Reving issues

1982 XJ650. It ran well until I changed the oil, now it won't rev up. It starts and idles well, but won't rev up. When you try, it just backfires badly thru the carbs. Also, if you watch the tach it seems to be bouncing erratically. Maybe an electrical problem? :?:

 

Have you checked your oil level?

On the center stand it should be halfway up to 7/8 of the way full.

How much oil did you put in?

Can you take us through your process?

 

Possible you disconnected a spark plug? Seen it happen, idles but won't do anything else. Oil level, good thinking Woot. I have a brother who did his first oil change on my Max and put 5 quarts in. Blew every seal in the motor. Thanks bro, I had nothing better to do. I still talk to him, I just don't let him work on vehicles alone any more. Jandphisted, please recount what you did, step by step with as much detail as you can recall. Woot will nail your issue, rest assured.

 

I refilled it with 2 2/3 guarts. It is approx. 1/2 way up the window. I drained the oul and changed the filter. I also changed the rear final drive oil, refilling it to the top.

 

When I put the new oil filter in, I put the filter into the housing, and put the spring next to the engine, holding the filter to the outside of the housing. Was this the correct position for the spring? Also, I looked at the spark plugs, and they are all dark. Seems to be running a little rich, but that doesn't explain why it WAS running okay, then not after the oil change.

 

The filter should be the closest to the engine block, followed by the washer (don't throw this away, it sticks to the old filter and so many people, myself included, overlook this piece), and finally the spring (which should be between the filter housing and the washer). I expect your plugs would show a little rich since you haven't been able to get it up to speed to clean it off. Remember a slight rich condition is normal for start-up. I'm not sure where your issue might be. Anyone?

 

I switched the oil filter around yesterday. Also checked the flow from the petcock. It still won't rev up. When I try, it backfires badly thru the carbs. Also, the right side turn signals won't flash. They light up, but won't flash. I changed the flasher unit and checked all the wiring. Thoughts?

 

Thought:

Seems like you have more than one issue going on here. Cant see how they would all connect to an oil change...

For the oil change it gives you a volume in cc's of oil to put in the bike. There are conversions available on the net to tell how much oil to use. I use motor cycle oil only as we have wet clutches...

umm... electrical now...

Are both bulbs good? Switch sticking?

Check the obvious first.

 

The combination of a lack of throttle and an erratic tach usually means the TCI has a short. You can check Dave Jackson's site on repairing cold solder joints or look around ebay for a replacement. A good way to check is to put your TCI in another 650 and see if it displays the same problem. Then I would check my ground which is at the left side of the TCI board and after making sure it has good contact try the good TCI from the other 650 and see if your bike runs like it should. IF you do it in this order you won't risk damaging a good TCI.
When TCI's go bad you will either get a suddenly dead engine or a poorly running one at idle or even at a certain RPM with an erratic tach. The tack gets it's info from the TCI and when it misfires the tack goes nuts and the timing is off causing either no fire or incorrectly timed fire.

 

I agree with Blue Maxim. The only way it would backfire through the carbs are:

Bad intake valve - so combustion is going the wrong way.
-or-
Firing at the wrong time - i.e. - when the intake valve is open.

Hopefully it is not a bad valve, and I would suspect not. So - you have something wrong in your ignition or valvetrain timing. Did you check timing?

An easy way to do this on my bike:

(This sounds stupid, but it worked.)
I put a skewer (the shiskabob kind) in the number one cylinder through the spark plug hole, and then I looked at the timing mark on the wheel attached to the crankshaft on the left side of the bike (can't remember what this is called). Then I manually turned the bike, and made sure the skewer was highest when the mark was on TDC! Sounds stupid - but it worked.
Of course, if your timing chain is loose, this can change once the bike fires up! Then, you would need a timing light to check timing. I hope your chain is okay! If it is the tensioner, then it is possible that the cam sprocket jumped a link, and the intake valves are opening at the wrong time.

 

Nothing stupid about it richard03, this will get the piston to TDC, check with the mark alignment, then take off the valve cover and check that the cams are lined up with their timing marks.