jetting??

[smokerguy2005]

hey guys new to the site lovin it so far...

here's the thing bought a bike off my buddy, it has pro circuit full exhaust and v force reeds, he never jetted the bike, don't know what my elevation is i'm located next to detroit.
when I kill it and try to re-fire it is dead, keep fouling out plugs
put new plug runs great for a little while but you can tell after 5-10 min of riding that the plug is getting fouled, I mix at 40-1
bel ray oil H1R.

it seems like it is running way too rich

any help is muchly appreciated.

thx Randy

 

[mathd]

could be the plug temp too.
what are you using for plug?
if you use br9es you can use a hotter plug like a br8es.

if this dosent help, then you will have to jet.
Look for jetting on this site, lot of info.

 

[Patman]

Jump over to Eric Gorr's home page and you'll find some free jetting info as well a his book that will be invaluable with most anything dirt bike mechanic related.

 

[Matt90GT]

First dont change the plug temp to fix a jetting issue. It will cause more issues. The plug pulls heat from the combustion chamber. So running a hotter plug will be more prone to detonation.

 

[Rich Rohrich]

First dont change the plug temp to fix a jetting issue. It will cause more issues. The plug pulls heat from the combustion chamber. So running a hotter plug will be more prone to detonation.

The plug DOES NOT pull heat from the chamber.

A spark plug’s heat range simply refers to its ability to transfer the heat generated from the electrode tip, through the porcelain insulator, to the cylinder head. How quickly this happens defines the terms hot plug and cold plug.

A hot plug means that the heat transfer from the electrode is slow, causing the plug to operate at a higher temperature. A cold plug has a faster rate of heat transfer from the electrode to the head and operates at a cooler temperature.

While it is possible (but difficult in most MX bike cases) to run a plug with a heat range that is too high for conditions and make the plug overheat, and possibly lead to pre-ignition as a result, the heat range of the plug does NOT change the temperature in the combustion chamber, and changing the heat range will not make an engine prone to detonation. Pre-ignition and detonation are very different things with very different root causes.

Most dirt riders can (and probably should) go a step hotter on the stock plug, unless they are incredibly fast or spend a lot of time in areas where they run at WOT. While I'll fully agree that plug heat range is not a fix for bad jetting, you'll never get an engine to run consistently right with a plug that is too cold for the application.

If the plug runs at too low a temperature then it will never clear the deposits from the insulator and these deposits will quickly cause a short circuit path and start random misfiring which is really hard to track down. It will keep doing this until it finally fouls completely.

No one ever hurt an engine running too cold a plug, and the Japanese engineers know this. So they spec a safe heat range plug in the engine stock so riders who can't or won't tune the bike will foul a plug rather than causing other problems.

You can't read jetting on a plug that is too cold. Until the plug is running at the proper temp to clear deposits off the insulator, you are just spinning your wheels.

Get the plug heat range right, then get on with the business of tuning.

here's the thing bought a bike off my buddy, it has pro circuit full exhaust and v force reeds, he never jetted the bike

Chances are good that if the engine is mechanically sound (no right side crank seal leaks etc) you can start with a one step hotter plug than stock. Check the pilot jet size and if it's stock you can go one step leaner as a start. Then move on to going one step leaner on the needle and see how it goes. You can't hurt the engine with those changes, worst case if you go too lean it will bog or maybe be a bit harder to start. Forget about the main jet till you learn a lot more about tuning. Most riders spend so little time on the main jet that if you left it out they would barely notice.

Here's a link to one of Eric Gorr's old articles that will help make sense of the tuning process : http://www.chicagostories.net/ericgorr/EG_Carb Tuning.html