Jump to content
  • Sign up now

    Registration is quick and easy 

Carb balance = high revs...WTF?!


Pete
 Share

Recommended Posts

So i finally got everything in place to balance the carbs on my blackbird today. God knows when the last time they were done was, certainly not within the last 20,000 miles! Anyway, it was running a bit lumpy so I thought I'd sort it out.


It all started well, all fairing and tank taken off, auxillary fuel tank in place, I'm set up to balance carbs 3+4 and away I go. It did need doing, the levels were off...


...and I don't know where it went wrong but at some point (I've now balanced or tried to balance 3 times) the revs have gone through the roof at idle (3000-3500 rpm) and I can't bring them back down! I've fiddled with the idle screw and that does nothing - even backed all the way out the bike still revs high.


Another clue to someone that may be able to help is that theres a frequent popping from the exhausts - not sure if that's a giveaway? Only thing ican think is that it's running lean, but I've not touched the insides of the carbs / the jets so can't see how that would be affected?


Any ideas massively appreciated, really don't want this to ruin my Easter weekend!

Link to comment
Share on other sites

Back off the idle adjusters one at a time until the revs come down. One of them should be a master. Set air/pilot/idle screws to recommended settings and start again. You will have to find a happy medium between the master and the others. Don't forget the throttle adjuster in the middle ? :mrgreen: :mrgreen: :mrgreen:

Link to comment
Share on other sites

Nice one fellas - Stu, you're only in Hull, so about 150 miles away, that's all! And I make a mean cuppa tea :lol:


So I've not checked Idle adjusters - what the hell are they? They sound good...alls I've been messing with are the three screws used to balance 3+4, then 1+2 and then the one in the middle to balance them all. Not checked pilot screws either because it was running OK before I started (apart from dicky idle) - would the pilot need messing with usually?


I HAVE checked throttle cable and that seems OK. that said, if I "decelerate" past the stop position, ie put a bit of opposite pressure on the grip it levels the revs out, but rises again after I let go.


When I blip the throttle it's taking longer than usual to return to idle. Going to check for air leaks tomorrow (somehow...!) but can't see how I'd have one as it wasn't there this morning!


Thanks all! Keep up the suggestions please!

Link to comment
Share on other sites

sounds like throttle cables or something like that to me have you checked the return cable too as they work together and if the return is too tight it can cause the throttle to stick


yeah 150 miles is not far for you to ride to my lock up :lol: if you can get it to me i can sort it :wink:

Link to comment
Share on other sites

sounds like throttle cables or something like that to me have you checked the return cable too as they work together and if the return is too tight it can cause the throttle to stick


:up: :up: :up:

deffo!!!

Link to comment
Share on other sites

Ok team,


You've convinced me that it's something to do with the throttle cables, and I reckon the return "close" cable is not tight enough...ie it aint closing fully. That said the throttle does snap back nicely, just not as far as id want it to...but it does have a good positive snap.


There's slack in the "open" cable, as specified in the manual, but the close is just not closing it enough. I can't seem to work out how to make it close though, the cable adjuster nut doesn't seem maxed out but I'm just stuck really!


Could be totally wrong of course!


Some pictures:


Not the best photo, but this shows the top of the idle adjuster screw, and where the throttle body bit should be resting on it. It doesn't touch it...

http://i976.photobucket.com/albums/ae248/peteblakemore/4478b4b8.jpg?t=1333794175


This one shows the cables at the bar end - the pull to "open" has an adjuster nut, the pull to "close" does not.

http://i976.photobucket.com/albums/ae248/peteblakemore/58f53533.jpg?t=1333794168


In the belly of the beast - the nut at the top shows the pull to "close" cable, the one at the bottom is pull to "open". I can't seem to do much more with the "close" one...

http://i976.photobucket.com/albums/ae248/peteblakemore/4ed9431d.jpg?t=1333794163


Thanks all!

Edited by Pete
Link to comment
Share on other sites

To find out if the cables are too tight run the bike and turn the bars if the revs rise or fall then they are too tight


It could also be the centre adjuster too depending on the set up its hard to guess without looking!


A loose return shouldn't stop it closing but a tight throttle will


At least you have cruise control now :lol:

Link to comment
Share on other sites

Ps at the throttle end wind that adjuster all the way in to see if it makes a difference also check the throttle grip for any slack

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...

Important Information

Terms of Use Privacy Policy Guidelines We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.