ADVrider

ADVrider (http://www.advrider.com/forums/index.php)
-   Airheads (http://www.advrider.com/forums/forumdisplay.php?f=85)
-   -   The trouble(s) with this '81 R100 Airhead (http://www.advrider.com/forums/showthread.php?t=657820)

Rapid Dog 02-06-2011 10:04 AM

The trouble(s) with this '81 R100 Airhead
 
1981 R100RS recently gone thru, fresh heads, coils, wires, plugs, dual plugged.

Weird buzz in '81 R100 on start.
I've been fiddling with the carbs, starting the motor alot.
I've had the starter rebuilt as a note. Also a new ICU under the tank.

I noticed a few times (and this is a new one) that when I push the start button I hear a buzzing sound under the tank, like a relay or something, just before it wants to actual turn the starter motor. This is intermittent.

What's that? Is it a starter relay going south?

Rebuilt carbs won't adjust.
Soaked the carbs in Pinesol for 48 hours (disassembled).
Blew out all the passages with compressed air and reassembled with al new o-rings and float needles (shot).
The right side is still sputtering and backfiring at idle.
Anything below 2500 RPM and it surges and sputters.
WFO it seems to run good but of course, backfires when you shut the throttle.
I even ran it around the local loop with the synch port rubbers of by mistake, didn't seem to make much diff in the way it ran. Weird.

While synching I see that the right side idle screw doesn't seem to have any effect on the Twinmax readout when adjusting it. Checked cables for free play etc, cables are new. Diaphrams are good.

Worn out idle screw? I'm going to order up a new one for both sides Monday.

Generator stays on light dimly.

This is minor but the gen light never seems to go completely off even at highway speeds. I've cleaned all the contacts, battery is charging.

Haven't figured this one out at all.
As a note, the voltmeter goes whack and pins of and on on the + side, I have a fresh one coming this week, we'll see how that pans out...


Neutral light inconsistent.

Half the time I have to pull in the clutch to start as the neutral light does come on., sometimes it does. Totally intermittent.
I cleaned the clutch switch at the lever, it works fine. Cleaned contacts at both ends of the neutral switch wire.

Do these switches act up or just die?

Any insight from those in the know is appreciado..
.:ear

fishkens 02-06-2011 10:23 AM

Weird buzz in '81 R100 on start.
Starter relay? Sure sounds like it. Remove the tank and put your finger on the relay when trying to start. If the buzzing is coming from the relay it's probably on its last leg. You can take it apart and clean it but it's best to replace it.

Rebuilt carbs won't adjust.
Idle screw? If turning it doesn't affect the idle speed then the circuit seems to be clogged. Try blowing it out.

Generator light on dimly.
Dim alt lamp? I had that condition for years. Tried cleaning contacts, etc. It finally went away when I replaced the diode board with Rick's. Not certain if it was the board or contacts but that fixed it.

Neutral light inconsistent. Do these switches act up or just die?
Yep. My guess is that you'll be pulling in the clutch lever more and more until it's 100% of the time and the neutral light never lights. Bad neutral switch at the tranny. They go bad regularly.

Country Doc 02-06-2011 10:24 AM

I had almost that exact same carb issue on my slash 5. Turned out that there was a tiny, tiny, tiny little passageway JUST behind the butterfly that sprays fuel for idle and just off idle, up to about 2k rpm where the main part of the needle takes over most of the fuel delivery.

I forget the name of this passage. I could not even see it on my carb, as it was just gummed up flush to the surface of the carb throat, and was invisible. I needed a magnifying glass, tiny sharp needle, and I had to compare side by side with the other carb to figure out where the hole was supposed to be.

Ok, correction , all this troubleshooting to find the passage was actually done by bmwrench, after I tried to sync my carbs and adjust them a thousand times and couldn't get the thing running right.

maybe worth a look.

dc

supershaft 02-06-2011 10:32 AM

Take the tank of and see which one it is. It can't get much simpler than that.

Did you make sure the two small holes in the carb for the idle circuit are positively clear? It takes compressed air IMO. IF your carbs are good , you have got leaking valves. Listen with a leak down tester. They will not idle right with leaking valves.

Test the diodes. Make sure nothing is grounding on the hot side of the diode board. Make sure none of the other wires are shorting out somewhere they are rubbing on something. Just LOOKING is a good test for this. Make sure your brushes are making good contact. Find a good rotor to try. In this situation, testing it might not show the problem.

When the light is acting up, test the switch at the leads. If it tests good you have got to trace the wires. It's probably the switch.

Good luck!

Rapid Dog 02-06-2011 11:32 AM

Take the tank of and see which one it is.
Trouble is, the buzzing is new, definitely under the tank, but doesn't happen all the time.
Charged the battery overnight.
Just went out there and removed the tank. Hit the starter several times, no buzz...weird. I have a feeling it's got to do with lack of juice from the battery.

