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Old 08-05-2008, 04:15 PM
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eDJ eDJ is offline
Motorized Bicycle Elite Member
Join Date: Jul 2008
Location: Wayne National Forest
Posts: 531
Default Re: As the Engine Turns!

Just by way of suggestion, if you visit a dollar store you can probably find a bartenders measure there. It's like two small cups joined together at their bottoms. The larger is 1 1/2 ounce and the other is 1 ounce. (a jigger & pony in bartending lingo) Then if you find an empty 1 liter water bottle you can scale down your test mixes. 1 liter is roughly a quart. You can also use a 2 liter soda bottle later when you get the mix ratio you like. Thus you're mixing 1/4 and 1/2 gallon quantities using the bartenders measure and bottles. Now you can mix small experimental quantities till you get it right for your bike. Run the different mixes and read your spark plugs. Do this first.

But get yourself some measuring tools to mix with, a couple or three new spark plugs to use for testing and take your test mix and plugs and tools out to an open stretch of road where you can run all out for a few miles without interuption run test your bike. Then quickly shut down the engine (kill switch) pull over and let the engine cool enough that you can pull the plug and read the color. If you have a friend who can follow you in a car or whatever they can observe your exhaust for smoke etc.

It's hard to find a site that details reading 2 stroke plugs it seems. If your plugs are wet and black you are too rich with oil and fuel. You don't need a photo to know that.

This view is of plugs from a 2 stroke engine. To the left is an acceptalbe plug
and to the right is a good running plug. I drew some black lines on the ground electrode to try and better define it from the center electrode.

These three plugs may be acceptable for a 4 cycle engine but would be far too lean and hot for a 2 stroke engine. If you pulled these out of a 2 stroke it would be a sign that you need to enrichen your carb or check your ignition to see if the point gap and timing degrees BTDC are set properly. Plugs that look like this could signal failure, perhaps burn a hole in your piston etc.

Reading plugs in any engine is one of the skills any engine tuner should learn early. There's plenty of info from plug manufacturers for 4 cycle plugs
such as NGK's site with FAQ's.

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