Honda CM250 Starter Clutch Issue | Page 3 | GTAMotorcycle.com

Honda CM250 Starter Clutch Issue

The nipple for this tube was full of dirt and debris so I believe that through this passage way dirt was making its way into the float bowl and repeatedly clogging the pilot jet. Which was causing the hard start, I had to clean the carbs a few times but I thought that the nasty tank was causing the problem so I put an inline filter on the tank but still ended up with a clogged pilot jet yesterday. This to me makes perfect sense.
 
I was confused because after putting the fuel filter on the fuel line and just having cleaned the carbs I thought the pilot jet was clean and the issue was something deeper - low and behold clogged pilot jet again. There still may be an issue with the starter on the bike but if that becomes an issue ill replace the whole system - I like roadghost's idea of a kickstarter but the girlfriend does not so perhaps a whole new starting system of cheap ebay parts is in the future for me
 
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Trials said:
If it is a vacuum hose it will be connected to your intake manifold somewhere, that is the 'only' place your motor produces a vacuum.

If it is open at one end and either aims upwards to keep out water or downwards to drain out fuel, then you are looking at a drain or vent pipe. (atmospheric pressure)
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Yes, that is right mostly. It is essentially an intake/outtake vent for atmospheric pressure. It is vented to the outside and that is the problem because it sucks in dust that gets onto the vacuum piston walls and stops it from sliding properly. The result is the A/F mixture gets screwed up as the piston seizes in position. I'm not sure why it wasn't plugged into the intake at the other end, perhaps to keep it independent of the main intake pressure. It's so sensitive that just a gust of wind blowing against the bike was enough to drop speed 5-10km/h in my experience. I only discovered the problem by blowing compressed air on the bike and it would stall. I was like WTF? It's an important little hose I'm sure a lot of people disregarded.

This Keihin carb uses a seal for the vacuum piston. Later Keihin carbs were designed with a rubber diaphragm (for Harley Blockheads). The CM250's carb was used on a few other bikes, like the CB750 which I believe used 4 inline. All of them have this atmospheric vent.
 
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Roadghost said:
Yes, that is right mostly. It is essentially an intake/outtake vent for atmospheric pressure. It is vented to the outside and that is the problem because it sucks in dust that gets onto the vacuum piston walls and stops it from sliding properly. The result is the A/F mixture gets screwed up as the piston seizes in position. I'm not sure why it wasn't plugged into the intake at the other end, perhaps to keep it independent of the main intake pressure. It's so sensitive that just a gust of wind blowing against the bike was enough to drop speed 5-10km/h in my experience. I only discovered the problem by blowing compressed air on the bike and it would stall. I was like WTF? It's an important little hose I'm sure a lot of people disregarded.

This Keihin carb uses a seal for the vacuum piston. Later Keihin carbs were designed with a rubber diaphragm (for Harley Blockheads). The CM250's carb was used on a few other bikes, like the CB750 which I believe used 4 inline. All of them have this atmospheric vent.
Click to expand...

on your filter flow is to the carb?
 
mistersouthpaw said:
I was confused because after putting the fuel filter on the fuel line and just having cleaned the carbs I thought the pilot jet was clean and the issue was something deeper - low and behold clogged pilot jet again. There still may be an issue with the starter on the bike but if that becomes an issue ill replace the whole system - I like roadghost's idea of a kickstarter but the girlfriend does not so perhaps a whole new starting system of cheap ebay parts is in the future for me
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Woody's cycle salvage near perth has tons of parts for that bike if you discover you need anything that would be expensive new.
 
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