lack of power (well even less power) during cold weather

[geezer]

in the morning time on my way to work it could be around 40 degrees and the bike has no power, i can barely pull up hills at 40mph. while on my way home its 70degrees and the bike is back to normal again pulling 45-50mph up the same hills. my theory is its the lean jetting of the bike, when the air coming into the carb is cold there is not enough fuel to completly ignite the charge, and when its warm outside the airfuel ratio is back to normal lean condition. anyone ever tried moving the carb jetting up one notch? possitive impact even without modding the intake or exhaust?

[blaine]

Originally Posted by geezer

in the morning time on my way to work it could be around 40 degrees and the bike has no power, i can barely pull up hills at 40mph. while on my way home its 70degrees and the bike is back to normal again pulling 45-50mph up the same hills. my theory is its the lean jetting of the bike, when the air coming into the carb is cold there is not enough fuel to completly ignite the charge, and when its warm outside the airfuel ratio is back to normal lean condition. anyone ever tried moving the carb jetting up one notch? possitive impact even without modding the intake or exhaust?

If you go up one number on the main jet and adjust your idle mixture (out about 1/2 turn richer) You will find a big difference in performance.You should try the idle mixture setting first,that may fix your problem without re jetting.
:cool:

[alanmcorcoran]

I think you might have something clogged in the works. I've ridden mine in 40° and 70° (ride it year round, although 40 is about as low as it gets here) and the only time I had power issues was when I also had carb issues. What kind of gas mileage are you getting? If it's less than 60ish it could also indicate clog/jet issues. My gas mileage dropped off a lot (40mpg-ish) when my carb was effed up.

[blaine]

Just a afterthought:Have you tried putting your choke on part way to make the bike run richer when it is cooler to see what happens?
:??:

[geezer]

ive had the carb apart many times now and they should be clean still, but on the other hand i never did add a fuel filter.. but i doubt its got a clog, the bike runs way to normally for there to be any issues with that. can you get to the mixture screw with the carb on the bike? ive never seen the screw so could you tell me where it is? i never would have thought to add choke while i was driving. so if the bike returns to normal with some choke applied then it needs richer jetting? i was able to go 200 miles on my last tank so i know im still getting good fuel economy. i have never owned a bike that was so tempermental lol! its almost like its unhappy to get up in the morning, just like me lol :neener: so what about the needle? should i also shim it if i decided to richen up the main and mixture screw? also does fuel economy suffer if you tweek the carb? i would assume not much at all becouse your using less throttle to get the same amount of work out of the engine, right?

[alanmcorcoran]

I've never been in there, but I've seen many posts that describe a plug you need to drill out (I think this is limited to the US version.) Many GZ250 members have successfully done it without harm to the bike. Do a search on mixture screw and you may find step-by-step. In general, folks seem to have had better results with messing with this than the jets.

[blaine]

If the bike runs better with the choke partly on, than it needs to be richer,as that is what the choke is doing.The idle mixture is plugged from the factory and needs to be drilled out to gain access to the screw.There is a good description of drilling out the plug in the manual.It is in front of the float bowel on the left side.If you re jet you will also shim the needle.When I done mine I found a big difference in performance.You should notice it more as the American models are set leaner than the Canadian models.I found very little difference if any in mileage.
:cool:

[geezer]

i did a search on the mixture screw and couldnt find any pics on which one is the screw, so i went outside and directly under the carb are two brass colord caps, now which one do i drill? cause it would kinda suck to drill a hole in the carb :hide:

[blaine]

I don't have me G.Z. any more so i can't remember which one is which. The plug over the idle jet is thin aluminium,the other one is solid.You can perice the plug with a self threading screw.If I recall the solid plug is more of a copper color in the center.
:cool:

[geezer]

i found it using google image, it brought me back to this site and it was a mexican doing the write up, i cant belive his bike was capable of 87 mph, i call bs. :biggrin: the bike is already screaming bloody murder at 70mph