Picked up a Cub 1641 for a backup
 

Hello all... it's been a while since I've been active on here, or with Cubs in general. Last summer I picked up an 1872 and 1862, and both are down currently. The 1872 has a driveline issue, and it ate up the bearing on the input shaft which in turn ate into the input shaft itself and started leaking transmission oil. It's been leaking and I finally had time to dig into it a little bit, and that's going to be an expensive fix, so it's down for now. The 1862 has a charging issue, likely the flywheel magnets need re-glued, which means engine pull and tear down to get into that. I just don't have time for this stuff right now, with kids growing up, and I got roped into coaching soccer for U10 this year and I never played soccer or had an interest in it myself, but my little boy who is now 9 took an interest in it. It's been good for me though because I've been getting more exercise and trimmed about 15lbs off my gut in just two months. :biggrin2:

But I need to get to the point of all this... I went looking for a cheap backup mower to fill the gaps, because apparently two was not enough. I came across a really good condition 1641 with a 48" GT deck. It even has good plastic! I've had these before so I have familiarity with it. It has 1100 hours, and I will be going over it changing fluids, filters, etc. It runs fantastic and starts up instantly. However... it has this issue after I open the throttle up it will start blowing heavy smoke (definitely oil) and I can see it is moist in the muffler exit for about 1-2 minutes. It starts out strong and then fades. Almost like it's sucking oil in through the breather. If I let it just idle it does not smoke, until I open the throttle. If it's a crankcase breather issue I would think that would be smoking all the time. I don't think 1100 hours is too bad for a well maintained vanguard engine. The engine bay and engine is completely spotless. No leaking anywhere. No grass clippings, dirt, etc.

So, any ideas of what to look for? I can do a compression/leakdown test on it, but my (now smaller) gut tells me it's not rings or compression related.

Are the seals on the crank leaking? Oil level?

Seals are good. I'm thinking it's an internal head gasket failure. I've noticed if I start the engine and leave it idle for a while it does not smoke. It's when I throttle it up that it smokes and then gradually goes away. The oil goes down with the smoke, but I do not see any oil coming out of the engine anywhere. The muffler outlet gets wet with oil too while it's smoking and dries up when it stops. I mowed with it until the deck belt broke three laps in, and it does not smoke more under load.