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Author Topic: Fresh plug  (Read 1127 times)

Guaire

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Fresh plug
« on: April 19, 2013, 04:53:44 PM »
I cleaned the K&N air filter and re - oiled it. I installed a brand new plug and rode about 25 miles. Looks rich. The old plug looked rich. When I get time I'll pull the Mikuni and see what I've got running. Any suggestions, cautions....? Here's some plug pix.

ace.cafe

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Re: Fresh plug
« Reply #1 on: April 19, 2013, 05:37:20 PM »
If the plug was subjected to various throttle settings during the riding, and shut off at idle, there is no way to adequately gauge which jet(s) might be rich.
It could be as simple as too rich of a setting of the idle air bleed screw. Or it could be rich all over.
Plug chops done at certain throttle positions will more likely yield answers to which jets need attention.

Most street riding is done between 1/4 to 3/4 throttle, which means the needle jet and needle position will be the most influential mixture items to look at.
« Last Edit: April 19, 2013, 05:40:06 PM by ace.cafe »
Home of the ACE Fireball 535 Bullet,  Ace GP Hi-Lift Roller Rocker Head Conversion. Pistons, cams, etc. Highest performance Bullet engine mods available anywhere.  AVL mods available. UCE kit coming.

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Guaire

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Re: Fresh plug
« Reply #2 on: April 19, 2013, 05:40:35 PM »
Thanks, Ace. I'll start by doing an air screw adjustment.

D the D

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Re: Fresh plug
« Reply #3 on: April 19, 2013, 06:31:51 PM »
Guaire,
If you do check the jets they can be removed by just removing the float bowl with a short screwdriver instead of removing the whole carb.  Be sure to turn off the petcock and put something below the carb to catch any spilled gas.  You still have to remove the carb to mess with the needle height, needle jet, or measure the float height correctly though.  Been around this a few times lately.
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Re: Fresh plug
« Reply #4 on: April 19, 2013, 07:50:58 PM »
On the Mikuni TM32 you need to take the carb off and remove the slide to change the needle setting. Its probably the same process for which ever Mikuni you have. After the pilot jet the needle is the second thing you will want to tune followed by the needle jet...and then the main jet.
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High On Octane

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Re: Fresh plug
« Reply #5 on: April 19, 2013, 08:58:43 PM »
I'm sorry...  What the hell is "plug chops" and what is it's function?

Scottie
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ace.cafe

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Re: Fresh plug
« Reply #6 on: April 19, 2013, 09:28:02 PM »
I'm sorry...  What the hell is "plug chops" and what is it's function?

Scottie

Plug chops are a way to isolate each major throttle position's mixture setting, by isolating the jets which control the mixture in those throttle positions. With these types of carburetors, you can be lean in one throttle position, and be rich in another. This process allows you to tune each throttle range and the corresponding jets.

The process is like this.
Put a piece of tape or other indicator pointer on your throttle housing, like an arrow pointer.
Put a piece of tape wrapped around your throttle grip. Then use a magic marker on the tape to mark the 1/4, 1/2, 3/4, and Full throttle position, so that they correspond with the pointer when you are at these throttle positions.

Use a new plug.

Then, take the bike out and ride at one of these throttle positions for a few minutes so that the plug can get enough time to get its color. Hold it at that throttle position the whole time without changing it, so that it isolates that throttle position only. When you get to a safe place to pull over to check the plug, cut the engine and pull in the clutch, don't change the throttle position until the engine stops,  and coast to a stop on the side of the road and check your plug for color.
If the color is a medium tan, or something around that, it's pretty good for that throttle position, and you can try the next throttle position, etc.

Throttle positions and their corresponding jets are:
Idle = Pilot jet and bleed screw
1/8 = Throttle slide cutaway
1/4 = Needle jet mostly
1/2 = Needle jet and jet needle combination(they actually overlap in function from 1/4-3/4)
3/4 = Jet needle mostly
Full = Main jet

Doing this will give good even throttle results with proper mixture settings all thru the whole throttle range, and should eliminate any hiccups, bogs, or flat spots in the entire throttle range, and prevent lean conditions from causing engine damage, and keep your fuel economy at its best.
« Last Edit: April 19, 2013, 09:47:27 PM by ace.cafe »
Home of the ACE Fireball 535 Bullet,  Ace GP Hi-Lift Roller Rocker Head Conversion. Pistons, cams, etc. Highest performance Bullet engine mods available anywhere.  AVL mods available. UCE kit coming.

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High On Octane

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Re: Fresh plug
« Reply #7 on: April 20, 2013, 12:34:58 AM »
Right on!  I was not aware of that trick.  Once I'm up and running I'll make sure to do that.  Thanks for the info!

Scottie
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Ice

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Re: Fresh plug
« Reply #8 on: April 20, 2013, 02:12:41 AM »
Guaire, exactly what plug is that ?

I can break it better,,,,at night, in the rain, on the trail,, 20 miles from nowhere.

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Guaire

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Re: Fresh plug
« Reply #9 on: April 20, 2013, 12:39:05 PM »
Ice, it's a B8ES. Not an 'R'. The cap is the resistor, 5K.

jdrouin

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Re: Fresh plug
« Reply #10 on: April 20, 2013, 04:19:44 PM »
Another little thing that can sneak up on you is the rubber grommet at the base of the enrichener plunger. It can pop off the lip it's attached to and prevent the enrichener from going all the way off, causing an excessively rich running condition. I was fouling plugs like crazy last year until a forum member suggested it.

Turns out that was my problem, and it was easy to fix with some silicone gasket sealer that can bond rubber and metal. Don't remember what I bought but I can check my garage when I get home, if you like.

The grommet in question is circled in yellow on the attached picture.

Guaire

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Re: Fresh plug
« Reply #11 on: April 20, 2013, 11:22:50 PM »
Thanks, JD, I'll take a look at that. Although my carb is a Mikuni, it shares a similar part.
  nfield is offering the K&N air filter for $10. I'll get a new one. Next, I'll dial in the low speed on the lean side and see where that gets us. After that I'll open the Mikuni and catalog the whole setup.
  I cleaned and re - oiled the K&N, but for ten bucks I'll have a new one. K&Ns are known flow flowing lots of air. I'll track this down, one thing at a time.

Guaire

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Re: Fresh plug
« Reply #12 on: April 25, 2013, 12:52:17 PM »
I ordered a new K&N to make sure I'm getting the best air flow. On this Mikuni there are two adjusters. I assume one is the low speed air adjuster, and the other is the 'throttle stop', similar to an Amal. Which is which? On the air screw is screwing it in rich and screwing it out adding air [lean]?
  When I get the new filter I'll remove the carb and see what I have for jets, needle and slide settings and take it from there.
Cheers,
and thanks,
Bill

Blltrdr

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Re: Fresh plug
« Reply #13 on: April 25, 2013, 02:05:44 PM »
I don't understand why you would order a new K&N to replace one you already had. Unless it was damaged those filters will last the life of the bike with cleaning and oiling every so often.

Check this out: http://www.mikuni.com/pdf/vmmanual.pdf
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Guaire

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Re: Fresh plug
« Reply #14 on: April 25, 2013, 02:16:27 PM »
For $10 it's worth it to know for sure, I'm getting the best airflow. I already used the K&N kit, but who knows.