Plug chops

[Satsol67]

I have seen some of you guys talk about plug chops. What is the advantage of doing this? Is this something you want to do ONLY if you have motor mods? Like porting. Or is it good to do with no mods?

 

Thanks

[watkins]

A plug chop is a method of checking the jetting of the carbs. When you start slapping on parts jetting needs to be done. Basically you warm the bike up. Then throw new plugs in it and go WOT through all the gears.. when you are topped out in 6th, pull the clutch in and kill the motor and stop. Then take those plugs out, slap the old ones back in and ride home. Then cut the threads off of the ones used for the WOT runs, you are wanting to look at the bottom of the porcelin to see what the smoke ring looks like. You want the smoke ring to be a nice tan.

[Satsol67]

Thanks i understand now!

[Animalman294]

It is mainly done if you change the flow rate of the incoming air or the fuel. You need to balance the air/fuel mixture or ratio. This is done when you open up with K&N, pods, pipes, larger carbs, port work, new head, new domes, new reeds, well you get the idea............

[canyncarvr]

re: 'nice tan'

 

Sorry, but...not exactly.

 

Color is not the issue.

 

Back up a bit. re: 'Why do it?'

 

Because it is one of the methods useful to a rider to determine what his machine is doing jet-wise. WOT plug chops are probably the most common, but the test can be done at any throttle position. It's important that it be A throttle position with no movement of the throttle during the test because any movement means a different carb circuit will come more (or less) into use. The WOT part is easy because there isn't generally a whole lot of question WHERE that throttle position is.

 

Maybe you've seen masking tape on throttle grip flanges with pen marks on it? That's how you determine where you're at in the throttle range for something other than WOT plug chops. Carb circuits do overlap a good bit, so the results of such testing will likely be less than simple to figure out.

 

Yes, you pull the clutch (unload the engine from the trans..just a hint of decel braking will change what the plug looks like), hit the kill switch, and stop. Also 'chop' the throttle (drop the carb slides).

 

The color of the plug insulator tells you things about fuel additives and heat, but not mixture. What you're looking for is the width (thickness?) of the ring at the base of the insulator. A ring one mm thick is generally considered to be 'right on'. Of course, that means your margin of error is close to zip. Premium performance? Yep. Maybe burning things up? Yep. If your ring is over 2mm, consider a jetting change (in the circuit you tested, natch).

 

How long to run it? It doesn't take long for the ring to show. If you're at all thinking you are lean you're better richening the circuit your going to test and work down from too-rich. That's much safer than trying to work up from too-lean. You may only get one chance at the test if you approach thing from the latter. Less than 30 seconds will leave a mark..considerably less than that, actually. The longer you run it the darker (more defined) the ring will get. In real short tests, the ring may not go completely around the insulator.

 

Modified or not, your machine will work better AND be more fun to ride if it's jetted correctly. Running what someone else runs in THEIR bike is not helpful to you. Machines vary and the same machine on the same day (atmospheric conditions make a difference) but with different riders will NOT run the same way and may well require different jetting if you want to make it as close as you can get it.

 

Different plug types won't have much if any effect on this. If you like to run a High$ palladium fine wire, you don't have to burn $18 for a couple of plugs to do a chop test. Use a couple of less expensive -ES plugs. You will get the same information.