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Plug chop advice / reading for WOT

  • Thread starter Thread starter Guest
  • Start date Start date
Steve said:
I am sure the principle is the same, but I wonder if 2-strokes color the plugs a bit differently than 4-strokes. :-k
Click to expand...

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.
 
Last edited:
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.
 
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.
 
JonnyC said:
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.
Click to expand...

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.
 
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.
 
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.
 
AMK said:
The 50:1 leans and the 32:1 richens.
Click to expand...

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.
 
tkent02 said:
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.
Click to expand...

Thank you, I get it wrong even when mixing for my chainsaws:rolleyes:.
 
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.
 
Not to hijack but I bought a couple of Stihl's and it's mixed 50:1. They told me with Stihl oil I can run that mix in anything.
Apparently not.
 
It depends ultimately on stoichiometry. SO yes maybe the Stihl works miracles?
I do recall 50:1 Bombardier oil being crazy expensive compared to generic oil in the 80s
Never killed and engine on generic though.
 
Cipher said:
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.
Click to expand...
Thanks, much appreciated.
 
ddlaz said:
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.
Click to expand...

Here's a follow-up. I got my velocity stacks installed, and I do indeed have a stumble/hesitation at cruising throttle position once the bike warms up (which indicates rich to me, and my plugs have more soot than I've ever seen on a plug, but who knows what circuit is causing that because I haven't done a chop yet). I switched back to filters and it has the same issue, just not as bad. I tried switching the main to DJ155 and initially it felt great, but on subsequent rides it was performing like crap. This is when I realized I drilled way too big of a hole in my slides. Got that resolved (back to stock size, not dynojet size), but it didn't help.

So I'm starting back at square one and making sure I have the right main jet to start. I'll try some more plug chops, but if those don't work I'll take it to a local shop to put it on the dyno. $70 a pop though. But it very well might end up that there isn't enough vacuum with velocity stacks for the slides to operate properly, and I'll have to start all over again with filters.
 
Please don't tell me that you're trying to run open, unfiltered velocity stacks on a street bike...
 
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