My 2007 1700 Silverado has just rolled 4500 miles. Since new it has never idled the same RPM twice. I have had it in several times and was told it was carbon build up and sold me the ring free treatment. I followed the process as directed with no change. I pulled the plugs at 4500 to inspect. The front 2 were clean & normal. The rear 2 were black & fouled. I took them to the dealer and got the same story. More ring free treatment. I cant beleive this is normal. I replaced the plugs with new. What is going on for real here?

Seems this is a normal problem , several here have experienced this same problem, I have also. The rear head runs hotter than the front one. Maybe someone else will chime in and help. .......In the tech articles it explains how to check the float level, could be that your float level is too high. The Roadstars seem to come from the factory too rich, some have even made adjustments to the accelerator pump on the carb that seems to help.

It might be as simple as running at too low an RPM. I tend to run the gears about a bit, and when I check or change plugs, the rear are darker, but not fouled. I also drop a bit of Marvel Mystery Oil in the gas tank at least with every other fill up. Over 26,000 miles in the past 27 months and not had any issues with poor performance due to plugs or the dreaded "SVS."

,What octane gas are you using.Should be 87.
Whoops Soba,Thanks for catching that .I had a brain fart

...or 87, in my case - regular.

Both cylinders run off of the same carburetor. You can't run overly rich on one and too lean on the other.

Due to emission regs, factory settings are not rich... they simply can't be. They tend to run as lean as they think they can make it.

You should tell us about your riding style. Not running the RPMs up in gear, and lugging around in higher gears and lower RPM would seem to be a more likely cause.

If they're telling you carbon is the issue, run a decarbonizer in your gas, and don't be at all afraid to run up against the rev stop, or at least some higher revs than you might normally.

As a lover of pure torque, I tend to lug it, but since I know that can be a source of problems, I also do some lively runs at higher runs just for 'insurance' purposes to prevent any possible carbon build-up.

Shoot, man, every run, as you are able, you gotta blow that carbon out! Yeehaw!

seems like they don't want to adjust the valves, which would be my guess.

does anyone run iridium plugs in their bikes?

i run them on 2 other bikes and they're great--20,000 miles on iridium plugs on my triumph speedmaster.

maybe the iridium plugs run too hot?
http://www.sparkplugs.com/results_appOther.asp?otherMotiveID=227210&mfid=1

cat

My rear plugs are always darker, but the bike runs perfect. Couldnt get any better , all the power she has plus average of 46 m.p.g. Never could get the rear ones to get any lighter so I quit worring about it. Hasnt hurt it.

Questcap wrote:
Both cylinders run off of the same carburetor. You can't run overly rich on one and too lean on the other.

Actually it is technically possible for that to happen. There are many factors which can contribute to this and they may or may not apply in this case.

At 3000 miles my rear cylinder quit and the bike wouldn't start. The dealer jetted it when they put the pipes on when I bought it 0 miles. They tried to jet correct 5 times but it would miss and carry on after a few K miles. I finally decided I could do a better job after the warranty ran out. It took me several tries to get it right but all plugs are gray (may be a little lean) but she runs better than she ever has and I know the best way to cure SVS. I increased my pilot jet size and leaned out the needle and the main was what it should be for the air cleaner and pipes I have. You have to get each part right for the pipes, air cleaner AND make sure you have no air leaks exhust or intake. Then ride the crap out of it keep the rpms up DO NOT LUG the engine.