intermittent starting

[evdog]

So first time on this form and i have not found anything related to this subject and i seems as though there are some smart fellows out there.

I have a 1982 heritage special 650 all stock except for the proper ngk plugs with proper gap and the problems is this; i go to start it and sometimes it starts within two three rotations of the engine. Other times it takes five or so seconds to fire, yet other times i crank it, stop, crank it, stop because it will not start. leave it for a minute or five and it may start or may not. If i use the kick start it starts every time without fail. The bendix gear and spring have been replaced. A known good/fully charged battery has been used and also another battery wired in to make sure that there was plenty of juice. At 1.5 turns of the air/fuel mixture screw the problem is there also at 2.0 turns and 3.0 turns. It has one coil for the bike with two wires, of course, so I was thinking of testing the wires but they do not look like they just unplug from the coil. The only one thing that stands out a bit is at idle there is a pop out of the exhaus every now and again at idle.

Any insight would be great thanks

 

[gggGary]

This simplified diagram (found in tech) shows how it is wired.

The TCI acts like electronic points and advance, making and breaking the ground path of the coils. The 12 volts from the battery goes though the main fuse to the ignition switch then to the kill switch finally on to the hot side of the coil. ( there are 4 or 5 connectors in that path also). So a weak contact or connection anywhere in the circuit can reduce spark enough to make hard starting, especially when the starter motor puts a big load on the battery. That current has to return to the battery through several ground wires and connections also. Your ground strap and other ground connections should all be cleaned and checked.
Yes the HT wires are permanently bonded to the coil. Do not crank the bike unless you have grounded plugs in the caps. Check voltage at the coil red wire when cranking, what is it? Is the spark bright and blue when cranking the engine with the starter?

The stock fuse box is a notorious weak spot, the fuse holders rot and crumble making poor electrical contact.

Everything is 30 plus years old several things may be succumbing to old age. Contacts inside switches often corrode making poor connections

 

[Macmorgan]

Great web site with a lot of info. Have a problem w/82 XS650. I won't go into all the issues found on this friend's bike but right now I cannot get a continuous spark. Looking at a grounded plug and pushing the starter button gives me a one spark and then nothing. If I keep pushing the starter button I get a spark for every push but nothing continuous if I hold the button down. Any thought would be appreciated. Rotor's new, ign. box looks good inside. all connectors have been checked. Took side-stand switch out of harness because it was intermittent and put jumper in plug.

Any thoughts would be much appreciated.

Mac Morgan
Hockessin, DE

 

[jd750ace]

Same as above really. You are getting too much voltage drop in your start cycle when using the starter. Normally this can be verified by volt meter, but if it kick starts easily, then you need to check your ground connentions and your primary leads, both the hot and the ground, for corrosion and loose connections. You can lose as much as 2 volts across multiple poor contacts, and the TCI likes a good positive 11.5 volts or more to work well.

 

[gggGary]

One spark only, means you don't have a working TCI or pick ups. go through the factory trouble shooting procedure, it basically tests if everything is working except the TCI, if everything else works then the TCI "is the problem" swap in a known good unit to confirm.

 

[Macmorgan]

This bike had belonged to another friend who had a number of problems with it:

Leaking T fitting
Inop fuel petcock
Discharging battery

When we got the bike it started and ran fine although a volt meter showed it wasn't charging. A RO from a local independant mc shop showed a replaced RR and stator (appeared to be the same units sold by Ricks).

After sorting out the T fitting and petcock the bike still started and ran fine but no charging. Checked the rotor and it ohmed out around 1.9+/- so a new one was ordered from MikesXS. When I pulled the old stator I noticed the pick-up leads had been wrapped with ele. tape that was oil-soaked and starting to un-ravel. Apparently the shop had cut the 3 leads, soldered them back together and wrapped them in tape. I re-did the job and used heat-shrink covering and put it all back together. But, still no charging. The bike would start and run fine but would not show more then 12.2volts at any rpm. Then checked the 3 wires from the stator and only got about 12 volts AC at any RPMS. Ordered a new stator from Ricks, installed it and then started having the spark problem. It would turn over with no ignition and then backfire once or twice. I know the coil is firing because I can get it to throw a spark intermittenly. I guess it could be the TCI or the pick-up but why it started all of a sudden is a mystery to me!

