Persistent vacuum leaks and cold #1&4

[ejether]

Hey all,
I'm working on a friends 1983 GS850G. It's in really good shape except that she brought it to me surging and popping. I've dipped the carbs, but new jets in, replaced the intake boots and air box boots as I've seen here that this is a really common problem. I noticed that the vacuum line for the petcock was split too so I've capped that off.

Even after synching the carbs it's still got hanging idle and revs when I spray around with starter fluid. I'll order the o-ring kit tomorrow and put those in there but I'm curious what else I could have missed and the temperatures on #1 and #4 are way lower. I switched the could around to eliminate a bad coil but there was no change. #1 & #4 were still cold.

Im at a bit of a loss and don't want to keep wasting my friends time and money if I'm missing something super obvious. I feel like I've hit all the common issues I could search on the forum here.

thanks!


and please forgive my crappy iPhone typing!

 

[Guest]

You did replace the O-rings on the intake boots?

 

[ejether]

You did replace the O-rings on the intake boots?

Yes, new carb boots, carb boot o rings and airbox boots.
The only thing I know I haven't replaced are the carb o rings in the cycle orings kits.

I'm stumped

 

[Nessism]

It's a bit perplexing that you dipped the carbs but reused the O-rings?

Make sure the airbox endcaps have good foam and seal properly against the side of the main airbox. Same thing for the air filter.

Did you vacuum sync the carbs or just bench sync?

You need to do something about the petcock. You shouldn't run the bike in prime other than to test it.

Where are the pilot screws set? If you have a hanging idle I'd put them at 3 turns open and then tune from there.

Lastly, how long since the last valve adjustment? If you say you don't know go straight to the Newbie Mistakes link in my signature.

 

[ejether]

It's a bit perplexing that you dipped the carbs but reused the O-rings?

Make sure the airbox endcaps have good foam and seal properly against the side of the main airbox. Same thing for the air filter.

Did you vacuum sync the carbs or just bench sync?

You need to do something about the petcock. You shouldn't run the bike in prime other than to test it.

Where are the pilot screws set? If you have a hanging idle I'd put them at 3 turns open and then tune from there.

Lastly, how long since the last valve adjustment? If you say you don't know go straight to the Newbie Mistakes link in my signature.

Just checked the valves, they are all in spec.
Vacuum Synchronized the carbs with a Motion Pro tool.
Tuning is being done with an auxiliary tank. I haven't put the tank back on as I haven't tracked down all the vacuum leaks yet.
I've had the pilot screws anywhere from 1.5-4 turns (usually starting at 2.5 and working from there) out trying to get it to settle down.

I will check the air filter and airbox seal.

The leaks I have found with starting fluid seem to be on the front of the carbs. Thats where I get the most response in the revs.

I'll be getting the o-rings and re-cleaning the carbs at that time. I'm jut hoping there isn't something else I may have missed.

 

[Spyderman]

when you say the front of the carbs am i to take it you mean the engine side not the airbox side
i ask because if you have an issues on the engine side and you have new intake boots and o-rings then they are not the correct boots
if they were the correct boots then they would be sealing up correctly at the carb throat and at the head
just a silly question are all the carb sinking ports sealed up???
as well you have said you cleaned the carbs and replaced the jets did you blow compressed air through all the small openings in the carb followed by carb cleaner to be sure that there are no blocked passageways and did you replace all the orings in the carbs after dipping them

 

[ejether]

when you say the front of the carbs am i to take it you mean the engine side not the airbox side
i ask because if you have an issues on the engine side and you have new intake boots and o-rings then they are not the correct boots
if they were the correct boots then they would be sealing up correctly at the carb throat and at the head
just a silly question are all the carb sinking ports sealed up???
as well you have said you cleaned the carbs and replaced the jets did you blow compressed air through all the small openings in the carb followed by carb cleaner to be sure that there are no blocked passageways and did you replace all the orings in the carbs after dipping them

I do mean the engine side
All the parts are brand new Suzuki brand oem
The sync ports are in the boots and they all have the screw and sealing washer that they came with in them
I did spray carb cleaner and blow air through all the ports and jets.

Only non OEM parts so far: I replaced the hardware holding the boots to the head with socket cap screws of identical dimensions

 

[Nessism]

Although rare, it's possible that the throttle shaft seals are creating the vacuum leak. I'm surprised we don't get more of this but fortunately we don't. Replacing those is not trivial but doable.

 

[ejether]

Although rare, it's possible that the throttle shaft seals are creating the vacuum leak. I'm surprised we don't get more of this but fortunately we don't. Replacing those is not trivial but doable.

Thats the one I'm worried about of...
The bike had been sitting for a long time, I got it running again and it was running fine until this. (The rubber bits finally gave up)

Is there a good way to pin point the vacuum leak? Starting fluid isn't exaclty precise. I've heard of using an unlit propane torch but I' haven't had a lot of luck with it.

