I know, corny title, ....couldn't help it.
A couple months ago I bought a 1972 MF10 with a rebuilt engine and new carb. PO says it's been sitting for awhile, that's why it won't idle right. He's got a shop in the back yard and several project cars that he's working on and a couple GT's so he should know what he's talking about right? I've been cleaning and recleaning this Walbro 34 carb with the idea that there must be a plugged passage on the idle side. The last time I boiled it, and it still wasn't any better. I had found the warped flange several cleaning ago and flattened it out with 400 grit wet/dry paper and a flat surface.
I finally gave up on cleaning the carb and turned my attention to the Solid State Ignition since all I need is fuel, air, and a spark to make it run. When I pulled the flywheel, using a puller as I should, I noticed quite a bit of dirt and rust on the magnets. Okay, I'll clean it up and while i'm there replace the timing pins. The replacement pins had heads on them and the instructions said to press them in until the heads bottom out and adjust the SSI to the proper air gap. Now, I'm savvy enough to know that if you change the pin height, you change the timing so I was extra careful to take measurements. See where this is going?
The original pins didn't have heads and looked a bit dinged up but I measured them the best I could with the backside of a pair of calipers. The taller pin stood .255" off the edge of the flywheel and the shorter was .190" proud. When I pressed the new pins in they were .200" and .130 respectively. I readjusted the SSI to have .006" clearance, hooked up a timing light and on the second time it turned over it was off and running at a real nice idle....just from the gas in the float bowl.
Cleaning things up and replacing the flywheel key (since I'm there anyway) probably didn't do more than give a little better spark, but I'm convinced that the "professional rebuild" that was done some years ago fouled up the ignition just enough to cause the timing to fire a bit early or a bit late and gave the impression of gummed up carb.
I found the head a bit warped and flattened it to cleanup, put a new head gasket on, and new Belleville washers on the head bolts where the lock washers had been since that was how it was suppose to be. It sat and idled for about 15 minutes before I shut it down to cool. I need to retorque the head bolts tomorrow night and then replace the flywheel shroud and it should be fine.
I couldn't wait to get in and share. Thanks for reading.