Carburated SV help. - TwoWheelForum: Motorcycle and Sportbike forums
 
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post #1 of 16 (permalink) Old 05-12-2005, 07:12 PM Thread Starter
 
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Carburated SV help.

My power jumps up and downt the revs. One week the power comes on around 5000rpms and the next it comes on around 7000rpms and everywhere in between! I thought i had a vaccum leak somewhere and couldnt find anything. Where am i supposed to make my power? And how can i fix this. Carb cleaning, synchronizing, etc. Plugs are good, fuel is clean. Help is appreciated.

One more thing, the little screw and spring adj on the throttle link between the carbs and the idler adjuster... how much of what? I cant get THAT right either.



Speedwerks i know youre out there somewhere.
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post #2 of 16 (permalink) Old 05-13-2005, 07:05 AM
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Are you getting good gas everytime you fill up?

Are you waiting till your tank is almost empty every time you fill up... like the same milage on the tank when you fill up?

When's the last time the spark plugs were changed?




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post #3 of 16 (permalink) Old 05-13-2005, 01:55 PM
 
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I'm cheap and I'm lazy, so the first thing I would do is replace the spark plugs. Then I would check the ignition timing to see if it advances correctly. After that I would check the valve clearances. If it still didn't run right, I would check for vacuum leaks before checking fuel.

Then I would check the air filter, fuel filter, and fuel pump (if your's uses one). With a V, the carbs shouldn't be too hard to get to. Try lifting up on the needle piston with your finger. It should go up with just a little resistance and come back down smoothly. If not, you have to take off the carbs, take off the tops and clean the piston, walls, and passages. Then take off the float chamber and clean all the jets. Set the float level and put it all together.
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post #4 of 16 (permalink) Old 05-13-2005, 03:47 PM
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Yeah all of that!!




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post #5 of 16 (permalink) Old 05-13-2005, 05:06 PM Thread Starter
 
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Quote:
Originally Posted by Gas Man
Are you getting good gas everytime you fill up?

Are you waiting till your tank is almost empty every time you fill up... like the same milage on the tank when you fill up?

When's the last time the spark plugs were changed?
Yeah the low fuel light is on when i fill back up. And thanks to your "Octane" thread i only use exxon/mobil. Plugs are 7mo old.

Quote:
Originally Posted by NoWorries
I'm cheap and I'm lazy, so the first thing I would do is replace the spark plugs. Then I would check the ignition timing to see if it advances correctly. After that I would check the valve clearances. If it still didn't run right, I would check for vacuum leaks before checking fuel.
Is checking timing difficult? It has to be nearly universal for bikes so where do i start? I just hope i dont have to take the carbs apart.
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post #6 of 16 (permalink) Old 05-13-2005, 06:12 PM
 
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cant help but im trying to have my name on the whole list
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post #7 of 16 (permalink) Old 05-13-2005, 06:19 PM Thread Starter
 
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ok
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post #8 of 16 (permalink) Old 05-13-2005, 06:32 PM
 
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Valves are mechanical. They will not vary day to day.
Timing is mechanical. It will not vary day to day.
The fuel pump will not change power delivery. It will only make the bike not run or cut in and out (the float bowls in the carbs will run dry if the fuel pump isn't supplying them).

Something intermittant is generally ... a pain in the ass And usually electical. Coils, battery, etc.

Define "power comes on". What exactly is the bike doing differently each day?

(I might not get back to you till after the weekend, I'm leaving for the track in the morning and we're closed Monday because ... we'll still be at the track )

- Roach
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post #9 of 16 (permalink) Old 05-13-2005, 06:35 PM
 
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Quote:
Originally Posted by JK_DILLA
Plugs are 7mo old. Is checking timing difficult?
Even if the plugs are 1 day old, if they get any gas on 'em they can become fouled. Stock weak coil, resistor spark plug wires and resistor plugs make a weak spark. See if you can get the same plugs without a resistor. My Honda calls for NGK DPR9EA-9, but I use NGK DP9EA-9. Notice there's no R (resistor) in the plugs I use.

