Top End, Jetting, or Ignition

[Tdel]

Hello all,

I have an issue with my 95 RM-250. The bike was running great all summer. I put a new top end in late spring, new boysen power reeds about 4 weeks ago, and many other maintenence items (clutch plates, water pump, chain sproxket, tires). The bike over the last two days, hotter and much more humid, has lost it's punch from the upper mid range and up. I did a compression test last nigh with the bike warm and got about 215 psi. The plug looked ok. While riding I stopped and added a couple of twists to the air screw and this seemed to add a little more power up top, but no where close to what the bike is capable of. I changed the premix ration from 16 ounces per 5 gallons to about 14 ounces per 5 gallons (motul 800 synthetic). I also checked the reeds last night and they look like new. So, I gues I am wondering if this seems like a jetting issue or a ring issue. Perhaps a spark issue.

thanks,
Tdel

 

[Tdel]

I also failed to mention that the bike would not idle, and the idle was turned all the way up.

 

[PINGERS4LIFE]

14oz for 5 gallon i think that isnt enuff i go about 4 oz per gal

 

[reelrazor]

"hotter and much more humid............a couple of twists to the air screw and this seemed to add a little more power up top..........changed the premix ration from 16 ounces per 5 gallons to about 14 ounces per 5 gallons....."


The weather richened the bike, you leaned it (a tiny bit on anything over 1/4 throttle) with the screw(if that, 'turns out' does not necessarily mean leaner-depends on which carb you have), and then richened it on every circuit with your mix change(less oil means more gas as a percentage gets through the jets).

It won't idle because you tried tuning the upper end with the idle air screw.

Try dropping the needle and/or stepping down a size on the main and tuning the screw for best idle.

Remember what you current jets/needle settings are for when the weather cools.

 

[Tdel]

Hey guys,

I just wanted to follow up on the problem. A couple of things really led to my issues, first as pointed out I richened up my fuel by reducing my ratio, I had an older plug in the bike and the real kicker, I over oiled my filter with FFT, plus it was a little wet from some creek crossings. All those factors lead to the bike running like crap. Last night (cool and dry) I replaced the plug, readjusted the air screw, added new leaner fuel, and changed the filter, and the bike had its top end back it is still idling slow and dies without throttle blips, which is very annoying. Any suggestions?

thanks,
Tdel

 

[Someone]

No 2 stroke I've ever owned would idle except when cold started with choke. Some people will say that it should or shouldn't, but I have never had one to idle without blipping the throttle. It's not a pain for me, I guess cuz I am used to it.

 

[Studboy]

You may have sucked some dirt, water, or air filter oil into the small air passages in your carb. I've had this happen before, and it produced similar symptoms. Take the carb apart and spray everything out with carb cleaner and compressed air.

 

[reelrazor]

".....it is still idling slow and dies without throttle blips, which is very annoying. Any suggestions?"

The big-ish flathead screw on the right side of the carb(idle adjustment)? Turn it in until you get an idle it will hold, then using the mix screw, look for the highest idle at that setting. Once you find that high idle spot, turn the idle adjustment screw counterclockwise until it just starts to stumble, then back in a 1/4 turn, then mix screw again for highest idle,....repeat until lowest clean idle.

(make sure the bike is fully warm before even touching any carb screws and the lowest reasonable idle for a two stroke single will be in the 1000-1500 rpm range and if it won't do that then the pilot circuit is fat or lean))