No Acceleration at 40MPH

anesde · 05-09-2015, 11:40 AM

I did a search and couldn't find anything so I figured I'd start a new topic. I've been getting to know my 2003 gz250 in the past month and from what I've read about top speeds and acceleration I think something is wrong. On flat roads the bike does not get above 45 even with wide open throttle in fourth gear.

It wasn't running when I bought it but all I did was put a new battery, new spark plug, and dismantled/cleaned/reassembled the carburetor. I did go an extra half turn on the pilot screw and shimmed the needle (not a true shim, just switched the position of the washer per one of the topics on this forum). I also changed the oil to synthetic (bike had about 6000 miles when I bought it). The engine sounds good but power doesn't translate to the wheels.

I weigh ~170 lbs so I don't think its a weight problem. I did take the windshield off but I don't think wind resistance should keep me from hitting 60-65.

At a loss for what it could be - any suggestions?

Water Warrior 2 · 05-09-2015, 02:38 PM

I wonder if the air filter is plugged up a fair amount. To check the filter it must be removed and inspected. Air flow is from the inside to the outside( reverse to what we normally see in filter systems). The inside gets dirtier than the outside.

The airbox is a sealed system. You can't drill holes in it to increase airflow, all you will accomplish is feed dirty air directly into the engine.

anesde · 05-11-2015, 12:48 PM

Changed the air filter and still have the same issue. Went from 2.5 turns on pilot screw to 1.75 turns and no change either.

From what I read it seems that this could be a symptom of a slipping clutch? I don't really know how to gauge whether or not it is slipping. I don't have problem shifting gears but I do notice that between halfway and full throttle the engine revs up but doesn't actually move any faster. Any thoughts?

Fawlty · 05-11-2015, 02:20 PM

Quote:

Originally Posted by anesde

I don't really know how to gauge whether or not it is slipping. I don't have problem shifting gears but I do notice that between halfway and full throttle the engine revs up but doesn't actually move any faster. Any thoughts?

OK, find a long uphill stretch of road, get into 4th gear at about 40mph or 5th gear at about 50mph, then try and accelerate using full throttle, if your revs increase, but your speed doesn't, your clutch is slipping.

Water Warrior 2 · 05-11-2015, 08:02 PM

Ah, more info to work with. Likely as suggested..........clutch adjustment needed.
Secondly...........did you do an oil change and exactly what kind of oil did you use? You must use moto specific oil or the clutch will likely slip. Must be a JASO certified oil for wet clutches.

5th_bike · 05-11-2015, 10:46 PM

When adjusting the clutch cable, keep in mind that the clutch handle (grip) needs to be moving freely about 1 cm at its tip.

**jonathan180iq** · 05-15-2015, 04:29 PM

Can the bike rev up, strong and loud, if it's in neutral?

anesde · 05-16-2015, 09:44 PM

Changed the oil two months ago and used synthetic royal purple 10w-40. Also changed spark plug back then - guy at Napa told me it was NGK DCPR8E

I thought it was the oil so I changed back today to Castrol GTX conventional 10w-40. Only had about 70 miles with the synthetic - what a waste!

Anyway the bike did not perform any better so I thought maybe the spark plug. Looked up the spark plug and found the internet says it's NGK DR8EA, not what I have in there. Took the old one out and it's black - covered in soot. Not wet which is what I thought I might find. Took her for a quick spin after changing the plug. I think I notice a slight uptick but it got dark so I'll have to wait until tmrw

Water Warrior 2 · 05-17-2015, 05:20 AM

Quote:

Originally Posted by anesde

Changed the oil two months ago and used synthetic royal purple 10w-40. Also changed spark plug back then - guy at Napa told me it was NGK DCPR8E

I thought it was the oil so I changed back today to Castrol GTX conventional 10w-40. Only had about 70 miles with the synthetic - what a waste!

Anyway the bike did not perform any better so I thought maybe the spark plug. Looked up the spark plug and found the internet says it's NGK DR8EA, not what I have in there. Took the old one out and it's black - covered in soot. Not wet which is what I thought I might find. Took her for a quick spin after changing the plug. I think I notice a slight uptick but it got dark so I'll have to wait until tmrw

I think you answered your own question, slipping clutch. Both oils you mentioned are for car use, not bike use. You must use a JASO certified oil. Look on the oil container for the designation. Shell Rotella, Dino or Synthetic will work fine and are the cheaper than most others. Had excellant results in 2 of our bikes with the dino variety.

gz4me + · 05-18-2015, 02:11 AM

I agree with Water Warrior 2. Wrong type of oil. I have dealt with this problem in the past while working on friends bikes. One was a Honda Rebel and two were Suzuki. Problem went away after changing to correct oil.

