OK guys I am close to finishing my 350x/250x conversion. Last week I couln't wait to start it I had it mostly together, I had the header pipe on, no silencer, intake all together (of course), nos 350x carb, fresh oil, fresh gas. Well, the problem is that it does not want to be kick started. I have given it a little encouragement by pull starting it, two or three pulls and it started, after I got it started it would kick start on first or second kick when still warm. I have done some more work getting it together, i.e. the exhaust and throttle cable, and have tried just kick starting it but it does not want to start. I have some finishing work to do to it still but was hoping to get some ideas for me to think about before I start getting into it. The electronics are for a 350x, the motor seems to be fresh and had been stored with oil in it. Could it be a jetting problem? valve clearance need adjusting? old rings? I would think that these things would keep it from running right but not from starting. Any ideas would be greatly appreciated.

 

Are you sure the enrichment passage is clear in the carburetor ? The 350x carb uses an enrichment system for starting rather than a choke plate , if that passage is blocked you will not have any more fuel going to the engine with the choke on . I would check this first since you say it starts ok warm . The 350x engine was never known for easy starting and most of it was related to carburetion . If you have a 250x or a 300ex carburetor on the 350x it will start easier and run better. I had a 250x/350x conversion with a modified engine and I resisted going to a 300ex carb, but when I did the engine started easier and ran much better.You should also make sure the decompressor cable is not adjusted too tight . I would check the valve lash and compression just for piece of mind.

 

Thanks for the reply 87250r88.

I have never heard of this enrichment system. So does this system choke automatically or only when I put the choke on? I have tried starting it with the choke on and off in 40-55 degree weather.

I have a large aftermarket Keihen (never could spell or say correctly) carb that I was using for my modified 250x engine. I hesitated on using it due to more than likely having to rejet.

The decompression cable seemed ok. It is not too hard to kick over.

Would you happen to know what the valve lash should be? I do not have a manual but I would imagine it's checked at TDC on the compression stroke?

I do not have the equipment to check the compression strength should I take it to my dealer to check or is there another way to check? The compression does seem to be strong but I would like to know what it is and what it should be.

Thanks!

 

The choke does not work automatically. On an enrichment type system , when you put the lever to choke (rather than closing a choke plate) there is a plunger that moves and opens a passage that allows fuel to pass through thus creating a richer mixture. If that passage is blocked or the plunger does not move there will in effect be no "choke"
Does the Kehin that you used on your 250x engine have a choke plate ? Do you know what size it is ? If it worked good on your modified 250x engine , it can most likely be jetted correctly for your 350x engine .

When the "T" mark on the flywheel is lined up with the pointer and the engine is on the compression stroke the valve lash on the intake should be .003IN and the valve lash on the exhaust should be .003In with a stock cam. After you adjust the valves and before you turn the engine , check the decompressor adjustment. There should be 0.5MM - 1.5MM free play at the tip of the decompressor lever.

There is only one way to check the compression and that is with a good quality gauge and the proper length adapter to screw into the head. A dealer should do this for a nominal charge.The correct procedure for checking the compression is 1. warm up the engine 2. stop the engine and remove the spark plug 3. disconnect the decompressor cable 4. insert a compression gauge 5. open throttle fully and operate the kick start pedal several times . The compression should be 178 PSI + or - 14 PSI