Blown top end; how to clean up?

[noiseguy]

OK guys, here's what I have. '94 Honda Elite with seized top end. I haven't taken it apart yet to see what it looks like, but I suspect the mis-connected oil pump and oil starvation caused it to overheat and seize.

My guess is that I will find little bits of piston. Everywhere.

So here's the question: Do I need to crack the case on this engine, or can I flush it out with, say, some 2-stroke premix and wash the stuff out that way?

I can inspect the bottom-end bearing for side clearance and crank bearings for play with the engine fully assembled, so that's not a reason to tear down. I can replace the top end with either a kit or a used OEM replacement.

Thoughts on this? I know that some of the answer will come after I take it apart; for instance, the rings only may have seized with the piston more or less intact. But I wanted to collect some input b/f I proceed with the teardown.

[Wheelman-111]

Greetings:

Noise, I'd crack the cases. You know you won't be able to sleep without knowing there are new bearings and seals in your rebuild. It only adds an hour...

[Bear45-70]

In a normal piston meltdown, if you can call any meltdown normal, you rarely if ever get melted pieces of aluminum back into the case. This is because the intake charge is very cool, relative to the combustion chamber temperatures and super cool when it comes to molten aluminum. The exception to this is if you actually melt a hole in the piston, then all bets are off. If you have no hole in the piston and find no melted aluminum in the intake port from the case to the cylinder then I would not worry about it.

FWIW, I have never had melt aluminum reach back into the case, but I never holed a piston either. I have seize a couple of high performance engine at high enough RPM to bend and/or break rods though.

[maddog]

it should be only rings and even if the wrist pin gave out just pull the engine fil the case with gas, shake and pour out the broken parts, if the crank doesn't turn only then will you have to split the cases, if you need a new oil pump buy a sym-dd 50 $40 vs honda $140

[noiseguy]

Thanks guys. One of the reasons I'm hesitant to split the cases is that I don't have the proper tools to split it on hand. I guess I could make some, but it adds a lot to the project complexity.

I'll dig in and see what's going on.

I'm sure the oil pump still works. PO hooked the oil pump output to the carb vent; you can see traces of oil all over the side of the carb. There are other oddities as well with the hookup that were obvious to someone that's familiar with these carbs. Unfortunately for PO, it ran when he was done and it smoked itself after about 10-20 minutes of low-speed riding.

[Bear45-70]

An idle speed seize takes real work and talent. Beside stupidity and ignorance. Very, very sad.

[jesse8931]

bear i ran a briggs and stratton motor at 12 thousand rpms down a drag strip and threw the whole crank with rod and piston still on out the side of the block.

[Bear45-70]

bear i ran a briggs and stratton motor at 12 thousand rpms down a drag strip and threw the whole crank with rod and piston still on out the side of the block.

You are aware that Briggs & Stratton never designed an engine to run above 4000 RPM?

[noiseguy]

I think that may have contributed to why it blew up Those are splash lubed, right? I can't imagine how it possibly could have run at that RPM; the valves would be floating at that point and you'd lose compression (no piston/valve interference on a side-valve.)

Are the Briggs cart racing engines limited to 4K as well?

[scooterwerx]

i knew a chick who raced jr dragsters, they ran b&s motors, completely modified, forged internals, billet everything, on alcohol. her dad said the race motors cost about 10g!!! they sure sounded like they were spinning 10k+

[Bear45-70]

A couple of the Briggs racing engine are rated for 6000 and 7100 rpm, but these are the only two hot rod motors and are all hand built and hence VERY expensive. But you are still running a lawn mower engine and when you hot rod them you end up with the same thing you get when you super hot rod a 50cc scooter, SHORT LIFE.

[jesse8931]

i had almost 5k in the motor

[Bear45-70]

i had almost 5k in the motor

That's the reason I quit drag racing, too much money require to stay competitive in the Sportsman Classes. I went boat racing and my first National Champion engine (Stock motor, the boat was only $1200 and did 90 mph) and cost me only $2500 and that included 3 custom racing props at $300 each. Then with some sponsor's money, I when into the factory race engine classes and still had less than $10,000 in 2 complete engines, plus 2 spare long blocks. Finally a sponsor approached me with the offer of a pair of $10,000 Champ Class racing 2 Liter motors (8600 RPM and 132 mph on my boat) Nothing for me to do but run them with his name on the boat and he paid for that too. But I was in for way less of my money than was involved than either of my last 2 race cars.

[jesse8931]

its was not good at all but it also made close to 20hp

[Bear45-70]

its was not good at all but it also made close to 20hp

My stock lawn mower make 20hp.