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TR 250 slow running issues

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I have a TR 250 and am having difficult setting the slow running. Choke off, slow running screw retracted but engine running at 1500 rpm. With air filter off I can observe that the valves are lifting by about 1 mm. Once the engine is off these drop down freely to close. I have disconnected the servo and blanked it off but no change. These stromberg 175 CD2 carbs appear quite complex. I am thinking there must be air leaking somewhere. Any suggestion as to what might be the cause and how do I correct it 

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Hi RIchard,

That's a lot of rpm for a leak. First ensure the throttle linkage allows both throttles to close.

Assuming your TR250 has all its original plumbing you can check the SMITHS PCV valve diaphragm, the throttle bypass valves and if these are OK you may have a manifold gasket leak.

The carbs are not so complicated but are not adjustable per se, other than float level.

Parts for the carbs may actually be more available here in the 'States where they all were sent originally.


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Hello Richard and welcome to our forum.

I have changed the title of your post, to better reflect your question, and hopefully encourage

more response.


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Hi Richard,

As Tom said my first port of call would be the throttle linkage it can be a pain if not adjusted properly or loose on the ball joints, also the shaft bushes on the bulkhead tunnel fail causing the shaft to be loose, is the return spring attached. Other than that air leak , choke still on or possible ignition timing issue or bits of it all 1500 does seem high for an air leak.

Hope the Buckeye pdf works if not go on the site as there are write ups on how they work, overhaul and set up.

Regards Mark.


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As already mentioned your problems are probably due to the linkage which is easily checked by just disconnecting it, if it turns out that it's not the linkage, along with the buckeye wright up ed h who  posts regularly on here has done an article on disabling the various emission gadgets. I found  these gadgets to much effort to set up properly so using ed's article I removed them  from the equation on my 72 US TR6 which has made life with Strombergs much simpler. Ed's artical is http://bullfire.net/TR6/TR6-20/TR6-20.html


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