starting and backfire problems

[masterkeosk]

I have an '03 GZ that I got from a friend that let it sit for about two years. I ran some gumout and some berryman's b12 through some new gas and new spark plug and it's up and running mostly. The first few times I had to spray the air filter with starter fluid to get the bike to start. I don't have to do that now since I've ridden it a few times. However it takes awhile to get it running somewhat smoothly without the choke on. It takes a couple tries before it will stay started while giving it gas, after a couple minutes it will idle on it's own with the choke about half way on. A couple minutes later it usually idles fine. Generally at this point I deem it ok to ride without it stalling. It never stalls at this point unless I don't put it into first correctly. THen throughout my ride it will back fire, generally toward the top end of a gear or if the revs are kinda high when I upshift. I did read on a different post that it might just be the idle turned up to high, which I haven't been able to try yet due to rain (YAY cincinnati) I will be trying this in the morning and hope that it works. Sorry for the length I just wanted to give a fairly good explanation of what's going on with the bike and also I tend to get a bit wordy when I've been drinking.

[Easy Rider]

However it takes awhile to get it running somewhat smoothly without the choke on. It takes a couple tries before it will stay started while giving it gas, after a couple minutes it will idle on it's own with the choke about half way on. A couple minutes later it usually idles fine. Generally at this point I deem it ok to ride without it stalling.

The little beasts are set very lean even when everything is working right. Your situation sounds about like mine was when I traded it in a few weeks ago. Your choke story is probably not normal......when coupled with your backfire report; looks like it is leaner than it should be.

Do you have a stock air filter? Check the rubber boots on each side of the carb. A vacume leak can cause the symptoms you describe......or an air filter that is less restrictive than stock.......or even a missing cap on the air box drain tube.
Failing all that, the carb probably needs a removal and manual cleaning. I'd be tempted to turn it over to a good mechanic.....if you can find one.

I have also heard that valves out of spec. can cause that; if they haven't been checked lately it might be a good time.

Idle speed should be adjusted ONLY when the engine is fully warmed up; highly doubtful that it will help your present problem any.

[masterkeosk]

Everything is completely stock. The air filter is the original, just under 800 miles on it but is like five years old or so. Think changing it might help?

[Water Warrior 2]

Everything is completely stock. The air filter is the original, just under 800 miles on it but is like five years old or so. Think changing it might help?
Have you actually checked the air filter. If the bike sat for a long time some small critter might have set-up housekeeping in there. Also check the filter inside and out. The air passes from the inside to the outside so the dirt and grunge will be on the inside.

[Easy Rider]

Have you actually checked the air filter.

:plus1:

Have a good look at it in the sunlight. If it looks like it is stained with oil, probably should replace it.
I doubt that is necessary with that kind of mileage......unless there ARE critters in there !!

[masterkeosk]

I have had the air filter out to spray some starter fluid on it the first few times I started the bike but didn't pay real close attention. I don't remember it looking discolored or anything and I definitely didn't look at the inside. It's supposed to rain here in cincinnati the next few days so I'll give that a look when things dry out. Thanks guys!

[Easy Rider]

I have had the air filter out to spray some starter fluid on it the first few times I started the bike

Mmmmmm......it is not necessary (or desirable even) to remove the air filter to use starting fluid; just squirt some into the hole. If you DO remove it, you should LEAVE it out and spray into the air box.

[Charlie Foxtrot]

I'm experiencing a similar problem minus the back fire with my 99' GZ250. My bike has also been sitting for about two years. I run 87 it in and it sat with about a quarter of a tank. I dumped in a bottle of gas treatment and filled the tank the rest of the way with 89 hopping that this would clear out any gunk that may be in the carb as a result of sitting for so long. The engine will run roughly with the choke fully on but when I push it back it cuts off between half and a quarter choke. I pulled the spark plug and it wasn't fouled. I checked to make sure it was sparking and it was. The only thing I can think it would be is the idle set screw is not set right or that the fuel line may be partly blocked and its just not getting enough fuel when the choke is off.

Any suggestions would be greatly appreciated.

[mrlmd1]

Both of these bikes sitting for a few years may just have dirty gummed up carbs from old evaporated gas. If they were running before they sat, there is no reason to start messing with idle set screws and other adjustments.
First off, the old gas should be dumped, emptied completely, not mixed with additives or new gas. You are just diluting the new gas with old crap. You may also have some water from condensation and crud in the bottom of the tank from sitting so long.
A good dose of carb cleaner should be run through, given time to soak, maybe for a whole day or two, then emptied out from the bottom of the carb. Running it through in the gas as you try and get the bike running may not be sufficient to clean it out. After the carb is cleaned, then put in new fresh gas and try to start it. If that doesn't work, the carb may have to come off and be more thoroughly cleaned.
The bike runs on 87 octane, anything higher is no benefit and may make it run worse.
The three things that make an engine run are air, fuel, and spark.
In this case if the air filter is clean, there is a spark as would be expected, the problem is in the fuel delivery and the dirty carb and old gas is the most likely offender. Adjusting other things at this point may just compound your problem and make it harder to solve and fix.

[Easy Rider]

Both of these bikes sitting for a few years may just have dirty gummed up carbs from old evaporated gas. If they were running before they sat, there is no reason to start messing with idle set screws and other adjustments.


:plus1: Precisely....on all the points. :tup:

It was a mistake NOT to drain the old gas before you tried to start it.
Now the carb will probably have to be taken apart and cleaned.
IIRC, about $100 at most dealers.....or independent shops.

It would also be a good idea to add an inline fuel filter at the same time.

[mrlmd1]

Easy and I agree on something - WOW! :2tup: :rawk: :)

[Charlie Foxtrot]

Update:

Yesterday I drained all that gas and extra crap that I added from the tank. I removed the petcock and fuel line and pulled the tank off. Then I pulled the carb off and sprayed it out with Carb cleaner (this stuff gets really cold) and reinstalled it. I checked the fuel line for blockage and took what carb cleaner I had left and blew it through the gas tank. I put in a new spark plug and reassembled everything and filled the tank about halfway with fresh 87 and nothing else. I then attempted to start it but it didn't start until I moved the set screw back where it was suppose to be set. Once I got that in the right spot the bike fired right up and will continue to run with the choke off. It idles and runs great now. I also took apart the petcock and hosed it down with carb cleaner.

[mrlmd1]

Nice going! Glad to hear the problem's solved. And it wasn't that complicated and shouldn't recur.
In the medical world, that kind of thing is called atrophy of disuse. In other words, things have to be used on a regular basis to keep them in good form and operating properly. Use the bike, it'll actually be healthier and last longer as it'll be maintained better. :2tup: :)