A little pining under load

[njemnjem]

When I'm at highway speed and go to pass or similar hard load condition I get a little bit of pinging. Not dominant like some four cylinder cars but I can hear it. If I back off a bit (I do) it goes away. I'm sure there are multiple possibilities but what are the most likely ones? Thanks.

[nealart]

Which year and model?

The reason I ask it because there was a change in needle position for 1975 that might read one way in your manual and be another setting on your bike.

This was the case for my 1975 R90.

Otherwise, you can take the heads off and clean out all the accumulated carbon that is probably in there.

And you might try adding some octane boost in the tank and see if that helps.

[20774]

An earlier post said he had a '92 R100RT.

- What kind of gas are you using...octane rating?
- What kind of gas mileage do you get?
- Do the plugs show evidence of running lean (very, very white with deposits) or are they sooty or are they in-between (tanish is the target)?
- When's the last time the carbs were overhauled, settings checked, and carbs synched?
- Where's the full advance timing mark when you reach full advance? The timing might be somewhat advanced which could contribute to pinging.

[PGlaves]

Typically pinging under load as described is caused by the compression in the cylinder being too high for the octane rating of the fuel. In some cases it may be caused by the timing being overadvanced for the rpm and load conditions.

It can also be caused by "hot spotting" caused by a glowing ember in the combustion chamber or too hot a spark plug tip. If caused by the spark plug it won't happen for very long because the spark plug will soon malfunction, by the way.

If the timing is set to specification (check both at idle and at full advance) and seems to be moving smoothly - and if you are using the octane fuel specified for the bike - then the probability is that you have a carbon buildup in the combustion chambers and on the piston tops.

Sometimes fuel additives such as Seafoam my do an adequate job of decarbonizing the combustion chamber. If you try this - then change the oil to get any carbon crust removed and out of the oil.

In the end you may well find that the best way to decoke the engine is to remove the heads and manually remove the carbon buildup.

It is also possible that the fuel mixture is going lean under heavy acceleration, which causes short term, and maybe long term overheating in the combustion chamber.

In any event - if you can hear it it is akin to hitting the top of the piston with a small hammer and is not good for the engine internals - particularly pistons and rod big-end bearings. It is worth the trouble to find the cause and fix it. (Lecture mode off now)

[lkchris]

Try shifting to lower gear when passing.

[njemnjem]

Thanks guys. Plugs look good. Fuel is the same as always that didn't use to ping. Timing looks about right. I did switch to a needle jet rated for my altitude a while back but didn't realize lean could cause ping. I'll switch back and see what difference that makes.

[Boxerkuh]

You say that you are always using the same gas, but my stations are having up to 10% Ethenol in it. I have been adding gas additives every couple of tank fills. That is know not to be good for valves...