sparkplugs

[gkr]

what heat range do people run for leopard 125 and do you change it depending on the weather. still trying to get my head around it all. Please explain hot and cold plugs in lamens terms.

[mike]

Heat range in a plug is dependent on a couple of things. Engine load, Ambient temp, Fuel Mixture etc. The heat range is there to help stop the plug from fouling and aid self cleaning . If its too cold it could look black and sooty or even wet. Too hot and it will possibly burn out the porcelain in the middle ( chunks missing or bubbling). It Could even melt the electrode or wear prematurely. What you are shooting for is a firing temp between 500c and 800c. We cant really measure this so just check out your plug to tell you what is going on.

Plugs can be made hotter or colder by changing the insulator length inside the plug around the porcelain. Longer insulator means colder plug due to the insulator sucking the heat away from the tip of the electrode. Shorter insulator length makes for a hot plug due to the heat being drawn away from the electrode tip a lot slower, hence it being hotter.

After a race you may come in and check your plug and see it all sooty and black and think the jets are off. It may well be the plug heat range so maybe try going to a hotter plug and compare.

Normally I run a NGK B9 or a B10 and swap them depending how they look.
For you I would start with a B10(colder plug) and go from there. Each number difference is around a 70c to 100c change in temp in the plug.

Remember all the symptoms of the heat range in the plug can be caused by other factors such as bad fuel, poor fuel mixture, incorrect timing etc. So make sure you understand all that first before you start. Don't want you to go blow the engine to bits.

Below is a link for plug heat ranges and types that should help you out. It is a guide only.
www.kartbay.com.au/UserFiles/1369-Files/File/Spark%20Plug%20Comparisson.pdf

Plugs are very in depth on how they work and I haven't covered all of it. But I hope this helps you out a bit more in understanding how they work.

[tom]

Good info there. I run a leopard and use a Denso IW29. I haven't had any problems with plug fouling or melting. I run this heat range under all conditions.

[gkr]

thanks for the help guys I understand a bit more now