Idles at 5k after clearing a pilot jet??? HELP!

[gs45082]

Hey guys I?m stumped here. I?ll give you the TLDR first: R&R?d carbs, unclogged one pilot jet, revs will not drop below 5000 RMP when started.

Bike is a 1982 GS 450 TXZ, with the BS34SS (CV) carbs. Running pods and straight pipes, 135 mains (vs 115 stock), and needles at stock height. Idle air screws are both at 1.5 turns out. Valves were adjusted weeks ago. With this configuration it runs great at higher RPM/high load and had a really low lumpy Harley-ish idle. It has always started easy, hot or cold. But it had a pretty loud afterfire when you closed the throttle at high RPMS, and I was under the impression that upping the pilot jet by a size would help or cure the afterfire. It also had a little kind of a burble or flat spot that came and went at sustained speed, but I think that?s due to a questionable plug boot.

So I pulled the carbs (I had forgotten that the pilot is located in the bowl of these carbs) and removed the pilots, and discovered that the cylinder 2 pilot was completely blocked. Air tight. The other pilot was fine, and with a little cleaning the blocked one was good to go. I replaced the old pilots with the upsize 47.5 pilots, put the bike back together, pods and all (expecting to take it on a test ride), and it fired right up as usual with choke, then revs immediately climbed to 5000. Turned off the choke and it falls flat on its face like it usually does when first started and very cold. Turned it off and backed the idle adjuster until it lost contact with the butterfly shaft, confirmed that the throttle cable was slacked, and visually verified that the butterflies were closed. Slides rise and fall nice and smooth just like always. Tried different combination of choke, throttle, mouth holding, etc., but nothing changed. Twist the throttle it revs right up, and falls right back to 5,000 RPM.

Going back to the last good configuration (except without a blocked pilot), I put the old pilots back in. Fired her up and the exact same thing happens. Revs straight to 5k. Acts just like you were holding the throttle, nice and smooth, both cylinders running fine, just free revving. It seemed to me that a vacuum leak would usually not affect both cylinders and probably wouldn?t run so nicely, but the ether squirting around the intake pipe trick didn?t turn up any leaks. Just to be sure I hadn?t screwed something up seating the carbs, I pulled the carbs back out, warmed and lubed up the boots and re-installed, once again no change.

I pulled the carbs back out and opened up the diaphragms, thinking maybe the needle had come unclipped or there was some mechanical interference but nothing was out of the ordinary.

I left it there yesterday, I think my next step will be to put the dry carbset back on, and while cranking with the ignition on spray ether around the boots and see if it tries to fire. Could it be anything else going wrong? I?m really stumped at this point, it was running like a top Monday night when I brought it to the shop, before I tore it down.

Sorry for the long post, I was trying to get all the details in there. What the heck is going on here?

 

[tom203]

So the throttle plates appear just about closed and yet idle rpm takes off...leaky "choke" plungers ,leaky carb boots,or leaky o-rings at carb boot/head interface.

 

[gs45082]

Throttle shaft is sticky. Think that's my problem! Boom!

Now for the fun part, tearing it all apart

 

[gs45082]

Overdue update: I freed the throttle shaft (still not completely sure what exactly was binding), and there was NO CHANGE!! Ordered new Suzuki intake pipes, with new O-rings, and again no change. There is no vacuum leak between the carbs and the head, it is air tight. I'm starting to think there is something wrong with the carbs, but nothing adds up. Throttle plates are completely closed, and it still fires right up and purrs right along, only idle is about 4000 rpms too high!

Any ideas from the carb gurus??

 

[chuck hahn]

Leaky rubber plugs over the pilot jets will let a little extra juice slide by...maybe recheck and twist them in nice and tight???? Cable routing pulling the throttle open???? What about the cables at the grip.....grip returns fully to the untwisted stop?????? Cables have just a little slack at the crab throttle linkage??? Maybe try readjusting the cables down there???

 

[exdirtbiker]

when you wick the throttle open, it will stop when the carb slides "hit the roof". WHACK.
let go... let the springs slam the carbs closed.
CLACK ! when the slides bottom out. find the idle adjusting screws? remove them. leave them off for a minute. try it again.
If no change, then I'm stumped

Edit- I didn't realize you have CV carbs. above still applies, but it sounds different.

 

[gs45082]

Leaky rubber plugs over the pilot jets will let a little extra juice slide by...maybe recheck and twist them in nice and tight???? Cable routing pulling the throttle open???? What about the cables at the grip.....grip returns fully to the untwisted stop?????? Cables have just a little slack at the crab throttle linkage??? Maybe try readjusting the cables down there???

The throttle plates are closing completely, the cable is slacked and idle speed adjuster is backed out to the point it doesn't contact the throttle. What plug is over the pilot jet?

