Engine pinking

[Sylvester]

Hi. My airhead pinks around the 3000-4000 rpm mark. I can ride round it by going easy (er) with the throttle but it still bugs me. Timing is spot on but the engine has been tweaked by Steve Scriminger in that it has a seibenrock kit on it with the heads machined to fit the 1000 barrels. I will try lifting the needle a tad to see if it makes any difference. just wanted to know if anyone has a cure? It pinked before as well so its nothing that's been done by Steve.

 

[jfheath]

Just a thought from a different bike that I had that used to pink when hot / under load / heavy acceleration - things that helped:

Higher octane fuel.
Avoid E10 fuel - if you can. That stuff certainly made it worse.
Heavier grade oil. I was using 5w30 for UK riding, but it was too thin for the hotter continental climate and the engine ran hotter. 10w40 was much better.

Taking my house keys out of the fairing pocket helped too !

 

[DrFarkoff]

Hi. My airhead pinks around the 3000-4000 rpm mark. I can ride round it by going easy (er) with the throttle but it still bugs me. Timing is spot on but the engine has been tweaked by Steve Scriminger in that it has a seibenrock kit on it with the heads machined to fit the 1000 barrels. I will try lifting the needle a tad to see if it makes any difference. just wanted to know if anyone has a cure? It pinked before as well so its nothing that's been done by Steve.

Run higher octane fuel or Back the timing off a degree or 2 so instead of 6 degrees btdc make it 5 degrees or 4 degrees and see what happens

 

[mikeyboy]

You need to check the timing when it’s fully advanced,
The bean can may have weak springs on the adv mech,or the stops may be worn,causing the timing to be over advanced through the midrange or at full adv.

 

[Micky]

My old R100RS (1979) pinked just as you've described. Got some special 'spacers' to fit between the barrels and crankcases to reduce compression, but before fitted sorted it by using Boyer Bransden electronic ignition

 

[Kenny]

Maybe squish clearance is to tight now with the new pistons/tuning etc. If you don't want to meddle with the timing just yet, try a leaded fuel additive to see if it disappears. Probably not the correct solution
but easiest to try first ?

 

[Sylvester]

I always use the highest octane fuel I can get my hands on. I’ll back off the ignition first. I checked the advance with a strobe. Didn’t seem to far out. One of my “to do” list items was the Boyer ignition but it’s been so damm reliable I’m loathe to screw with it. A bit off subject but I’ve found another 100 gs PD near me for €4800 and I’m struggling to find a reason not to get it. The bodywork looks as if it’s been sprayed or wrapped but still looks tidy.

 

[Sylvester]

Maybe squish clearance is to tight now with the new pistons/tuning etc. If you don't want to meddle with the timing just yet, try a leaded fuel additive to see if it disappears. Probably not the correct solution
but easiest to try first ?

I had issues with one pot running hotter than the other earlier this year and wondered how different the compression was in each cylinder. I bopped down to a local bike shop I buy my tires from and he checked the comps for me. They are high for sure, the mech and the owner were suppressed how much puff the old girl has got.

 

[mikeyboy]

How high was the compression?

 

[mikeyboy]

The motor in my scrambler has 11 to 1 omega race pistons,rs cylinder heads and a 328 fast road cam,
Running seimens ignition ,dyna coil, Taylor leads,even on posh fuel it pinks a bit,ive retarded the timing back to 4 deg.
But under full load it still pinks.

 

[richie moore]

Hi Mike you need to stop it pinking, it could be a bit lean,but i would start by setting full advance to 1 flywheel tooth before the Z mark and try it, if it still pinks go another 1/2 a tooth. it is often better to use a twin plug advance unit and add some ignition than a single plug and retard because of idle and off idle timing. the exhaust and heat can also play a part in a pinking problem.

 

[Sylvester]

How high was the compression?

I don’t know how accurate the gauge used was but according the the graph produced, just under 11. I was more concerned that the comp was the same. The difference in running temp I had was caused by different float heights.

 

[mikeyboy]

Hi Mike you need to stop it pinking, it could be a bit lean,but i would start by setting full advance to 1 flywheel tooth before the Z mark and try it, if it still pinks go another 1/2 a tooth. it is often better to use a twin plug advance unit and add some ignition than a single plug and retard because of idle and off idle timing. the exhaust and heat can also play a part in a pinking problem.

Ok thanks Richard,
I have a twin plug module for the Siemens system ,I’ll fit it and reset the timing as you have described.
Mike

 

[Sylvester]

Timing retarded, pinking gone mission accomplished. Still feels strange deliberately retading the timing. Runs much better. I also got a bit radical this morning and chopped an old screen I had in half. Just fed up with the wind noise/buffet. Had a much reduced noise ride into work this morning. I will get grief when I get back, not sure my neighbours appreciated an early morning fettle.

 

[DrFarkoff]

Timing retarded, pinking gone mission accomplished. Still feels strange deliberately retading the timing. Runs much better. I also got a bit radical this morning and chopped an old screen I had in half. Just fed up with the wind noise/buffet. Had a much reduced noise ride into work this morning. I will get grief when I get back, not sure my neighbours appreciated an early morning fettle.

The R80ST would pull from nothing with the low CR I have maintained that if you want "power" you need more CC's, revs and highish compression Plus of course getting fuel in there and out again
Its amazing what the old ST could do so well, with so little BHp Especially with that SWEET SWEET handling Don;t mention the brakes

 

[Sylvester]

The R80ST would pull from nothing with the low CR I have maintained that if you want "power" you need more CC's, revs and highish compression Plus of course getting fuel in there and out again
Its amazing what the old ST could do so well, with so little BHp Especially with that SWEET SWEET handling Don;t mention the brakes

My fave mod has been to junk the "Tail" Tyres and put the pirelli scorpions on. Doesn't sound like a land rover coming down the road and goes round bends much better. I'm not going off on an adventure anytime soon so no need for the knobblies anymore!!!!

 

[Garry H]

If it's pinking in the midrange and the timing is set corrcet at full advance
If you just retard the timing until it stops you will have too little advance everywhere where it is not pinking
The best option by far is to reduce the advance where the pinking occurs
And the way to do this is to modify the advance curve by altering the spring tension
You can either fit some slightly stiffer springs or bend the tabs slightly ( combination of both is the best )
I have done this on a few moded air heads and cars over the years and it is the best way by far
Because it retains the power that you loose by retarding the timing too much to remove the pinking in one area
Trouble is it does involve a fair bit of trial and error...But worth the effort
Best done on a dyno but you can do it with a few road test also