No/slow acceleration. No top end.

GilHirien · 07-21-2014, 11:14 AM

Hey all. First, Thanks for the wealth of knowledge and support already on these forums and all the contributors. I have spent hours pouring over all kinds of topics on this site which were informative, helpful, and also gracious when user error was discovered.

Secondly, on to the problem at hand. I have had my GZ for 2 years. It ran for most of 1. Finances always being very limited, it sat for about a year with little progress made. I ended up having to replace my crankcase due to other problems and now all is reassembled. Those issues have been resolved leaving a newly discovered one. I have no top end power at all. Timing is dead on; I followed the maintenance procedure to the letter when reassembling everything. I have adjusted valves back to spec. They were horrendously tight and not sealing. No gap at all. Intake has been set to .008 and exhaust to .012. Piston was at TDC on compression stroke. Many thanks to the great instructions found in other threads for this. I did a compression test which yielded 180 peak psi which is solidly within normal operating range (140-199) though I will test again as I don't think it was quite warmed up enough.

It will crank right up with a little choke and seems to handle throttle just fine in neutral. It does not want to run without choke but can be coaxed along slowly, but starts running badly or at least inconsistently and may or may not cut off. If I turn the idle adjustment to increase the idle as far as it will turn, it will run with no choke at all without cutting off, but badly (roughly the same as it is with half choke and normal idle speed).

Out of neutral it will pull with no throttle to maybe 1/4 throttle but pretty weakly. It does better with more choke. It will pull a tad harder, but still will not increase past 1/4 throttle. If I give it more throttle than that it will start sputtering and lose torque, and when throttle is released it will backfire, pick back up slightly and resume running at no throttle to 1/4. It does this in first and second gear. It will not take any throttle at all in 3rd or above, and will not pull at all in 3rd or above. I cannot maintain 25 mph in 3rd on mostly flat ground.

To me this sounds like fuel delivery problems. The tank sat with very little gas for a very long time. Bad gas was purged and replaced with new gas and seafoam (3 oz. or so). There was a good deal of crud in the tank, petcock, fuel line and carb when I first tried to start it after reassembly. Petcock was removed and cleaned. Fuel line was likewise. Carb was pulled, opened up, and cleaned to the best of my current ability. No inline filter yet but working on it. I thought that I cleaned it pretty well when I had it off before, but it may need more thorough work beyond my current skill set.

Thoughts, comments, observations, suggestions, pointing and laughing (as long as it includes the previous as well) are all welcome.

**jonathan180iq** · 07-21-2014, 11:25 AM

But in all seriousness - let me just ask a few questions for clarification.
Can you rev the bike up just fine in neutral? Can you, at any point, get the bike to idle properly in neutral without using choke?

If the bike won't run without choke then there is an issue in the carb and/or in the choke circuit. If you know what you're doing, I'm going to suggest just pulling it again and cleaning everything, one step at a time. I feel like there's just a blockage somewhere in there.

To check the petcock for debris, pull the fuel line and see how it flows in PRI. I think if that flows smoothly then don't worry about the petcock. Do the same similar tests for each system, making sure it operates as it should off the bike, before buttoning everything back up.

GilHirien · 07-21-2014, 11:40 AM

It SEEMS to rev pretty well in neutral. Better immediately after startup than after it has run for a little. After warm up it starts popping pretty good when you let off the throttle in neutral. It will idle in neutral fine without choke as long as the idle speed is in the proper range. Too low and it starts wanting to cut out as I understand is normal. Out of neutral it will still idle just fine at first, but after it warms up it doesn't idle as well. Adding choke seems to let it idle better after this happens.

Flow at the petcock after cleaning is just fine. But the first couple times I ran it, a check of the fuel line did find some flakes of crud. Less, the more it has run. This was before I removed and cleaned the carb. I did initially find blockage in one of the jets and cleaned it out. Its definitely possible that the seafoam knocked some stuff loose and blocked it again, but since it seemed to rev ok in neutral, I wanted to get other opinions for things I may have missed. I try to be thorough, but by no means am I perfect.

**jonathan180iq** · 07-21-2014, 12:47 PM

Ok - Flush the tank again. Sitting for so long you have no idea what's floating around in there.

This all just feels like a fluid flow problem - in the tank, in the lines, and in the carb itself.
A good cleaning doesn't do you any good if it immediately gets clogged back up with junk.

Popping can be fuel delivery, but it can also be a lean mixture - it's what happens when people decelerate after having holes punched in the exhaust, for example. Ensure that there are no vacuum leaks and that the headers are sealed going into the head.