 

[gggGary]

you replaced the stator and now it doesn't spark, the area to be looking at would seem to be the stator and how the pickups are mounted to it. did you split the pickup wiring out of the old stator bundle? Can we see a pic?

 

[Macmorgan]

Hi Gary
Thanks for the reply. These older bikes never cease to surprise me - you fix one thing and then something else rears it's ugly head. I've been working on a number of bikes for friends recently - CB400/4s, VTR250, XS750, a couple of Vespa and my own bikes (all of which are running). I'm still trying to attach a couple of photos - every site seems to have it's own method of attachment.

Currently I am looking at every component and connection. I re-wrapped some of the wiring harness that was coming apart which may have caused something to disconnect If it is the TCI, can't figure out what caused it to fail for no reason. The pick-ups ohm out at around 750 and don't show any shorts to ground or to each other. I saw an interesting YouTube clip where a GM ign. module was excited with a soldering iron! May try it.

I'll let you know what or if I find anything.

Mac

 

[gggGary]

Here's a hint; unplug the voltage regulator see if it starts.

If that works your pick up magnet is weak or somehow the new stator has the pickups further from the magnet search weak magnet for fixes.

The plugs will fire once when the TCI is de-energized. hint the TCI on 82-83 bikes won't fire if the side stand is down.

 

[Macmorgan]

Thanks! We Honda VFR800 owners (I have 2 98s) have been dealing with RR problems forever. The little VTR250 had a discharging problem when sitting overnight. I took one of my old RR, removed the burnt plastic plug housing, replaced the 3 connectors and plugged it into the VTR harness and solved the problem. I'd love to know what causes all these electrical issues although I suspect it's all the fiddling we do.

Mac

 

[gggGary]

Yup a lot of hondas have bad rr's I swapped out my wife's annoying 750 shadow rr for a chinese replacement with a decent heatsink, problem solved. One XS650 issue is the field coil's magnetic field can "swamp" the magnetic field from the little magnet that activates the pick up signal to the TCI Unplugging the RR de-energizes the rotor.

 

[Macmorgan]

That's an interesting thought. So, is it possible to re-magnetize the rotor? This one's brand new from Mike's. It's the first part I replaced due to low readings on both rings.

 

[gggGary]

More like "remagnet" the rotor. You can field test with a screw driver the little magnet should have a "strong" pull. IIRC Some of those mikes rotors sat closer to the engine increasing the distance from the magnet to the pick ups, weakening the field. While we are here, the stator has a small cut at front bottom that has to fit over a pin in the crankcase. If it isn't aligned on that pin the stator will sit slightly crooked.

 

[Macmorgan]

You offer up some interesting ideas. I do know of the locating pin from your charging system writings - quite good I must say. I've taken a break from the XS brain teaser exercise but fyi, the sequence of events went like this:

Bike ran with the new rotor but wouldn't charge above 12.2 volts at any rpm. Checked the voltage of the 3 white stator wires at idle and higher rpms; never saw higher then 12 volts AC.

Installed new stator, virtually identical to the old one; swapped over brushes and ign pickup. Kept blowing 20 amp fuse which turned out to be the positive brush lead shorting out on one of the screw; re-insulated with shrink-wrap. No more blown fuses but also not starting; only a couple of backfires when the random spark ignited the fumes in the exh. pipe. Checked ign pu leads which both ohmed out at 750. Ummm, could the leads be the problem?

I have to think that the TCI was working up until the stator was replaced. Could the shorted brush lead cause some type failure in the TCI? Don't know because there's no way of testing it as far as I know. I did check the diodes and got a reading in one direction but not the other. Really don't want to buy a used one with no guarantee. Well, good night for now.
MM

 

[scabber]

Welcome to the site. Not an expert but if I'm wrong an expert might jump in. The new rotor worked with the old bad stator. Since the stator old was bad the field windings weren't producing a strong magnetic field the bike ran. The new stator is producing a stronger magnetic field creating interference with possible weak magnet no start. I think if you unplug the regulator and the bike starts the magnet on the rotor is weak. I don't think the shorted brush wire would damage the TCI.

 

[Macmorgan]

Finally pulled the ignition pick-up leads, cleaned up the po messy solder joints, shrink wrapped the splices, recovered the leads and replaced the connectors at the plug end. That solved the problem.

 

[gggGary]

Great! Those darned PO's and their dirty little tricks.