May be on a Harley

[MasterGuns]

Just recently my 86 VR has taken ill. She was running real well and strong until just last week. All of a sudden she seems to be lacking in power throughout the rpm range.

 

I have synced the carbs and they are right on.

 

Suspecting that the boost sensor may have crapped out, I checked the vacuum at #2 and it is good and when reconnecting the vacuum hose to the boost sensor, the rpms pick up. That, as far as I know is a sign the sensor is working and advancing the timing.

 

New plugs installed not too long ago and appear to burning well. New wires and caps as well.

 

Just last night, I pulled the air box top and filter and started the motor. Number two slider (the carb/cylinder providing vacuum to the boost sensor) is not bouncing/moving at all. I will have to pull that carb cover to check out what may be going on or what isn't going on and hopefully I can resolve the problem; quickly.

 

What would be the symptom of one slide not working? I checked out the diaphragms not too long ago and all checked out; no holes, old but no holes. Perhaps the vacuum port that directs vacuum to this slider has somehow gotten clogged or something. Nbr 2 is firing because the pipe gets hot immediately after starting cold.

 

If I can't figure this out quickly, I will still be at the rally; however, I will be on my Ultra.

 

Any ideas or advice about a faulty slide.... I am all ears.

[Squeeze]

Maybe the Diaphragm is torn apart, maybe the Diaphragm sperated form the the Slider (happens), maybe the Slider is stuck (happens).

 

Normally you can move the Slider with two Fingers or carefully using a Screwdriver. If the Slider moves without sticking, you'll find the Culprit inside the Diaphragm Bowl.

[Yammer Dan]

May have blown a diaphragm for some reason. I would check that one again.

[Marcarl]

You might have lost the little rubber o-ring that sits at the bottom of the diaphram cover. You also may have a plugged port, airway, so when you pull the cover clean the ports with some carb cleaner. Seafoam won't help as it only cleans where it can get to, and if something is plugged, it can't get to it. Seafoam also does nothing for airways, so you need to do the carb cleaner thing. I've done 3 1st gens in the last few weeks and it out them back on the road, so, yes, it is an issue and can be fixed.

Warm up the scoot, take off the airbox, and then clean all the ports and airways you can find, leave it for a bit and then do it again, maybe use a little low pressure air to help out. This is not what you would call a carb rebuild, does nothing for parts that are worn or out of adjustment, but does seem to clean the important area to get things running again.

[MasterGuns]

I am ever so anxious to get out here and head home to do everything you guys instruct. I know the slider isn't stuck as I could move it carefully using a screwdriver. Forgot to mention that. I will also use carb cleaner to clean up the vacuum port in that carb.

 

What would be the symptom of a stuck or inoperable slider in only one carb? How would it affect performance? Would it be a subtle effect or drastically reduce performance?

[Squeeze]

Just open that d....d Diaphragm Bowl and look what going on there, or NOT ...

 

You already could have been back by the Time

 

Not that i have anything against you riding your Harley, but this nice 1Gen should be back on the Road were she belongs ...

[MasterGuns]

Hey Squeeze, I will, I will; I have to put in my hours here at the slave pit first.

[Condor]

What would be the symptom of a stuck or inoperable slider in only one carb? How would it affect performance? Would it be a subtle effect or drastically reduce performance?

 

The symptoms would probably be exactely as you discribed. Sluggish, lack of power. #2 is probably getting enough fuel to heat up via the idle circut, but doesn't pull due to lack of fuel at the higher R's. You either have a huge tear in the diaphragm or the assembly has come apart... I think...

[Snaggletooth]

If you don't have new diaphragms and the old ones "look good", like mine did here is something you can try.

 

Mine looked fine holding them up to a light but I didn't think they were quite right. I picked up a can of spray Dip It at the hardware store. I cut the threaded top section off of some gallon milk jugs and dropped the slider assm. inside leaving the diaphragm cupped on the outside. A little masking tape over the metal backing plate to keep it clean. A couple of coats of Dip It on the outer side of the diaphragms and let them sit overnight. Popped them back in in the morning at the bike fired up better than it had and ran like a gasoline soaked cat.

 

I only did the outside not to risk any Dip It peeling off and getting sucked into the carbs.

 

Even though the looked good they most certainly were not up to specs. I ordered new ones and kept the treated ones for spares.

 

If you have one with a tear it can be patched with Liquid Electrical Tape. A patch, it's not a fix. But it will get you by for a while.

 

If you can reach into the throat of the carb and push the slider back with a screwdriver and it snaps right back you may have a problem with the diaphragm. I noticed after my spray treatment that the slider moved back into place rather slowly and about the same with the new diaphragms installed.

 

Anyway, something to consider.

[Venturous Randy]

With the bike at idle, spray some starter fluid up under the carbs around the runners into the heads. It sounds like you may have a vaccum leak to me, even though the carbs synced.

RandyA

[MasterGuns]

With the bike at idle, spray some starter fluid up under the carbs around the runners into the heads. It sounds like you may have a vaccum leak to me, even though the carbs synced.

RandyA

 

 

What are the runners? Thanks

[Dano]

They are the intake manifolds, the black rubber boots just under the carbs. If it's leaking at the carb/manifold junction, you're pulling vacuum below that when you are synching, so you are just compensating for the extra air coming in above that.