Plug chop advice / reading for WOT

[JonnyC]

Thanks ddlaz!

But 126 mains!!?? BS32SS carbs, right? I have the Mac 4-1 with Delkevic muffler and baffle removed, and the dual pod filters, but stock internals. How could the jet sizing have been that much different from what DJ recommends? Did you do all of the steps that the DJ kit specifies, including using their needles?

As for the run being short, I don't see how I could do a longer run especially with staying in 4th. Maybe I have to make multiple runs back and forth?

[ddlaz]

Yes, BS32SS carbs. Even the GS750E stage 3 kit comes with only 124 and 130 mains -- albeit different motor, I believe it's still a bs32ss carb. Yes I did do all of the steps - slide hole drilling, air correctors, needle and clips. I had velocity stacks and it ran ok, very rich but it had a weird bogging at cruising speed/rpm. Took off the stacks and put on filters but it was severely rich to the point it didn't want to go anywhere. Plugs were sooty. took filters off and it ran great but still rich on the top end.

You are free to do it in 5th but you'll probably be running 90+ mph on flat land before you get some color. I just don't want to be blamed for your speeding ticket. Key is to ride WOT in the higher RPMs. I checked google earth for a long straightaway then did an elevation profile check on it to find one with a slope.

Also, the porcelain may need to get warmed up a little before being able to take on color. I like to warm it up by riding around spiritedly for a couple minutes.

Give it a shot and let me know how you fair.

[azr]

The plugs are showing lean obviously but how is it actually running?

[JonnyC]

It runs OK. No dead spots, but it does feel slow. Of course I don't have another 650 to compare it to, and I never rode the bike stock.

I'm going to try and get some more plug readings.

[Steve]

Not sure about anyone else, but I noticed that the article was at kawtriple.com.

I am sure the principle is the same, but I wonder if 2-strokes color the plugs a bit differently than 4-strokes.

.

[JonnyC]

I am sure the principle is the same, but I wonder if 2-strokes color the plugs a bit differently than 4-strokes.

I was wondering the same. In the articles about doing this type of a reading I don't see them mention that it's for 2-strokes, but even the video I linked was a 2-stroke.

EDIT:
Linked to from one of the articles I mentioned, I found this written by Gordon Jennings - http://www.strappe.com/plugs.html

"Air cooled two-stroke engines often will respond favorably to a slightly richer mixture, which provides a measure of internal cooling; some four-stroke engines give their best power when the mixture is leaned down to such extent that the last trace of soot deep inside the plug completely disappears."

So it seems I went down the wrong path with this insulator check. Damn internet. I'll be sure to warm up the plugs a bit before doing the plug chop procedure, and I'll just read the plug like normal.

[geol]

STEP ONE Use some normal spark plugs. Who knows if plug reading is the same with those things. Never seen the like. STEP TWO Get some MIkuni 125 or 130 main jets and use a pilot jet one size larger than stock. It is hard to understand jet kit jet sizes. With regular plugs, you don't need to go in top gear at redline. Use 3rd or 4th gear and hold it at 500 rpm less than redline for a mile or so. Much less likely to establish as land speed record.

Last, if you can pull redline or near redline in top gear, your main jet size is likely about right. If you can't get to redline, it is too small and if too rich, you will smell it and it will feel soft. The plug chop thing is fine but you have to use your other senses as well to get the main jet right.

[Cipher]

What? This is a silly post,
Those plugs have not got any discernible marking indicating that this OP is indeed trolling.
Who the heck cant peer down the side of the plug? What a waste of time and money.

[AMK]

I just chopped the threads to see the base of the porcelain. The first run I did was with a new plug on cylinder 4. The second run I did a few weeks later I tried it on cylinder 1 instead.

Apparently this is for 2 strokes only. I stole this from another forum.

http://www.thumpertalk.com/topic/860635-how-to-correctly-read-a-plug/

If you like to read.

Also they were talking about oil\ fuel ratios richening and leaning the mixture on another two stroke site. The 50:1 leans and the 32:1 richens.

My conclusion would be there are different plug reading from two stroke to four.

[JonnyC]

Haha, they were normal plugs, before I cut the threads off to inspect them. The problem with using Mikuni jets is the taper profile on the Dynojet needle is completely different, and the stock needle has no grooves for adjustment.

So I subscribe to Finnegan's Garage on YouTube, and in episode 14 he talks about using a doctor's inspection scope for reading inside of the plug. Sure he's doing this for V8 motors, but at least it's not a 2-stroke. So I think there is some validity to the idea.

[Cipher]

certainly different readings on 2 strokes. Many years ago growing up we had logical folks who surmised that adding extra oil to the mix was good for the engines as the spring came. Sadly they were enleaning the fuel mixture just as their ski doo was operating in an ever warming environment,
Yah cant teach a heniz pickle anything though. Let em destroy their engines its a make work project.

[tkent02]

The 50:1 leans and the 32:1 richens.

You have that backwards. More oil = less fuel, so the mix is leaner. Odd as it seems, adding too much two stroke oil can actually lean it out to the point of burning a hole in a piston.

[Cipher]

exactly what it does! so much misery borne of old wives tales and shucks grandpa did it ad nauseum

[AMK]

You have that backwards. More oil = less fuel, so the mix is leaner. Odd as it seems, adding too much two stroke oil can actually lean it out to the point of burning a hole in a piston.

Thank you, I get it wrong even when mixing for my chainsaws.

[tkent02]

I have some that run 40:1, some use 50:1, the stuff looks the same once it's mixed up. Something bad is going to happen sooner or later.