# Bolens 1256 Zenith Carb/Wisconsin TRA12D issues



## Remy Courtois (Sep 3, 2019)

Hello, all I am new to Wisconsin engines and Zenith carbs but not new to repairing engines. I just bought 3 Bolens husky 1256 tractors with a bunch of spare parts and attachments. I had a running engine but it had a major oil leak thru the head and burned a lot of oil because of a warped head. I ended up swapping the engine out as well as the carb, but it still would not start. However, the carb that I replaced (The one I took out of the old engine) worked before on other engines. So I messed with it for a bit and got it to sputter on starting fluid but it would not stay running on gas even though there was gas in the tank. For whatever reason, it would not get into the cylinder. Currently, I am trying to figure out what the cause of the gas not burning or getting into the cylinder. I am willing to buy parts if needed or a new carb. Any help would be greatly appreciated. (Note engine has spark and attempts to run)


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## Bob Driver (Nov 1, 2017)

All small engines have to create crankcase vacuum when the piston travels down on the intake stroke in order to draw fuel through the carburetor. 2-stroke engines will not even attempt to start without crankcase vacuum, but it's just as critical on 4-strokes. Both Briggs and Kohler say a minimum -4" of WATER for vacuum. The testing problem for DIY mechanics is that most vacuum gauges available read in inches of mercury (Hg). You need either a water manometer, or a DTI-33 electronic vacuum tester to get an accurate vacuum reading in inches of water. Crankcase vacuum leaks are common for engines that have sat around for a long time. Leaks can come from the main crankcase seal, either crankshaft seal, carb base gasket, valve stuck open, poor ring seal.... 

At the moment, you just need to know if you have enough vacuum to draw fuel through the carb (you said it tries to run). A poor man's way to find out is with a small piece of tin foil wrapped over the carb intake. Take the plug out and turn the engine over with full choke (I use a variable-speed drill with a socket adaptor on the flywheel nut). Full choke creates max vacuum and keeps the tin foil from getting lodge the carb. Slowly turn the engine over and watch the tin foil, it should flex hard toward the carb opening. If it tries to blow off, you've got an intake valve that's not sealing. This test will tell you if you're getting ANY vacuum to draw fuel, it doesn't tell you if it's the minimum of -4" you need. For a that you'll need a cheap water manometer and a flow through plug that fits the dipstick tube opening.

https://www.amazon.com/RadonAway-50...hvlocphy=&hvtargid=pla-4584413737681204&psc=1

If you find very little, or no vacuum, with the tin foil that's why you're not getting fuel drawn into the cylinder. If that's the case, you can test for vacuum leaks with that drill set up and a spray bottle of soapy water. Spray the solution on the main case seal, both crankshaft seals, and the carb base seal. Slowly turn the engine over and look for bubbles. No bubbles.... Rings, or valves aren't sealing well enough to create the -4" of vacuum.


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