Choke questions

[Shocka311]

Is the choke on these supposed to open the throttle plates? My bike has been starting like shit and I took the air box off and when I choke it the plates don't open. When I open the throttle plates manually it fires right up.

[shredex]

I think you mean the butterflies.

the choke only allows more fuel into the A/F mixture to get you a richer mix to get the bike started from a cooler temp.

sometimes when started you gotta bleep the throttle a bit and the bike will start up...just dont do it to much and flood it

[Shocka311]

my bike is getting too much fuel when starting. it won'y start because its not getting enough air. the choke just dumps more fuel in without opening the throttle plates adi letting more air in so it just mekes it worse. like I said, my bike takes forever to start, unless I holt the throttle plates open so it gets more air, then it fires right up. and there aren't butterflies in our carbs. butterflies run horizontal, closing the throttle then flip towards vertical to let air in as the throttle is open. Butterflies are also usually on throttle bodies, not the carbs. but anyway, the choke is not supposed to open those i guess so what should I do to get more air when starting so it doesn't take me 5 min and a dead battery to start my bike?

[Luke-a-Tron]

I don't know where you got the idea that the throttle plates are not butterfly valves. They are.

Does your bike idle OK once it's started? It sounds like your carbs need a tear down and new gaskets.

If giving it a little throttle gets it to start right up then just go ahead and do that. It's not going to hurt anything. Just don't rev the shit out of it as soon as it starts (one of my co-workers does this every time he starts his car and I cringe every time).

[Shocka311]

I don't know where you got the idea that the throttle plates are not butterfly valves. They are.

Does your bike idle OK once it's started? It sounds like your carbs need a tear down and new gaskets.

If giving it a little throttle gets it to start right up then just go ahead and do that. It's not going to hurt anything. Just don't rev the shit out of it as soon as it starts (one of my co-workers does this every time he starts his car and I cringe every time).

Maybe I'm talking about something else then. I thought the throttle plates were the vacume actuated slides right at the top of the carbs just under the air box, the throttle plates I guess are the butterfly valves down inside, my bad. It idles after it starts, runs for a bit and warms up. Right after I get it started I have to keep on the throttle or it dies. It won't start with a little throttle cause it has too much fuel and not enough air. Giving it more gas just makes it worse. It litterally takes about 3 straight minutes of turning it over before it'll start, then it just barely runs at about 1500 rpm for about 3 minutes. I have to just keep barely on the throttle to keep it running while it warms up, if I give it any more it floods it and kills it. I know its just not getting enough air. I have a #30 pilot jet in right now. I live in utah so i'm about 4k feet above sea level. think i need a smaller pilot jet, if so how much smaller. Oh and i did just pull the carbs apart. Everything looks good in there.

[Luke-a-Tron]

Does it smell really gassy when you're cranking it? Have you tried pulling the plugs after a bit of cranking?

I think it might be a bit premature to blame this completely on a too much gas/not enough air situation. Warn or improperly gapped valves will often initially manifest themselves as a difficulty in starting. Have those been checked recently? Another possibility is the coils or the plug wires. In my experience this occurs more frequently in bikes that are stored outdoors.

So I guess the important question underneath all of this is how sure are you that it's a flooding problem?

[Shocka311]

Does it smell really gassy when you're cranking it? Have you tried pulling the plugs after a bit of cranking?

I think it might be a bit premature to blame this completely on a too much gas/not enough air situation. Warn or improperly gapped valves will often initially manifest themselves as a difficulty in starting. Have those been checked recently? Another possibility is the coils or the plug wires. In my experience this occurs more frequently in bikes that are stored outdoors.

So I guess the important question underneath all of this is how sure are you that it's a flooding problem?

So here's the overview of the problem and everything i've done, sorry if some repetes, i just coppied and pasted this from another forum. My 1990 600 takes about 3 min straight of turning over to start, then 3 min of warming up till I can ride it. It's been running REALLY rich and I know its starting really rich cause I get the nice black cloud when it finely starts. I recently tore the carbs down and checked them and everything looks good. The dumb ass who owned it before had a #50 pilot jet in it so I switched it back to a 30. I just put new coils, plugs and ignition wires in and that helped on performance but not starting. I've checked the valve clearance and there are a few that are very slightly out of spec but not enough to cause this. I had it apart last night and when I was starting it I held those vacume actuated slides on the top of the carbs open and it fired right up so I know its just not getting enough air while trying to start. I'm not sure what to do to fix this. Should i get a smaller pilot jet or what? The choke doesn't help either, just dumps more gas in and floods it more. It also hesitated right off of a stop and at WOT. Don't know if this is caused by the same prob. I live in Utah at 4k feet so do you think I just need to get some smaller jets all around? I have to push start my bike every morning cause I've f*ck up my new battery trying to start it.

