QuestionQUESTION: I have an MF 202 with cont z134 gas... it backfires top end when accelerating and no power, have re-gapped pts, tappets, set timing using timing hole 4degrees TDC, rotor pts to #1 and pts just opening... still backfires, rotating distributor does not fix... removed timing cover and gears are aligned... what's next?
ANSWER: Hello,
See if pulling the choke out part way will help. If so, then it is running too lean from either a fuel supply or carburetor problem or a vacuum leak. Check the manifold and carburetor mounting bolts for tightness. A bad condenser or coil will cause it also. You could try replacing points and condenser. Look at the ignition system with the engine running at night in the dark. You might notice sparking around the distributor cap and plug wire area. Carefully inspect the distributor cap and plug wires, or replace them.
Good luck,
Arnie
---------- FOLLOW-UP ----------
QUESTION: Thanks Arnie, Also planning to overhaul bottom end... what is the best way to remove the wet sleeves, and what is the proper way to measure these and the bearings on the crank shaft for replacement?
Many thanks,
WM.
AnswerHello,
The best way to remove the wet sleeves is with a sleeve puller with the proper size plate to fit the bore. If you don't have access to these, they can usually be driven up from below with a maul and a heavy steel bar used as a punch on the edge of the sleeve that protrudes inside the block. Cover the crankshaft with rags so the side of the bar doesn't hit accidentally against the rod journals and scratch them up. Once you get them to move a little, they will be loose and can be pulled out by hand. To measure the inside bore, use a bore gauge, or a telescoping gauge and micrometer or digital caliper. Measure in 2 places 90 degrees apart. If they are OK, you don't need to remove them. If the pistons are not removed, you don't need to do anything else with them, but if you remove them and plan on reusing the same pistons and sleeves, then you will have to hone the sleeves and install new rings. The bearings should be measured with Plastigage obtained from an auto parts store. Remove a bearing cap and wipe the bearing and crankshaft dry, cut off a little piece of Plastigage which is like a thin plastic string, and place it on the bearing surface. Put the cap back in place and torque it to specs making sure the crankshaft doesn't turn. Remove the bearing cap again and measure how much the plastigage squished. The paper wrapper it comes in has a comparison chart on it to tell you the clearance in thousandths of an inch. If all the bearing clearances are within specs, you are good to go. If any of them have excessive clearance, then the crankshaft should be measured with a micrometer in 2 places, 90 degrees apart. If the crank is out of specs, it should be ground and undersize bearings installed. If the crank is still within specs, then just replace the bearings with the same size.
Arnie
