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Old 04-25-2016, 08:44 PM   #1
05gz250
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Having real hard time with Carb.

Hey guys,I'm new to the group and was wondering if anyone can help me.
I have an 05' GZ250. When ever I try to start the bike I always use full choke, but I always need to keep my hand on the throttle... if I let go the bike falls flat on its face. The air filter looks good, doesn't look like the carb has any "gunk" in it. I have tried adjusting the pilot screw ( on the engine side) turned it out 2.5 turns, seemed to run fine at first, but I don't know if it was because the bike was kind of warm. So I tried it out the next day when the engine was cold, and it failed like usual. So today I brought it to my boss ( a service manager ) and he said it sounds like there could be a leak as when the bike is nice and hot it seems to run fine. I have now currently turned the pilot screw to 1.5 turns. are there any idea out there that could help?

and also, I saw on here that people were getting the bike up to 70 mph but the most I can seem to get it to is about 60 mph... and when ridding at 60 and a strong wind is against me i drop right down to 50 miles even with the throttle wide open. Is this normal for anyone else?
sorry for the long post, just wanted to get everything out there right away.



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Old 04-26-2016, 02:36 PM   #2
gzed
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Hey 05gz250,

Do you know the last time the valves were adjusted of checked? This is normally one of the first problem spots on this bike. When they are out of spec it can be hard to start the bike cold and the overall performance is impacted.

It is pretty normal to use choke to fire up the bike, but should not need it after a minute or so after its going.

When you said the carb didn't look to have any gunk, did you take it apart and look? I have to use seafoam (or any other carb cleaner) every other fill up to keep the bike idling happy.
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Old 04-26-2016, 03:09 PM   #3
Vegas Street Rider
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The bike should do 70 as long as there is no wind or uphill grade. A strong headwind will normally affect your speed by at least 10mph or more depending on how strong it is. The GZ is a little light on power. Your weight can also be a factor (no insult intended). GZED is right on checking the valves for starters. Don't know that seafoam would be necessary that often unless your fuel supplier's tanks are contaminated. I have yet to need valve adjustment or seafoam for the carb, but I have an '09' GZ with only 15,000 miles on it. I am sure others will come online to give you some other suggestions to check that are better mechanics than I am.
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Old 04-26-2016, 05:52 PM   #4
05gz250
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I have done a valve adjustment on it last year in probably August, I seem to do one every season. I don't really seem to notice a difference in the starting when they are adjusted...
As for the choke, I have to have it on for a good 5-10 minutes, if i turn it off I have to keep the throttle to about 3/4 to 100% open.
As to the speed dropping, that makes sense. I am a small guy 5'11 @ like 150 lbs soaking wet so I didn't think that would be an issue, but if its normal, it's good to know.

And I realized I forgot my bike has about 10,000 miles on it.
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Old 08-22-2016, 09:50 PM   #5
speerman84
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My bike (also an 05) has what sounds like the same problem.
I did a carb rebuild and it seemed to help a little, but not much, and it quickly reverted to it's old ways.
Getting it to start cold is always a challenge. It needs full choke/full throttle to get going and flooding is often the result. Until the engine's nice and hot it won't idle unless the choke is full, and often times the first decent start or two it won't even idle with a full choke and just dies.
I'm considering buying a new oem carb, but I'd rather not spend the $350+ if I don't have to. Is there anything besides the carb that could be causing these issues?

Last edited by speerman84; 08-22-2016 at 09:56 PM.
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Old 08-23-2016, 08:25 AM   #6
blaine
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In the first post it is stated that the pilot screw is set at 1 1/2 to 2 1/2 turns out.....That is too lean to start good cold.My bike was the same way till I adjusted the pilot screw with the bike idling warm for best idle. (About 3 1/2 turns).....The bike than started much easier when cold & you could easily tell the difference in the exhaust tone.....These bikes are extremely lean from the factory causing hard starting cold.
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Old 09-08-2016, 07:36 AM   #7
b1pig
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Howdy.

My wife's GZ has a VERY finicky carb. If it has ANY fuel left in the bowl after being parked up for more than a few days, the bike does not want to run properly the next time its ridden.

Every spring, I have to pull her carb, disassemble it, and soak it in cleaner. Once its broken down, I brush all parts clean and I use carb cleaner to blow thru the orifices. I usually start her pilot screw around 2.5 turns and adjust to suit.

Something comes to mind. The GZ has a "on-prime-res" selector. There is no "off". There should also be a small vacuum hose running from the top front of carb to the back of the fuel selector. its not a "pump" per se... but the intake pulses allow fuel to flow when in on or reserve. in "prime", this bypasses the "pump" and allows direct flow to the bowl.

If the float is misadjusted or the float valve sticks open, it can allow fuel to overflow the bowl. Higher bowl levels can also enrichen the fuel mixture.... if the overflow is bad enough, yes it can also flood the engine. Forgetting and leavind the fuel selector in "prime" is also a good way to wind up with fuel in your oil. another bad experience.

Remember, that if the engine is flooding, there will be a VERY strong odor of raw gas from the engine when trying to start, or a very strong exhaust odor (maybe with black smoke) when running. A lean condition can sometimes seem like a rich condition, but absent the fuel odor.


all bikes are different to one degree or another, but going out on a limb here, it would seem to me that your bike is suffering from not ENOUGH fuel at the right "circuit". Meaning passages are either blocked or restricted by crud. The absolute BEST way to combat that is remove, disassemble, soak, scrub, spray and maybe add some compressed air to blow it out. obviously reassemble and run it. I'd definitely be starting with 2.5-2.75 turns out on the screw.
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Old 01-31-2018, 02:09 PM   #8
speerman84
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I had the same issue - SOLVED!

I know this thread is sorta old at this point, so it might not help the original poster, but it could help someone, so I'm adding this.
I have an '05 that had the same problems. I had power issues, wouldn't hold idle unless it got hot, needed to use the choke all the time, etc.
Turns out I had a bit of a head gasket leak! As things heated up, stuff would expand and mostly fix it, but it wouldn't quite live up to its potential.
Changed the head gasket (and cleaned everything in there while I had it open) and voila! Works like a charm! Best it's ever ran!
In fact, it worked so well that the extra power made the clutch start slipping and I had to replace my plates and springs!

Hope this helps someone.
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Old 02-03-2018, 12:46 AM   #9
Razorburns
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Actually this helps a lot for me. Mine (2001 model) has a bit of an oil leak that seems to be coming from the valve cover and/or head gasket area. Getting it checked soon. Your post encourages me more so.
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