too lean? will it grenade

[yarrowkevin]

I got it perfectly jetted for power, and throttle response, this is one tire spinning yee haw bike :yeehaw: , But after a plug check itrs as white as casper :yikes: I know its lean , I dont wish for my bike to explode but what do I adjust to richen it. with the higher jets it doesnt have the same response, I ended up with 155 main, 42 pilot ,midclip position, its about 85 degrees at 900 feet , please adviseI wish to be safe than sorry and broke!!

 

[Nice Guy Eddie]

hmmm I'm a little suprised that a 155 with a 42 and in midclip is lean like that.... that is where my bike is set up and I'm still a bit rich at 500' and 80 degrees.... pretty darn good response on the throttle

are you sure you don't have air leaking from somewhere?... (carb boot?.... crank seal?)... you will never get it jetted right if you have a leak...

unfortunately 'perfectly jetted for power' means too lean to last... don't jet soley on power, you need to do plug tests.... and yours are saying 'tone it down or blow it up' from what I gather here...

If you know how to jet it you know the answer to 'what do I adjust to richen it?'

 

[Colorado Mike]

Are you running the stock plug heat?

 

[Studboy]

If everything is mechanically good, then go back up a jet size. What kind of fuel are you running? If it's pump, I wouldn't want to jet that lean because the fuel is sometimes a jet size or two different from batch to batch.

Also, make sure that you are reading the plug properly.
This thread should enlighten you, I know that I was when I read it.
http://www.dirtrider.net/forums3/showthread.php?t=92818

 

[Roland C]

A "white as casper" plug doesn't necessarily mean it's too lean. That just means it is running hot (not necessarily too hot, either). To check your main jet, do your standard plug chop on a brand spankin' new plug. Get up into fourth or fifth gear quickly and go wide open throttle for 30 seconds or so, then chop the throttle and hit the kill switch. Put an old plug back in and when you get back home take a hacksaw (or whatever works) to the plug chopped plug and cut the threads off at the base of the threads. Look for the mixture ring at the base of the ceramic - don't look for darkness, look for thickness. If it was a brand new plug and only run for 30 seconds, the ring won't be very dark. It should be in the 2mm thickness range or so. That means your main jet is good. If the ring is thicker than 2mm, you are too rich. If it is under 1mm or barely visible, you're too lean. The tip of the plug is likely to be white if you are jetted correctly and riding hard. My plug is pretty white even when I'm slightly rich on jetting if I'm riding on the pipe a lot. Hope that helps.

 

[skipro3]

A perfect plug will be white on the tip of the insulator. It's down at the base of the insulator that will tell you the tale of too lean or rich. There are many threads with photos, (I know 'cause I've posted 'em) that show just what I'm talking about here. Do a real WOT plug chop and check the plug by cutting the threads off the plug to read correctly. Not sure of how to do a WOT plug chop? Check the first thread in this forum and follow the links to Canadian Dave's site. It think you will find it there.
If your plug is blistered, then I would say it is too hot. White is what it should be. Most folks are too nervous to run it white so they look for an overall tan or chocolate brown color. Also, your bike should start giving you plenty of notice that you are getting too lean before damage occurrs by the sounds it makes during the plug chop. Mine did.
You also might want to pull the head and check your piston crown and the area under the piston for damage or signs due to lean conditions or overheating. An overheated combustion chamber will cause carbon build up on the bottom of the piston as fuel cycling through the crank comes in contact with a too hot piston.
Roland's post on how to perform a plug chop should include that you chop the throttle, hit the kill button, AND pull in the clutch all at the same time. This is very critical to get a good reading.

 

[yarrowkevin]

thanks for the help, I never thought of the cutting of the plug before, I have been doing the flashlight trick, it is running a little warm. so I ll double check everything :worship: