[Certified Rookie]

Hello all, i’m working on my first motorcycle, a 1981 CM200T (12volt) to be exact. It has been a task to start the bike since I bought it a few months ago. I’m finally at the point where I have what I need to start the bike, and nothing happens. The kickstart turns the engine, but won’t start combustion. The electric start (hooked up to an alternate 12V source) turns the pistons, but again, doesn’t start combustion.

I have tested the spark plugs and they produce spark.

I have observed the carb bowl fill, and the amount of fuel in the fuel line go down while trying to start the bike (petcock OFF).
I have tested the carb mounted choke in both positions while trying to start the bike
I have tweaked the throttle position while trying to start the bike
I have tried starting in neutral, clutch in and out.
I’m not quite sure what the issue is, as the bike has only 3000 original miles and the engine seems to be perfect on the inside. I’m wondering if anyone has any suggestions. Also, if you’re interested, here’s the story so far:

When I got the bike, the carburetor was nowhere to be found, so I purchased a copycat carb from ebay that matched the bike alongside the manifold in order to bolt onto the engine

I’ve swapped the engine oil and spark plugs with their respective new replacements. Plugs are also gapped correctly.

I’ve lubed the cylinders with marvel oil and have rotated the pistons like butter with the kickstart lever AND starter

i’ve cleaned the fuel tank of rust and installed new lines and an inline fuel filter

i’ve ordered a spare 12v ignition coil that i’ve discovered that I might not need, as it gives the same multimeter readings that the original (which I thought was faulty) read.

RUST, SO MUCH SURFACE RUST. Tons of rustoleum jelly and wire brush time

 

[66Sprint]

Are the carb screws set to their specified preset positions?
ARE the "kill" switch AND the ignition switch both turned to on/run?
Good battery connected?
TEXT me......

 

[Certified Rookie]

Are the carb screws set to their specified preset positions?
ARE the "kill" switch AND the ignition switch both turned to on/run?
Good battery connected?
TEXT me......

Yes, carb screws are set to their preset positions. The key is in the ignition and the lights all come on. I assume the kill switch you’re referring to is on the right handlebar, which is set to “engine run”. As far as a battery is concerned, I figured a battery is an accessory for a bike without a 3 point system, so I just have the battery leads hooked up to a 12v source. The unit is called a Cen-tech 630 4 in 1 portable power pack. This unit could be the issue, but like I said, all the lights come on fine, and the starter turns the engine just fine too.

After turning the engine, I can smell fuel on the spark plugs, so i’m thinking it might be something electrical. But then again this is my first rodeo with a vintage bike, so i’m taking all of my ideas with a grain of salt!

 

[mike in idaho]

Check for spark before you start throwing new parts at it. Pull the spark plugs, lay them on the cylinder head with the wires attached and look for sparks as you turn the engine over. There should be battery voltage at the points connection with the points open and no voltage present with the points closed.

 

[Certified Rookie]

Check for spark before you start throwing new parts at it. Pull the spark plugs, lay them on the cylinder head with the wires attached and look for sparks as you turn the engine over. There should be battery voltage at the points connection with the points open and no voltage present with the points closed.

I have spark, i’ve grounded the plugs against the engine case on both sides and confirmed that. As far as points are concerned, i’m positive this bike doesn’t use a points system. The 1981 model of the CM200T was the first model year to move away from the 6V points system. It instead uses a 12V system without points. Now i’m not a genius as far as what all is included in the ignition system, but as far as I see, I just have an ignition coil, and possibly a CDI (not sure what it would look like or where it would be).

I say all of this to say that the bike has spark.

Now another question, is there such thing as weak spark? I’m under the impression that any spark will ignite and cause combustion. Even if it’s a weak spark though, I feel as if the engine would at least TRY to start. I’m getting nothing but turning.
Anyway, i’m on my way to the auto store to swap engine oil. With all of the times i’ve tried to start it, I don’t want a flooded engine to be another thing holding me back.

 

[Certified Rookie]

A couple months have set in and i’m just cleaning up and taking another look at this bike. I noticed that there was a decent sized gap where the exhaust should exit the engine. Is this something that could be causing all of my issues? Do you need an exhaust to start and run a motorcycle engine?

