Uneven power when starting and from 35-45mph

[VTXorcist]

Hi all, I just bought a used GZ. I knew from the get-go that it had a crack in the exhaust, just before the megaphone where the pipes converge. I bought a new-to-me exhaust (used off ebay) and I'm waiting for it to come in.

My problems are two-fold and may or may not be related. I sometimes lose power in 1st and 2nd gears (occurs even after the bike warms up). The bike starts moving then putters out no matter how much twist I give the throttle. If I lay off a bit, I can usually keep it from stalling and eventually coax it up to where I can shift to 3rd. It's intermittent; some of the time I can twist and the little engine roars in 1st and 2nd, no problem.

Also, around 35mph up until 45mph, if I cruise in 3rd or 4th, I get really uneven power. The speed stays relatively constant, but I can feel the bike jerking under me. Below 35mph, it will cruise contentedly in 3rd or 4th. Above 45mph, it gets happy and cruises without complaint in 4th or 5th.

I was thinking maybe the exhaust had something to do with it, so I'm waiting for the new pipe and hoping it will fix the problem. In the meantime, has anyone experienced these problems and do you have any recommendations for diagnosis and fixes?

Thanks!

[Easy Rider]

I was thinking maybe the exhaust had something to do with it, so I'm waiting for the new pipe and hoping it will fix the problem. In the meantime, has anyone experienced these problems and do you have any recommendations for diagnosis and fixes?


WOW.....I leave town for a few days and all KINDS of new members show up !!
Welcome.

First, are you sure there is really a crack in the exhaust and not just the "normal, on purpose" drain hole that resides in about that position ?? :shocked:

I doubt that is causing your other problem anyway.
Have you run any carb cleaner through it?
Have you checked the air filter?
Might want to inspect the carb boots and vacume hose for loose/leaks.
Also, the cap on the carb drain hose is necessary; you can't just leave it off.

And, lastly, you might want to drain the float bowl AND the tank as you might have some water or other "crud" in the bottom of the tank.

[VTXorcist]

Yikes! No's all around. What does the drain hole in the pipe look like? I may have bought a new exhaust for nothing!

The rest I can figure out with a little googling, thanks!

[Easy Rider]

Yikes! No's all around. What does the drain hole in the pipe look like?

You should do all that other stuff before you start taking anything apart (like the carb).
It is also possible that you are describing a slipping clutch but the description is a little off for that.

The drain hole is about 1/8 inch, I think. Easiest way to find it is to start the bike and idle just long enough that the middle of the muffler starts feeling warm. Then shut it off and wait. A drop or 2 of water should drain out.......the cooler the outside temp. the more water you will see.

OR you can use a mirror. The drain hole will probably appear as a rust spot about the size of a dime......with the hole in the middle.

Good luck!

P.S. Yes, you can fit a small fuel filter in the line. Get one that has a paper or ceramic filter (not screen). It fits in the middle of the rubber line if you cut about 1/2 inch of hose OUT. You should get some spring clamps to secure it; they don't usually come with the filter. That would be a good time to drain the tank and floats too. Plan ahead; Sunday is not the best time to install the filter......just incase you need to go get a new piece of hose !!!

[VTXorcist]

Ah ok then this is definitely a crack. I can fit two fingers into it.

Thanks for the info, Easy!

[Easy Rider]

Ah ok then this is definitely a crack. I can fit two fingers into it.


If it is that big, it might be affecting your performance a bit......but not likely that is the whole story.

[burkbuilds]

I'm with Easy on that, clean out the fuel system first check air filter and spark plugs are cheap and easy to install but you definitely don't want to leave that old exhaust on there with that big of a crack you might end up burning your valves if you do then it's headache time!

[patrick_777]

WOW.....I leave town for a few days and all KINDS of new members show up !!

Some aren't too bad either.

[Water Warrior 2]

[quote="Easy Rider":67rlngvv]WOW.....I leave town for a few days and all KINDS of new members show up !!

Some aren't too bad either.[/quote:67rlngvv]

No no no Patrick. They are all good until they prove themselves otherwise. We do have a good group of folks on the forum. New and old have to suck it up and accept the ocassional criticism but overall this is one of the best forums. We don't even have a GZ in the stall anymore but I like being here. How many forums are that comfy ??

[Easy Rider]

[quote="Easy Rider":2graf2qp]WOW.....I leave town for a few days and all KINDS of new members show up !!

Some aren't too bad either.[/quote:2graf2qp]

As opposed to the OLD members.....????? :neener:

I'm sure the newbies will be pleased that you approve. :roll:

[VTXorcist]

Update on the problem; I haven't had a chance to do any work, but I took it for a quick spin yesterday to see if I could be a little more specific about the symptoms.

It revs and then loses power at idle, 1st, and 2nd. It seems particularly bad until the bike has had 10 minutes or so to warm up, and then it still happens occasionally. Basically, I twist the throttle, it starts to rev, and then goes back to idle and sounds like it's going to stall. Then, if I keep the throttle twisted, there's a chance it will either stall or, if I'm lucky, catch again and start revving. If it stalls, it starts right back up again, no problem.

I'm going to try as many of the above recommendations as I'm able to figure out & am comfortable doing on my own this weekend. If anyone has any other suggestions or diagnoses in the meantime, please let me know!

And thanks for all the info so far. You guys/gals are right; this is a comfortable forum!

[bonehead]

It really sounds to me like you have a valve adj. problem. Have you checked the adj or do you know when it was done last?

[Easy Rider]

Basically, I twist the throttle, it starts to rev, and then goes back to idle and sounds like it's going to stall. Then, if I keep the throttle twisted, there's a chance it will either stall or, if I'm lucky, catch again and start revving.

That sounds a LOT like what happens if you try to run it without an air cleaner element in place.........SO I think it is likely that you have too much air/not enough fuel going through the carb. That's the easy part; not to figure out WHY !! :biggrin:

[Water Warrior 2]

The combo of a holed exhaust and no air filter(?) will play havoc with any fuel delivery to the cylinder. As mentioned, check for an air filter. A new filter and a properly intact exhaust may be the answer to the running conditions. I would suggest not tearing the carb apart until the other 2 things are dealt with. Use the KISS principle.

[VTXorcist]

UPDATE:

You know that crack in my pipe? Well, I finally got the new pipe in the mail today and went to replace it just now. I removed the rear support bolt that holds the megaphone in place... and it fell off! The dang thing was cracked clean through. I'll let you know this weekend if it helps at all, once I've had a chance to take it out for a bit.

[VTXorcist]

Oh and I replaced my spark plug and checked the air filter; it looks good and I cleaned it with compressed air per the service manual.