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Discussion Starter · #1 ·
Hi ,

So I'm french ( I'm not a riot ! ) , sorry for my messages.. i you don't understand, please tell me.


I have 3 CB 250G F ( military)

2 are working , but the engine rpm seems not good :-( , sometimes it doesn't go to the idle but stay at 2 or 3000 rpm ... I have to look for the issue
1 are is not working ( starter KO , carburetor blocked ) .. so work forecasted


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with small lights...
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Welcome to the group. We do have members near you who may be familiar with your bikes, they are a model I have not seen before. Are they common in France?
 

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Discussion Starter · #3 ·
as far as I know ( from websites and CB parts list ) , this model is a based on CB360 and is specific for french army .
Due to french regulation (tax incentive in 70s) the engine is a 250cm3 instead of 360.
The army request a fuel tank bigger then it's a fuel tank coming from CB 750 cm3.
 

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Welcome, Cool bikes
 

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Welcome to the forum. Those are awesome bikes, I have never heard of a military version of the CB250/360. We will be glad to help with your running problems. It is very common for the older CV carburetor equipped twins to not idle well. Usually it is tracked to air leaks around the rubber isolators that mount the carburetors to the head and the felt seals around the carburetor throttle shafts. The isolators are made of rubber and they deteriorate and harden over time. Replacements are available and don't cost much. Honda OEM are better than the aftermarket isolators. The aftermarket ones I have seen have thin flanges against the head. Be careful not to over torque.
The felt seals can be oiled by connecting (tape) the carb body to a shop vacuum, placing your hand over the open end of the venturi and spraying a light aerosol oil around the throttle shafts. The traditional way of trying to locate air leaks by spraying the carb body with some kind of cleaner doesn't really work. Just assume they are leaking and try this. It worked on both my CB450K5 and my GL1200. You might want to consider replacing the diaphragms too.
 

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Hi Birdy I'm going to be near Cahors for a week in July. What are the chances of renting something with two wheels and a motor in France? A small motorcycle would be great but I'd even consider a scooter. A great way to see the countryside if I dont get taken out by priorité à droite haha
 

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Welcome, sounds like its at least running on both sides. 250/360s are very dependent on a proper carb balance, they will hunt for an idle if they are out a little and will race if one side is way out compared to the other. This has to be done with a manometer or balance gauges and an operating temp engine. They are a bear to do correctly without the proper tool as well. This is a link to one of them, there are several versions but basically they are a long socket that fits over the lock nut with a hollow handle that allows a flat screwdriver down the center to do the adjustment. https://www.z1enterprises.com/carb-adjustment-tool-set.html

Also might check the timing as they will also do the same thing if one side is more advanced than the other OR the advance unit is not functioning correctly and is not returning to the no advance state fast enough. This is usually a sticky unit or worn springs.

Interesting thing I'm wondering is what they had to do to get the 750 tank on that frame. I know a 450 tank will fit, did not know that one would.
 
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