It takes compressed air IMO.
Yes, shot a good blast straight up he idle screw hole, gas sprayed everywhere..:D

test the switch at the leads

I'll give that a try for sure.

supershaft 02-06-2011 11:41 AM

That in no way guarantees that those wholes are open. You have to block the mixture screw and the idle intake at the back of the carb at the same time and then squirt air up the pilot jet boss look and see it BOTH holes are working.

Good luck!

SOLO LOBO 02-06-2011 11:54 AM

Quote:

Originally Posted by supershaft (Post 15124911)
That in no way guarantees that those wholes are open. You have to block the mixture screw and the idle intake at the back of the carb at the same time and then squirt air up the pilot jet boss look and see it BOTH holes are working.

Good luck!


Another way to tackle this is to use carb (or brake cleaner), insert the plastic extension tube into the various carb body passages and spray.. then block the hole the spray exits with your finger and spray again, and then reverse direction.


IIRC, the idle passage exits in two places, in the throat of the carb as well into the body.. you need to pull our the needle jet and mains for that one.

But, as said above, if the idle screw doesn't do anything, you do have a blocked passage. No if, ands or buts about that.

supershaft 02-06-2011 12:33 PM

Quote:

Originally Posted by SOLO LOBO (Post 15124997)
Another way to tackle this is to use carb (or brake cleaner), insert the plastic extension tube into the various carb body passages and spray.. then block the hole the spray exits with your finger and spray again, and then reverse direction.


IIRC, the idle passage exits in two places, in the throat of the carb as well into the body.. you need to pull our the needle jet and mains for that one.

But, as said above, if the idle screw doesn't do anything, you do have a blocked passage. No if, ands or buts about that.

Actually the idle circuit is completely separate from the passage way that goes to the atomizer on top of the main jet stack. The other whole in the back of the carb is for the idle circuit.

boxerboy81 02-06-2011 04:17 PM

http://www.advrider.com/forums/[IMG]..._Diagram-1.gifI would use something soft that won't damage the jets and circuit, like fishing line, and feed it in and out of the two holes that effect the idle circuit, #1 & #2 in the picture. Then I'd spray it thru with carb cleaner and compressed air.

http://i228.photobucket.com/albums/e..._Diagram-1.gif

supershaft 02-06-2011 07:03 PM

Quote:

Originally Posted by boxerboy81 (Post 15126890)
http://www.advrider.com/forums/[IMG]..._Diagram-1.gifI would use something soft that won't damage the jets and circuit, like fishing line, and feed it in and out of the two holes that effect the idle circuit, #1 & #2 in the picture. Then I'd spray it thru with carb cleaner and compressed air.

http://i228.photobucket.com/albums/e..._Diagram-1.gif

That diagram doesn't show the air jet at the back of the carb and its path to the idle jet. It's very important!

Rapid Dog 02-07-2011 08:04 AM

...cconcerning the 'slow jet' or idle jet (internal), it has a spring like the idle mix screw (external). When I installed this I screwed it all the way in.
Is that correct?

Rapid Dog 02-07-2011 09:27 AM

Generator light stays on dimly.

I've removed the alternator and rotor, checking all connections to be clean in the interim.

According to Antoine's website and others, resistance should be between 3.4 and 3.74 if the rotor is 'good'. Rotor measures resistance at 3.9 ohms.

Quote
"Lower rotor resistance means that charging can begin at lower RPM. There's no reason no reason to use earlier, higher resistance rotors except that the larger diameter of the /5 rotors (smaller air gap between rotor and stator) gives more power.

Interestingly enough, the bulb for the charge light (which is in series with the rotor) changed in wattage over the years in keeping with the varying rotor resistance."


I was told by the PO that the bulbs had been replaced in the gauge cluster with new bulbs.
Could it possibly be that the bulb is the wrong type so it reads wrong due to the 3.9 ohm the rotor is showing?
I am suspect of the replacement bulbs because I can see that the high beam blue lens on the tachometer looks melted...

supershaft 02-07-2011 09:42 AM

The isle jets don't have springs.

It sounds like you need some manuals RD?

Your rotor is testing good but they very often test good when they are not. That is why I recommended that you test it last because you often need a known good rotor to try to see if that is it. Rotors can work when they are static. The problem is that they need to rotate to work.

I don't know about the instrument lights. I do know that too hot is too hot and probably too bright? I have never experimented with different watt charge bulbs.

Rapid Dog 02-07-2011 10:10 AM

...looking at the Clymer manual it shows a spring on the idle jet (internal), which indeed mine has...check your manual Super.

Quote:

That is why I recommended that you test it last because you often need a known good rotor to try to see if that is it. Rotors can work when they are static. The problem is that they need to rotate to work.
I understand that they rotate and can become non working dyamically. I don't understand what you mean by 'test it last'.

I have the parts out of the bike now...so, rotor measures as good per the Clymer manual.

supershaft 02-07-2011 11:17 AM

That is the mixture screw, not the idle jet.

Test it last because you don't need a known good part to test the rest.


Times are GMT -7.   It's 05:14 PM.

Powered by vBulletin® Version 3.8.5
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Copyright ADVrider 2011-2014