66cc internal noise question

GoldenMotor.com

ddesens

Member
Jun 27, 2011
173
0
16
New Port Richey, FL.
Hi guys, my 5th build with a 66cc has a potential problem. Can you listen to the noise my engine makes in my you tube video and tell me what you think?
http://youtu.be/-_rubV8Fg44
The motor is a rb80 from bgf. I thought it had excessive play in the needle bearing for the piston pin. He sent me a new pin and bearing. I installed and it still makes this noise. Motor is new with less than an hour on it. Plug color is light brown. Running opti2 oil like always. When the bike makes the tinging metal sound the bike slows down a bit. If its 4 stroking, its awfully loud. What do you think?
 

ddesens

Member
Jun 27, 2011
173
0
16
New Port Richey, FL.
Just a little update. I changed the plug wire to a new 7mm car one and regapped the plug to .035 from .023 just to see if there was a difference. Seems about the same. But it started pouring rain so I had to end my testing.
 

rustycase

Gutter Rider
May 26, 2011
2,746
5
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Left coast
I couldn't get the whole vid, but the first part did make a stoopid high pitched kinda noise.
Honestly, it just kinda sounds like a dumb chinagirl kinda noise... like why some guys put rubber hose on the fins, or silicon pucks between 'em???
It's like the rings are crashing against the lip on the ports, and amplified by the design.
Perhaps you could try to chamfer the upper and lower edges of the ports just a very little bit??? It WOULD change your timing a bit, so I wouldn't do it too much or there would be noticeable consequences.

...just an idea... I'd certainly get a 2nd opinion!

Good luck
rc
 

thegnu

New Member
Sep 15, 2011
982
1
0
freedom pa
mine makes similar noises but no loss of power , I listened to my motor with a long screwdriver like using a stethescope an found my noise was the clutch ring rattling against the case , got 168 miles on it an its getting quieter . my advice just do a through diagnostic of anything you think the prob is an go from there.
Gary
 

maurtis

New Member
Dec 14, 2011
707
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0
Kyle, TX
I have an RB80 with maybe 2 hours on it, and mine does not make that tinging/popping sound that yours does. It sounds similar to yours up until that sound starts, though. But I am also running 24:1 Briggs 2 stroke oil right now and am running rich, so I very well might hear that when I get my mix leaned out. But for now, I do not.
 

maintenancenazi

New Member
Oct 22, 2011
157
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0
Asheville
What plug, and what heat range are you running? Personally, I have found that the normally accepted heat range plug is a bit too hot. Causing pinging/pre ignition. I currently am running a B9HS, and in winter run between a B7HS and B8HS. Also, at least in my case running 93 octane has helped in eliminating the ping or rattle some seem to have.

Kind of makes me wonder if it is the squish band ( or lack there of ) in these slant heads that can cause this issue. In 2 stroke tuning I have heard that you should try to run the coldest plug possible that won't foul. Again, in MY CASE, it seems to get rid of this detonation.
 

ddesens

Member
Jun 27, 2011
173
0
16
New Port Richey, FL.
I rode it around for awhile tonight and it seems that it feels like pre-ignition/pinging. Opening the gap on the plug and changing the plug wire to a better one has made it not as bad I think. How/why I dont know. I'm using the stock plug that came with it. I'll run and get a b7hs after dinner I think and try that. The fuel is 93octane. This motor came with 2 plugs and the motor had been run at the factory or something because there was burnt oil residue on top of the piston when I took it apart and the plug was used that was in it. Smelled like old gas also.
 

biknut

Well-Known Member
Sep 28, 2010
6,631
409
83
Dallas
At the very beginning I thought it sounded a little tinny, but after that all I could hear was a fat guy snoring.

Nearer the end, in between the snores, a lot of the sound was normal to me. It seems like it's running ok.

I've had a small end bearing fail, and it doesn't sound like that. I had a crankshaft scrape the cases, it doesn't sound like that.

Sometimes these motors are a little like Harley's. It's best not to pay too much attention to noises they make, or it can make you psycho.
 

maurtis

New Member
Dec 14, 2011
707
0
0
Kyle, TX
After putting some more miles on my RB80 and running her harder, I am getting the same pinging noises with loss of power. Mine sound the exact same, but do not happen nearly as frequently as yours seem to. Always in the upper rev range, usually after getting completely warmed up and almost topped out, between 34 - 37 MPH. It does feel like pre-ignition. They come in spurts of about 1/4 - 1/2 second duration and when they happen, there is a momentary loss of acceleration, then back to normal.

So cruising along... vroooooooooooom.... ratatatatata... vrooooooooooom. I *think* these motors are the same as the Grubee GT5A, which people have reported to have problems with the head and heat.
 
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maintenancenazi

New Member
Oct 22, 2011
157
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0
Asheville
^^ That's exactly why I like running a colder heat range plug, it did indeed seem to help my little HT. You may also want to pull the head and check for carbon build up. When hot enough, little specks of carbon can glow red hot, just like a glow plug.

Edit, I think it also depends on what kind and ratio of oil you are running. I run Opti-2 at 80-100 to 1, so in that case at least you probably can run a colder plug.
 
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gubba

New Member
Dec 29, 2008
149
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0
jacksonville, florida
the factory says that when you start it that is the first time it has run

the ngk plug b5, b6 b7.... the higher the number the lower the heat range...

i use b5HS or B6HSon all my builds... over 30 now...



stay dry
gubba
 

rustycase

Gutter Rider
May 26, 2011
2,746
5
0
Left coast
My Mighty 48 Skyhawk does something like that...
On a WOT run through the radar trap it feels, and sounds, as though a compression release lever is pulled.
It did this when jetted lean, and when jetted fat.
No evidence of head gasket leakage, or any problem with the plug when I got home and pulled it.

I am thinking my cdi has a gremlin and will swap it for another.

Good luck
rc
 

maurtis

New Member
Dec 14, 2011
707
0
0
Kyle, TX
Good clue, I wonder if the CDI cannot keep up? Maybe one day down the road, after a front brake and a good seat, I can get my hands on a Jaguar CDI.
 

577-Jersey

New Member
Mar 23, 2013
293
1
0
central western nj
Thats definetly a pre ignition ping sound,,try to play with timing like mentioned earlier,,maybe some octane additive might help also.This thread is a little old so you prolly got it fixed by now but I don't see an update?

Take care!