revving at a stop

having a problem that awhen i bring the bike to a full stop (like at an intersection) and i have the clutch in, the bike will start to rev. usually goes up to about 3500 and stays there. just replaced the plugs yesterday (they were really bad) and the problem seems to have stopped but i still get the smell of gas when i start the bike. my thoughts are that the revving was caused by build up of gas in float bowls of carbs because the spark plugs were not working effectively and now that they are new plugs, the fuel is being burnt.
any ideas?

 

Have you cleaned carbs lately?
Synced and adjusted them?
Color tune or chop tested the plugs?
Checked/replaced air filter? Checked for leaks?
Stock airbox or pods? If pods rejected properly?

Also have you check for rear brake delamination? It could save your life and takes about 30 min total (or less).

 

carbs have not been worked on but i did put in a K&N airfilter as soon as i got the bike.

 

just went for a ride and the revving problem is still there.

 

Time to work on the carbs. The bike is not adjsuted correctly for idle. And you can not correctly adjust dirty carbs. There are instructions in the FAQ section.

 

Mine was doing the same... Carbs are cleaner than a freshly minted penny, balanced and colortuned.. But I think I figured it out.. When I first balanced my carbs, I was working on a cool engine (because it saved me burning my fingers) and tweaked the idle knob so that the machine runned at the correct speed. I'm guessing that a warmed up bike burns petrol more efficiently, so the same amount of petrol makes the engine run faster.

I've rebalanced the carbs and tweaked the idle knob after a ride so the engine was hot, and I'm hoping the problem has been sorted. I'll find out tomorrow.

 

a couple of questions:
1. can the sync be done without the YICS tool?
2. if not, where can i get a YICS tool?

 

Yes. But it's far more accurate with one. All the yics tool does is block off the channels so that the chambers can't talk to each other. Undo the bolts, straighten out a wire coat hanger, and push it through so it comes out the other side, cut 2 inches or so from the bottom of your least favourite teeshirt, hook it onto the bottom of the coat hanger so you can now pull the teeshirt back through. You want a tight fit, and some teeshirt needs to be hanging out at either side, hey presto, your yics tool is made. Leave the coat hanger attached when you pull it back out, that way if it rips, you can pull the remain out. Hope that makes sense?

 

made the tool

 

You sure did. Except it won't work. The END (where it tightens up, where it goes into the motor) has to SEAL against the side of the cyl block as well. You have no provision for that.

Get ahold of a picture of the real thing, you'll see what I'm talking about.

 

Hey blackthunder,
My 81 XJ550 is was doing the same thing. I had just cleaned the carbs, replaced the boots, and replaced the air filter with a UNI.

I found:
1) my throttle stop screw needed to be loosened - I had adjusted it slightly during the disassemble.
2) the cool vs hot engine made a big difference
3) I think my choke cable was sticking. I lubed it, along with a few other cables, and noticed that the RPMs became more consistent

 

Your old plugs ‘were really bad’ for a reason. You should diagnose that reason.
Could be running too rich.

As other’s have suggested, the carbs could need cleaning.
Or
As Swissjon and absolin wrote, could be as simple as proper idle screw setting when engine is hot.
Have you tried adjusting the idle down with engine hot? The choke should then idle up the engine when started cold.

Put in some more info about the bikes history to help us with diagnosis.

 

Lol. After that, took my bike out and guess what. Still revving. Put a colortune plug in and found it was all over the place. Dismantled the carbs (again) and cleaned everything (again) and this time took the idle screws to bits and left them in carb cleaner for an hour. Left carb cleaner in the float bowls for about 4 hours while I put the engine back together. Turned the engine over to spit out the carb cleaner (and hopefully give the valves a bit of a clean) and then colortuned and balanced (twice) until she was spot on, and now she's purring.

As I've seen written so many times here there's no shortcut to cleaning carbs. She'll have you doing it right, whether you take the time the first time or the fifth time. Only thing I can suggest is take your carbs apart again, follow the guide to the letter put her back together, colortune and balance until everything is perfect, then the bike will run real sweet, you'll have much more power and like me, you'll learn loads.

Good luck.

 

the real deal

 

NO, that's FAR from the "real deal" it's yet another improperly engineered YICS tool.

I can scan and post a picture (from the service manual) of the real thing once I get home.

The one in the pic has the same issue as the one you made; however I believe IT is meant to be left in and the plug replaced which would eliminate the "end leak."

Leaving the tool in is not recommended, however.

 

@bigfitz52: if you could post a pic that would be awesome

 

How about this???

 

so if i add a thick rubber washer inside the large washer (and maybe add a bigger washer) it should work

 

THAT'S what I'm talking about.

Yes, as long as the washer(s) you're adding allow it to seal to the motor it should work.

 

Fitz.. Can you do me a favour please?? Can you do a quick sketch of the interior of the YICS chamber, so I understand what this thing is doing? I've a fair idea from peoples descriptions, but I've got a very visual brain, so pictures are worth 1000 words or more to me. It's just, in my imagination, there were 4 tubes coming down into the YICS chamber from each of the cylinder/carb inlets, and this tool only appears to isolate two..