My 650 keeps bogging down :(

I noticed this problem a few weeks after I purchased it last year. It is a 1981 maxim 650. While I am riding sometimes there is a sudden drop in power. Normally it revs up nice and smooth to 8000 rpm. When it bogs down it only goes smooth up to about 5000 rpm and it takes a lot of extra throttle to go higher than that. Is it dropping a cylinder? Is there an electrical problem? A Carb Problem? I NEED HELP.

The problem with this problem is that it is inconsistent. Sometimes I ride to work and it doesn't do it the whole ride, but does it on the way home. Sometimes it does it on the way to work then its fine on the way home. Sometimes it does it for a few miles then runs fine the rest of the ride. sometimes its fine for 10 miles then acts up the last few miles to work. Some times it is bogged down when I first start it up for the day and it stays like that all day. IT DRIVES ME NUTS. I disassembled and cleaned the carbs and it is still doing it. Any advice or suggestions would be great! Thanks in advance!

 

A couple of things that it could be:

Check your fuel lines make sure they are not kinked.

In the gas cap there is a vent that can get clogged make sure it is working properly.

Check your petcocks in tanks filters, make sure they are not clogged.

Check all your electrical connections. They can get corroded and need to be cleaned.

 

I have been planning on replacing the fuel line, so that will happen soon.

I looked at the petcock and the filter was clean, but the vacuum actuator mechanism may be faulty, any suggestions on how to check? I think I will replace the petcock vacuum hose while I'm at it.

The gas cap is brand new (replaced a few months after I bought it), so I don't think that is the issue.

I have had a feeling that it may be a gas deprivation issue. is it possible that the floaters in the carbs are sticking and preventing gas from entering?

Which electrical connections are you referring to? There are no doubt hundreds, any recommendation on a starting point? I have a theory that the devices that send electrical signals to the spark plugs may be faulty, any recommendations on how to test them?

Thank you for the advice!

 

do you have pods or stock? mine did that because po lost airbox lid and wind from certain direction would starve it for fuel.

 

Have you done any maintenance whatsoever, or did you believe that PO when he said that everything had already been done?

There are many things that could be the cause of the symptoms you are describing.

Go, read, learn, do. http://www.xjbikes.com/forums/index.php?threads/the-information-overload-hour.27544/

 

bad plug? - my exact symptoms this past summer on a trip (new plug solved the issue)
bad wire cap?
tci going bad?
Bad coil?

Shim clearances in spec?

Ridig in rain?

did you sync your carbs?
what did you set your floats at initially?

Simply setting the petcock to PRI and riding will effectively bypass the vacuum side of the petcock. BUT if you're floats are leaky and you're tending to flood out, then you're gonna end up with a crankcase full of gas if you don't put it back on RUN when you turn the bike off.

You're throwing out a " why doesn't my bike run right?" question, and we're just throwing out possibilities til we can get specifics.....in order to give specifics.

Dave F

 

As others have stated...too many variables; need lots more constants. Fwiw the petcock should be rebuilt. Problems occur when fuel is getting sucked through the diaphragm.

Gary H.

 

I have a stock air filter.

It couldn't hurt to swap it out with a new one, but the one in there looks pretty clean.

 

I have swapped the plugs, cleaned the carbs, changed the oil filter and oil, drained and replaced the blinker fluid, I even rotated the air in the tires!

The only regular maintenance I haven't done is cracked the engine open... which I am hoping to avoid.

 

I am just here for ideas.

I swapped the plugs ( I took them out a few weeks later and they were covered in carbon)

I don't know what a wire cap is, or a TCI.

I'll be testing my coils tonight.

I don't know if my floats have adjustments. Examples for this?

Thanks for the ideas

 

How would you suggest rebuilding the petcock?

 

Here's the best article on petcock rebuild:
http://xjbikes.com/Forums/viewtopic/t=25058.html

It's by the legendary BigFitz. Learn the name, his posts are better than Haynes Manual.

 

Thanks a ton!

 

Here is the link for checking carb float levels:

http://www.xj4ever.com/setting fuel levels.pdf

The wire caps or plug caps connect to your spark plugs. When you check the coils start with them in place by sticking your meter leads up inside the caps to touch the metal. They connect to the secondary side of the coils. Each cap should be 5K ohms, and the coils should be 11Kohms for a total reading of approximately 21Kohms +/- 20% with the caps in place. Should get a reading from 1 to 4 and 2 to 3.

TCI or Transistor Controlled Ignition is the module that controls the ignition and firing of the spark plugs by receiving input from the pick-up coils. The pick-up coils are located under the engine cover on the left side, and are maintenance free. The TCI is a black box located under the left side cover next to the Rectifier Regulator.

 

great article on the floats. Ill have to rip them open again and check to see if the floats hang too low.

 

have you checked the valve clearances? tight valves will cause a loss of power and you can't properly tune your carbs unless the valves are in spec.

FU

 

If you're plugs are carboning up, you're running rich. Could be out of spec shims, could be clogged air supply in carbs....

Most likely dirty carbs, but check shims if you haven't yet.

Running rich can be:

Too much fuel

OR

not enough air.

Either way , proportions are off..... Carbs are where proportions are mixed. Valves determine how/when the a/f charge gets into a cyl, how long it stays, and when it leaves

You said you cleaned the carbs---- what EXACTLY did you do?