I've used a smoking incense stick to search for leaks before with good results. Get the tip into proper ember form and get your bike into a garage, or anything that blocks wind, if you can.

GilHirien · 07-21-2014, 08:40 PM

Any other opinions, comments, concerns? This sound about right to everyone? I'd like to hear thoughts from one or two more people before I take the carb back off, though I also think/hope its just the carb. Thanks

Water Warrior 2 · 07-22-2014, 03:08 AM

Quote:

Originally Posted by GilHirien

Any other opinions, comments, concerns? This sound about right to everyone? I'd like to hear thoughts from one or two more people before I take the carb back off, though I also think/hope its just the carb. Thanks

You can trust Jonathan. His experience and judgement is of great value to all of us.

gz4me + · 07-22-2014, 03:59 AM

I agree with Water Warrior 2. Jonathan has been around a long time and has helped many on this site. After reading your thread, I would say Jonathan is spot on. I have followed his suggestions in the past and have had all positive results from them. Hope this helps.

GilHirien · 07-22-2014, 10:09 AM

Cool beans. I will pull the carb again today when I get off work and give it a good soak in cleaner. There are no vacuum leaks. That was one of the first things I checked. My exhaust is factory, no auxiliary holes added. Headers are sealed good and tight. A little popping I'm used to, as the bike did a little of that before, when it was running well. My main concern there is the sputtering and coughing when you apply throttle immediately followed by the popping and better running when you let off the throttle. I'll also take the opportunity now while the carb is off to find and install an in line fuel filter. Thanks guys. I'll keep you posted. Thoughts, comments, etc. still welcome.

mole2 · 07-22-2014, 02:48 PM

If it doesn't already have one install an inline fuel filter after you clean the carb and tank.

tudorv · 07-22-2014, 05:00 PM

Check the pilot screw on the carb (unless it's sealed). It adjusts the fuel mixture. Maybe when you took the carb apart, you changed its position.

07-21-2014, 11:14 AM	#1
GilHirien Member Join Date: Aug 2012 Location: Hattiesburg, MS Posts: 37	No/slow acceleration. No top end. Hey all. First, Thanks for the wealth of knowledge and support already on these forums and all the contributors. I have spent hours pouring over all kinds of topics on this site which were informative, helpful, and also gracious when user error was discovered. Secondly, on to the problem at hand. I have had my GZ for 2 years. It ran for most of 1. Finances always being very limited, it sat for about a year with little progress made. I ended up having to replace my crankcase due to other problems and now all is reassembled. Those issues have been resolved leaving a newly discovered one. I have no top end power at all. Timing is dead on; I followed the maintenance procedure to the letter when reassembling everything. I have adjusted valves back to spec. They were horrendously tight and not sealing. No gap at all. Intake has been set to .008 and exhaust to .012. Piston was at TDC on compression stroke. Many thanks to the great instructions found in other threads for this. I did a compression test which yielded 180 peak psi which is solidly within normal operating range (140-199) though I will test again as I don't think it was quite warmed up enough. It will crank right up with a little choke and seems to handle throttle just fine in neutral. It does not want to run without choke but can be coaxed along slowly, but starts running badly or at least inconsistently and may or may not cut off. If I turn the idle adjustment to increase the idle as far as it will turn, it will run with no choke at all without cutting off, but badly (roughly the same as it is with half choke and normal idle speed). Out of neutral it will pull with no throttle to maybe 1/4 throttle but pretty weakly. It does better with more choke. It will pull a tad harder, but still will not increase past 1/4 throttle. If I give it more throttle than that it will start sputtering and lose torque, and when throttle is released it will backfire, pick back up slightly and resume running at no throttle to 1/4. It does this in first and second gear. It will not take any throttle at all in 3rd or above, and will not pull at all in 3rd or above. I cannot maintain 25 mph in 3rd on mostly flat ground. To me this sounds like fuel delivery problems. The tank sat with very little gas for a very long time. Bad gas was purged and replaced with new gas and seafoam (3 oz. or so). There was a good deal of crud in the tank, petcock, fuel line and carb when I first tried to start it after reassembly. Petcock was removed and cleaned. Fuel line was likewise. Carb was pulled, opened up, and cleaned to the best of my current ability. No inline filter yet but working on it. I thought that I cleaned it pretty well when I had it off before, but it may need more thorough work beyond my current skill set. Thoughts, comments, observations, suggestions, pointing and laughing (as long as it includes the previous as well) are all welcome. Login or Register to Remove Ads
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07-21-2014, 11:40 AM	#3
GilHirien Member Join Date: Aug 2012 Location: Hattiesburg, MS Posts: 37	It SEEMS to rev pretty well in neutral. Better immediately after startup than after it has run for a little. After warm up it starts popping pretty good when you let off the throttle in neutral. It will idle in neutral fine without choke as long as the idle speed is in the proper range. Too low and it starts wanting to cut out as I understand is normal. Out of neutral it will still idle just fine at first, but after it warms up it doesn't idle as well. Adding choke seems to let it idle better after this happens. Flow at the petcock after cleaning is just fine. But the first couple times I ran it, a check of the fuel line did find some flakes of crud. Less, the more it has run. This was before I removed and cleaned the carb. I did initially find blockage in one of the jets and cleaned it out. Its definitely possible that the seafoam knocked some stuff loose and blocked it again, but since it seemed to rev ok in neutral, I wanted to get other opinions for things I may have missed. I try to be thorough, but by no means am I perfect. Login or Register to Remove Ads
	0

