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312Icarus
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I keep thinking my ‘68/2US is pretty well dialed, starts easily, runs great throughout the RPM range. The plug are just a bit whiter than I would like, with just a touch of brown on the grounded electrode. The temps are perfectly even between cylinders after a run.

My problem (such as it is) is that when I shut it off after a run, with a 1/2 block cool down before shutting it down, it tries to diesel once or twice after shut down, seemingly from the right cylinder. Should I pull the needle up one notch or try a little cooler plug? (Anybody have plug temp chart for compatible NGK plugs? I have not had the best luck with bosch plugs of late). I am running NGK B8HS plugs.

Once again, thanks for any and all advice,

Merry Christmas,

Icarus

wa1nca
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VBMWMO #8374
Ashfield Ma.
Joined: 09/27/2012
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NGK Plugs

NGK Plugs
The higher the # the cooler the plug
Most plugs the higher # a hotter plug

NGK B9HS cooler than B8HS
NGK B7HS would be a hotter plug than B8HS

Tommy

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54 R51/3 55 R50 64 R27 68 R69US 68 Sears Allstate 250 (Puch)

312Icarus
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Thanks Tommy, I found the NGK

Thanks Tommy,

I found the NGK chart on line. I will try to post a picture of my plug later for everyone to opine about.

Merry Christmas all,

Tony

312Icarus
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Here’s a couple of pictures

Here’s a couple of pictures of the plug...

  • 0e38b5a2-e952-496b-aae7-1a705234f8e7.jpeg
  • 36dcbf69-acf3-48a7-8334-839e1d99223e.jpeg
schrader7032
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San Antonio, TX
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I would first check

I would first check timing...I seem to remember in the past with older vehicles, that the timing might be slightly advanced.

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Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2

malmac
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Toowoomba, Australia
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the video probe

I have seen that sometimes a small patch of carbon can build up on the crown of the piston - which acts like a glow plug when the ignition is cut. A small video probe could look through the plug hole with the piston at bottom dead centre and confirm or deny this possibility.

Just a thought for what it is worth.

Mal

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312Icarus
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Will double check the

Will double check the timing...and I’ve got a Iphone boroscope I can peer in to have a look.

Thanks for the advice. Any comments on the plug condition?

T

wa1nca
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PLug condition

Too lean
Will run hotter but not sure if it would diesel
raise the needle both sides one notch and recheck plugs and see if that helps (at least 10 miles or more)

Kurt and Mal have good points to check

Tommy

  • dsc03646.jpg
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Tommy Byrnes
54 R51/3 55 R50 64 R27 68 R69US 68 Sears Allstate 250 (Puch)

312Icarus
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I’m leaning toward too lean,

I’m leaning toward too lean, but I’m going to check the timing first. Thanks for all the advice, I’ll chime in after I get a chance for another good ride.

T

Beemer100
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my advice would be to check

my advice would be to check first in what "speed region" it is too lean. Try to find a road on which you can go a 100km/h or even faster for 10 to 15km. Then shut off ignition and let it roll into a parking lot. Wait some time for the heads to cool down a bit and then pull the plugs. If coloring is fine then you know that your main jet is good. Then I would go to the idle circuit and make sure it is adjusted properly... lean a bit on the "fat" side. Last check goes to the needle.
Of course, ignition must be corrected first.

my 2 cents
Klaus

Twocams
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That looks pretty good to me.

That looks pretty good to me. That looks like a real new plug and you cant just ride 10 miles and say....
With older gas cars, bikes I would turn the idle down some and when you stop to park let it idle for a minute. This gives the bike a chance to settle down & engine get back to idle. Are you using ethanol gas or any additives can make it run a little lean too.

twocams

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Twocams
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92 R100RT
2004 Aprilia Atlantic 500cc Scooter

312Icarus
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Two cams, Indeed it is a new

Two cams,

Indeed it is a new plug, maybe 100 miles. I am using ethanol free fuel. I try to let every engine run easy for a minute or two before shutting down, to dissipate the heat. On the bike, just coasting the last few hundred feet before shut down to give it some free air.

Icaus

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