Cleaned Carbs - Can't Set Idle

[Steve]

This rings a bell - the lifter arms that pull up the enrichment plungers can be fitted upside down. It's a subtle difference but it affects running.

That is only on the VM-series carbs, not the BS-series carbs that are in question.

The "choke" activation is completely different, nothing can be installed backward.

However, if the wrong parts might have been soaked (for any length of time), they could have been destroyed.

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[DaveP]

OK, so it's running fine now but the idle creeps up after it gets warm, that's a pretty good sign of a vacuum leak. If you've replaced the o-rings between the carb boots and the cylinder head and those boots are supple and not cracked, the next place to expect finding one is where the intake side of the carbs mates up to the airbox. On my bike it takes just a little extra effort to get those right. The sleeves that fit over the throat of the carbs need a bit of attention to make sure they're well seated onto the carbs, I coax them into position by grabbing the lip of them with a pair of needle nose and moving them onto the throat of the carbs for a good seal. Working from there back making sure the clamps are properly tightened is important and making sure the air cleaner cover has a good seal is also important. There was a strip of foam on mine that had degraded over time, some weatherstripping from the hardware store took care of that problem.

Intake boots and o-rings are in good shape. No rubber bits were dipped including the choke plungers. Airbox side looks ok, but I will need to get some spray and see if I can sens any further idle change due to a vacuum leak.

Nothing is sealing the airbox other than the two slide on clips that hold the lid to the box. Nothing else would be expected there per the parts diagram.

This morning, turned the pilot screws closed by a half turn, so now 2 turns open. Started fine and idles nicely for about 10 minutes before the idle started to ramp up.

Should also add that the tank is off the bike this whole time and running off of a portable tank with the golf tee stuck in the vacuum line.

Dave

[LAB3]

Nothing is sealing the airbox other than the two slide on clips that hold the lid to the box. Nothing else would be expected there per the parts diagram.


Dave

You probably wouldn't find that seal on the parts fische on mine either, it's glued to the underside of the lid where it mates up to the rest of the airbox. In my case, a bike that was garaged for 22 years before I bought it, there was a just a small remnant of foam left and a strip of goop where that foam had once been bonded on.

[DaveP]

I think I have things straightened out, but not sure if I can do anything to make sure the problem doesn't persist.

Removed the choke and throttle brackets from the carbs again and the engine was running perfectly. Idling at 1,400 RPM and would react appropriately to throttle input. Went ahead and completed the carb syncand thought I was ready to go.

Reinstalled the throttle cable bracket, still good.

Reinstalled the chock cable bracket, RPM's started to climb again. Pushed in the choke plungers manually (pushed the end of the rod that connects the 4 chock plungers) and idle settled back down. It is just fractions of an inch that I can play with the choke plungers to either have the engine run correctly or accelerate with a little bit of chock added.

It is a simple push pull system for the choke. Not sure how to make the plungers reseat better.

The chock cable is fairly new. It was provided by the PO uninstalled when I bought the bike.

Happy with how it is running right now, but consistency without input would be nice.

Dave

[1948man]

Did you make sure there is a tiny bit of slack in the choke cable before it starts to actuate?

[DaveP]

Did you make sure there is a tiny bit of slack in the choke cable before it starts to actuate?

I have fiddles with it. A little bit of slack is present. It may have been not tracking well in the grove where the cable is anchored. Re-positioned so that it tracks better and will see how it goes today.

[tom203]

I’d guess one or more of choke plungers ain’t fully retracting when you close choke cable..until you manually push on them. Sadly this is impossible to determine which one could be the culprit with carbs mounted. Any one plunger hanging slightly open will give you an erratic idle.

[DaveP]

Definitely the chock plungers, but good to go now. Synched the carbs, put the tank back on, and out on the road for a 20 mile loop. Running well.

Thanks for the suggestions.

Dave

[steve murdoch]

Good to hear you got it sorted.