07-21-2014, 08:40 PM	#5
GilHirien Member Join Date: Aug 2012 Location: Hattiesburg, MS Posts: 37	Any other opinions, comments, concerns? This sound about right to everyone? I'd like to hear thoughts from one or two more people before I take the carb back off, though I also think/hope its just the carb. Thanks Login or Register to Remove Ads
	0

07-22-2014, 02:48 PM	#9
mole2 Senior Member Join Date: Dec 2009 Location: Longs, SC Posts: 1,469	If it doesn't already have one install an inline fuel filter after you clean the carb and tank. __________________ 2009 V-Star 650 Silverado Pearl White 2007 Suzuki GZ250 Black (sold)
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07-21-2014, 11:25 AM	#2
jonathan180iq Super Moderator Join Date: Jan 2007 Location: Dalton, GA Posts: 3,996	But in all seriousness - let me just ask a few questions for clarification. Can you rev the bike up just fine in neutral? Can you, at any point, get the bike to idle properly in neutral without using choke? If the bike won't run without choke then there is an issue in the carb and/or in the choke circuit. If you know what you're doing, I'm going to suggest just pulling it again and cleaning everything, one step at a time. I feel like there's just a blockage somewhere in there. To check the petcock for debris, pull the fuel line and see how it flows in PRI. I think if that flows smoothly then don't worry about the petcock. Do the same similar tests for each system, making sure it operates as it should off the bike, before buttoning everything back up.
	0

07-21-2014, 12:47 PM	#4
jonathan180iq Super Moderator Join Date: Jan 2007 Location: Dalton, GA Posts: 3,996	Ok - Flush the tank again. Sitting for so long you have no idea what's floating around in there. This all just feels like a fluid flow problem - in the tank, in the lines, and in the carb itself. A good cleaning doesn't do you any good if it immediately gets clogged back up with junk. Popping can be fuel delivery, but it can also be a lean mixture - it's what happens when people decelerate after having holes punched in the exhaust, for example. Ensure that there are no vacuum leaks and that the headers are sealed going into the head. I've used a smoking incense stick to search for leaks before with good results. Get the tip into proper ember form and get your bike into a garage, or anything that blocks wind, if you can.
	0

07-22-2014, 03:59 AM	#7
gz4me + Senior Member Join Date: Sep 2013 Location: Santa Maria, California Posts: 234	I agree with Water Warrior 2. Jonathan has been around a long time and has helped many on this site. After reading your thread, I would say Jonathan is spot on. I have followed his suggestions in the past and have had all positive results from them. Hope this helps.
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07-22-2014, 10:09 AM	#8
GilHirien Member Join Date: Aug 2012 Location: Hattiesburg, MS Posts: 37	Cool beans. I will pull the carb again today when I get off work and give it a good soak in cleaner. There are no vacuum leaks. That was one of the first things I checked. My exhaust is factory, no auxiliary holes added. Headers are sealed good and tight. A little popping I'm used to, as the bike did a little of that before, when it was running well. My main concern there is the sputtering and coughing when you apply throttle immediately followed by the popping and better running when you let off the throttle. I'll also take the opportunity now while the carb is off to find and install an in line fuel filter. Thanks guys. I'll keep you posted. Thoughts, comments, etc. still welcome.
	0

07-22-2014, 05:00 PM	#10
tudorv Member Join Date: Jan 2013 Location: Romania Posts: 36	Check the pilot screw on the carb (unless it's sealed). It adjusts the fuel mixture. Maybe when you took the carb apart, you changed its position.
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