Pinking (pinging)

[orabanda]

For my rigid AND plunger framed engines, we found on the dyno runs, that a B7Hs in the left cylinder and B6HS in the right cylinder, was the best combination. The hotter plug in the RH side helped correct the richness on that side that all of my A10's seem to have. An induction bias (tapered) spacer between the carb and head also helped. Both of these actions helped to even up the mixture in both pots.
Richard

[trevinoz]

Richard,
             Have you thought about having a head gas flowed to see what is happening?
Possibly a little work on the ports may cure the induction bias.

     Trev.

[orabanda]

Hi Trevor,
You have raised this very good point before, but I will not bother unless I have to remove the heads from the engines.
However, I will go to the trouble next engine I re-build.
Thanks for the tip,
Richard

[muskrat]

I agree t20, our bikes do run better on colder plugs with the modern wee water. The only down side is they can be a little harder to start when cold, and when started must be run up to temp. If started and stopped as soon as the choke is off plugs will foul.
 I'm running 9's in mine and backed off the timing to 28 degrees as well as a super rich mix and it still pings. I do as Rich and throw her back a gear or two.
Cheers

[Slymo]

Just took my 9:1 Super Rocket for 180 mile ride. It went well but was prone to pinking (does anyone but Aussi's call it pinging?) Im running N4 Champions so should probably change to N3's

[muskrat]

G'day Slymo.
I've found changing plugs in winter (hotter) and summer (colder) helps a little.
What grade fuel are you using? Higher octane takes longer to burn, higher compression quickens the burn.
If the plugs show a good colour I'd back the timing of a couple of degrees.
The slightest bit of pinging (detonation, pinking, stick in a can rattle) can have serious consequences.
Cheers

[Tomcat]

G'day Slymo, I run my bikes on 95 petrol as 91 always pings. Perhaps try 98 as well?

[muskrat]

G'day tc.
That's odd as the opposite should apply.
Suppose depends on the brand of fuel and the comp ratio.
I find the A7 with 7.5 runs and doesn't ping on anything but dish washing liquid 
 

[Triton Thrasher]

G'day Slymo, I run my bikes on 95 petrol as 91 always pings.

G'day tc.
That's odd as the opposite should apply

What do you mean, Muskrat?

[muskrat]

G'day TT.
Higher octane needs the ign timing advancec. Higher compression needs the ign timing retarded.
I was outwitted with my Cafe seeing 10.5:1 comp and 105 ocft fuel to go for std timing.  .
Still had to retard timing to 32 degrees.
Cheers

[Triton Thrasher]

Using petrol of lower octane than you need, causes pinking.
That’s why they call octane rating “anti-knock.”

Yes, higher octane fuel burns more slowly than low octane, requiring more spark advance for best running, all other things being the same.

[Slymo]

Ive had a thought that it might be something to do with one set of rings not bedding in. I seem to be making smoke from the rhs pipe and the oil level definitely dropped over the 180 miles. Might have to pull the head off and have a look.