Help!! Starts great, idles great but bogs down when any throttle is given....

[tytin110]

Hello there, I am new here but could use some help....I just bought an 81' XS650 a few weeks ago. It drove flawlessly on the test drive but shortly after getting home it began giving me trouble.

Symptoms: Starts well, idles well but it sputters and pops (doesn't die) when I apply the slightest throttle. The exhaust smells VERY rich (dark, wet spark plugs too). Since this began, sometimes I have to tap the starter/kill switch relay to get the starter to engage.

First think I noticed was that the carb flanges were cracked so I replaced them thinking it was sucking in additional air, no improvement. Next, after studying many of the tips here I went through the carbs....twice. There was some debris in one of the carb bowls but all the jets looked clean. The second time through I adjusted one of the floats, check. I also checked and cleaned the tank and petcock, all was okay there, too.

Heres the extra confusing part: I will SOMETIMES start and run great for a few minutes or several miles. I have noticed this occurs more when I have messed with the wires and relays....could it be a bad relay, ground or other connection or should I still be looking into the carbs?? Can I test the relays??

I LOVE this site, I have learned a lot already, thank you!!

The bright side is that I am learning a lot about my bike and I am excited to be it back on the road! Down side....cooler weather next week.

 

[retiredgentleman]

Welcome to the site.

Everyone says they cleaned their carbs, but many don't know what to look for. Did you actually remove the pilot jet and confirm it was completely clear?

When an engine won't rev up with throttle increase, it means the carbs are starving for fuel/air mixture which comes from the pilot circuit. Do you have the mixture screw set to the recommended number of turns?

Have you read the "Carb Guide" that is found in the "Tech" section?

There is a ton of good info in the "Tech" section to read over.

Very important that your battery is in good condition and that the charging system is working 100%.

 

[XSLeo]

Being an 81 it has the Transistor Controled Ignition. The TCI is very voltage sensitive. If your charging system is weak it won't keep the battery properly charged. This will lead to symptoms like yours.
Check your battery voltage when running at 2000 rpms or more. It should be around 14.5 volts, any less and your charging system needs attention, maybe just new brushes.
Leo

 

[PrinceJ57]

How long did you let it sit after you bought it? And did you have the battery on a float charger? Mine did the same thing turns out the battery was bad and ran good on the test drive because the PO had charged it the night before.

 

[tytin110]

Thank you for your tips:

When I cleaned the carbs I removed all the jets (3 that I could remove) and the brass tube, cleaned them in carb cleaner with a brush and finished cleaning them with an air hose and then sprayed carb cleaner and air through all of the passages throughout the carbs. One thing I still need to do is adjust the air mixture....3 - 3 1/2 turns, right?? I'll let you know how it goes....

Welcome to the site.

Everyone says they cleaned their carbs, but many don't know what to look for. Did you actually remove the pilot jet and confirm it was completely clear?

When an engine won't rev up with throttle increase, it means the carbs are starving for fuel/air mixture which comes from the pilot circuit. Do you have the mixture screw set to the recommended number of turns?

Have you read the "Carb Guide" that is found in the "Tech" section?

There is a ton of good info in the "Tech" section to read over.

Very important that your battery is in good condition and that the charging system is working 100%.

 

[XSLeo]

www.amckayltd.com/carbguide.pdf might get you there quicker.
Leo

 

[tytin110]

Thanks Leo, the only problem is I'm not able to get it to 2000 rpm's yet. I am going to check my air mixture and check/clean my electrical connections....hopefully after that I can get it to rev up to check the charging system. I did put it on a charger overnight but it did not help....

Being an 81 it has the Transistor Controled Ignition. The TCI is very voltage sensitive. If your charging system is weak it won't keep the battery properly charged. This will lead to symptoms like yours.
Check your battery voltage when running at 2000 rpms or more. It should be around 14.5 volts, any less and your charging system needs attention, maybe just new brushes.
Leo

 

[pumps]

Could it be low voltage causing the plugs not to have enough fire? Battery good but volts just not getting there? A guy on the kzrider.com forum I used to hang out at always used to say you can't chase ignition problems through the carbs. Read this and see if it sounds familiar. . I did this mod to my old KZ650. Hope this helps.
http://www.wgcarbs.com//index.php?option=com_content&task=view&id=12&Itemid=26