bike is losing power..?

[short stop]

I'm sorry to be such a n00b with this, but I wanted to get some opinions before I took the bike to the shop and simply tell them "it's broken! fix!!"

I've been riding my 2000 GZ250 for about 3 weeks now. No real issues with the bike...I lamented somewhat on its speed, and even got it on the highway once and topped out at 90kmh...oh well. I chalked that up to newbie upshifting. I've made a few longer trips with it and commuted once to work with it (36km each way) with no problems.

The past few days things have been going wrong with bike, and it's getting worse every ride. The bike is starting to "jerk" when I try and accelerate. Like the engine is "chugging", like it's not getting continuous power (before anyone asks, YES there's gas in the tank!). This happens mainly starting at 40+ kmh, and then gets REALLY bad when I'm 3rd gear trying to hit 60. The bike doesn't even rev past a certain point - if I try and give it some more throttle, it just starts chugging and struggling even more. If I get into 4th I get some relief, and get past the 60kmh mark, but I still struggle to maintain any kind of speed. Hills were a disaster, even when I downshifted.

The first 10km or so of my trip home from work, I did hear some odd noises coming from below me. I'd hear it while the bike would be particularly struggling, and it's hard to describe the noise other than saying it sounded like someone spitting, or a "pfst!" sound, crossed with a mild rattle. This soon stopped as the ride progressed, but the engine wasn't performing any better.

I'm not mechanically inclined...but possible carb issue??

[Sarris]

Replace the spark plug (cheap) and clean or replace the air filter (not so cheap). If that does it, OK, if not you may want to try some carb cleaner in the gas tank.

Good Luck!!

:chop:

[jonathan180iq]

This sounds like what was happening to me for about a week after I first switched over the 16T sprocket.

Here's why:

In my haste to get everything thrown back together, I somehow didn't notice that the crankcase breather tube had slipped off the bottom of the air box and had been cut nearly in half by the chain/sprocket. This was letting too much air into the carb and screwing up the mixture.

Also, you may want to check that all vaccum hoses are attached where they should be under the tank and into the carb. Those little hoses have no clamps on them and they can come off.

Lastly, I would suggest you check under the bike to make sure that your muffler is propertly bolted onto the header. There is only one connection down there and it if goes, you're mixture will be screwed up and you'll experience the symptoms that you have mentioned.

Based on the sounds and the rattle that you hear, I'd bet your muffler has come loose somehow.

[short stop]

Woop! Checked the underside of the bike quickly while taking the car out of the garage, and there's a small dangling hose! I'm assuming that's a vacuum hose. I'll go back out and take a closer look.

Muffler also looked good on quick inspection.

[music man]

there is supposed to be one small dangling tube under there it is the drain tube for the carb float bowl.

[short stop]

C'mon, can't you give me a moment of glory in figuring out the problem??

I mean...er....thanks. ;)

[jonathan180iq]

I think he was saying that you haven't figured out tue problem yet.
I'll throw you a photo late this evening.

[5th_bike]

I remember reading about a similar problem, and it was that the connection between the big black air 'tube' from the airbox and the carburator was not tight enough.

Oh, also check if the bottom of the bigger dangling hose (air box drain pipe) has the plug it should have. If it has no plug at the bottom, you need one.

[short stop]

I've checked everything (albeit with a newbie eye) and found everything to be connected tightly to the carb, not cracked or loose. Also found the cap on the end of the airbox drain hose. Could still be an issue with a gas tank vent, I suppose.

As for that original hose I found dangling....yes, there is one for the carb float bowl drain (alongside the airbox drain). I found that one. The original hose I found is not that....it actually comes from the battery.

Thanks, jonathan. I was just poking fun at myself. Not trying to be sarcastic or anything...just self conscious. I truly appreciate your help and suggestions!

[Easy Rider]

I've checked everything (albeit with a newbie eye) and found everything to be connected tightly to the carb, not cracked or loose.

OK, so then I guess we are back to spark plug, air filter and then carb. cleaner in the gas.

[short stop]

Yep, called the shop and they said they've cleaned out the carb and replaced the spark plug. They said she's running fine now. Problem hopefully solved! Thanks for the input, guys.