QuestionQUESTION: Howard,
Stumbled onto this site but am glad I did. Hope you can help. My '70 B has had a Mikuni (Solex) sidedraft since I bought it in '95. Car starts / runs extremely well - except in very hot temps when car has been off for 15 minutes or so. To start, have to hold accelerator to floor and it will start and clear itself out. Suspected flooding or percolation so replaced needle and seat, checked / rechecked float adjustment and wrapped exhaust in header wrap but to no avail. Installed adjustable fuel pressure regulator thinking pressure was too high and overpowering needle/seat. Ambient temperature needs to be 75 or higher for hard start. If cars sits for an hour and cools a bit it starts fine and I only have to momentarily hold starter. Any ideas? Thanks!
ANSWER: Hi Steve,
I don't know anything about the Solex but an engine that don't start hot is either too rich or too lean or flooded or has a dry float chamber.
Holding the throttle to the floor on a warm or hot restart is a normal symptom of a flooded engine. However another thing can be happening. Some carbs are prone to "heat soak" meaning the engine heat goes into the carb and gas and boils the gas in the float chamber which forces a lot of fuel out the jet and into the manifold thus flooding. A simple test of this is to set up a strong fan so as soon as you turn off the engine you raise the hood and turn the fan on blowing on to the engine and carb. Then see if it starts in the normal time it usually has a problem. If that works after several times then you can feel sure that is the problem and you should put a heat shield and insulator block under the carb.
Another thing that causes problems is too high fuel pressure and heated lines that cause fuel pressure to climb after the engine is turned off thus over riding the float valve. Test is to put a fuel pressure gauge on between the pump and carb and watch it after engine is off for a while to see if it climbs. I don't know about the Solex but most small engine carbs can't handle much over 1.5 PSI fuel pressure.
Howard
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QUESTION: Thanks for the prompt reply! I've looked for a heat shield but can only find one for Webers so I'll have to fabricate something from stainless. I like the suggestion about watching the fuel pressure regulator gauge after it sits. I'll do that but will have to wait a few months - I'm in New England and tonight it'll be 5 degrees!
I'm rebuilding my 4 spd w/ O/D. Need to replace 3-4 synchroniser and bearings. O/D works fine. Have a few articles I downloaded but other than the Bentley "Complete MGB" Manual (the big one at 500 pages) do you know of a good book or video on MGB tranny rebuilding?
Thanks again for the tips.
AnswerThe Bentley manual should cover the trans rebuild. Just be careful not to unload the sliding hub assemblies as it is a little work to reload the balls and springs. Also getting the OD back on the mainshaft when you assemble the OD to the trans can be a little tricky. Read the book. The alignment of the internal splines in the OD and the oil pump roller are points of interest in the book. If you have any questions in that area let me know.
You would be wise to replace all syncros while you are in there and look carefully at the lay gear shaft for pits. If any are noted examine the area in the lay gear that the needle bearings ride for signs of pitting also. The same for the bearing between the input shaft and the main shaft. If this trans is noted for jumping out of any gear you must examine the splines of the sliding hub of that gear and it's spline on that gear itself. If it had been jumping out of gear the sides of each short spline could be worn in a bevel shape.
Howard
