I had a customers Polaris 250 which needed a new carb. The Polaris Mikuni replacement was over 300.00 so I ordered the universal vm carb for a fraction of the cost. I played with this carb for days to figure out why it idled perfectly and topped out perfectly, that is once you got through the flat spot which would kill the engine. You didn't have to jump on it either, just a normal acceleration. I checked the float level 20 times or more, ordered numerous main jets to try but it still reacted the same when you accelerated.After several days of scratching my head I noticed a bald spot making me realize I had to call someone to figure this out. I called and talked to a gentleman at Carb Parts Warehouse. They are the US distributor for Mikuni. He asked me for some info such as the vehicle, engine displacement and model of carb which I believe was a VM-26 as well as a description of my problem. His answer was I needed a smaller fuel seat. I replied that it was not flooding out, idle is perfect and wide open throttle run resulted in a perfect plug color. I could not see wasting more money on a seat I knew would not solve the problem and told him so since fuel flows through seat filling fuel bowl until float rises and needle cuts off the flow. He disagreed and told me to replace the seat with a smaller one and guaranteed me it would fix my problem or he would refund me for the part and shipping and I would keep the smaller seat. He was absolutely correct but still I could not comprehend how the seat made a difference. When I put the VM34 on my 150cc I had called him to see if it would even work on my engine. I give him all the specs on my engine cam and head as well as numbers off every internal part in carb. After spending 40.00 on parts the carb I thought would not work performs perfectly. These people know slide carbs, very knowledgeable. So if you cannot get it right than google carb parts warehouse to get their phone number and give them a call. However have all your info ready to give him like engine displacement, mild performance cam, current jet sizes, slide, and needle numbers and a detailed description of the problem as to when it occurs, rpm's if possible.
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