A few Q'z

[Shaggz]

Hi.

I've recently bought a 93 RMX 250.
Have a few problems that I'd like to solve.

Main problem is when i really open her up it kind of splutters or holds back, then kicks in.
I changed the spark plug and it rides better but still same problem. I've noticed that it's probably time to re pack the muffler and also change or clean up my air filter. But would these be answers to my problem?

Any help would be much appreciated..

Thanks

 

[mandark1967]

Go here:

http://justkdx.dirtrider.net/

Click the tech tips link and read up on the jetting, carb tuning, and needle sections.

Though these are written for the KDX, they are applicable to every two-stroke motorcycle, and they are a great source of information.

 

[Shaggz]

Thanks..

I've been reading up on the jetting and I think I'd stuff it if I did it myself.
Is it a hard thing to do for a pretty newwie to it all?

 

[mandark1967]

It's confusing at first :bang: then, after you read those articles about 12-15 times, it all comes into focus... :laugh:

Seriously, though...Once you take about 30 minutes to understand the basics, you'll have it down.

divide up your throttle range into idle, 1/8, 1/4, 1/2, 3/4, and full.

Where in the range of motion does the bike start to sputter? (ranges can overlap, like 1/8 to 1/2 or 1/4 to 3/4, etc)

 

[Chili]

Before you get into jetting, start with the basics. Definitely get the air filter cleaned and properly re-oiled, this should be a regular occurrence after every few rides or even every ride if the conditions are bad. Take the carb apart and give it a thorough cleaning, making sure all the jets have no blockages. If the bike was stored for a period of time with fuel in the carb it can gum up the works and the bike may be having trouble getting fuel when you open it up. I bought an old RM125 that seemed to run fine but stumbled just like you mentioned after cleaning the carb it was better but still not right so I replaced the main jet and it ran perfect after that.

 

[Shaggz]

It's confusing at first :bang: then, after you read those articles about 12-15 times, it all comes into focus... :laugh:

Seriously, though...Once you take about 30 minutes to understand the basics, you'll have it down.

divide up your throttle range into idle, 1/8, 1/4, 1/2, 3/4, and full.

Where in the range of motion does the bike start to sputter? (ranges can overlap, like 1/8 to 1/2 or 1/4 to 3/4, etc)

I'd say it happens at about 3/4 throttle. up to half it's solid as.
Then runs pretty good at full, just that dodgy bit at 3/4.

 

[MotoKing_1990]

I have the exact same problem with my kx I replaced the air filter, jets, packing and it still does it. I am going to rebuild the engine becuase that might be the problem with mine, my compression is 70 and i dont think it should be that low!