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front cylinder spark plug

Mavagrand

Mavagrand

Senior Member
Got a quick question. Was outside dinking around with my bike. Decided to check the plugs. The rear is a nice golden brown, the Xied's are doing their job. The front was black and there was a little of what looked like oil seeping from around the threads. I did notice the front plug was not in as tight as the rear. I am running screaming eagle slip ons (the old ones from 1999) and have installed Xieds. Any ideas on what this could be. The bike is an 08 EGC and I have about a month left on the warranty. Need to know what you guys think, should it go in the shop??thanx

by the way, I did notice the smell of gas the last couple of times I've ridden her, pretty much since I put the SE's on.
 
Change plug (in front) make sure it's tight and ride long enough to heat up all then check again? let us know how it works out!:newsmile082::cheers:newsmile082:
 
Springer, appreciate your quick response. I did that. the new plug looked a lot like the old one. I then sprayed WD40 around the front exhaust flange, the bike's idle dropped..I figure I have an exhaust leak. Don't wanna deal with that now, so I hope the dealership will take care of it under waranty.
 
Stopping that exhaust leak solved the problem with my front spark plug. I just don't know how a leak in the exhaust could cause the plug to look like it was suffering from a rich mixture? Can one of you mechanically inclined explain it to me please??
 
Exhaust leak causes incomplete incomplete burning of fuel due to no exhaust scavenging (normally an advantage due to exhaust wave increasing the richness of air/fuel in exhaust adding to the combustion chamber mixture as part of the intake valve/exhaust valve overlap timing...hence unburned fuel goes out the exhaust valve when intake valve closed and end of combustion stroke exhausst blowdown clears out the unburned fuel.
 
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With an exhaust leak you are not getting the back pressure required for a full burn,also your exhaust won't scavange properly.

I would be more concerned about the SE slip-ons you are running,they were designed for your 88ci. engine and the flow rates just aren't right for the 96ci.

Here are the specs for 1999
Engine 1450cc,Twin Cam 88® Engine, Vibration Isolation Mounted

Displacement 1450cc

Bore x Stroke 3.75 x 4.00 in.

Compression Ratio 8.9:1

Carburetion Carburetor

And for 2008

Engine Twin Cam 96™

Displacement 96 ci (1,573.2 cc)

Bore x Stroke 3.75 x 4.38 in. (95.25 x 111.25 mm)

Torque 92.6 ft. lbs. (125.6 Nm) @ 3,500 rpm

Compression Ratio 9.2:1

Fuel System Electronic Sequential Port Fuel Injection (ESPFI)

with the compression ratio and the stroke being different you need an exhaust meant to flow better and scavenge the rear cyl. effectively IMO
 
if it has 02 sensors ,an exhaust leak gives a false sample to the sensor and appears lean .the computer adds fuel to the mixture ( fuel trim ) and keeps adding till it sees a responce from the 02 .
well thats how it works on cars anyway lol ;-)
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Ahh Jeezz, Steve. Just when I thought I had settled on a configuration, you go and get technical on me. So I need to either put my stock pipes back on, or buy yet another set of slip ons....jeez this bike is getting expensive.
 
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