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Jetting
https://vintagedirtbikeforums.alp-sys.com/viewtopic.php?f=28&t=4073		 Page 1 of 1
Author:  FRANK121 [ Tue May 28, 2013 2:00 pm ]
Post subject:  Jetting
What causes pinging? My 81 465 runs good but after a long wfo straight away, pings and goes ding ding ding ding when you let off the throttle going into a turn. The plug is a nice light tan grayish color and it starts on the first or second kick.
current jetting:

390 main
45 pilot
needle clip 2nd from bottom

I have been told that it sounds lean and I should try a 400 or 410 main and go up to a 50 or 55 pilot?

Earlier in the season it had a 60 pilot and a 380 main and it fouled plugs so I leaned out the pilot and increased the main to be safe? What do you think? Comments please! :D
Author:  Dave [ Tue May 28, 2013 7:24 pm ]
Post subject:  Re: Jetting
what octane is the fuel and what are you running the premix ratio at?
Author:  FRANK121 [ Wed May 29, 2013 7:22 am ]
Post subject:  Re: Jetting
93 octane pump gas
Silkolene @ 32:1
Author:  Dave [ Wed May 29, 2013 1:08 pm ]
Post subject:  Re: Jetting
that seems right,i don't know what heat range spark plug goes in these but maybe going 1 heat range colder may help.for example on NGK Spark plugs if you are running a B8ES or EV spark plug,going to a B9 plug could help.

another possibility is mixing in some race gas in your premix can raise the octane a bit and it could stop or make the pinging much less.

from what you said earlier,the fuel flowing from the petcock to the carb could not be enough.it sounds like it is either running out of fuel a little after a long hard pull.

another thing worth checking into is the possibility of air leaks through the crankshaft seals or there may be a problem with the cylinder base gasket or something like that.

is the ignition timing set right on it?

the 465 is not known to ping whereas a YZ490 is rather notorious for that problem.the plug color sounded good so it would not appear to be too rich or too lean.

you have a challenging problem there it sounds like.the big bikes so it would seem have some detonation problems,particularly the air cooled ones.
Author:  FRANK121 [ Sun Jun 02, 2013 7:02 pm ]
Post subject:  Re: Jetting
Update:

Today I put in a 50 pilot, a 400 main and left the clip on the 4th position. With the DG pipe it ran a lot better did not ping like it did before and still felt a little weak down low :(

I decided to tear it down and try the PFR pipe again :? Fired it up on the 1st kick and took off .... felt like a monster down low but sputtered and had a hard time revving all the way out? I decided to play with the needle before changing jets again.
I moved the clip up to the 2nd position from the top and ..... Wow :shock: Monster down low, revs good and doesn't ping :D The only thing is it is like 65 degrees today and overcast. When its 90 degrees I suspect I will have to go back to a 390 or maybe the 380 main? Hopefully, fingers crossed, it will stay running this good! :D I can't wait for the next race! :lol:
Author:  Dave [ Sun Jun 02, 2013 8:06 pm ]
Post subject:  Re: Jetting
looks like you went much leaner on the main jet as a 400 is much smaller than the 490.happy you got it running strong! :D
Author:  FRANK121 [ Mon Jun 03, 2013 7:10 am ]
Post subject:  Re: Jetting
I didn't notice the typo earlier. I had a 390 main in it before :?
Author:  Dave [ Mon Jun 03, 2013 12:57 pm ]
Post subject:  Re: Jetting
happens to the best of us.
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