Extremely high idle after rebuild. :(

[mullethunter3]

Hey guys! Been a while since I've been here. It took me 3 months and 2 moves to complete this engine rebuild. I took a '04 engine with a broken rod and swapped out the good parts from my broken '92 engine. (With this set up, I have no tach.)

Here's what's wrong. Everything is in place in the bike. Engine's in, carbs are in, everything is hooked up. I go to start it and it starts IMMEADIATELY (something I'm not used to). Problem is that it starts and stays at around 6000 RPM. I can rev it higher, but I turn it off to prevent damage to the new engine.

Investigation begins.

I remove the carbs and see that the idle set screw is not set at all. The throttle cable isn't even touching it when closed. I fix that, check my lines and try again. Start the bike, same thing. I let it go a bit longer because I am screwing the idle set screw both ways to try and get it to change the idle. No change. I see a small amount of what could be smoke from the oil on the outside of the cooling fins and turn it off immeadiately.

I quit at about there.

What could be wrong here? Now, when I first started this rebuild, I was dating someone who thought they knew what they were doing with engines... long story short, he doesn't. He's the one who took apart the carbs and put them back together. I cannot assume they are put together right, but I don't know where to look because I have never torn down these carbs. Could this issue also lie somewhere else?

Thanks for your help guys!

-Amanda

[tialloydragon]

Maybe your throttle cable was stuck or set too tight when you put it back on?  Loosen it up and see what happens.

[cboling]

I agree. The easiest way to diagnose (with only knowing a certain amount about the mechanics) would be to disconnect the throttle cable altogether. If you can, obtain a radiator overflow tank and some gas line from the local autoparts (around $20 or less) and connect that straight to the carbs. Loosen the idle screw all the way (unless it is already there) and then enable the choke by pressing the slide in with your finger or if the choke cable is connected, make sure it slides correctly. Then attempt to start. If you get a surge immediately, that could be the choke. Let the choke out and if still idling high, then the problem would likely be in the carbs / airflow / airleak. You can take a small hose (1/4 to 3/8") and use it like a stethoscope to identify where leaks are coming from. First listen around the carbs boots, then the cylinder head, exhaust seals, then valve cover, then vacuum line on the back of the left carb, and around the carb diaphragm caps.

That should give you a good starting point. It's a pain in the arse to track it down but I am betting that if you have no air leaks, you will find that the throttle cable is being "pulled" when you install the tank. What I have found easiest is to tighten the throttle cable all the way down then take a 10mm wrench and tighten the top nut to keep it from moving. Good luck.

[bombjack]

Did you you sync the carbs? If so, did you remember to put the vacuum caps back on. If not, your idle goes crazy.
Been there, done that, didn't even get a t-shirt 

[nhanxsolo]

Question is, what did you do to that guy before you broke up with him and has he touched your bike since then? 

[tt_four]

My first guess was that the throttle cable was too tight or the idle was too high, but if you say they weren't even touching, my next guess was the choke being pulled too tight. If that's not it I vote for an air leak. Maybe he forgot to put the little o-rings back under the top caps on the carbs?

I'd definitely do like other people say and make a smaller temporary gas tank so you can mess with it without needing the GS tank. I made one out of a small 20oz bottle with a spout on the lid for the hose, and a bicycle tube presta valve on the other end to let air in. Disconnect the throttle cable, choke cable, and screw the idle completely down so you can be sure it's not those. If it still idles high try spraying some wd-40 or carb cleaner around the boots and see if the idle goes even higher, which would point to an air leak.

[mullethunter3]

Did you you sync the carbs? If so, did you remember to put the vacuum caps back on. If not, your idle goes crazy.
Been there, done that, didn't even get a t-shirt 

I didn't put the carbs back together... so no? Maybe? IDK. Anyway, what exactly are the vacuum caps? Are they the little membrane thing in the top end of each carb? I know those are in.

[mullethunter3]

tt & cboling,

Thanks for the input. I'll be making a temporary tank tonight. I used to have one, but I think I left it at the ex's house.

I should note that the choke was not on while all of this was happening. I just kind of started it to see if it would work without it and this is what I got.

I'll post back to see let you know if anything has changed.

Amanda

[Allen]

I had this problem before, after I worked on it, and it worked, I could not get it below 6k.  Ended up that I had to hold the throttle open while I pull and turn out the idle screw all the way out, then finally the rpms dropped.

[tt_four]

The vacuum caps that sometimes go missing are the small black ones on top of the carbs. Not the large black caps that cover the whole top with the slide/needle/diaphragm under it, just a small little one maybe not even 1/4in wide.

Other than that, here's the bottle I made, just for ideas in case you were going to make one instead of just buying one. It was just a cheap bottle, and I've used it a couple times this spring and still have it, and nothing's melted, so I think it'll hold up for a while.



for the bottom I drilled a hole, stuck in the presta valve, screwed on the locknut that they usually come with, then just poured some gorilla glue around the outside.