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Wed Nov 18, 2009 11:28 pm

I have a '77 2L bus and know - at least according to the directions of the majority, it seems, of thesamba posters - I should time the ignition with a strobe at full advance. Thing is, I don't have a strobe light and have been doing it statically with a timing light.

It's not been running the best and there's a definite tinkling from the engine when pulling up hills in high gear. Having set the timing at 7.5*BTDC cold a day ago I get the engine good and warm taking the bus through the nearby hills.

With the tinkling (pinking?) noise, I stop to check the timing and notice the light now comes on at c.4*BTDC. Is this normal, the variation between the timing cold yesterday @7*BTDC and hot? Have my points or timing fallen out of whack in this time? The dwell is still steady though at c.49*.

I retard the timing to about 2*BTDC because of what I take to be pinking and take it for a spin. the tinkling has gone. I stop again to advance the timing, repeating this procedure several times until I'm up to 4*BTDC again - still no pinking. At about 6*BTDC the pinking has returned up hills in high gear.

What to do?

Wed Nov 18, 2009 11:36 pm

You don't want it to ping or knock. Retard it until it doesn't do so. You may have some hot spots in your cylinders that are contributing to the pinging. What plugs are you running? If the plugs are getting too hot that will cause preignition.

There are several things you can do to remove knock causing carbon from the cylinders. Very occasionally adding 2-cycle oil to your fuel at a 50:1 ratio seems to do a pretty good job.

Wed Nov 18, 2009 11:42 pm

They are WR7CC plugs. Does the gap contribute to pinking? Ambient daytime temps here between 20-30*.

Wed Nov 18, 2009 11:42 pm

what grade fuel are you burning?

Wed Nov 18, 2009 11:52 pm

Regular unleaded - 87RON? Read somewhere leaded fuel helped reduce pinking. Will "upper cylinder oil" (to replace lead in fuel) also reduce pinking, I wonder?

Thu Nov 19, 2009 12:05 am

Your plugs are a heat range to the cold side. You might try a set of WR8CC or equivalent. If your mixture is off it can contribute to hot running and pinging as well.

Thu Nov 19, 2009 12:57 am

With your temps, 8's are prefered, and 7's for hot climate.
I havn't seen leaded fuel around here in decades. That shouldn't be an issue. Try going up a grade in gas and see if that makes a difference. Usually pinging is just a matter of too far advanced timing.

Thu Nov 19, 2009 1:14 am

go up to the 89 or even 91 and see if that stops it. If the engine has some miles on it run some Techron through it.

Thu Nov 19, 2009 4:55 am

tomfreo wrote: What to do?

Either buy a real timing light and fix the vacuum leak or just sell the bus while it still has some value.

Thu Nov 19, 2009 10:04 am

tomfreo wrote: Ambient daytime temps here between 20-30*.

20-30 C is pretty warm, I'm guessing 7CC's would be OK....
I think NGK still makes non-resistors if you want to try them.

Thu Nov 19, 2009 10:57 am

Randy in Maine wrote: tomfreo wrote: What to do?

Either buy a real timing light and fix the vacuum leak or just sell the bus while it still has some value.
X2, from your other post it seems like you are under the impression that a few basic essential tools are going to cost more than another engine if you melt yours down setting things by ear. Believe it or not they aren't expensive and the money you'll save on needless spark plug purchases, wasted gas, etc. will pay for them in no time at all.

Thu Nov 19, 2009 6:32 pm

Thanks for all of your concerns, comments, etc. I've got a Bentley manual on order from the States and am trying to source a decent strobe light and 'snail' (?) carb balancer. In the meantime, when I'm not driving a 6V '61 beetle I drive the bus and need to do something without the aforementioned tools.

I checked the timing this morning, engine cold, and sure enough the timing was back up around 8*BTDC (static). It seems the engine hot and the engine cold make a **big** difference. Out testing it yesterday, I settled on around 5*BTDC to stop the pinging - this was with the engine hot. I adjusted the timing again this morning to 7*BTDC.

After checking for vacuum leaks (none discernible) I adjusted the mixture screws on the carbs and richened the mixture a little, thinking a lean condition might cause the pinking. Took it for a test drive and all issues are gone - I guess I've just got to watch for signs of an overly rich mixture. I can recall what they are, but I guess if noone here fancies letting me know, another of those tedious searches will inform me.