Can't get her to idle without choke

[GS1000HiAltitude]

Does anyone know if the boots from the carb to the airbox should be replaced? They aren't damaged but I can see they aren't sticking to the air box (they can be rotated). I have a 1978 GS1000E with a 1100 bore kit installed. I have the original VM26 carbs. I replaced the o rings in the boots from the engine to the carbs and I have the original air box and am using a K&N filter in it. I've adjusted the valves too. I can't get her to idle without the choke on which I am led to believe is a likely clogged pilot jet? I don't see how this is the case since I rebuild the carbs completely and it never idled without choke on from the get go. I'm at 5,200 feet but I don't see that being a problem, at least not idling at all. I've been working on the machine for 5 years now and would love to ride the thing at some point. Any help would be greatly appreciated.

[rphillips]

I'm known for asking silly questions,... Oh yeah, Welcome... but here goes, how far have you screwed the idle adj. knob in? how far up does the choke need to be for it to keep running? barely, half way, full choke?

[GS1000HiAltitude]

Thanks for getting back to me. The idle adjuster is now out of adjustment I'm sure, since I had it set after rebuilding the top end. I just adjust it to keep the idle around 1500 (I know this is fruitless because of all the other variables) and I have the choke fully open as it warms up. If I lower the choke it starts to stumble about halfway down and then dies almost immediately when I drop it all the way and that is even if the engine is warmed up. Doesn't really seem to matter how warm the engine is. I have the fuel screws 2 turns out and the air screws 2 turns out as well. I have fiddled with the screws ad nauseam. The carbs have been rebuilt (by me) with the kits available online. I didn't get the cheapest kit but I'm sure it's made in China.

[GS1000HiAltitude]

Sorry, but when you say idle adjuster do you mean the knob to adjust the throttle cable under the carbs? Apologies, I'm new to fixing/tuning bike carbs or restoring bikes for that matter.

[GS1000HiAltitude]

Ok, thanks for the help....

[alke46]

When you say you have rebuilt with kits......that makes me skeptical because we do not use kits in these carbs, just new o-rings. Did you soak each carb (completely broken down) in Berryman's carb dip for 24 hours each? And then did you run small wires through each and every passage? Followed by spraying carb cleaner though all passages? Then use compressed air to blow everything out?

There's a lot to do when cleaning is done properly. Short cuts will give you the opportunity to do it again soon.

[KEITH KRAUSE]

If the bike needs choke to start, even when warm, then it sounds like the pilot circuit isn't passing enough fuel at one or more carbs.
The pilot circuit in your carbs has several small passages and they clog easily, especially the small hole directly above the pilot fuel screws tip and the other small hole next to it. Look inside the carb throats at the bottom of the bore and you'll see them. These two are the most easily clogged or "varnished" by old fuel, non-operation, etc. You must clean and VERIFY that you see carb spray pass through those holes. Also, verify the air jet at the filter side is clear. Make sure all screws and o-rings are removed before spraying/verifying. The spray can harden the rubber.
Adjust float levels to .95 which is in the middle of the float level range. Verify all jetting is stock, including jet needle e-clip position. The loose intake boots between the filter and carbs will make the bike run a little leaner, which worsens your situation. It also allows dirty air inside. Have the clamps stretched and are at their adjustment limit? Is the K&N filter oiled properly? Once these things are taken care of the side air screws must be adjusted using the highest rpm method. Start with them 2 turns out. Also, your bike idles correctly at 1,000-1,100 rpm's. 1,500 is too high and compromises side air screw and pilot fuel screw adjustments. Set the throttle adjustment knob so it idles as I said. With the side air screws at 2 turns out, bike on the center stand is best, the bike fully warm and idling at the base rpm I said, start with carb number one and slowly turn the screw in either direction to achieve highest rpm. Then adjust the rpm's back to the base idle using the throttle adjuster knob. Repeat to remaining carbs. As for the pilot fuel screws, they are set at the factory using emissions equipment. Their adjustment will vary depending on each cylinder condition. On a stock bike, they are generally set between 1/2 and 1 full turn out from LIGHTLY seated. Considering your elevation, I would set them at 3/4 turn out and test from there.
Once the above is done, I suggest a vacuum synch. A bench synch is better than nothing but rarely gives good results. Bench synch the carbs carefully, set the throttle adjuster knob up a few turns so the bike will start, then do the vacuum synch.
A lot to do I know, but it's necessary when tinkering with these old carbs on these old bikes, especially when you don't know who has been working on the bike in the past.

[GS1000HiAltitude]

Thanks, Keith for your detailed description. I did rebuild the carbs with my limited knowledge (I used a Suzuki shop manual) but I most likely missed cleaning the pilot screw as much as was needed. I will give that a try and see what happens. I did buy a vacuum synch and, obviously, just need to get her to idle before I can use it. My first project will be to pull the pilots and clean them thoroughly and go from there. Thanks again for the help. Fingers crossed.

[Nessism]

The pilot fuel screws should be open no more than 7/8 of one turn. At 5000' elevation, 3/4 might be better. 2 turns open is way too much.

[zed1015]

. The carbs have been rebuilt (by me) with the kits available online. I didn't get the cheapest kit but I'm sure it's made in China.

You should junk the chinese jet kit and replace only with Genune Mikuni or Keyster..
There's a very good chance it's the source of your issues.

[phydeauxmutt]

Considering you have VM carbs, my first suspect would be broken tips on the pilot fuel screws.

VERY easy to break them off when "lightly" bottoming them to count turns going back out.

[Rob S.]

...junk the chinese jet kit and replace only with genuine...

I agree.........

[GS1000HiAltitude]

Thanks for all the help guys. I opened up the carbs bottoms and looked at the parts in there. I noticee that I put one of the float needles in backwards (doh). I don't know how that would effect the idling but I plan to clean and soak everything again and blow out with air and, hopefully it will run nicely. Fingers crossed. Thanks again for the sage advice. I will let you all know the end results.

[salty_monk]

Not sure exactly but it would either starve or flood it!

It's either a blocked idle jet, wrong settings or air getting in somewhere.... At your elevation you should be running rich if anything. (and yes a good seal on everything at the airbox is important).

Good luck!

You will find this useful https://gsarchive.bwringer.com/bikec...rb_rebuild.pdf


Also the index page - https://gsarchive.bwringer.com/

[gustovh]

Your bike might not idle until properly synced. Don’t forget to clean out the holes in the carb bowls that the pilot tubes fit into, if one or more is plugged you have idle issues as well.

V