05-09-2015, 11:40 AM	#1
anesde Junior Member Join Date: Feb 2015 Posts: 20	No Acceleration at 40MPH I did a search and couldn't find anything so I figured I'd start a new topic. I've been getting to know my 2003 gz250 in the past month and from what I've read about top speeds and acceleration I think something is wrong. On flat roads the bike does not get above 45 even with wide open throttle in fourth gear. It wasn't running when I bought it but all I did was put a new battery, new spark plug, and dismantled/cleaned/reassembled the carburetor. I did go an extra half turn on the pilot screw and shimmed the needle (not a true shim, just switched the position of the washer per one of the topics on this forum). I also changed the oil to synthetic (bike had about 6000 miles when I bought it). The engine sounds good but power doesn't translate to the wheels. I weigh ~170 lbs so I don't think its a weight problem. I did take the windshield off but I don't think wind resistance should keep me from hitting 60-65. At a loss for what it could be - any suggestions? Login or Register to Remove Ads
	0

05-11-2015, 12:48 PM	#3
anesde Junior Member Join Date: Feb 2015 Posts: 20	Changed the air filter and still have the same issue. Went from 2.5 turns on pilot screw to 1.75 turns and no change either. From what I read it seems that this could be a symptom of a slipping clutch? I don't really know how to gauge whether or not it is slipping. I don't have problem shifting gears but I do notice that between halfway and full throttle the engine revs up but doesn't actually move any faster. Any thoughts? Login or Register to Remove Ads
	0

05-11-2015, 08:02 PM	#5
Water Warrior 2 Senior Member Join Date: Dec 2006 Location: Squamish B.C Canada Posts: 11,409	Ah, more info to work with. Likely as suggested..........clutch adjustment needed. Secondly...........did you do an oil change and exactly what kind of oil did you use? You must use moto specific oil or the clutch will likely slip. Must be a JASO certified oil for wet clutches. Login or Register to Remove Ads
	0

05-11-2015, 10:46 PM	#6
5th_bike Senior Member Join Date: Oct 2007 Location: HoCo, Maryland Posts: 1,349	When adjusting the clutch cable, keep in mind that the clutch handle (grip) needs to be moving freely about 1 cm at its tip. __________________ 2005 "Saturn Black", stock + tach
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05-09-2015, 02:38 PM	#2
Water Warrior 2 Senior Member Join Date: Dec 2006 Location: Squamish B.C Canada Posts: 11,409	I wonder if the air filter is plugged up a fair amount. To check the filter it must be removed and inspected. Air flow is from the inside to the outside( reverse to what we normally see in filter systems). The inside gets dirtier than the outside. The airbox is a sealed system. You can't drill holes in it to increase airflow, all you will accomplish is feed dirty air directly into the engine.
	0

05-15-2015, 04:29 PM	#7
jonathan180iq Super Moderator Join Date: Jan 2007 Location: Dalton, GA Posts: 3,996	Can the bike rev up, strong and loud, if it's in neutral?
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05-16-2015, 09:44 PM	#8
anesde Junior Member Join Date: Feb 2015 Posts: 20	Changed the oil two months ago and used synthetic royal purple 10w-40. Also changed spark plug back then - guy at Napa told me it was NGK DCPR8E I thought it was the oil so I changed back today to Castrol GTX conventional 10w-40. Only had about 70 miles with the synthetic - what a waste! Anyway the bike did not perform any better so I thought maybe the spark plug. Looked up the spark plug and found the internet says it's NGK DR8EA, not what I have in there. Took the old one out and it's black - covered in soot. Not wet which is what I thought I might find. Took her for a quick spin after changing the plug. I think I notice a slight uptick but it got dark so I'll have to wait until tmrw
	0

05-18-2015, 02:11 AM	#10
gz4me + Senior Member Join Date: Sep 2013 Location: Santa Maria, California Posts: 234	I agree with Water Warrior 2. Wrong type of oil. I have dealt with this problem in the past while working on friends bikes. One was a Honda Rebel and two were Suzuki. Problem went away after changing to correct oil.
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