CT70 won't start HELP PLEASE

wwCT

wwCT

New Member
I have a 1971 CT70 that refuses to fire. It has spark and fuel, as well as compression. It was running fine a couple of years ago, but since we moved it from my grandmother's house I haven't been able to get it to start. I wondered if it was a timing issue, but that wouldn't be fine and then all of the sudden be off, would it? I am completely out of ideas. I am pretty new to engines so any advice would be greatly appreciated.
 
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b52bombardier1

Well-Known Member
Buy the shop manual for the inevitable tune up knowledge that it will require. A few tools such as feeler gauges and small metric tools will be needed because I predict that a valve adjustment is needed.

How good is the compression? My lower limit is 100 PSI vigorously cranked with the throttle wide open. Most of these bikes got absolutely zero maintenance since day one and need a no holds barred, Texas-style, no kidding, COMPLETE tune up.

Rick
 
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wwCT

wwCT

New Member
The valves were another thing on my list to try and check. As for the compression, I don’t have an actual measurement but the resistance in the starter feels the same as it did when it would start on the first kick, though my very inexperienced feeling may not be the most accurate measure to go by.
 
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kirrbby

kirrbby

Well-Known Member
When I get a new, non running, beater...
Remove ALL old gasoline...add fresh fuel.
Clean carb...this COULD wait...clean if no start.
Clean and set points to .016 inches.
Set valve adjusters/rockers to .003 inches.
Clean spark plug and put a tablespoon of fuel into the hole before putting the plug back in.
Key on.
Fuel on.
Kill switch set to run.
Put the bike in 2nd or 3rd gear.
Walking beside the bike start pushing it around in circles in the driveway or street...push start it.
Open AND close choke...open AND close throttle as you're pushing.

This gets the engine spinning, sparking, and sucking air and fuel.

Old gas is a VERY likely problem.
Valve adjustment is a VERY likely problem.
Dirty points.
Good luck.
 
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MiniBike Mike’s Garage

MiniBike Mike’s Garage

Well-Known Member
I bought an SL70 in 1992 for $40. Previous owner claimed he couldn’t get it to run and was sure it was getting fuel, had good spark and good compression. I took it home and pulled the cam gear cover and the timing was way off. They had sheared the woodruff key on the crankshaft and the flywheel had moved slightly…..enough that it wouldn’t run. Replaced woodruff key and bike started first kick. Still have that bike.
 
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wwCT

wwCT

New Member
I really appreciate all of the advise, and I will definitely be checking out the cam timing and the valves as suggested. I should probably have mentioned it in my original post, but this bike is in pretty good shape. It was bought in the 70s from its original owner and has been in the family ever since, and has been maintained pretty well, save the last couple years when it just sat. Don’t know if this may influence any advise, but just thought I’d throw it out there.
 
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power6994

Active Member
The pilot jets block very easily.

One way to test if it's firing is to put some engine start spray into the motor. If it fires, you've got a blocked carburettor.

As Kirby said fuel is a very likey issue
 
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Tripod

Tripod

Well-Known Member
WarnerSteel said:
I bought an SL70 in 1992 for $40. Previous owner claimed he couldn’t get it to run and was sure it was getting fuel, had good spark and good compression. I took it home and pulled the cam gear cover and the timing was way off. They had sheared the woodruff key on the crankshaft and the flywheel had moved slightly…..enough that it wouldn’t run. Replaced woodruff key and bike started first kick. Still have that bike.
Click to expand...
My first ct70, a silver tag, i picked up for 425. Non runner, guy had tried all sorts of stuff. I got it home and noticed the crankshaft would spin but not the flywheel when kicked over. Just needed a flywheel key. This was in 2013...
 
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ktheake

Active Member
And if your going to use ether to try and start this motor - use very sparingly - meaning just a sniff to get an initial start -
It's use is only to quickly prove it's a fuel issue and emptying a partial can usually just washes the cyls dry , soo best to just introduce a bit of fuel in the plug hole and prove it's a fuel issue . Meaning carb is generally in need of a clean .
 
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power6994

Active Member
ktheake said:
And if your going to use ether to try and start this motor - use very sparingly - meaning just a sniff to get an initial start -
It's use is only to quickly prove it's a fuel issue and emptying a partial can usually just washes the cyls dry , soo best to just introduce a bit of fuel in the plug hole and prove it's a fuel issue . Meaning carb is generally in need of a clean .
Click to expand...
Great point
 
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wwCT

wwCT

New Member
Well I adjusted the valves and it still wouldn’t start. I may have done it wrong, but it’s a pretty simple process. I’m pretty positive that it’s not a fuel issue since the carb has been cleaned twice, though I might shoot some starter fluid in there anyway. Are there any other likely issues? Again, the bike’s in pretty good shape and was running fine until after the move when it sat.
 
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cjpayne

cjpayne

Well-Known Member
Put a jumper wire from the stator plug to the coil. We need to start eliminating some things. Before that, take an ohm meter and check for ground from your engine to the rear shock mount, then from the engine to your ignition heyhole. I'm wondering if you have a "half assed"/corroded ground somewhere
.
 
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wwCT

wwCT

New Member
If I’m getting spark, doesn’t that effectively eliminate anything to do with the electrical side, save ignition timing? Again I’m pretty new to this whole thing but that’s my understanding.
 
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