[shredex]

you should try turning uo the idle a bit and maybe sync the carbs
its weird about the holding the slides open thing. i wonder if you have to strong of a spring in there thats not allowing it to open from suction alone .

[reelrazor]

I've checked the valve clearance and there are a few that are very slightly out of spec but not enough to cause this.

Out of spec which way? Tight?

ANY tightness will cause this.

Tight valves = loss of compression.

Loss of compression = poor vacuum

Poor vacuum means the carbs don't work worth dick.

cracking the throttle open compensates a little for poor vacuum...allows the engine to develop enough compression to start.

No matter what, if you have to crank for three minutes, you HAVE a fundamental issue..that WONT get better on it's own.

To answer your original question....the 'choke' isn't actually a 'choke' as in it doesn't operate a butterfly to block off air.....it is actually an 'enrichment circuit' which adds FUEL. It does this by pulling plungers on each carb that open a passage for fuel to flow (via vacuum) to a spot next to the throttle plates (which ARE butterflies and vice-versa).

Might be worth checking the 'choke' (enrichment) plungers are sealing well/completly closing....if they leak it is like the enrichment is ON all the time.

[Shocka311]

the valves that were out of spec were just a little tight. and BARELY cracking the throttle open helps it start a little better but it still takes forever. I guess i'll be readjusting my valves sortly. They are rattly as f*ck too. I'll give that a shot and let ya know how it goes. thanks

[Shocka311]

you should try turning uo the idle a bit and maybe sync the carbs
its weird about the holding the slides open thing. i wonder if you have to strong of a spring in there thats not allowing it to open from suction alone .

They open when the bike is running and I give it gas, just like they are supposed to. I've messed with the idle screw too and I have it set right. I just had my carbs synched but I'm not sure the guy even did it. Where can i get a cheap carb synch tool or is there any way to do it without one? I'm on a tight budget at the moment.

[shredex]

viewtopic.php?f=32&t=2950

[reelrazor]

the valves that were out of spec were just a little tight. and BARELY cracking the throttle open helps it start a little better but it still takes forever. I guess i'll be readjusting my valves sortly. They are rattly as f*ck too. I'll give that a shot and let ya know how it goes. thanks

"..just a little tight.." as far as valves go is like "..just a little pregnant...."

Long cranking to start is THE classic indicator of poor valve seal.

BUT, that said....tight valves are QUIET valves...rattly up top comes from excessive lash-or wiped out cam chain tensioners, OR wiped out cam bearings.

I'd at the very least give that thing a compression test...preferably a compression leakdown test.

Synching carbs wont make that much difference for starting. YOu should be able to bench synch the carbs and make it start better than "3 minutes of cranking".


On the coldest mornings, first start of the day, mine starts in literally less than one second of cranking.


And, the 'black cloud' after starting just tells me that you just cranked it for three minutes....NOT that it is waaay rich. There's gonna be a bunch of unburnt fuel flying around after that much cranking. You get way rich with an FZR and it's gonna foul plugs almost immediately.

[Shocka311]

Well I got it fixed last night. It was totally the valves. All of the exhaust valves were really tight and two intake valves were loose. I got the right shims in there and it fired right up, and holy shit its like riding a new bike. There are still two exhaust valves that ended up a bit tight but much better. The two that are off are by about .004 but the dealer was closed by the time I got it put back together and I really didn't want to pull anything apart again when it was getting dark. I figure its starting and not rattling now so that'll be a job for another day. Thanks for al the help, you hit it right on the nose reelrazor.

[reelrazor]

Glad you got it figured out.

Gotta make sure the mechanicals/fundamentals are all good before you do any kind of fine tuning, really.

I'd try to get back in there and get the two that are still out of spec into spec, ASAP, if I were you.