Jump to content
Sign in to follow this  

Hot hanging idle

Recommended Posts

Hello!

I just got a new, to me, bike! I moved from a ktm 250sx into a 2006 rmz 450! And I love it! Omg I never want to stop riding..

Back on topic, I went riding for 2 hours. Bike ran great, kinda hard to start but thinking it may be partly me?! About a half hour before I called it a day, if I revved the bike it would come down some but hang above idle for 2 seconds then would return to idle.. Bike was hot, doing some tight trails, wasn't boiling the coolant or nothing.

What could cause this?

I stripped down the plastics to check every thing over and found the plug wire was not snapped onto the spark plug, but that's all I found!! I did drain the bowl on the carb but found no dirt or water in the fuel. I haven't got the bike got since then so I can't say if it's still doing it but I'd imagine it is...

Any advice would be helpful!

Share this post


Link to post
Share on other sites

Adjust the fuel screw for a perfect idle when hot. If the idle 'hangs' turn the screw out about 1/32nd of a turn and retest. Remember, never open it more than 2.5 turns from gently closed.

Share this post


Link to post
Share on other sites

William is right on the money as usual. A hanging idle is lean. The best adjustment of your fuel screw will give a nice clean throttle response at the bottom 1/8-1/4 of the rev range. Usually you will find this at max idle rpm with the mixture screw and then slightly leaner (turned in) for a minor rpm drop. Keep in mind that the range of the mixture screw is typically 3/4 to 2 1/2 turns out from GENTLY seated. If it runs better outside this range then your pilot is dirty or the wrong size.

Something to remember: the fuel screw may need attention with temperature and elevation changes. It's not a one-time adjustment.

Share this post


Link to post
Share on other sites

Not quite right. The fuel screw/pilot jet operate all the time. With a cold engine, you also use the choke (actually, it is an 'enricher'). Once the engine is warm, you ride. Typically after fifteen minutes or so, the engine is hot, fully up to temp. Then for the balance of your day, you are running at 'operating temps'. This is the normal temperature of the engine. So this is what the jetting is adjusted for.

A fuel screw is a fine adjustment of the carb pilot (or slow) fuel circuit. In truth, the pilot jet and the fuel screw are sperate systems that operate all the time. Think of the pilot circuit as a 2" water pipe and the fuel screw, a garden hose with you adjusting the spigot(fuel screw). The 2" pipe flows all the time and then you get the exact proper volue adjustment with the spigot/garden hose.

Share this post


Link to post
Share on other sites

So there could be some thing that was obstructing the jet ? I can start it right now and it's perfect, idles fine, revs fine. But after I rode for about a hour and a half it would hang just above idle for 1-2 seconds then return to idle. I read a lot about the hot starts on these, could it be some thing with that ? Or that a different scenario lol I just want to figure it out, also where's a good place to purchase a repair manual for my bike, I want to check/shim the valves, as I'm starting to believe this may be the problem with my hard starts

Share this post


Link to post
Share on other sites

Somehing like a speck of dirt in the carb bowl, that agitation caused to go to the jet.

 

Does the problem still exist? Did you remove the cap on the botton of the carb and look for debris in it? Do not make the mistake of over analyzing and fixing what is not broken.

 

For a manual, see the dealer. There are no copies that are legal other than OEM, Haynes, or Clymer., I stick with OEM.

 

Valves typically are the cause of hard to start when cold only.

Share this post


Link to post
Share on other sites

Ok got the start problem solved I believe! The spark plug boot was not snapped onto the plug , and the plug was pretty fouled up, I'm thinking from not getting the right spark ?

But it started right up in 2 kicks and the same hot. One problem down

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

Sign in to follow this  

×