87 Yamaha FZ700, stalls out randomly when taking off- Carb cleaning?

[El Bushnaynay]

I'm a new rider, and finally got a chance to take the FZ out for a long ride this past weekend. The bike runs phenomenal and doesn't seem to have any problems while driving, but I noticed that when I come to a light and try to take off again, on occasion the bike will stall out. I doesn't seem to matter how much throttle I give it, it just dies. It happened to me once on my ride home, and took over 4-5 times of restarting and getting on the throttle to get the RPM's to respond at all. During most of the ride, this was not a problem, as I came to many stops and didn't seem to have the same effect. Knowing very little about carb operation, I am looking for suggestions from the experts.

1987 FZ700 with 25K on the clock.

Thanks

Geoff

[DaveZX6r]

Unless you have some crazy chunks of crap floating around in your bowls and randomly clogging and unclogging it doesn't really sound like carbs to me. Sounds more like spark. Do you have a copy of the fsm or a Haynes?

[DaveZX6r]

When does it stall? As soon as you give it gas, when you start to let off the clutch, etc. Before it stalls is other any idle issues? Or does it sound perfectly fine right up till it dies?

[El Bushnaynay]

Yes I have a copy of the manual for the bike (Clymer). It's probably a good idea to replace the plugs anyways. It only stalls as soon as you give it gas. It idles perfectly fine otherwise. I'll pull up to the light with the clutch in, wait a bit while its idling, then as I go to get on the gas and let off the clutch, it just dies. It also dies with the clutch in as I try to give it gas. It doesn't matter if I give it a little or a lot of throttle, still dies.

[JohnnyV]

Clogged mains would cause issues similar to this. If the pilots are fine it would idle great, but with the mains buggered it would gag like a mofo when trying to gas it

[El Bushnaynay]

But if the mains were clogged, would it be as intermittent as it is? It seems to only do it every once in a while. The bike rode fine on throttle for most of the day.

[drop]

accelerator pump?

[DaveZX6r]

But if the mains were clogged, would it be as intermittent as it is? It seems to only do it every once in a while. The bike rode fine on throttle for most of the day.

Not really when carbs clog they clog period. It still wouldn't be a bad Idea to pull them and clean/ inspect them but it doesn't sound like a Carb problem.
Plus its alot easier to change your plugs and check your wires than to top apart your carbs if you've never done it before.

[Rossco]

Could also be a vacuum issue

[El Bushnaynay]

Thanks for all the tips guys. I've never done carbs and was planning on having an experienced bike mechanic do the work, but I'll look into the easy stuff first. Time to pick up some plugs, maybe a fuel filter, and do a fresh oil change anyways.

If it were a vacuum issue, where would be the first place to check? Top of the carbs? Someone had mentioned that maybe its pulling too much vacuum on the tank due to a plugged vent line. I'll check into a few things. Unfortunately it's hard to replicate the problem, since it happens so infrequently.

[DaveZX6r]

Carbs are easy to do. Its just that the first time you do it your going to spend a bunch of time just staring at parts thinking what is this? The first time I pulled my carbs I spent hours. Last time was like 45 mins? There's no reason you can't do it yourself just plan on possible downtime if you tear a seal or something. Where as changing a plug is relatively danger free.

[El Bushnaynay]

Im definitely not opposed to doing the rebuild myself, as it would be a good project, but I also don't want to rebuild them if they don't need it.

[DesmoTull]

Geoff, call me offline man. We'll get you all set up. You've got a too rich condition.

Trust me... with the shit they use in gas these days, they need to be rebuilt.

With 25k on the clock, my money is on it needing a good douching, replacement of the worn needle and needle jet, and making sure the float height is set... and you should be GTG.

PS - Read this. Great resource.

[El Bushnaynay]

Jet kit on order, now I just need all the OEM rubber parts.

[dontpanic]

Vacuum-operated petcock with a bad line?

[El Bushnaynay]

Got the carbs out and found clogged pilot jets. In the process of doing the jet kit and cleaning everything to put back together. Should be riding again really soon. Doesn't the fz look sad?

[El Bushnaynay]

I finally completed the carb rebuild, and through in a Factory Pro jet kit for good measure. New Float needles and adjusted the float height across the board, new fuel filter and replaced the broken petcock on the tank (couldn't shut it off before). Put the carbs on the bike and fired right up. Seems to be much more responsive on the throttle and idles purrrfectly. Last thing on my list is the carb sync and I should be good to go. Thanks for the advice guys. Can't wait to get back out and ride.

[Degsy]

Wirelessly posted

Yay! Nice work.

[El Bushnaynay]

Wirelessly posted

Yay! Nice work.

Thanks Degs! Your definitely made the right call in having me get new float valves as well. Mine had obvious wear marks in the rubber where they seal.

[scottieducati]

Just don't trust this guy to torque anything on a motorcycle. Years of VW wrenching has his torque feel set to retard strength.

[El Bushnaynay]

Just don't trust this guy to torque anything on a motorcycle. Years of VW wrenching has his torque feel set to retard strength.

truth right there.....

[El Bushnaynay]

Okay, so the bike runs a million times better now that I've done the carb rebuild. I still need to sync them, but that should be done in the next couple of days. The only question I have for people, is what would cause the idle to hang when getting off the throttle? It is very slow to come back to idle when I blip the throttle. Is this most likely due to the sync, or maybe a vacuum leak? Any advice in the meantime while I get the sync done would be appreciated. Thanks!

[Degsy]

Wirelessly posted

Slow to come
Back to idle is indicative of a vacuum leak.

[El Bushnaynay]

figured.....

guess I'll do some diag and see what I can find

[El Bushnaynay]

Carbs are all sync'd. No more idle hang. Runs a little rich, according to Degs, but that'll be something to deal with this winter.