A couple years ago, my Honda felt sluggish. I used my 32-year-old Sears inductive timing light to check the timing. Hooked the inductive clamp on the No.1 spark plug wire, took off the crank cover, and aimed the light at the rotor. The "T" mark lined up at idle (should be the "F" mark), and stayed there when reved. The spark advance unit was faulty ($50 from Honda). After putting the new unit in, it worked correctly. If you or a friend doesn't have a timing light, you can rent one or I think you can still buy them.
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post #10 of 16 (permalink) Old 05-13-2005, 11:27 PM
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Have you changed the plugs?
You may have a loss plug or wire.
How old is the battery?

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Currently ride 1987 GSXR 50, 1996 Ducati M900, 2005 GSXR 1000
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post #11 of 16 (permalink) Old 05-14-2005, 07:17 AM Thread Starter
 
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Quote:
Originally Posted by SpeedWerks.com
Define "power comes on". What exactly is the bike doing differently each day?
- Roach
The rpm that the bike pulls hard fluctuates. Sometimes at 5000 sometimes at 7000 and in between. The weather has been just about the same so i dont think the atmosphere has anything to do with it.

Quote:
Originally Posted by jeeps
Have you changed the plugs?
You may have a loss plug or wire.
How old is the battery?
Ill pull and inspect the wires today. Its raining today so ill ride tomorrow. And ive had the battery since i bought this bike. 7-8-9 months, i dont remember exactly. If the bat wasnt doing its job i would have probs starting it right? No prob starting though.
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post #12 of 16 (permalink) Old 05-14-2005, 09:02 AM
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Quote:
Originally Posted by JK_DILLA
The rpm that the bike pulls hard fluctuates. Sometimes at 5000 sometimes at 7000 and in between. The weather has been just about the same so i dont think the atmosphere has anything to do with it.



Ill pull and inspect the wires today. Its raining today so ill ride tomorrow. And ive had the battery since i bought this bike. 7-8-9 months, i dont remember exactly. If the bat wasnt doing its job i would have probs starting it right? No prob starting though.
Usually but,
if the battery or charging system is not doing its job, the bike will run funny. (not Good)
I have had the same issue with another bike.
The battery was fairly new and the bike didn't want to start when cold.
After I got it started it never ran to it potential.

I had another bike that I broke the plug wire at the plug.
It ran fine until WFO.
It to was lacking in power and the power came on every where.

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post #13 of 16 (permalink) Old 05-14-2005, 09:35 AM
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Quote:
Originally Posted by JK_DILLA
Yeah the low fuel light is on when i fill back up. And thanks to your "Octane" thread i only use exxon/mobil. Plugs are 7mo old.
Glad it helped....




-Chris
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post #14 of 16 (permalink) Old 05-14-2005, 11:49 AM
 
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As a start I'd check the plugs (condition and gap), the plug caps, and the plug wires. Also check the output of the voltage regulator/rectifier, and also the resistance on the coils. As a long shot, you might also check the carbs and make sure the slides are opening and closing smoothly and all the way, and that the diaframs are good.

Weird stuff that comes and goes is usually electrical - mechanical things usually do not degrade, spontaneously improve, then degrade again except in the case of something intermittantly sticking (like in the carbs).

- Roach
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post #15 of 16 (permalink) Old 05-14-2005, 10:28 PM Thread Starter
 
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Now that you mention it, last time i had the airbox off i did notice the piston valve on the rear cylinders carb wasnt closed all the way. Could THAT be the whole prob?
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post #16 of 16 (permalink) Old 05-15-2005, 11:40 AM
 
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Quote:
Originally Posted by JK_DILLA
Now that you mention it, last time i had the airbox off i did notice the piston valve on the rear cylinders carb wasnt closed all the way. Could THAT be the whole prob?
JK, you can tune a carb until the world ends, but if you don't have a hot spark at the right time it don't mean nothing. That's why all the books say to check ignition first. But maybe your slides are sticking. They should be even and move smoothly (check post #3). If you have to clean them, send me a PM. I have an article somewhere on how to clean the carbs on an SV.
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