Honda ST90 can timing issues

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Gunnar

New Member
working on an st90.
I am losing my mind over this bike and I’m sure I’m overlooking something real stupid so I’m here for help.

New DID cam chain.
Loosen cam chain.
Line up stator to TDC
My dot on the cam sprocket is always a little off. I would say when the dot is perfectly aligned the T is about a quarter inch or so from the mark on the case.
When T is aligned the dot on the cam sprocket sits about halfway with the top of the notch on the head.
Not hitting valves. Great compression.
Here’s my big issue.
Static timing the bike with a test light, when I hit F light comes on. Everything as it should be. Won’t start. It seems I have to retard timing quite a bit to get it to kick over and run and when it does it runs like shit.
Have gas, spark, compression. The cam on the actual ignition has been on both ways to no avail.

Any ideas?
 
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b52bombardier1

Well-Known Member
Definitely a spark advancer problem.

Has this engine ever ran well for you or was it DOA when you got it?

Does the spark advancer move freely? Could be rusty and dirty.

Since it sounds like you can at least get it to run badly with the points plate moved from a non stock location, that rules out assembling the spark advancer 180 degrees out of phase.

Is that what you meant when you wrote "The cam on the actual ignition has been on both ways to no avail."

Rick
 
G

Gunnar

New Member
flywheel key is fine and not sheared.
The advancer cam has been installed both ways. And is clean and freely moving. I have done pretty much everything I can think of with the exception of a new coil and condenser so I’m going to try that and see what happens
 
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b52bombardier1

Well-Known Member
Let's go back to your comment about the cam dot being a little off - 1/4 inch. Timing chain too stretched to get consistent timing? It's a frequent thing with these motors . . . poor or non-existent oil changes.

Rick
 
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b52bombardier1

Well-Known Member
Weak springs in the advancer can't pull the arms back in when idling. Makes for some interesting timing measurements.

Don't buy anything for a coil just yet. And even then, only buy one from Dr ATV for either an ST90 or a CT90 - same coil. Many coils offered on EBay, etc. are for a CDI ignition and won't work for an ST90 or a CT90.

Do you have a copy of the shop manual showing pictures of the various flywheel indicators and marks and what the normal position of the points plate should look like?

Have you tried running a 12 volt strobe timing light here? Works the same way . . . just hook it up to a 12 volt car battery.

Rick
 
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