lacks power on the highway

[geez250]

Hello all,

Just bought a 2009 GZ250 today. 2200 miles.

I know it might just be the nature of this machine, but it really seems to lack power. I had trouble getting it above 60 today. I did hit 70, but not for long.

The only mods on the bike I know of are a windshield (a pretty big one, it stretches from handgrip to handgrip), a seat back for the passenger, saddle bags, and a highway bar. Everything else seems to be stock.

I am in El Paso, where the average altitude is 3800 feet. If I assume the bike still has the original main jet, is 3800 high enough to cause problems?

Thanks for any suggestions!

geez250

[alantf]

I live on Tenerife, and the climb up Teide (the volcano) of 12,196 ft is doable. But, then, mine is the European bike, so the carb is factory set much richer than the American bikes, which have to comply with the nanny laws on emission. Looks like you'll have to mod the carb. Search, and you'll find good info on this. :tup:

[raul10141964]

mode the carb and the air cleaner

[golem]

El pasoan here too, I changed the front sprocket and did the carb mod and it did the trick for me, I'm pretty satisfied with my bike at the moment.

[geez250]

Thanks for the replies guys. I really want to make sure this bike is running in top form.

Golem, do you still have the original jets in it? What is the carb mod you reference? I've been reading up on this site and there seems to be quite a few different things that can be done to the carb, what is it in particular that's good?

Thanks!

geez250

[geez250]

OK, so I found the thread on the needle shim modification, it sounds like that is pretty much the same thing as increasing jet size... it's kind of a "cheat" is how I would describe it.

Also, I see there is a plug called the "epa plug" that should be removed for access to an air/fuel mixture screw. Not sure what part of the powerband that is for though.

geez250

[blaine]

Air/fuel mixture effects idle to 1/3 throttle. :) ;)

[raul10141964]

the main jet control the maximum among of fuel at fool throttle, I use 140

the needle shim correct the flat spot at mid throttle

The pilot jet control the idle, seating the screw between 2.5 and 3 turns improve the cold star and the cold idle

modding the filter improve the air intake an combine whit the bigger main jet increase the HP

the pic show my air filter

[5th_bike]

Another suggestion, if the valves have never been checked/set at that mileage, it may need it.

[jonathan180iq]

Air up your tires too - Simple things make a big difference on this bike.

[geez250]

OK, I think I got this figured out. Correct if I'm wrong please.

The GZ250 has four carb circuits: idle, idle to 1/3 throttle, 1/3 to 2/3 throttle, and 2/3 throttle and above.

So to set my bike up for 4000 ft elevation operation, I should:

First, I need to set the idle mixture. Simple enough.

Then, remove the EPA plug and adjust the idle to 1/3 throttle mixture.

Then, do the needle shim mod to set the 1/3 to 2/3 throttle mixture.

Then, increase the size of the primary jet to set the 2/3 to WOT mixture.

Sound right? I did notice that I'm getting the bluish discoloring on my exhaust pipes after a high speed ride. Uh-oh!

Thanks!

geez250