Mild pinging under load @ low rpm. Cause?

[Dogma]

it occurs in the 3-5k range, under load.

It gets worse when the engine gets hotter? This problem all but disappeared for me after a top end rebuild. Of all the things I did, cleaning the carbon out is the only thing that I can figure would have impacted this.

The water cleaning can also be done by dripping water into the vacuum adapter port (normally used for carb balancing) while riding. Don't use enough water to kill the cylinder, you need the combustion to turn the water to steam. I did this once, and though I could see through the spark plug hole that the piston was clean, I think I should have kept going for quite a lot longer. When I took the top end off (for other reasons), the head was still carboned up, and the carbon on the valve faces was still thick and hard enough that it just about had to be chiseled off.

[LarryJ]

tried a tank of 91 octane today, in more moderate weather (80F). Still pinging in the 3-5k range. am awaiting the new carb boots & o rings. Will do the water spray just prior to pulling the carbs. Sounds like Medussa is pretty carboned up! We'll see.

[Steve]

Silly low, like 1500 - 2000.

Sorry, that's not "silly" low, that is "STUPID" low.

Especially two-up and up hill.

Just because there are five gears does not mean you have to be in the top one all the time. In town (especially two-up), third gear would be appropriate. Over 40 mph or so, hit fourth, over 50 or 55, go ahead and hit fifth.

If you are on a two-lane road and need to pass someone quickly, don't be afraid to downshift TWICE and then hit the throttle.
You will then experience why you gave up your V-twin.




Anyone else noticed that we are now handling THREE problems per thread?

Started with GelandeStrasse, then dorkburger and LarryJ tried to get help, too.

.

[tkent02]

The water cleaning can also be done by dripping water into the vacuum adapter port (normally used for carb balancing) while riding. Don't use enough water to kill the cylinder, you need the combustion to turn the water to steam.

What he said... I use a two liter bottle and an aquarium air valve, turn it so it just trickles into the vacuum synch port. I do it going down the highway, one cylinder at a time. Get it good and hot, open the valve a little, and do a whole two liter bottle into each cylinder, it should make a difference. Might take a few times to get it good and clean.

[GelandeStrasse]

Sorry, that's not "silly" low, that is "STUPID" low.

Especially two-up and up hill.

Just because there are five gears does not mean you have to be in the top one all the time. In town (especially two-up), third gear would be appropriate. Over 40 mph or so, hit fourth, over 50 or 55, go ahead and hit fifth.

If you are on a two-lane road and need to pass someone quickly, don't be afraid to downshift TWICE and then hit the throttle.
You will then experience why you gave up your V-twin.




Anyone else noticed that we are now handling THREE problems per thread?

Started with GelandeStrasse, then dorkburger and LarryJ tried to get help, too.

.

In the name of science I like to push my vehicles to their limits. It's like an OCD, In this case I wouldn't change down unless I had to or wanted to, "how low will it go? Ok so it pings below 2000 loaded two up, that's good to know, I wonder if they all do that, the old twin didn't. Best I change down sooner". I'm actually mightily impressed with how low it can go!

Sorry, that's not "silly" low, that is "STUPID" low.

Stoopid! That's me
Flat twin not V

[chuck hahn]

And you don't have the low end torque in the GS as the other bike did..thats why it pings if the gear selection is too high for what your requiring of the engine.

[tkent02]

Ok so it pings below 2000 loaded two up, that's good to know, I wonder if they all do that, the old twin didn't. Best I change down sooner". I'm actually mightily impressed with how low it can go!

No, they don't all do that, the GKs seem more prone to pinging for some reason. All of them do better when operated at a proper RPM.

[Steve]

I'm actually mightily impressed with how low it can go!

Yeah, I can do that at times, too. All of our 850s (we have had up to four here at one time) are surprisingly tractable down to about 1500 RPM, and will pull away from about 15 mph going around a street corner in fifth gear. We don't do that often, especially with any kind of a load (two-up, uphill ).

Stoopid! That's me
Flat twin not V

Still a "V", just a 180-degree V.

.

[chuck hahn]

And 2 up its gonna require more attention to gear selection and RPMS also...especially on the inclines and passing.

[LarryJ]

the pinging that I am getting is under normal "around town" acceleration, when it's fully warmed up, light throttle, 3-5k rpm. I don't lug it. So, that's why it is disturbing to me. Probably a lot of carbon build up from PO's who ran it pretty poorly & skipped a lot of msintenance (from what I can tell, valves were way out when I got it, etc.)

[chuck hahn]

Carbs vacuum synced? Checked the timing? Where are the mixture screws at? Baseline starting point on CVs is 2 out from seated.

[LarryJ]

carbs thoroughly cleaned, new boot o-rings & vacuum synch'd. Haven't checked the timing (engine doesn't appear to have had much major maintenance. half of the valves were way out.) So, after water spray treatments & new intake boots, that'll be where I go. Boy, bringing back an old, unmaintained ujm sure is fun!!