Warning....Newb Carb Question

[Bruce Palmer]

Any over filling will just overflow into the engine and get burnt, no big deal.

We have had a couple of situations related to us from the field that ought to be discussed.

One customer said his carbs were going thru damper oil like crazy. The reason? He was filling clear to the threads at the plunger cap. Yep it'll go thru oil like s**t through a goose because everything above the top of the tube will get sucked right into the engine.

Another with "running issues" finally admitted he was doing some tuning by putting 90W gear oil in the dampers.

[beandip]

the use of different oils in the carbs seems come up every few months . Nissan in the manual I have, it recommends 20w. Since it is not available everywhere I have been told 10w30 will suffice. I have heard everything from brake fluid to 90w gear oil being used. including water! In my own use I was using ATF then Marvel Mystery oil, because this was recommended. I hadn't read the Nissan info. I was having a stumble coming off idle. It acted like ignition in this regard. I could not find the source of the stumble for the life of me. I switched to 20w after reading the Nissan info and the stumble vanished. Looking into this further for a reason, I learned that , using a thinner oil causes the vacuum piston to rise too quickly causing more air to enter the engine BEFORE the fuel mixture had a chance to increase. This causing a momentary lean situation. In a race scenario when keeping the engine up in the high revs/power band the piston is always up anyway and it is not a factor. But on a engine driven on the street it is a different matter. It may make a difference for those of us that live in high-altitude parts of the country like Denver. I have been using 20w exclusively for almost 8 years , not that long I know, and have been vary satisfied with the performance. Both off idle and all through the range of the engine. I use Fork oil. I found 20w fork oil at the cycle shop, bought a qt and have given some away and still am using the same quart.

[blue 72]

Yeah, ATF is a detergent, so it'll just clean the intakes a bit as it goes through. I overfilled mine once, but just wiped up the spill from inside the bodies, around the needles. Like Bruce said, no big deal.

I also tried a much heavier weight oil at one point in time, but didn't like the throttle response (hmmm... wonder why:rolleyes:). I may try straight 20 weight next time I find some. I do live at 6000', so some more experimenting may be in order.

Edited October 4, 2008 by blue 72