1978 CT70 Revival

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MisterLou

New Member
I guess these bikes aren't as simple as I thought they'd be. o_O

Trying to revive a '78 CT70 from it's slumber. Started with a leaky fuel tank- replaced that. Found a mouse nest under that. Cleared it out and saw some damage to the wire insulation in that area. Repaired that. Carb mounting flange snapped. Replaced that. Bought a new battery. No start.
Checked the plug. No spark.

What I found is that there are a lot of links when you search "Honda Trail 70 no spark". Pulled the motor so I could get to the spark plug coil and fluffed up the mounting are to reground the new coil. Checked the coil separate from the harness. Got spark. Traced continuity from the battery harness down to stator...all good there. Checked the "loop" at the top of the harness. Continuity is good. Replaced both stator coils as supplied from CHP. New condenser. New points. Stressed out on the condenser soldering as soldering is not my strong point and read all the posts about how critical this is. Seemed pretty solid. Gapped points. Did the whole test light, points check and the test light dimmed accordingly. Did a visual points check and they're definitely opening and closing. Checked continuity on the wiring from the condenser to the points, up to the harness plug and it was all good. Still no spark.
Read more about bad condensers. So pulled the condenser- checked it by charging it and discharging it multiple times. All good. Replaced it anyways. Checked the replacement first. Charge/discharge. All good. Better soldering this time. Still no spark.
Thought I'd check continuity with the run/stop switch on the handlebars. It seems to work. Still no spark.

What am I missing?


What started as a simple fluff up (new headlight, bulb replacements, oil change, tune up) to get this bike sold is now turning into a real head scratcher.
 
kirrbby

kirrbby

Well-Known Member
We're you sure to connect the points wire in the right place...outside of the insulating washer??
Do you have good connection between the spark plug wire and the boot?
Have you tried a new/different spark plug?
How did you gap the points...by the light, or, what measurement?
Did you try cleaning the points, or lightly sanding the contact surfaces clean?
Try unplugging the wires from the kill switch?
1700501340089.png
 
kirrbby

kirrbby

Well-Known Member
Next time you're in there, take some good, close, pictures of the stator plate. To show...wires...your soldering...everything.
 
M

MisterLou

New Member
kirrbby said:
We're you sure to connect the points wire in the right place...outside of the insulating washer??
Do you have good connection between the spark plug wire and the boot?
Have you tried a new/different spark plug?
How did you gap the points...by the light, or, what measurement?
Did you try cleaning the points, or lightly sanding the contact surfaces clean?
Try unplugging the wires from the kill switch?
View attachment 79723
Click to expand...
Thanks for the reply.
I definitely have the points connected outside the insulator and not grounding on the body of the points.
When I tested the coil, I sent it 6V direct and got good spark on the plug.
I gapped the points with a feeler gauge. My flywheel has the slots in it so I can see what I'm doing.
I'll try sanding the points in spite of them being new.
I did disconnect the kill switch. Took the headlight out and pulled the wires. Wondering if I should've jumped them?
 
kirrbby

kirrbby

Well-Known Member
Some points co.e with a thin coating on them...like clearcoat...to keep them from rusting. Should be removed.

What feeler gage did you use tho...what dimension?

No need to jump the kill wires. The kill switch only kills the engine...by grounding out the coil. Disconnecting those wires or just the black one should allow the bike to run.

You could try the jumper trick that you read in the no spark threads...
Disconnect the engine plug, AND the small coil wire. Then run a jumper wire from the black wire from the stator, to the small black wire on the coil.
This will eliminate everything else and ONLY connect the ignition circuit...
Good stator, good coil, good connections, good plug, good SPARK.
 
M

MisterLou

New Member
@kirrbby Well I jumped the small black wire going to the spark plug coil to the black wire on the plug going to the stator and got no spark. Which means I got something wrong in the stator. Thanks for that diagnostic tip! So at least I know the problem is down there.

Wondering if there is a way to test the condenser connections without undoing the soldering?
 
Robert thran

Robert thran

Well-Known Member
Next time you have the mag off try scraping the back side of the primary coil where it touch’s the stator plate as they coat them with the same coating they use on the points..that way you know for sure it’s grounded…. Also the wire that comes out of the primary coil that soldiers to the condenser needs to have the coating scraped off before soldering.. i use a razor blade..I know these are long shot things to do but with everything you’ve already done it’s got to be something inside the mag assuming your main coil and wires are good.
 
kirrbby

kirrbby

Well-Known Member
Definitely try a new spark plug.
Pics of the stator my show us a obvious problem.

Did you make sure to keep any bare wire well away from the BODY of the condenser?? Those soldered on wires should ONLY contact the center of the condenser. Too close to the condensers outer housing...a spark can jump there...that's a short.

.016 INCHES is where I usually set the points too. But if I don't get spark...I always try setting them a bit smaller for a try...maybe .014 or 5.
 
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M

MisterLou

New Member
IMG_3274.JPG



Here's a shot of the current (no pun intended) set up. I will look again to see if I'm touching the outside of the condenser.
Last night I switched out all three wires that go to the condenser to try and "start over".
Checked that the grounding wires on the coils aren't touching anything else and it's close but not touching. I have a bunch of old (and difficult) cars and i can't believe how touchy this little bike is. When it was parked a few years ago, it ran. This all started with a leaky fuel tank and the carb flange breaking. I thought tossing in a new set of points and condenser would be simple enough. Ugh.
 
kirrbby

kirrbby

Well-Known Member
The arrow points to what I'm calling the body of the condenser. No bare wire should pass close...or touch against that.

The circled areas look suspect to me.

You should be able to pull on each of the 3 wires...if they are NOT soldered in well...they will usually just pull right out.
IMG_3274~2.JPG
 
M

MisterLou

New Member
Latest update:
Spun up the stator with a drill, got the yellow wire from the stator harness on a test light and grounded it- got a light. So I know the lights/horn stator coil work. Double checked the spark plug coil again just to make sure I wasn't losing my mind. Grounded the body of the coil to - on the battery, ran battery + to the black wire while grounding the plug to the engine block and it sparked quite good!
My ohm meter is not sensitive enough to measure the resistance in the ignition stator coil but it is a brand new one from CHP, so I'm ass-u-me'ing it's good. Should !?
Which leaves only the condenser. I now have a total of 3. The original and two replacements. I charged/discharged all of them and they all pass that test. I'm not the best solderer but all three wires are on there solidly and do not appear to be grounding out. have given them all a good tug and they're not moving. Before this last solder attempt I went through all three wires and got them free of solder and then sanded them a bit. I even put some electrical tape around the edge of the condenser just in case. Still no spark.
Maybe it's time for a new stator ignition coil and condenser #4?!
 
Robert thran

Robert thran

Well-Known Member
You might want to try a new condenser from honda and when you solder it try not to get it super hot during the soldering process.. I’ve had a lot of cheap condensers crap out after a short time so now all I buy are factory Honda ones,,,I’ve also had great luck with stay clean ( see pic) with just one drop after you get all your wires locked under the condenser tabs you can just touch the solder and you will get a quick fast solder bond without over heating the condenser..I never seen a new aftermarket primary coil that wasnt good but I’m sure it could happen..?
 

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G

Goofaroo

New Member
It appears that you’re not getting good flow on your solder joints. I don’t know what’s in that bottle but if you’re using it as flux that might be the issue. The only flux I’ve ever used is a paste and comes in a tin.

Maybe I’m wrong and this “bottled” flux is all the rage these days but it certainly appears that you aren’t getting good flow.
 
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