Not sure if the picture speaks for itself, but that little black sliver is completely empty. I can see inside that little cavity. I even stuck a little zip tie in just to make sure I wasn’t going crazy.

 

[stockton350]

That wouldn't stop the bike from firing up. What's the state of your air filters? Have you tried using starter fluid?

 

[mike in idaho]

A couple months have set in and i’m just cleaning up and taking another look at this bike. I noticed that there was a decent sized gap where the exhaust should exit the engine. Is this something that could be causing all of my issues? Do you need an exhaust to start and run a motorcycle engine?

View attachment 316549
Not sure if the picture speaks for itself, but that little black sliver is completely empty. I can see inside that little cavity. I even stuck a little zip tie in just to make sure I wasn’t going crazy.

Needs pulled apart and the pieces assembled in the correct order.

 

[Certified Rookie]

That wouldn't stop the bike from firing up. What's the state of your air filters? Have you tried using starter fluid?

The bike doesn’t have an air filter at the moment. The carb is connected to the original air box, however the front plate of the air box is missing, so it’s not doing anything.

As far as starter fluid, yes i’ve tried and failed lol. When I used that it still didn’t even want to fire, didn’t even try

 

[Bill H]

Your motor has a CDI. If the coil checks ok you need to check the stator , if it checks ok the CDI is probably bad. You cant test the CDI. Do you have a full service manual? You can have spark and still not start with a bad stator and or CDI.


Bill H

 

[Certified Rookie]

Your motor has a CDI. If the coil checks ok you need to check the stator , if it checks ok the CDI is probably bad. You cant test the CDI. Do you have a full service manual? You can have spark and still not start with a bad stator and or CDI.


Bill H

I went in last night and tried to test the CDI with a multimeter. I couldnt get any good readings at all, so I think it’s just user error. Im going to be testing it out again with an assistant and a better multimeter tonight. I also lucked out and found the exact page I needed posted online (I’ll post it below to pass it on to any time travelers from the future).


How would one go about checking the stator? I’d have to pull off the side of the engine case to access it, but once I get there i’m not really sure what readings i’d be looking for.

 

[Bill H]

The readings for the stator are in the same manual you are looking at probably on the next page. I dont think you can test the stator with a standard OHM meter. I think it takes Sanwa sp 10d type or a Kowa TH5H type meter.

Bill H

 

[Certified Rookie]

Update:
Thanks to a very gracious fellow 81’ CM200T owner, through some parts swapping, I now know that my CDI and my Carburetor are fully functional. This leaves me with some answers, but ultimately more questions. Since I know the carb is good, I believe this mostly throws air/fuel out of being a possibility. I sill need a solid way to test my Stator.

If anyone has access to a 81’ CM200T manual, that would mean the world to me.

I’m going to be going through wiring to make sure everything is connected properly. This feels like it could be a simple thing that i’m overlooking.

 

[Certified Rookie]

Okay, after an enlightening talk with 66Sprint, we have successfully pointed our finger at a likely issue. The intake valve may be bent. The reason this might be the issue is because while i’m turning my engine, I can actually feel air pushing OUT of the intake manifold. Air in this location should only ever be directed IN, sucking towards the engine. Supposedly a bent valve can be caused by leaving the bike at high RPMs for even as little as 5 minutes.

ALSO, through talking with one of the old mods, I have learned that the moderators here on Hondatwins have created their own forum.

PM FOR INFO

They have a large fountain of manuals and knowledge available to members, and are EXTREMELY HELPFUL. I highly recommend checking that out.

 

[Certified Rookie]

An overdue update: Despite being nervous, (first engine i’ve ever worked with) I tore into the top of the engine to discover that four out of four of my valves need to be replaced. Almost all valves were critically bent! I’ve gone and ordered more, but this solves my compression issue! If I can just take care when reassembling the engine, maybe, just maybe, I’ll manage to fix the bike. I will update when I receive the parts and get the engine back together again.

A flashlight showing just how much space was present between the valve and the seat (the rest were about the same)


Pro tip: Don’t trust the seller when they say the bike has good compression. Check it yourself using real gauges and not just the thumb method!

 

[mike in idaho]

When you get the valves out, look the valve guides over closely for signs of cracks from the bent valve stems.