Random Shut Off as I'm Slowing Down

[Pickax]

Lately I've been having a problem with the GZ where it shuts off while I'm slowing down.

Sometimes it happens when I'm coming up to a red light and after I get it started again it will shut off as soon as I roll the throttle on at all even if I keep the clutch completely disengaged.

Other times, when I slow down to make a turn it will shut off if I downshift a gear or two.

It always seems to happen when I'm squeezing the clutch lever and after I downshift. As I said, sometimes it happens when I'm going all the way to first and other times it happens in a turn when I'm going to third or something.

As a note, I didn't notice this until after I changed the oil recently. I started using Castrol Syntec. It doesn't have any friction modifiers or energy conserving labels so there's no obvious sign that that's the issue but let me know if you know of any reason it could be. The bike is a 2005 and has about 1500 miles on it.

Thanks a lot for your help!

[Joho]

It sounds like the engine is shutting off because the idle is too low. Try adjusting it a bit higher (turn the idle adjustment clockwise) and see if that helps.

[Badbob]

Is your idle speed set correctly?

Does it stall at idle? When its cold? When its hot?

New oil will not make it stall.

Did you mess with anything else?

[Sarris]

Also, check that the vacuum hose from the carb to the fuel petcock is attached.

[Easy Rider]

Originally Posted by Sarris

Also, check that the vacuum hose from the carb to the fuel petcock is attached.

And to expand on that a bit, it sounds like you are running out of gas.....at low speed....which could mean that your idle jet is plugged.

Check to be sure the choke is OFF.
Check idle speed; might be too low.
Check for vacuum leaks.
Run some carb cleaner through with the gas.

[Pickax]

I adjusted the idle and the bike is running great now. Thanks a lot for the help!

[Mandachan]

I've been looking through the forum a bit, and this seems to be the closest thing to what me and my husband are experiancing with my little GZ250. We just bought a 2001 - we knew it had SOME issues when we bought it.


I'm thinking whoever had it before (the guy we bought it from only had it 3 weeks, and was letting her go cause his wife basically said "I'm never going to ride so just get rid of the thing"). He had started working on it, but we're kinda thinking he really had no idea about it either - since when we got her the FIRST thing we did was do a complete oil change and empty out the overfilled oil.


Basically, she's having some real issues idling - especially when you first start her. We've played with the idle - and unless you turn the idle on really high - she won't stay idling(She IS ridable, just every now and then once you get her going she'll stall at a red light or stop sign). And even with it high, you still have to give her gas. My husband seems to think that it's idling wayyy too high. (Course, this is the first 250 he's worked on, and his prior motorcycle experiance is a ninja 650). I tend to agree with him that the motorcycle should at least be able to idle without having to yank the throttle every now and then. We've added some marvel mystery oil to both the oil and the gas to help clean it a bit - but I can't drive it till we get the new front brake pads and new tires (Brake pads ordered, tires will be gotten next week). Oh yes, we have the choke on whenever we start and run her - we're in florida. My husband thought that was rather odd considering it was 85 outside when we were working on her.


The throttle doesn't have as much slack as it should - is this something that we can do ourselves or go to a dealership and have them adjust? We've checked the air filter - it's new, replaced the oil filter with the the oil change.


Also, my husband seems to think there's some unneccessary noise coming from the engine - i can't describe it to you - he did the ole screwdriver stuck to the engine. I did some searches, only thing i really found was the chain might be loose - but checked the chain and that was in good working order.


Btw, it's a 2001 GZ250 with 7000 miles on it. It's been dropped on both sides (as far as we can tell). We're just trying to put some elbow grease into her and get her running for me. You know, it's kinda fun working on her too. (Shhh, don't tell my husband i said that!).

[Sarris]

Mandachan, I would suggest a few things;

First put a new spark plug in and run some fuel system cleaner through her. Use the type you put in the gas. I personally like "Seafoam". This alone may solve your idle issue. Old bikes that have set around a while have more than likely developed varnish in the carb. GZ's typically like to idle at 1000 to 1200 rpm. The idle adjustment is the white knob on the bottom of the carb.

Second, she probably needs a valve adjustment. See the service manual on site. Manual download is here: http://www.gz250bike.com/forum/viewtopic.php?f=3&t=27

Third, GZ motors are a bit noisey. Unless it's really clanging, it's more than likely normal.

Fourth, replace BOTH tires, tubes, and rim strips. You should NEVER ride on motorcycle tires over 4 years old, as the sidewalls get stiff and could crack and fail.

Fifth, the throttle cable adjuster is the knurled knob assembly at the top of the cable by the grip. Also adjust per the service manual.

Sixth, I live north of Tampa bay and use the choke every morning. The GeeZer is a bit cold blooded. I leave the choke (actually an enrichener) on (about 1/3) for about the first 3 or 4 miles.

Seventh, I would suggest getting the Marvel out of the crankcase and refilling with new clean oil. Friction modifiers can make your clutch slip.

Welcome to the forum. I hope that this helps. We need another Floridian on the Locator Map if you're up for it.

:2tup:

[Mandachan]

Thank you for your advice.


We'll be changing both tires. And the spark plug. And I told my husband about the noisy thing but he didn't believe me. (Lol!). I'll be downloading the manual tonight.

[Easy Rider]

Originally Posted by Sarris

Mandachan, I would suggest a few things;

First put a new spark plug in and run some fuel system cleaner through her. Use the type you put in the gas. I personally like "Seafoam".

TIME OUT !!!

The first thing you MUST do is get the MMO **OUT** of the gas and especially the OIL. You should NEVER put any additives in the oil of a motorcycle with a wet clutch. That includes MMO and Seafoam. They will ruin the clutch. As long as we are on the subject, you also should NOT use any type of oil that says "Energy conserving" on the label.

In addition to the carb cleaner (at twice the recommended rate in 1/2 tank of fresh gas)and the plug, you need to check the air cleaner to be sure it is stock and clean and stick a coat hanger down the muffler to be sure there isn't a wasp's nest blocking it. A stock GZ will not run worth a crap with the wrong air cleaner and won't hardly idle at all without choke.

Seafoam is OK but Original Gumout Carb and Choke cleaner or Berryman's B12 are somewhat better.

Once you have it running better, then you can come back here and re-read Sarris's post; it has a lot of good information.......but there isn't much point in buying new tires if there is a serioius problem with the engine !! :biggrin:

P.S. In addition to Sarris, we have another GZ expert in your fair state. Bad Bob is up north, I think.