1972 RV90 Ping at IDLE

Just picked this beautiful machine.  I new when I picked it up that the pinging was not normal, but was infatuated with the bike nonetheless, and its a cool Dual Sport that is street Legal and I Can teach my kids how to ride.

 

 

I have already gone through 1 tank of gas...I was hoping the pinging was due to the old fuel or low octane...

 

pinging is still there.

 

I am putting in 91 Octane from Chevron.

 

Its a Oil Injected bike, so I don't need to pre-mix....

 

Every post I read is usually about pinging at throttle or WOT...Well, this ping is occurring at Idle and light throttle, but goes away after 1/4 throttle to WOT....

 

I have tried multiple Spark plugs...

 

It had a B6HS on it when I bought it...Gap was kinda too big, about .44 - I have read that its supposed to be at .28

 

I then tried a 725 Autolite, cause I thought that I needed a hotter plug because the B6HS showed that it was running on the rich side...

 

After more reading about this, I have noticed that I was supposed to get a COLDER plug...

 

So I went and bought a 4093 Autolite, which is about a B7HS equivalent....

 

It was still pinging...

 

I took off the cylinder head, and I found the dome pretty gummed up...

 

I cleaned it and smoothed it out...

 

Started it up, damn thing still pinging....but during the test ride, I found that the bike had a little more giddy up...

 

I have not ridden a 90cc bike before, but I think it was similiar to the 80cc and 100cc XR I had several years ago...

 

ok...

 

so I kind gave up...said to myself, to leave it, cause it seems to run fine, and the pinging is gone when riding 3rd and 4th gear at any speed over 15mph....

 

the following morning, I started it...

 

the ping was gone....

 

I did not retune anything before parking it for the night....

 

after about 60 seconds, (assuming as it warmed up)  the ping was coming more and more....and then again back to its normal 'pinging idle' state...

 

I said, ok...

 

maybe I need an even COLDER plug!

 

So, I went and purchased a B8HS.

 

I replaced it and started it cold from an overnight...(I live in Socal, its not cold, just a state of being cold start)

 

 

well, it pinged like before...no change, it pinged immediately...didn't even need a 60 warm up....

 

Gap was the same at .28...

 

 

I must say that I have been trying to mess with the air and fuel mixture screws...but never changing the ping state...

 

I tried cleaning the carb, cause it has a leak from the overflow...

 

Will re-jetting the bike resolve the idle ping?

 

Do I even need to worry or care if it runs good, just pings on idle and very low rpms?

 

 

Thanks for reading my story. I normally just like to read other situations and learn from there, but I am really starting to love this little critter, and I want it to run like a top!

 

I already ordered new GBC Street Force Afterburn tires, and waiting on some new signals.

 

I repainted some rust frame pieces and cleaned it up nicely...

 

Help me please.

 

Are you sure that thing is pinging ??  Like to hear it but my moneys on a bit of piston slap not pinging.

Are you sure that thing is pinging ??  Like to hear it but my moneys on a bit of piston slap not pinging.

 

 

That would be my assessment as well. Detonation (pinging) at idle but not under a load is so very unlikely that I wouldn't even consider it as a possibility.

 

I would strongly urge you to pull that top-end and measure everything before the piston sheds a skirt and turns a $200 job into a $500 job.

 

While you have it apart, examining the edges of the piston crown for erosion will tell you if any detonation has actually been occurring. Detonation will give the piston crown a "sand blasted" look, like this:

 

orig_24829781_u7E8.jpg

 

 

 

 

 

One other possibility...are you sure you aren't just hearing the normal "ting ting ting" sound of a two-stroke expansion chamber it idle?

Edited by Chokey

That would be my assessment as well. Detonation (pinging) at idle but not under a load is so very unlikely that I wouldn't even consider it as a possibility.

 

I would strongly urge you to pull that top-end and measure everything before the piston sheds a skirt and turns a $200 job into a $500 job.

 

While you have it apart, examining the edges of the piston crown for erosion will tell you if any detonation has actually been occurring. Detonation will give the piston crown a "sand blasted" look, like this:

 

orig_24829781_u7E8.jpg

 

 

 

 

 

One other possibility...are you sure you aren't just hearing the normal "ting ting ting" sound of a two-stroke expansion chamber it idle?

 

Chokey, this piston has issues even beyond detonation.. just that one score I see was from a major sand grain getting in the motor!!

 

Shame on whoever didn't clean the air filter lol

Chokey, this piston has issues even beyond detonation.. just that one score I see was from a major sand grain getting in the motor!!

Shame on whoever didn't clean the air filter lol

I realize that, I was just pulling a picture off the 'net that was a good illustration of detonation damage.

