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Mikuni carbs adjustment on ‘95 ural/dnepr

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Changed out carbs to Mikuni. When I started the engine went to about 840 rpm with choke open. (Top low??) After a some minutes I turned the throttle and ramped up the rpms. This went smoothly, but went I released the throttle the rpms went down and below the idle speed (choke still open) and after a short time the engine died. This happend twice and when closing the chokes after some minutes the engine died.

1. Why did my rpms dropped below Idle even with choke open after I released the throttle?
2. Must adjusting carbs and minimum idle speed be done when running on 1 cilinder with choke closed?
3. What is a normal Idle speed for my TM16 from ‘95?
4. What speed should the engine run when choke is open? I would expect more than 840 rpm’s.


with regards


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Update: it seems my left ciøinder is not working as the head stays cold. Tried to adjust idle speed and air screw without any effect. Difficult to se if petrol is running. 
The right cilinder seems to work fine, gets warm but after running several minutes it starts to make popping sounds, only when warm.

any suggestion how to se if fuel is blocked, without opening the carberator?


any idears why the right cilinder start makkng sound after several minutes (5+) running fine??

Thanks in advance


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Disconnect the fuel line from the carburetor, hold a container under it, and turn the petcock on. You should get a nice flow of fuel. Other than that you must remove the float bowl to access the needle valve, float, and be able to check the passage for obstruction between the fuel inlet hose connection and the needle valve seat. You could also have clogged jets and passages connected to them. Carburetors like the ones you have are not complicated and can be reassembled in only one way. Just make sure you have a clean area to work on when taking the carburetor apart and have small containers for keeping the small parts in while it is apart. 

There are several reasons the cylinder can make noises. Someone experienced can usually determine what is causing them. It could be a vacuum leaks between the carburetor and head intake port. The valve lash may be set too tight or even too loose. There could be a leaking head gasket or the valves may be leaking. The carburetor needle valve my not completely stop fuel flow when the fuel bowl is full or the needle valve may be sticking every now and then causing the carburetor float bowl level to drop causing a too lean condition resulting in noise and when the noise is made it jars the needle loose allowing the float bowl fuel lever to rapidly return to normal. You've just got to look at everything to find the problem.  

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My experience with Urals and Mikuni carbs suggests the popping sounds are the result of air leaks in the compliance fitting between the carb and the cylinder head.

Those parts require replacement over time, as they harden and crack.  If you don't know how old those compliance fittings are, expect to replace them with new ones, at least as a prophylactic measure.  That could make your experience much easier and enjoyable with these machines.

I always ride with spares compliance fittings sealed in plastic bags, in my "spares kit."  I've only ever needed them when I didn't have them with me. Go figure...


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Thanks for your reply’s. My rubber manifold adapter har some cracks, but when looking for new ones nothing seems to fit my manifold. My engine is a 650cc and bolt distance is 53 mm and intake opening is 33,5mm. It looks like the ones installed where adjusted, by adjusting the holes. 

so my question: is there a perfect fit or do I just order the mikuni one and adjust?


other question: my thick rubber hose from airfilter to carbs is putting pressure on the carb which will increase the danger for cracks in the manifold adapter. Which type of hose can I use some is more flexible? Any suggestion?


thanks in advance.


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