crackling noise from engine

Are you suggesting running 87 octane unleaded, ethanol laced "regular"?

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Well, that is what I have been running in my stock 850 for many years and it runs beautifully, also for what it's worth my motor is recently rebuilt with 9 to 1 comp

why? does your standard non Combat motor require a higher premium octane to run cleanly?

1up3down said:

Are you suggesting running 87 octane unleaded, ethanol laced "regular"?

Click to expand...

Well, that is what I have been running in my stock 850 for many years and it runs beautifully, also for what it's worth my motor is recently rebuilt with 9 to 1 comp

why? does your standard non Combat motor require a higher premium octane to run cleanly?

Click to expand...

I put a JSR .023 head gasket to try and up the pitiful 8.5:1 a bit. It absolutely pings in protest when there is a load of fake premium pumped in there. You must have the timing back way off to allow 87 usage. :shock:

Factory shop manual recommends minimum 94 octane premium with 8.5:1 compression and timing set at 28 degrees BTDC. More compression, more octane necessary.

Danno said:

Factory shop manual recommends minimum 94 octane premium with 8.5:1 compression and timing set at 28 degrees BTDC. More compression, more octane necessary.

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The method for computing octane as listed in the Factory shop manual is different than the method currently used in the USA.
I believe the "94 octane" quoted equates to 89 octane in the USA. My '74 850 with a base gasket, an eyeletted head gasket and
on standard bore runs fine on 87 octane. I have no complaints about how fast it is.

According to the conversion chart I see the Autolite 63 converts to Champion N9Y and N11YC.

Quite a range difference from the standard plug N7Y.

lazyeye6 said:

Danno said:

Factory shop manual recommends minimum 94 octane premium with 8.5:1 compression and timing set at 28 degrees BTDC. More compression, more octane necessary.

Click to expand...

The method for computing octane as listed in the Factory shop manual is different than the method currently used in the USA.
I believe the "94 octane" quoted equates to 89 octane in the USA. My '74 850 with a base gasket, an eyeletted head gasket and
on standard bore runs fine on 87 octane. I have no complaints about how fast it is.

Click to expand...

Here in the US of A the octane reported at the pump is the average of the sum of the Research Octane and Motoring Octane ((R+M/2)). Never had a problem running 87 Octane in my 74 850 Commando, even after bumping compression with Omega pistons to 10.25:1 and a mild cam. Well, there was one time in the beginning but it was attributed to lack of drain hole drillings behind the oil ring on one piston. The oil had nowhere to go and caused detonation on that one cylinder when hot. Excess oil in the combustion chamber can (and does) cause pinging. I had read where it reduces the effectiveness of the Octane but I like to think of it as overwhelms the ability of the Octane. Regardless, once the oil passages were drilled, detonation and smoking ceased. Keep in mind that these were fresh and clean piston crowns and combustion chamber with little to no coking.

If I were Danno I would confirm ignition timing (don't rely on timing placard in primary case), check jetting, check plug heat range; maybe a fresh set of plugs and do a plug chop. Maybe Danno has a lot of coking in the combustion chambers. Of course Danno could just keep on keeping on with the higher octane since it is working.

C V Carb users sometimes think you can whack a throttle ' on ' under any conditions .

Generally you need to ' milk the throttle ' on occasions , sometimes to avoid pinking ,
normally at low rpm , high load , where wide opens not ging to do a lot . Air to slow to pick up the juice , so goes lean .

That Said , was obviously the wong heat wange . Good way to Melt Pistons - to hot a plug . To cold pottering around in winter might oil them ,
only had that happen once . Had a few autos where theyd fitted NGKs and only tightened them onto the washer lightly .
seein new they have a crush washer , they need a good half a turn from ' contact point ' , or they wont earth properly - so stutter and fart .

CLEANING plug & Head threads and a drop of oil or grease is essential in ALLOY HEADS , grit or grot'll stuff things nicely . Koper Kotes good .

Anti Seize - Anti Gall - Heat proof . Any uva recomendations for Spark Plug Grease ? :?:

Tonight I changed out the needles and needle jets for new. The old needles were not only about a hundredth of an inch smaller in diameter, they were an eighth of an inch shorter, making the center clip position the equivalent of a new notch below the lowest. And a drill bit shank that passed loosely into the old needle jets wouldn't even start in the new ones. Took a short spin up the road as it was getting dark and I noticed it running much crisper, less blubbery and idled much better. I think I'll stick with Premium fuel.

nickguzzi said:

Retarding the ignition means the plug fires closer to TDC (top dead centre) ie less degrees advance.
Less time for the burn, so less pressure as the piston goes over TDC, less chance of a kickback or detonation. Hopefully.

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Hi.
It means that retarding makes a easy start?
Ciao
Piero

Retarding reduces the chance of kickback but does not necessarily help starting, idle stabilisation curves on Electronic Ignitions advance the timing for more reliable tickovers, on bikes with manual advance levers the factory manuals tell you to set the lever to half advanced for starting.