Hi Guys!

 

Thanks for all the responses.  I really appreciate all the help.  I was searching more on the web about piston slap. It sounds similar to it, but then again, why does my slap go away after a certain RPM?  The ping usually goes away after I hit 12mph and all I hear is the sound of the beautiful exhaust tones...as I slow down, the pinging starts to happen again...

 

again, not sure how much torque and giddy up this '72 motor is supposed to give, but I am 210lbs (on a good day) and it has decent pickup with this ping...

 

hmmmm...actually, I am starting to have flashbacks of my XR50...semi automatic...well, I think I was also 40lbs lighter then...so nevermind...

 

I am sending some pix from the piston head and chamber and a video for sound...

 

Its taking awhile to send from my phone...I will send it right when it loads.

 

 

Thanks again!

 

 

The sound goes away above idle because inertial loads keep the piston pressed against the exhaust side of the cylinder.

Is the dissipation of the ping at above idle speeds normal if my problem is Piston Slap?

Here are the pics...I have to resize the video file...too large...errrr

S4 Pics 2904.jpg

S4 Pics 2916.jpg

S4 Pics 2913.jpg

S4 Pics 2914.jpg

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S4 Pics 2923.jpg

That would be my assessment as well. Detonation (pinging) at idle but not under a load is so very unlikely that I wouldn't even consider it as a possibility.

 

I would strongly urge you to pull that top-end and measure everything before the piston sheds a skirt and turns a $200 job into a $500 job.

 

While you have it apart, examining the edges of the piston crown for erosion will tell you if any detonation has actually been occurring. Detonation will give the piston crown a "sand blasted" look, like this:

 

orig_24829781_u7E8.jpg

 

 

 

 

 

One other possibility...are you sure you aren't just hearing the normal "ting ting ting" sound of a two-stroke expansion chamber it idle?

I love that sound  :ride:  say it again ,  :lol:

Pull that top end and rebuild it with new parts , if that ring has snagged the exhaust port it has probably damaged the cylinder  , broke a ring or broken ring lands already. Don't run it anymore you may get lucky but doubtful. 

That's not pinging, it's KNOCKING. Something is BROKEN. Stop running that engine before you do more damage, and tear it down.

 

If the piston is in backwards, it could very well be the cause of the issue. The ring ends have to be located in specific positions in a two-stroke to not snag in the port windows. With the piston in backwards, the ring ends are probably snagging the edge of the exhaust port, and it's amazing it's actually still running.

 

You're going to find damage when you take it apart. If you really just bought it, you should take it back to the guy and demand your money back, on account of he's an idiot.

I just did my first rebuild!  YEAH!  LOL

 

Sweatin' my booty off out in this Socal heat in my garage...

 

But believing the seller that he rebuilt the top end, I just undid and redid everything.

 

as stated above, we can see the piston was upside down...

 

also, I believe the piston rings were not in its proper seating when I took it all apart

 

 

Well, the piston looked ok...the rings weren't effed up and the rivets on the piston for the rings were not shaved off...

 

soooooo

 

I put the piston right side up...

 

Happily the gasket was not ruined on the bottom cylinder...to the bottom end..bolted everything up...

 

I fired her up...I was so so so so so so so so so happy to hear just the sweet sound of thump thump thump!

 

NO MORE PINGING!

 

THANK YOU TO ALL WHO COMMENTED.

 

I am noting here now for search purposes on WHAT HAPPENS WHEN YOUR PISTON IS UP SIDE DOWN!

 

:)

 

In believing the seller, it was barely 40 miles on the upside down rebuilt piston...20 miles from him, and I test rode it for about 20 miles as well....

 

 

Here is the post of video after the rebuilt rebuild....LOL

 

https://www.youtube.com/watch?v=gC8G8TkHpuw&feature=youtu.be

 

I can laugh now... :)

 

Now to remedy the carb overflow leak...   :)

 

I learned so much....thanks guys!  I love it!

 

 

 

I just uploaded and watched the finished video...it sounds like there is still a ping there, but its not really as bad or evident as the video sounds like...

 

Anyway. My weekend feels so accomplished now!  YAHOO!

REBUILD COMPLETE! 001.jpg

REBUILD COMPLETE! 002.jpg

REBUILD COMPLETE! 003.jpg

REBUILD COMPLETE! 004.jpg

REBUILD COMPLETE! 005.jpg

Edited by jjeromeg1

That thing seriously needs a proper rebuild with new parts , a piston kit for that thing can't be more than 50 bucks on ebay. But if it's ok with you . Clean and oil that airfilter that piston has some good dirt scoring. May want to check the position of that oil injector too, the cable stretches and starves the engine for oil. 

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