 

[gs45082]

when you wick the throttle open, it will stop when the carb slides "hit the roof". WHACK.
let go... let the springs slam the carbs closed.
CLACK ! when the slides bottom out. find the idle adjusting screws? remove them. leave them off for a minute. try it again.
If no change, then I'm stumped

Edit- I didn't realize you have CV carbs. above still applies, but it sounds different.

I'm thinking you're onto something here. When you start it up, you can see the slides lifting as soon as the motor catches, they bounce a little but stay around a quarter of the way up. Whack the throttle and they go wide open no sweat, then settle back down to that 1/4 of travel position. Acting just like the butterfly was slightly open.

What do you mean about the idle adjustment screws? Just remove them and see what happens?

 

[60ratrod]

there is supposed to be a rubber plug that goes into the pilot jet tube to prevent excess fuel from flowing through the pilot circuit. the pilot system is fed off of the main jet circuit until the needle starts moving at about 1/4-3/8 throttle, providing a straighter shot for the fuel to flow into the motor. otherwise, below that range, the engine is running off of the pilot jet circuit, including the choke circuit. if you don't have that plug, the carbs will dump way more fuel than it's supposed to dump in.

this is the plug in question

 

[gs45082]

there is supposed to be a rubber plug that goes into the pilot jet tube to prevent excess fuel from flowing through the pilot circuit. the pilot system is fed off of the main jet circuit until the needle starts moving at about 1/4-3/8 throttle, providing a straighter shot for the fuel to flow into the motor. otherwise, below that range, the engine is running off of the pilot jet circuit, including the choke circuit. if you don't have that plug, the carbs will dump way more fuel than it's supposed to dump in.

this is the plug in question

Hmm, I need to look at that, however the bs34ss looks a lot different. As you can see in the picture, the pilot and main jets are actually housed in the bowl, the pilot screws in from the top and the main from the bottom through the drain plug. Where would that rubber plug be located on mine? I may need to snap pictures when I take it back apart.

 

[JTGS850GL]

No pilot jet plug on a 1982 450TX that I'm aware of. I think the pilot jet pulls from it's own fuel well.

 

[exdirtbiker]

another "out there" guess...
I had more than one "used bike that never ran worth a %$#@" ... come to me with the main jet laying in the bowl. It fell out while running.

Also - did you make -very- sure your floats are adjusted to correct fuel level, and is the float needle / valve actually sealing to prevent "bowl overflow" ?

and if I guess what the problem is, do I win a prize ???

 

[60ratrod]

I didn't know that there's a totally different bs34ss that's used on the 450's. I was just kinda assuming that all bs34ss's were the same, just different numbers of them and different jetting for the engines. the more you know..... and knowing is half the battle

 

[gs45082]

another "out there" guess...
I had more than one "used bike that never ran worth a %$#@" ... come to me with the main jet laying in the bowl. It fell out while running.

Also - did you make -very- sure your floats are adjusted to correct fuel level, and is the float needle / valve actually sealing to prevent "bowl overflow" ?

and if I guess what the problem is, do I win a prize ???

Good thinking but yes floats are set per the manual and needle valves don't leak, every time I mount a set of carbs I flip them upside down and blow in the fuel line to make sure they close!

Should I drop you a Budweiser in the mail as a consolation prize?

 

[Brodavid]

Have a 1982 gs450t doing exactly the same thing. Similar results pulled carbs airbox checked everything can't figure out why the idle won't come down. Any help would be appreciated

 

[gs45082]

Have a 1982 gs450t doing exactly the same thing. Similar results pulled carbs airbox checked everything can't figure out why the idle won't come down. Any help would be appreciated

Hey I got it figured out, the carbs were so badly out if sync one was held open quite a bit. Been riding her around on some errands, feels like a dirtbike after the gs1000 around for weeks.

@Brodavid, are you absolutely certain the throttle cable is slacked? What changed when it started idling high?

 

[gs45082]

Here's a pic

 

[Brodavid]

Original problem was that it started and ran and installed when shifted into gear brought it home checked everything out pull the carbs clean the carbs inside and out put it back on and the idle was high. Check the slack in the throttle cable and took the throttle cable completely off the idle went down but then it chugged installed. Took the carb apart again and did a more thorough cleaning pulled diaphragm slides needles pilot jet everything I could think of the carbs spotless. We did the airbox check the throttle cable we ran it so it was no problem with the cable put it all back together and it still idles at 5 grand. Also check the sync bench check that and it seems fine.

 

[60ratrod]

Bench sync is a good starting point, but a vacuum sync should get rid of the idling problem. A bad sync will mimic vacuum leak issues

 

[Rob S.]

You said starting on full choke causes 5k rpm rev, then turning the choke off kills it?

What about slowly backing the choke down a bit at a time?

It's normal, according to Cycle World, for my bike to start instantly on full choke, with idle then climbing to 4500 rpm and rising unless the choke is quickly backed off to about half.