talking about?

[vmxrider]

What year IT175 are you talking about?

1980 G model.

[cyclegod]

They are somewhat different in design to earlier 175 mufflers in not being a strait-thru design, between the baffle and the inlet they change direction and this part can block up with carbon and oil quite easily. I have replaced my stock muffler with these items.

http://www.ebay.com.au/itm/Exhaust-Honda-MC-16-21-28-NSR-125-150-250-Carbon-Fiber-/160458191052?pt=Motorcycles_Parts_Accessories&hash=item255c0db0cc

With

http://tyga-performance.com/site/product_info.php?cPath=71_815_854&products_id=2415
http://tyga-performance.com/site/product_info.php?cPath=71_815_816&products_id=1152

I cut the inlet pipe off my stock muffler and wlded it to the flange bracket

[vmxrider]

Thanks cyclegod, might get one of those if no other cure can be found. Can't beat the price including shipping!

[Lozza]

Took me a while..........................

Could be one of a hundred reasons, but excess heat is what starts deto. Your stinger/sliencer could be partialy blocked.