bob58o
SuckSqueezeBangBlow
This is a plug I ran a long time ago while trying to sort the jetting with a bike. It was new to start with. For anyone that cares to play, what are its secrets?
Lean and too much timing? Maybe too hot of a heat range?
New member... am I doing it right?
- Thread starter Kozi
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Lean and too much timing? Maybe too hot of a heat range?
65ShelbyClone
Active member
Answers:
1.) Yes, there was too much timing for the fuel.
2.) The mixture was not lean, but actually quite rich.
3.) The heat range was colder than stock.
4.) It has five WOT 1-2-3-4 gear pulls on it and was shut down right after the last one. No idling or cruising around on what you see.
The engine was an aircooled 630cc single running 91 octane with 9.8:1 compression and a stock cam that was mild even by stock standards. The head was ported and it had full race exhaust. Most of the time it would ping in hot weather.
It was a tough one and even I wouldn't have gotten it right without knowing all that beforehand. It was meant to illustrate how hard it can be to do tuning only by sparkplug. It was rich to begin with and the plug says it needed more fuel even though it was already losing power from too much fuel.
I couldn't do anything about the ignition or compression, so I added a bigger cam. Fixed the pinging and made more power.
1.) Yes, there was too much timing for the fuel.
2.) The mixture was not lean, but actually quite rich.
3.) The heat range was colder than stock.
4.) It has five WOT 1-2-3-4 gear pulls on it and was shut down right after the last one. No idling or cruising around on what you see.
The engine was an aircooled 630cc single running 91 octane with 9.8:1 compression and a stock cam that was mild even by stock standards. The head was ported and it had full race exhaust. Most of the time it would ping in hot weather.
It was a tough one and even I wouldn't have gotten it right without knowing all that beforehand. It was meant to illustrate how hard it can be to do tuning only by sparkplug. It was rich to begin with and the plug says it needed more fuel even though it was already losing power from too much fuel.
I couldn't do anything about the ignition or compression, so I added a bigger cam. Fixed the pinging and made more power.
bob58o
SuckSqueezeBangBlow
I’ll take your word for it, but White on the ground strap is usually indicative of a lean mixture?
Nothing about that plug says rich.
I’d like to see the fuel ring at the base of the insulator if I really wanted to guess the WOT mixture.
Nothing about that plug says rich.
I’d like to see the fuel ring at the base of the insulator if I really wanted to guess the WOT mixture.
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bob58o
SuckSqueezeBangBlow
so I added a bigger cam. Fixed the pinging and made more power.
Is dynamic compression ratio a good way to pick Octane?
A month ago i’d Say sure, but recently I’ve read about VE and DCR.
Bigger cam means less dynamic compression at low RPM- but what about a tuned engine operating at peak torque when volumetric effiency approaches 100%. As VE approaches 100%, doesn’t DCR approach SCR?
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