Could it be my brushes?

[52Chevy]

I haven't been out and looking at my bike in a while. But it is backfiring when I try to start it.

I know the headlight should turn on after a good kick. Mine does not.

I have a 1980 XS650, replaced the motor with that of a 74 or 79 I believe(can't remember off hand). The motor I installed was a points ignition, but I eliminated the points and left my TCI ignition on the bike.

Any insight?

 

[rebel542]

Probably not brushes but you don't give a lot of info. How long has it been sitting? Has it ran since the engine swap? Is the battery charged? Homemade wiring or OEM? The more you tell us the better answers you'll get. Hope this helps.

 

[52Chevy]

It sat for a long time before the engine swap. I don't know how long the engine was sitting before I bought that. Since the last time I started it up its been about a month or two. I set it off to the side of the garage after it backfired on me twice and really bummed my ankle. So this isn't just a "since it's been sitting" thing.

It has ran since the swap. I started it up a few different times before I started having problems. It has OEM wiring, minus in line fuses I installed. All fuses are good.

The battery was brand new when I first started it up, and I later took the battery out, and hooked it up to my Batter Tender Jr. while I haven't been working on it.

 

[rebel542]

Did you use your original 80 model alternator rotor. The early pre-80 rotors can't trigger the ignition.
I'm assuming you looked at your plugs already? Insert a spark plug in one of the caps and lay it on the head and kick it over to check for spark. Carbs will probably need cleaning after sitting for long periods, like a year or so.
Hope this helps.

 

[52Chevy]

Yes, I transferred the rotor from my 80. I have spark on both cylinders, brand new plugs. The carbs were supposedly cleaned before it was stored. But I haven't torn into them yet. It will turn over a few times when I kick it, but then when I try again let's say the third time it kicks back.

 

[weekendrider]

Check your timing.

 

[rebel542]

I think the timing is factory set but you could still have a problem there. If you didn't get the keyway in correctly your timing could be way off. Take the alternator side spark plug out and turn the engine counter clockwise, ignition OFF ,until piston is at top of cylinder. Your T mark should align when piston is at top. If not find your lost woodruff key and install it. If it aligns look to fuel.
Hope this helps.

 

[52Chevy]

Between work and school I don't have much time to get out there anymore.

My plan as of right now is to take off the left side cover, and re-check rotor installation and make sure everything is ok there.

I am hoping that I find something I overlooked before, as it ran fine before, and then all of a sudden it didn't wanna start anymore.

I am suspecting (and almost hoping) that I just forgot to torque down the rotor bolt, and that the rotor is loose, causing slop in the timing and causing a misfire.

 

[freddy3]

Did you ever disconnect or remove either of the coils or their respective wires? If so, recheck to be sure you've got the correct wire going to the correct coil. If they're reversed, you'd have trouble starting and misfiring.

 

[52Chevy]

I did disconnect plug wires and reinstall them to swap motors, but it ran after that just fine.

 

[52Chevy]

I pulled it apart and this is something interesting I found.

Is this possibly the problem??

 

[gggGary]

Well that's not good but probably not the "won't start problem" if the battery is charged and you have spark. Check your slip rings for 5.6 Ohms between them while you have the stator off. If you do then don't worry about the chipped bakelite.

The stator has a slot that needs to line up with a pin in the crankcase it's easy to miss this. Often the rotor rubs on the stator when it's not lined up.

View attachment 16089

 

[52Chevy]

Would that cause the backfire?

 

[gggGary]

Not too likely... but not impossible. Describe the backfire? Out the carb or the exhaust? when you kick it or when you shut off the ignition?

 

[Take Warning15]

I think the timing is factory set but you could still have a problem there. If you didn't get the keyway in correctly your timing could be way off. Take the alternator side spark plug out and turn the engine counter clockwise, ignition OFF ,until piston is at top of cylinder. Your T mark should align when piston is at top. If not find your lost woodruff key and install it. If it aligns look to fuel.
Hope this helps.

Not to hi jack, but can you elaborate a bit, I'm new at this and have the same problem. What "T" mark? Is this stator to rotor? Can't the stator only go on one way? I have a 75 650b if it matters.

 

[52Chevy]

gggGary, It backfires when I kick it. I have dislocated my ankle twice now trying to start the bike... I believe I am getting it setup correctly, pushing the piston to the top of the compression stroke, allowing the starter to come all the way back up, then pushing down all the way.

Take Warning, don't worry about hijacking, could be helpful to both of us.

 

[gggGary]

Well I can't promise anything but... Check your pick up coils, there are three wires gray orange and black. you should see 700 ohms from the black to the orange and from the black to the gray. Unplug the connector to test. It's found at the back of the engine. So my WAG is maybe one coil is out and you are getting just the advanced spark. IE before TDC. I don't know if that can happen but at least if you test you will know if the pick ups are good (or not).

The way this is supposed to work is; the TCI sees a signal when the magnet passes each pick up coil then fires the ignition coil at the correct time depending on engine speed.

 

[gggGary]

Did you know there are TWO six pin connectors by the backbone? They can be plugged into the wrong component, one is for the TCI the other is for the voltage regulator.

 

[52Chevy]

Thanks Gary, you really have been very helpful during this whole thing. I'll have to give that a look tomorrow.

I think the thing that confuses me the most is that it was running just fine, and after running it for about 5 or 10 minutes I wasn't able to get it started again, it kept kicking back.

So I'll check this out tomorrow. Hoping to track down the issue soon. I'd like to get it running before winter so I can pull parts and work on those inside i.e. brakes, carbs, paint etc. I dont have an accessible indoor space to store it for the winter.

 

[52Chevy]

Thanks Gary, you really have been very helpful during this whole thing. I'll have to give that a look tomorrow.

I think the thing that confuses me the most is that it was running just fine, and after running it for about 5 or 10 minutes I wasn't able to get it started again, it kept kicking back.

So I'll check this out tomorrow. Hoping to track down the issue soon. I'd like to get it running before winter so I can pull parts and work on those inside i.e. brakes, carbs, paint etc. I dont have an accessible indoor space to store it for the winter.