Bike starts up idles on choke, dies with choke off our when warm

[Scrambled]

So those screens were NOT on the seats. What do I do from here? Do I get a jet kit with all new jet pilot and main jet components and just rebuild the entire thing? Here is a pic on what it looks like.

I apologize for the dog hair on the towel. We have two back labs and they are shedding this time of year!

I thought that was pubic hair but we won't know for sure until after it comes back from the CSI lab.

Find out who that pubic hair belongs to , I bet you they screwed your carbs.

 

[evans_search]

I check the vacuum with a syringe and a piece of tubing. Also how I operate my fuel valve while synching carbs, for those without a test tank.

I'm sorry but I'm not sure exactly what you mean. However, the one thing the PO (Previous Owner) did do was change the petcock when putting on the new tank so it is likely something is wrong with the vacuum. Although, when I got the bike to run I noticed after getting it to run for a while and then shutting it off when I opened the gas tank I got a sucking sound. So the vacuum must have been working to get that negative pressure in the tank right?

 

[evans_search]

So far here is what I know on this bike. The tank and petcock has been replaced. Those screens aren't on the float needle seat piece and when the bike does run it stops running when it gets warm. What are the screws in this picture under the butterfly throttle body spring though? I haven't been able to find out what they are? They look like fuel/air mixture screws but these are VM34 Carbs.

 

[littlebill31]

Those are BS34's, stock on the '80+ XS650. Don't worry about those screws.
Did you have a pilot jet and the rubber plug that goes over it?

 

[evans_search]

Those are BS34's, stock on the '80+ XS650. Don't worry about those screws.
Did you have a pilot jet and the rubber plug that goes over it?

Yes and Yes. I have both.

 

[evans_search]

I thought that was pubic hair but we won't know for sure until after it comes back from the CSI lab.

Find out who that pubic hair belongs to , I bet you they screwed your carbs.

LOL I didn't even see that hair until I had already posted the picture. You are probably right.

 

[littlebill31]

Your carbs are CV (Constant Velocity), not VM's is what I meant.
Check to see what the numbers are stamped on the main jet, pilot jet, and the needle jet too.

 

[jd750ace]

Your tank should not be under vacuum. It should be vented to atmosphere. That usually causes fuel starvation. You internals need to be cleaned for sure. All that dingy brass can be made to look like that new float valve when properly cleaned. Not sure if it's pine-sol territory, but some folks here know. I always use phosphoric acid, because I have it at work.

 

[evans_search]

I have bigger problems now gentlemen. In all my rookie wisdom I was cleaning rust around the battery area and disconnecting stuff so I could get to things. Now the bike starter doesn't even turn on. I broke some kind of tiny black box looking thing with two connections that were soldered inside of it in trying to see what it was. I think it was the starter switch. Better Order a new one.

 

[evans_search]

Your tank should not be under vacuum. It should be vented to atmosphere. That usually causes fuel starvation. You internals need to be cleaned for sure. All that dingy brass can be made to look like that new float valve when properly cleaned. Not sure if it's pine-sol territory, but some folks here know. I always use phosphoric acid, because I have it at work.

We definitely live in Pine-sol territory. Wouldn't coca-cola also work here too? I think the acid used in it is phosphoric acid too? I'll have to check on that.

 

[jd750ace]

Colas use phosphoric acid too, although I've never tried cleaning brass with it. Ammonia is another very effective brass cleaner.

 

[littlebill31]

I broke some kind of tiny black box looking thing with two connections that were soldered inside of it in trying to see what it was. I think it was the starter switch. Better Order a new one.

Take a couple pictures of it, or anything, and post them on here. That helps a LOT. We can help if we can see.

 

[gggGary]

+1 more pics of the carbs too! specially inside.

 

[evans_search]

Take a couple pictures of it, or anything, and post them on here. That helps a LOT. We can help if we can see.

I figured out what it was. It was the starter relay. I have replaced it and now the bike starts fine so that is the good news. However, we are back to the same damn problems with the carbs.

 

[evans_search]

I hooked everything up. Filters and all. This time I left the gas cap open on the bike when running it and it ran great for about 5 to 8 minutes. Here is a list of what happened until finally the bike won't do anything now but idle at 4000rpm.

Constants = Gas cap open, Floats adjusted to 27.3mm inside the bowl, Air Mixture screws 3 turns, new NGK Iridium Plugs, New Battery

1) Choke pulled out two clicks and hit the starter button. The bike jumped up in idle and wouldn't come down at first. Played with the choke going back and forth between 1 click and 2 to keep the bike running and RPMS at around 3000. Then after a while the bike started to idle perfectly.

