Air Box Drain Hose

[Guest]

I just have a quick question about the drain hose on my 1982 GS550 air box. IS it supposed to be open or is it supposed to be plugged?

I have been working/ fighting with this bike for over 6months now, and I have replaced head gasket, base gasket, set valve clearance, cleaned carbs half a dozen times, installed new carbs boots and o-rings, installed new to me coils, known good set.

just yesterday I did the relay mod for the coils since I was getting almost 2V of voltage drop. now I'm getting .1v.

I have the bike running decent where it will idle but still surges just a tad, probably need to sync the carbs. that doesn't concern me though because it idles at 1200 no problem. But when the bike is cold it has no throttle response unless I feather the throttle, once it warms up it is better but still bogs down at half throttle then revs fine. By the way the throttle concern i have is when I'm not moving, when I drive it I don't have the bog at half throttle.

Could it have anything to do with the air box drain?

[Steve]

Airbox drain hose should be OPEN, and it has nothing to do with your current situation.

You say you have "cleaned the carbs half a dozen times". That tells me that at least the first five times were not done properly. Any assurances that the sixth time was properly-done?

Where did you set your mixture (pilot) screws? When properly set, they will ensure a proper mixture for idle operation, which will aid the transition to mid-throttle.

Knowing that you have an airbox drain hose, it would be a safe assumption that you have an airbox installed, not pods. How about the exhaust? Stock pipes or a header? You might need to richen up the pilot screw and/or shim the needle a bit to richen up the mid-throttle mixture. Of course, all this assumes that the carbs have been cleaned properly and synched.

Your bike might idle at 1200 "with no problems", but that does not mean the carbs are synched. Please do that and report back.

.

[tom203]

Hey, it's too cold for these poor critters up here- let's pray for spring! Anyways, I have not investigated the airbox drain hose , but I figure it's a one way device (a ball sitting in hole) so it doesn't let air up into box, but would let fuel drain if needed. Why don't you just plug it and see if bog changes.

[JTGS850GL]

Syncing the carbs is a must do kind of thing. Anytime the carbs are apart or the valves have been adjusted you need to do this. It's amazing how much of a difference it can make on overall smoothness.

[curtie94]

Ok will do I will sync the carbs. yes I cleaned the carbs correctly the last time. I stripped them and soaked them over night then made sure every passage was clean. The bike does fire right up.

I started with the mixture screws at 2 turns out then adjusted them but I don't seem to get much of a change in idle when I adjust them. Where should I set them? 2 turns? 2 1/2 Turns?

[Steve]

2 turns is a bit on the lean side. I usually start at 3 full turns (these are full 360-degree turns) out from lightly-seated. After the bike warms up enough to run well off-"choke", I will slowly turn the screws in, listening for engine speed changes. When the speed drops, turn the screw back out about 1/4 turn, go to the next carb.

If you do this while the sync gauges are still attached, you will see the vacuum on ALL cylinders drop when the engine speed drops. It might be easier to see the drop than to hear it.

Also note that not all the carbs will require the same screw setting. On my son's 650, three of them were between 2 1/4 and 2 3/4 turns out, but one required about 4 turns before it would run properly.

.

[curtie94]

ok I just did the carb sync and what a difference already. no more bog. I do get a op when I let off the throttle through. Ill go ahead and do mixture screws now.

[JTGS850GL]

You may need to do the sync again after you get the mixture screws set. Shouldn't be a huge change though.

[Steve]

You may need to do the sync again after you get the mixture screws set. Shouldn't be a huge change though.

I have never noted a change in the sync when the mixture screws were adjusted, but leaving the gauges connected while adjusting the mixture is what led me to noticing the difference in vacuum level when the engine speed dropped.

.

[curtie94]

I just did the mixture screws and id didn't really seem to change the idle speed at all I did notice a slight difference in vacuum though. it idles the same but It is crisper when I crack the throttle open. the true test for all of this is on a cold start how it will run.

Thanks guys for your help.

If there is anything else I could do Im all ears.

Curtis

[mrbill5491]

When I got my new air box drain hose it had a removable plug. The old hose at one time just had a piece of foam in it. I unplug mine after a long ride to make sure nothing is there.

[eil]

Glad you're getting it solved, but I didn't see this part of your original post addressed:

But when the bike is cold it has no throttle response unless I feather the throttle, once it warms up it is better but still bogs down at half throttle then revs fine.

That's pretty much by design. A cold engine needs waaay more fuel than a warm engine. Engaging the choke compensates for this by dumping fuel into the intake. But when you twist the throttle it severely leans out the mixture, leading to poor throttle response. You can get acceptable throttle response once the engine is about halfway warmed up but you don't get full response until the choke is off and the engine is completely wamed up.

[curtie94]

So when the engine is cold it won't have throttle response?

If its normal then I'll stop messing with it. Because it still does it.

[eil]

Yep, totally normal. Within reason, anyway. (It shouldn't take five minutes to warm up before the bike is rideable, for example. More like 30-60 seconds is what I get on my bikes depending on ambient temperature but others here think even that's on the high side.)

[curtie94]

For me I can turn the choke off after 20-30. Once I start riding I'm all set though.