Carboned spark plug?

[Anonymous]

I have been in the process of rejetting my 82 gs1100 for pipes and emgo pods. I started with the Dynojet kit and its recommendations. I currently have 175 main jet, drilled out slides, and the needle is set at the second slot form the top. I have great lowend power. The power totally falls off at 4-5000 rpm. I read the plugs after a 2-3 mile rip and they are black and carbonned-up. What does this mean?

[earlfor]

Re: Carboned spark plug?

It means your main jets are way to big. To determine jetting, always start with the main jet, high end, and work down.

Earl

I have been in the process of rejetting my 82 gs1100 for pipes and emgo pods. I started with the Dynojet kit and its recommendations. I currently have 175 main jet, drilled out slides, and the needle is set at the second slot form the top. I have great lowend power. The power totally falls off at 4-5000 rpm. I read the plugs after a 2-3 mile rip and they are black and carbonned-up. What does this mean?

[Anonymous]

What size jet should I try next?

[Jeff Tate]

I'm not positive, but I believe the kits come with Mains in the 140 range for 1100s. It's been so long since I put them in I don't recall for sure.

[earlfor]

I can only give you my bst guess. My 1150E is stock with 120 mains. Vance and Hines suggest going up two sizes if installing their 4 into 1 header but retaining the stock air filter system. Jets come in increments of 2.5, so adding only a header would suggest jet sizes in the 125 to 127.5 range (the #2 and #3 cylinders are jetted differently that #1 and #4) Removing the stock air filters/box and installing pods would likely require an additional 2 jet sizes larger, for a total of 4 sizes. That would be something in the range of 130 to 135 for the mains as a place to start. I would start with about a 135 and see what the plugs looked like. If theyre still black and it wont pick up top end, then youre still too big.

Earl

What size jet should I try next?

[Anonymous]

Thanks for the suggestions. I guess I'll have to go back to trial and error for a while.

[KEITH KRAUSE]

Hi. Are you the guy who drilled out your slides at the wrong angle?
If the slides are damaged you will never be able to properly re-jet. If the vacuum is compromised the carbs will draw fuel incorrectly. Did you replace them?
At what throttle position were you to get the black plug reads? If you were below 3/4 throttle then the main has not taken over fuel flow yet. The needle position regulates fuel flow at less than 3/4 throttle down to about 1/4 throttle. At this point there is an overlap with the pilot jet.
I believe your Dynojet needle has 6 grooves in it. Right now your needle is in #2 which would be the second to the leanest position, but the plugs are black. I think you said before the carbs are clean. Something's not right here. That's why I asked if the slides are damaged.
Again, what throttle position is giving you the black plug reads? Are you doing the "chop" test to get the most accurate reads?

[Anonymous]

Keith, The slides are good as far as I know. I drilled at the same angle as the original hole. The black plugs are at full throttle where the bike revs out. What is the chop test? Another thought , could poor coils and wires cause something like this?

[Anonymous]

The chop test is when you've got your bike running at full throttle. let it go and hit the kill switch. That way you know that your bike was running on the main jet circuit when you killed it. Take a look at your plugs before running it again and note the colour. If they're carbon fouled, main jets are too big. If they're white, main jets are too small. If it's a nice tan, then you know the problem isn't with the mains.

[KEITH KRAUSE]

Dynojet gave you more than 1 size of mains did'nt they? Have you tried the smaller mains? You should be able to get the jetting right with what they supply. You can still go 1 groove leaner on the needle too, but to have the clip in the top position seems unusual. Are you sure you re-assembled the needle and it's plastic spacers in the correct order? My '79 1000 has a thicker plastic spacer above the needle clip and a thinner one below the clip. Do you have a similar set up? I'm also wondering if it's possible they gave you too large of mains. A phone call could verify? What do the instructions/part list say? Are the carbs SYNCH'D? Is there any chance the float levels are too high? If you temporarily take off the filters, does this help?
Yes, if you have a weak spark you will not burn the mixture well and the plugs would be black. Does your ignition have a "CDI" box or similar that could also cause a weak spark? Did you check your ignition advance for correct timing/operation?
Lots of questions, but there are a lot of things that can make a bike run rich.
Did you have the carbs completely apart and possibly re-install the diaphragms/pistons wrong? How about the throttle valves and their operation? Are all the various o-rings properly installed?
Are you using the correct heat range sparkplugs?
Maybe if you can give us detailed info on what you've done, we can troubleshoot better.

[Anonymous]

I know that I don't have the plastic spacers on the needles. Would that really cause much of a problem?

[KEITH KRAUSE]

I know that I don't have the plastic spacers on the needles. Would that really cause much of a problem?

Do you mean your carbs don't use the plastic spacers, or do you mean you did'nt put them back in? On my VM carbs if the thicker plastic spacer on top of the clip is not replaced, the needle will be too high up, being pushed up by the spring. This will cause a much richer mixture than anticipated. It will also cause a metal to metal friction problem.
I have seen people make this mistake before. They think the jet kit does'nt re-use the plastic spacers. All carbs are different. I just thought I'd mention it as a possibility.
It seems strange that your bike is running so rich but you have the needles in the next to leanest position.
What about my other questions?

[Anonymous]

I realize that this discussion is pretty much past the wondering what happens to the spark plugs, but I figured I'd still post this URL to a good resource on spark plug reading: http://www.dansmc.com/Spark_Plugs/Sp...s_catalog.html.

Happy day!

Michael

[Anonymous]

The original needles had the plastic spacers and I didn't place them on the new needles. The other stuff you suggested I did't get time to do yet.

[Billy Ricks]

You need those plastic spacers, otherwise it's going to be way too rich as the needles are allowed to be pushed up too high by the spring under the clip on the needle. You did reuse the spring I hope?