XJ 650 not properly revving from idle?

Ok so i bought an xj 650, the guy left it out in the rain, anyways i fixed all the rust and it was running fine. My petcock must have been clogged or no longer working so i bought a manual petcock (Plugged up the vaccuum line) and hooked that up. The bike was running perfectly fine before the petcock was clogged up. So i was putting it on prime to run it for a couple of days since the regualr fuel line wasnt working right due to the petcock.

so i just recently plugged up the vacuum line and hooked it all up. New petcock and whatever, so i hook it up and put it all together. I turn the petcock ON and start up my bike. Starts up fine, choke on, works fine, starts up well. After a good 2 minute warm up with the choke on or so, it will idle fine. (I think i forgot to mention we also replaced the fuel line and fuel filter. put a metal motorcycle fuel filter in)

when i go to give it gas however and i pull on the throttle, it chokes and sputters for a second before revving up.

When i SLOWLY turn the throttle, it revs up fine.

When the bike is running, it revs up fine, switches gears fine, etc. But from idle, when pulling on the throttle, it does not rev, it sputters and THEN revs.

What is the problem here? My brother believes the carbs may have been adjusted if there was a leak or something (in the vacuum line) and now that we plugged up the line, it may be getting too much gas and now the carbs need to be re adjusted?

Also, i need to take it on the high way tomorrow to the registry.. should i be safe to ride it? (Like i said, rides fine, just problems revving from idle) I need to ride it for about 20 minutes each way and then i wont be riding it much until the problem is fixed (If its a big problem)

what is the problem here?

 

anyone?

 

Mine is similar and I've never been able to quite get it yet - something to do with the off-idle action in the carb, but I'll be buggered if I can find it. The good news is that it doesn't affect the riding too much, and after some riding and really getting warmed up mine seems to work quite well.

 

i go by if it stutters and hesitates but keeps going, it's rich but if it stutters and quits, like right now, it's lean. no playing with the throttle, take it just off idle and see what it does.
a 1/4 turn is the world, 1/8 is a lot, the width of the screw slot is about right, one tweek a day for about a week and you'll have it.
you have to ride it, garage tests are only half the story

 

hmm, so the carbs need to be cleaned to fix the problem, but it isnt really an issue?

ok, thats good to hear. as long as it doesn't affect the bike for now.

 

hmm i got confused here (Sorry im not a bike expert yet haha)

yes if i pull on the throttle while its sitting there once its warmed up, it will sputter a bit and then eventually rev up after getting by the sputtering.

what do you mean by take it just off idle? Ride it?

and what is 1/4 turn and 1/8, and what screw are we talking about tweaking?

im taking it out to the registry tomorrow so ill report back if i have any other troubles but right now it rides fine but doesnt rev up properly when idle..

 

-VALVE CLEARANCES.

-Float levels
-Carb sync (Bench sync, followed by running vac sync.)
-Idle mixtures.

In that order.

 

So check these 3 out ?

 

Actually you need to check your valve clearances first! You can work on these carbs until the cows come home, leave and come back and if the valves are not right you'll get nowhere fast. Once you get the valves in check, you can move on to carb issues. Here is a great how to by Bigfitz on the whole valve shim process http://xjbikes.com/Forums/viewtopic/t=14827.html

 

All five. (Two steps to sync, bench first then running vac sync once the carbs are back on the bike.)

Valve clearances first.

Then mess with the carbs; you won't get an accurate vacuum sync with out of spec valves.

Of course, the carbs need to be CLEAN before proceeding with any adjusting.

 

dam this is going to take forever. Is the bike ok to ride temporarily? It isnt going to cause more problems is it? It seems to run great, just problems revving up from idle... too much fuel or something.

Ill have to take care of those steps eventually but if i can put it off for now i will.

also the bike has 14000 miles so why is it that i already have to tear apart the engine and replace all these valves? Is that really the issue with 14k miles?

also why is this all of a sudden a problem now that i replaced the petcock from vacuum operated (When it broke) to manual?

 

Nobody said anything about tearing apart the motor and replacing valves.

You need to check the valve clearances. And adjust as needed. This is done by changing shims.

This is a normal maintenance procedure; it was to have been done initially at 3000 miles; then again every 5000 miles afterward.

If IGNORED you may end up needing to replace a valve or two, or repair even worse damage.

What I gave you are the basic steps to ensure the motor is in a proper state of tune in accordance with the maintenance schedule. I don't think the problem started because you replaced the petcock, unless you failed to cap off the now unused vacuum port. I think the problem started because the bike is getting closer and closer to the mileage at which damage due to neglected maintenance can occur.

It's not an expensive or overly complex process to CHECK your valve clearances. If they're in spec, you move on. I suspect you'll find adjustment necessary. DO IT. The longer you put it off and continue to ride, the greater chance that you will actually cause damage.

A little effort now can save a whole lot of work down the road.