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1978 Honda Twinstar CM185t
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Discussion Starter · #1 ·
My husband has been trying off and on for 3 years to get this Twinstar running without luck.

Problem #1: There was no spark initially, but he put in a new ignition coil, spark plug wires and spark plubs, and battery and he was able to get a spark!

Problem #2: Can't get it to start:
  1. Put in a new carb, but it didn't make a difference so he put the old one back in. The new one had vacuum lines that the old one didn't and he didn't know what to do with them
  2. He checked the timing. It appears to be factory-set so he has no reason to believe the timing is off.
  3. He is wondering about the vacuum connected to the crank case.
    1. He doesn't know anything about it and hasn't touched it. He says air is supposed to be pulled through the carb and he can feel suction, but is wondering if something's not right
    2. There are vacuum lines connected to the air cleaner and also into the crank case.
  4. He tried idle mixture screw at different settings with no luck.
Any ideas? I'm attaching a photo of the part in question - it's the black thing in the lower right of the photo.
316003
 

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The hoses are to direct gases from the motor to the air intake to cycle them thru the motor instead of venting.to the air.
I have not worked on a 185 so wont comment on it. Go to the net and buy a Honda full service manual . Spend the money and buy an original the after market manuals are junk. Read it from cover to cover and you will have a better understanding of whats going on with the motor. They are informative and have lots of good photos.

Bill H
 

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Your story so far is shockingly similar to mine. I have a 81’ CM200T. It is almost the same bike, apart from some electrical differences. As Bill stated, the hose coming from the crank case releases displaced pressure from the engine back into the airbox as a way of “recycling” the vapors and air. It looks as if it is connected correctly, and should not be necessary for the engine to start anyway.

Is the engine trying to start? Or is it just turning with no combustion whatsoever.

Are the spark plugs wet after turning the engine?
 

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1978 Honda Twinstar CM185t
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Discussion Starter · #4 ·
Is the engine trying to start? Or is it just turning with no combustion whatsoever.

Are the spark plugs wet after turning the engine?
So, it is trying to start, there is some combustion and the spark plugs are not wet!
 

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I would have him start (again?) with a thorough carburetor cleaning. Sounds like the at least one or both jets, and or the passages in the carburetor body are clogged.
 

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Discussion Starter · #7 ·
I would have him start (again?) with a thorough carburetor cleaning. Sounds like the at least one or both jets, and or the passages in the carburetor body are clogged.
He says he did as thorough a cleaning as he could, even put a new one in without any luck.🤔 it’s a mystery!
 

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So, it is trying to start, there is some combustion and the spark plugs are not wet!
He says he did as thorough a cleaning as he could, even put a new one in without any luck.🤔 it’s a mystery!
Hmm. Maybe the tank/petcock/fuel line is clogged. Is the carburetor slide and throttle cable operating like they should?
Maybe you can post a video of start attempts so we can help troubleshoot?
 

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Discussion Starter · #9 ·
Maybe you can post a video of start attempts so we can help troubleshoot?
I’ve just uploaded a video of him trying to get it to start. He’s able to get a bit of a sputter where it seems like it will start but then it gives up right before it does. At first there was no sputter, but then he sprayed some starter fluid into the carb thing (?) and got some sputtering action.
 

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Sounds to me like it’s a combination of not enough fuel and slow cranking. And or the timing is off.
Before I cleaned and rebuilt my carburetor, (again), it would sound almost like that, and still does now when it’s cold. I have to start it with the choke on. Can he try to kick start it?
 

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I'd make sure the battery was completely charged. Then make sure the spark plug gaps are to spec. Confirm you've got fuel in the carb bowls.
There could also be a vacuum leak at between carburetor and intake manifold connections. (Too much air for the fuel going in)
 

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Discussion Starter · #14 ·
Thank you everyone - we’ll report back with any progress!
 
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