2) While idling around 1200 RPMS the bike warmed up and with the choke off I twisted the throttle and RPMs would jump up quickly (it was much more responsive this time and didn't die...at first) then RPM's would stay up high around 3000 to 4000 and come down very slowly

3) Bike continued to idle fine for a while. Then I twisted the throttle and it died but it would start back up. Then after a couple of times it wouldn't start so I took a look at the fuel line going from the Gas Tank to the Carbs and it didn't have any fuel in it

4) I checked the tank and no gas was coming out. I put the tank back to prime because once it started I took it off prime to run. When going back to prime this second time no gas would come out

Now gas won't come out of the petcock and fill up the fuel line and I can't get the bike to stop idling at 4000 RPMs

So I left the bit sitting for about 5 or 10 minutes on Prime and came back to it. Fuel had finally started to fill up the line. This time I closed the lid on the gas tank, took off the vacuum line attached to the Petcock and hit the starter button.

The engine came on and started to idle around 1200 RPM, then after about 15 seconds the RPM started to climb until it reached around 4000 again so I shut the bike off.

Here the interesting part. When I opened the cap on the gas tank, I could hear air get sucked into the gas tank. What would cause this to happen?

On the bright side, at least the bike is running. I have a small oil leak under the engine now but at least the bike runs. I will get to that leak later, I need to get these damn carbs figured out so I can stop feeling like I need to go to special Ed class instead of work.

I can make a video if it helps you all. Let me know.

 

[jd750ace]

The hanging at high rpm is a typical sign of a lean coasting condiiton. Your petcock sounds like it's thrashed. It should pour fuel like a fountain on prime. Your tank is also not vented. It should not build vacuum as the fuel is drawn out. It should be vented to atmosphere at all times. Leave the carbs alone for a while and work on the petcock. I think the tank is vented through the cap. I need some guru verification for that. Since you are able to establish a steady idle, and get snappy throttle response, the carbs are close enough to run and ride, but your float bowls are getting starved out for fuel due to the petcock and the venting. I say both because it does it with or without the cap on the tank open, and when it's closed, it pulls a vacuum.

 

[littlebill31]

Do you have 1 or 2 petcocks?
If one, then get the non-vacuum petcock from MikesXS and switch it. It's a world of difference. One of the first things I do.

And it does sound like a really lean mixture caused by an air leak to have that hanging idle. Double check, again, the carb boots, throttle shaft and seals, vacuum barbs and the mix screw.

Did you remove the mix screw and replace the mix screw, spring, washer and O-ring, in that order???? The O-ring, washer, and spring should always be replaced with a new set. The mix screw can be re-used, but the other parts need to be new.

 

[weekendrider]

The lean condition may also be a low float bowl level.
At least mine lean out(increase in rpm) as I run them to empty to the carbs.

 

[evans_search]

Your petcock sounds like it's thrashed. It should pour fuel like a fountain on prime. Your tank is also not vented. It should not build vacuum as the fuel is drawn out. It should be vented to atmosphere at all times. Leave the carbs alone for a while and work on the petcock. I think the tank is vented through the cap. I need some guru verification for that. Since you are able to establish a steady idle, and get snappy throttle response, the carbs are close enough to run and ride, but your float bowls are getting starved out for fuel due to the petcock and the venting. I say both because it does it with or without the cap on the tank open, and when it's closed, it pulls a vacuum.

It wouldn't surprise me if the petcock was thrashed as the PO replaced the tank and old petcock due to its condition. The guy said the petcock is new but that wouldn't make sense if these problems were occuring. The carbs were also "not touched" even though the screens were gone on the float valve seat. Makes sense. I'm going to take some advice here and probably just buy a new petcock.

 

[evans_search]

Do you have 1 or 2 petcocks?
If one, then get the non-vacuum petcock from MikesXS and switch it. It's a world of difference. One of the first things I do.

And it does sound like a really lean mixture caused by an air leak to have that hanging idle. Double check, again, the carb boots, throttle shaft and seals, vacuum barbs and the mix screw.

Did you remove the mix screw and replace the mix screw, spring, washer and O-ring, in that order???? The O-ring, washer, and spring should always be replaced with a new set. The mix screw can be re-used, but the other parts need to be new.

I have one and its on the left side of the tank. I didn't know I could just switch the petcock from a vacuum to a non-vacuum but I guess it makes sense. I would just put a cap on the other nipple coming out of the carb boot on the left side right?

I did not remove the mix screw or replace it. Is that something I should be doing too?

Could this issue also be related to the diaphram? I noticed when I had the carbs off that one diaphram would move more freely than the other one but it was minimal difference.