 

[ejether]

I guess there are not better ideas? I'll see what happens then I get that o ring git from cycleorings.com

 

[ejether]

O-ring came in. I put them in and it looks like the a/f screw orings I had in there had a smaller cord stock size. Also the choke orings were dry and compressed.

Here's hoping that it works!

 

[ejether]

Throttle shaft seals proved to be bad. Major vaccum leaks between #2 and #3, which probably why they were so hot.

 

[60ratrod]

I've done throttle shaft seals, and they aren't fun. fortunately, they are still available as I ordered a full set for my kz1000 which has bs34ss carbs. the hardest part is getting the screws out without buggering up the throttle shaft. get new hex countersunk screws and set them with loctite and you should be good to go

 

[ejether]

I've done throttle shaft seals, and they aren't fun. fortunately, they are still available as I ordered a full set for my kz1000 which has bs34ss carbs. the hardest part is getting the screws out without buggering up the throttle shaft. get new hex countersunk screws and set them with loctite and you should be good to go

New seals and screws ordered. Carbs apart and awaiting parts. I'm not looking forward to putting them back together..

 

[ejether]

New seals and screws ordered. Carbs apart and awaiting parts. I'm not looking forward to putting them back together..

Man, ordered parts are never there when you want them.

 

[60ratrod]

Man, ordered parts are never there when you want them.

I know right? at least when I order from partzilla, the parts are always at my house in 2-3 days. when I get around to swapping the parts on the other hand, is another story. ejether, what I did for replacement butterfly plate screws is I took one of the least buggered screws to my local ace (I usually do all my random hardware runs at ace since they have the best selection of fasteners IMHO) and got a full set of 8 that were the same thread pattern as what came out of the throttle shafts. the ones I used were countersunk allen flat head screws and installed them with blue Loctite(the second time around. the first I used red because I didn't think i'd have to do them so soon). to get the old ones out, I carefully ground off the bulged tip of the original screws, then carefully applied enough pressure to removed them. they are going to be a PITA, because when they bulge the tip of the screw to peen it in place, part of the shank also expands, making them very tough to remove. if you are careful and take your time, you more than likely will not screw up the threads on the throttle shaft.

once you have the carb bodies separated, make sure to label/isolate all of your throttle linkage parts to which carb body they came out of. the linkage parts, throttle shafts, throttle shaft springs, and white end seals all matter where they go back to. but once done, you will not have to worry about those seals for probably another 15-20 years.

I suggest using the aforementioned allen screws since the JIS fasteners are really easy to bugger up when installing or removing.

 

[ejether]

I know right? at least when I order from partzilla, the parts are always at my house in 2-3 days. when I get around to swapping the parts on the other hand, is another story. ejether, what I did for replacement butterfly plate screws is I took one of the least buggered screws to my local ace (I usually do all my random hardware runs at ace since they have the best selection of fasteners IMHO) and got a full set of 8 that were the same thread pattern as what came out of the throttle shafts. the ones I used were countersunk allen flat head screws and installed them with blue Loctite(the second time around. the first I used red because I didn't think i'd have to do them so soon). to get the old ones out, I carefully ground off the bulged tip of the original screws, then carefully applied enough pressure to removed them. they are going to be a PITA, because when they bulge the tip of the screw to peen it in place, part of the shank also expands, making them very tough to remove. if you are careful and take your time, you more than likely will not screw up the threads on the throttle shaft.

once you have the carb bodies separated, make sure to label/isolate all of your throttle linkage parts to which carb body they came out of. the linkage parts, throttle shafts, throttle shaft springs, and white end seals all matter where they go back to. but once done, you will not have to worry about those seals for probably another 15-20 years.

I suggest using the aforementioned allen screws since the JIS fasteners are really easy to bugger up when installing or removing.

I always find that Partzilla is SLOOOW but maybe its just that I'm always ordering the hard to find parts that only come from Japan.
In any case, I've already got the carbs apart, screws out and all. I use the coin trays from a cash register to sort parts. Work really well and the curved up edges make getting the last tiny part out easy, just like a coin.

Parts arrive on Thursday and I leave on vacation Friday AM so I better get it done before I leave or my friend will be mad!

Thanks!



ThaI've already gotten the

 

[ejether]

HEEEELLLLLLP!

Throttle shaft seals replaced, orings all replaced, air box boots and carb boots replaced...
and it's still got vacuum leaks between the carbs.

How I'm testing:
starting fluid through a red straw on specific places.

Repeat:
HEEEELLLP!

 

[Guest]

Possible pinched intake o-ring.

 

[ejether]

Possible pinched intake o-ring.

Do you mean the o-rings between the carb boots and the head? I don't think thats it, when I sprayed starting fluid directly in that area, it doesn't rev. Only whey I spray on the throttle shafts between the carbs.

??