Inside two cylinders not firing?

[datter]

Hi all, my bike ran pretty well last season with the exception of an intermittent thing with one cylinder not firing. The right handside inside cylinder would just occassionally not fire, and I could tell as that pipe was cool.

I'm just trying to get her sorted out for the spring now after she spent the winter covered in my driveway. On firing her up I now find that both inside cylinders do not fire at all. I managed to get it running briefly on just the two but there was a lot of excess fuel and backfiring, of course.

Any suggestions about where I should start looking for the problem? I've ridden most of my life but repair and whatnot have never been a strong suit.

Thanks
datter

[fvincent]

Inside Two

Start with the coil circuit. Coil itself wires ETC...

Floyd

[datter]

I've got the tank off and have poked around a bit for loose connections and things like that. Everything that should be attached seems attached, though I'm not entirely sure how to go about actually checking the coil itself to see if it's working properly.

All the fuses seem ok too, for whatever that's worth.

[datter]

hmm, can a near dead battery cause troubles like this somehow? Mine is definitely in need of a charge.

[trbig]

Under the left side cover, your pickup coils are located. The wires get brittle over time and break while moving back and forth from the vacuum advance. The wire is probably cracked somewhere. Do a search for pickup coil repair. One of these pickups operates 1&4 cylinder... the other one operates 2&3.

BUT... that being said, if the bike was running fine when put away and now is just started the problems, it could be corrosion somewhere. You'll need a multi-meter to check continuity between things. "Looking ok" doesn't really mean anything on electrical connections. It's just a game of hide and seek to find it.


Tod

[datter]

Well I'm now charging my battery as it was nearly dead, and will look into the pickup coil wiring as soon as I can find them. Under the left side cover you say? All I find in there is the cavern my battery was in, though I may be misunderstanding.

Before I continue with that though, I need to sit for a bit as I just cut my hand open on a related matter. Sweet.

[xswilly]

he means the left side cover of the motor
when you take it off you will find the pickup coil wires under it along with the vacaum advace can

hope this helps

[datter]

ah that makes more sense. If I hadn't drank so much whiskey last night I might be quicker on the uptake. I'll look into it as soon as I stop bleeding.

[mitch]

Help

You have a great resource close to you by the name of Bruce Doucette phone him im sure he will help you out. You might need to clean the carbs as well. Bruce can be reached at 1-902-827-3217
Doug

[fvincent]

Coil pickup

Ya could be. Search for the thread on checking your coil primary & secondary resistances. Another trick is to swap the coils, but its tricky. If the problem follows the coil, you nailed it. TC knows how to do that but I cant volunteer anyone

Floyd
'80G

[mitch]

East Coast

Us east coast boys stick together Floyd im sure bruce wont mind He knows them old bikes inside out and backwards, if he cant get it right its a parts bike.
Doug

[fvincent]

Wire

I think you nailed it with the pickup wire thought. As I recall from a thread of the past, the best replacement wire for that is the test lead wire used for multi meters. Got mine at Radio Shack for $8.00 for a pair. Loosely twisted core, hard to break.

Floyd
'80G

[datter]

Well I took the left side cover off and had a look. There are some very soft, supple (sp?) wires in there, white and blue if I recall correctly... and they don't appear cracked or otherwise worn. A length of them is covered with some cloth like covering... very nice set up in fact, and I'm inclined to think it's new.

I didn't see any means to check their validity with a multimeter as there was no bare wire to get at.

[TopCatGr58]

Hey Datter,

The 81 series ONLY uses a mechanical vacuum advance mechanism, the cent. adv. is built into the TCI! SO...the timing plate and wires don't flex anywhere as much as they do in the earlier systems, and are less likely to get damaged!

SO....first, YES a weak battery can cause problems. Sitting outside in the weather can also contribute to corrosion in the connectors. You need to pull the connectors for the coils, inspect for corrosion, clean, apply dielectric grease and reconnect. Before reconnecting, get a mulitmeter, and check the resistances of the + and - connectors....this is the primary coil....should be about 2.5-3.0 ohms. Next, put the meter into the ends of the two plug caps for the 2-3 coil, depending on type of caps and their resistance, it can read from 15K up to 25Kohms. Remove the caps from the plug wires...they unscrew. Check for corrosion in the wire ends, if green/white corroded, can cut off a 1/4" to expose clean wire. Clean the INSIDE of the plug cap where it fits onto the wire. DON'T use Dielectric grease,can actually prevent continuity when it gets inbetween the wire and plug cap screw!

Also, while cap is OFF, check it's resistance, shouldn't be more than 5-8 kohms, if higher, or open, then plug caps or the internal resistor is bad/corroded. They can be taken apart, little screwdriver into the spark plug end and then you can access the resistor, clean contact surfaces, retest, etc.! IF bad and can't get good continuity after cleanin,g then REPLACE plug cap with NEW.

Same thing for the coil. There is a tech tip on being able to replace the OEM coils with inexpensive ones from MikesXS!
T.C.

[datter]

Well, I'm printing some of this stuff off for later reference and will see how it goes. The battery is charging now so it should be good to go by the time I get home. I'm hoping that magically fixes the problem somehow, but I'm not really expecting anything.