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[Wheaters]

I usually run my supercharged Suzuki G10 powered Liege (kitcar) on supermarket super unleaded because the nearest garages to me selling "branded" V power or Ultimate are twelve miles away, usually in the wrong direction. That engine doesn't pink and it's got the standard 9.5 to 1 CR with up to 11 psi of boost shovelled in. It will run on the low calorie stuff (emergencies only though), but I wouldn't give it a lot of throttle on that. I do put branded Super in it when possible.

I run my other vehicles (a RE 350, a Honda CB750 and a Fiat Panda 1.2 on supermarket fuel, too). No problems at all.

[stinkwheel]

I can't really mess with the advance curve. It's got a crank-end electronic ignition. I wound it back to 30 degrees instead of 32 and it made little noticeable difference. I've got 2 base gaskets and both compression plates. When I look back at my build blog, I calculated CR as 9.09:1 with a deck height of 2.7mm. Dropping that further would be a ball-ache because I'd need to alter the tank position. I had to file the top off one of the rocker cover nuts as it is to get the tank on.



I suppose one thing I'll need to do is get a strobe on the timing. It was set up using a dead stop tool and the vernier scale on the stator.



It's running really nicely on the V-power and I'll be putting that in whenever I can. It was something I can carry a shot of to put in when I have to fill up at Strontian shop or similar I'm looking out for.

[Mark M]

I'd have thought that if you've retarded "full advance" to 30* your problem is not fuel but elsewhere. 2* (can't find the degrees symbol!) is quite a large step, about 7%, which suggests to me that the compression ratio is too high or the valve timing is too severe. Which backs up what BW says. On another point, I'm about to fit a 535 Accralite piston and barrel to my Bighead project and I did think the piston crown had rather sharp edges, is it worth radiusing them Paul? Sorry for the hijack! Oh, one more thing, when I built my wife's 250 Continental GT it pinked badly on full throttle, I added 105 octane aircraft fuel (from a friend, officer...) at about 10% which fixed it but once it was reasonably run in (say about 500 miles,) the pinking went away and never came back which suggests to me that heat generated by a tight piston and bore might be a factor?

REgards, Mark

[Andy C]

I would say that if something works for you, then stick with it. Castrol valvemaster & "branded" fuel works for me. Looking at this thread different things work for different folk. Hope your 612 continues to deliver. I hope to put some miles onto my re acquired 612 by the weekend, and hoping that it still goes as well as it did - I have had the motor apart and to the best of my ability put it back to how I remember it was. Proof of the pudding will of course be in the riding........

[Wheaters]

It might be worth trying a "colder" spark plug. One grade might make all the difference.

[stinkwheel]

Now spark plugs, for some reason, are something which totally went out of my head. Odd considering I rode pretty much nothing but 2-strokes for the first 10 years I was riding bikes.

[Barry N]

During my anti-pinking campaign, I tried the hotter NGK B9ES, instead of the recommended B8ES. If I remember correctly, it made little, if any, difference to the pinking – which I finally eliminated by other means (previously described). However, I continued using that B9ES and it’s still in there! Since there is no problem cold-starting (usually first or second kick) and no signs of fouling, I see no reason to change it. I run standard CB points with a PVL coil.

[Wheaters]

I see what you are saying but my understanding is that an NGK grade 9 actually runs cooler than an 8.
I fit a lower number than standard to prevent plug fouling because the nose of the plug runs hotter and a colder one on a tuned engine because it runs colder.
Air cooled engines generally need a colder plug than a water cooled one.

It's years since I've fitted one to anything but I recall that "Champion" plug numbers work the other way round to NGK.

[Count Johnny]

I've managed to convince myself that Slo Poke starts better, if I treat him to 'premium' fuel but, to be honest, Slo Poke drinks whatever I give him and doesn't seem to notice.



Plug is a B6ES.

[Barry N]

You are right of course, Wheaters! I was probably thinking of "harder" (as we used to refer to cooler plugs back in the day!).