OK, so I have not been on for a while. Life has been crazy.
A year ago, I had finished getting the 83 carbs in a good running condition (nice idle, ran really nice -- thanks QBS). It was starting to get warm (spring in Houston!), but drove to work one day, and it stalls-out pretty bad on a way to work (~13 mile ride early in the morning). Got it going, rode the rest of the way to work. Rode home without any issues.
A couple of days later I ride it about 4 miles and park at church in the morning. After getting home (afternoon), I notice that it is leaking gas out the overflow drain tube. I think, it was just an overfull tank, hot day, etc. Next day, it is spilling-out gas as soon as it starts-up. I didn't have time to deal with it -- started it a few times with the same results over the next few months.
I pulled the carbs off finally on Saturday. Pulled the tops off the carbs. Front is wet, rear is dry. I do a quick clean on the tops (ultrasonic using water). Set the float levels using Berryman B12 carb cleaner (to clean the bottoms) on the bench. I may have set the float levels a bit low (rather than too high, ie, 25-30mm). I capped the T drain on the front carb, and ran 2 tubes, so that I could tell if it is the front carb or the rear carb. I get it going (needed to swap an oil filled starter, but I already had a rebuilt ready to go). Runs pretty rough, but starts to go OK after a while.
I take it for a 1/2 mile ride to get some new gas. Stalls like crazy. No bottom-end or mid-range. Put in a couple of gallons of premium. Get it home again (3 more stalls). Idle it in the garage, and it not doing so well (hunting). That was Saturday.
I come home today from work, fire it up. Still not running good, AND the front carb overflow is spilling-out. But I do need to get it inspected. Get 1/2 a mile, stalls 3 times, no bottom end or mid-range. I turn around and bring it home.
What do y'all think it is? I am thinking the front float gets "fuel-logged" and then it overfills. That is all that I can think of.
Any other ideas?
That 91 Miata that someone posted at work is looking like a much better "mistress" right about now!
Thanks,
Evan
Overflowing means too much fuel in the carb, which could be dirt or rust in the float valve letting fuel by. Do you have a fuel filter inline? What condition is the interior of the tank? Are all the diaphragms in the fuel pump/ regulator/ recirculation system in good condition? Make sure the fuel lines are clear of foreign matter.
fuel out the overflow means one (or more) of 5 things:
--needle & seat are leaking (front, rear or both?)
--Petcock is leaking
--return path is restricted (goes back to petcock)
--drain screw o-rings are shot
--float levels need adjustment. you can safely drop them by 3mm. the overflow tubes i have measured vary in hight by 2-3mm, some were so low that the bowls would overflow with the correct float setting...
--Lucky
Thanks Fret Nut & Lucky for the responses. Yes to inline fuel filter. Yes to clean tank. The fuel pump seems to work well when I use my "test" tank (which has a place for the fuel to recirculate).
Lucky, I don't think the drain screw o-rings would cause fuel to run down the drain tubes (would run out the side of the carb though). The float needle & seat were both just ultrasonically cleaned, and seem OK.
I left the front float overnight in a bowl of gas to see if it would sink -- but seems unchanged this morning.
I think a blockage on the fuel pump-to-tank return line might be the real culprit.
Any thoughts on capping the return inlet on the tank petcock and having the fuel return line run into a T fitting with the fuel inlet (up stream of the inline fuel filter)? I would think that would be a modification that someone might have done to make 83 carbs work with an 82 tank....
-Evan
i've done that mod, it seems to work.
i'm pretty sure if you crack the bowl drains fuel will come out the overflow tubes, but i might be wrong, i don't really know much about these carbs....
Blocking the return line has never caused my '83 any operational issues of any kind. Evan, contact me. We need to get together.