Bike doesn't idle when warm

So I went to ride my bike for the first time today since re-doing a bunch of stuff. I rebuilt the carbs with an experience member on here, did valve clearances, rebuilt the Petcock, changed oil and filter and vacuumed synced. When I went to ride I would come to a red light and te bike would die and be hard to start. After that I get it restarted the idle is all over the place. The only thing I didn't change is spark plugs.... Would that cause this? If not what would I am really frustrated!!!!! Thanks.

 

Might have an air leak. Use the stating fluid or propane method to locate.

 

How "rebuilt" are the carbs? Throttle shaft seals? Did you break the rack? Soak or submerge the rack? How precisely did you set the float levels; were they verified individually for each carb?

It does sound like a vacuum leak; however I need to ask:

Do you have any intake or exhaust mods we need to know about? Are you running the stock airbox, air filter and exhaust system?

 

The rebuild was extremely thorough and everything replaced. Shaft seals, bowl gaskets, o rings everything. Stock airbox and filter and stock exhaust. Float levels were set according to Yamaha service manual. Thanks

 

Did you break the rack, remove the individual throttle shafts and the butterflies and replace the throttle shaft seals? Or was it a carb service according to the book? (They never admit you can take them that far apart.) The reason I ask is it's a common cause of your symptoms. Likewise uneven float levels.

That or it's a vacuum leak somewhere, or the bike wasn't fully warmed up when you did the vacuum sync.

If that's a YICS motor, did you block the YICS for the sync?

Have you verified that the little rubber boots on the vacuum spigots are soft and pliable, and not as hard as rocks and leaking once the bike warms up? It's a simple thing but it'll make the bike idle like crap.

 

Yes rack was broken, carbs were so clean you could eat off of them. All rubber seals were replaced. The caps are kinda hard I guess and no I do not have a yics tool but got them as synced as I could without it. Bike ran great before rebuild, I only rebuilt them cause they were leaking.

 

Get new little rubber caps first so you don't chase your tail.

Do a test for vacuum leaks using an unlit propane torch or starting fluid as suggested.

If no vacuum leak can be found, you'll need to go back and revisit your running vacuum sync.

Or go back and carefully do whatever you might have skimmed over on the carbs. Your symptoms say vacuum (leak or sync) or incorrect/uneven float levels.

A YICS tool isn't 100% necessary, you can twist an oily rag into a tight rope and pull it through the passage with a hunk of coat hanger wire to block it off. What tool/method did you use for the running vac sync? Where are your mixtures screws set?

A couple more questions: when you did the valve clearances, how badly out of spec were any of the valves? In particular, the exhaust valves? Have you done a compression test on the motor since the valves were put in spec?

 

Only two valves were out of spec and just barely. Like I said the bike ran great before the rebuild.... I just had one leaky carb I'm regretting touching them badly I guess if it ain't broke don't fix it lol. I put a ball valve of the vacuum like right before the guage when I did the sink to restrict the flow to help get a better reading. I didn't touch the mixture screws since they are plugged. Wet set levels were all correct... Ill buy new caps from autozone today and hope that helps..... If not I think she's gonna be for sale and imma buy me a new bike. Seems like I keep dumping money and time into this thing and never get to enjoy it.

 

Just did a compression test in order from 1 to 4. 140, 140, 140, 145.

 

The carbs aren't clean. You cannot properly clean the pilot circuits without pulling the mixture screws to flush them out. There are also tiny o-rings on the mixture screws that probably need to be replaced.

The more shortcuts you take, the more often you have to go back. How much time it ultimately takes is up to you.

Good compression numbers; that's a nice strong motor. The rest is up to you.

 

So not drilling out those plugs would cause it to idle in my garage but then not after riding for a bit?

 

No, but not drilling out those plugs, REMOVING the idle mixture screws under them and properly cleaning the pilot circuit passages will though.

Your carbs were not as thoroughly serviced as you think they were. The blocked screws are the idle mixture screws; the passages leading to and from them are very critical to how the bike idles.

Plus, as I said, there are tiny o-rings on those screws that are probably mashed flat and hard as rocks necessitating replacement.

When you're running the bike in your garage, it's not fully warmed up. Once you actually ride it for a few miles, it gets fully warmed up and becomes VERY FINICKY about things like float levels, vacuum sync and idle mixtures.

You have short-cut the carb service.

There is no quick fix, "turn this screw" type solution to this one.

You'll need to go back and do the carbs right; or you can fight with it forever. It won't run right until you do, that's just the simple hard science of the matter.

 

I haven't tried it myself but from what I hear, it might not be a bad idea to run some seafoam through them. It would be alot easier than removing your carbs again.

 

There's no way for SeaFoam-laden gas to get to/through the passages that need to be cleaned properly.

SeaFoam is not going to fix this. There is only one way to do it, and that's do it right.

Generally speaking, shortcuts aren't very effective in place of other shortcuts.