Experts, please diagnose this!!

[gluttonforpunishment]

hi, gang.

I've got a 150cc water cooled sym joyride scooter as a "gift", DOA, around 43,000km.

At first, the engine was seized, but with a wrench to the thing that drives the variator, I got it to rotate.

It wouldn't start with the battery b/c it kept getting "stuck" in one place, i.e. the starter would turn the engine over, but that's all.  The battery driven starter would work for a few seconds, hit a spot of high resistance, the engine wouldn't turn any more, and I would shut it off b/c of fear of burning up the starter.

So this is what I would like diagnosed:  when I revolve the engine with the wrench, it spins pretty freely till I hit a certain spot. At that point, I have to apply a fair amount of force (let's say 3X the normal amount) to get the engine through the rough spot, and then it spins easily again till I hit "the zone".

Before I take it apart (I'm not really sure it's worth it, and that's a big part of why I'm asking here) what do you think is the problem?

Thanks a zillion. 

[jmkjr72]

Bad bearing
Busted valve or valve train
Timing jumped
Could be a lot of things
Every time you spin it you are causing more damage

[gluttonforpunishment]

thanks for the diagnosis!
how would busted valve train be different than timing jumped?

what would the order from easiest to hardest be?

[Rebel]

A busted valve can fall down into the combustion chamber and make a hole in the piston, make the piston crack the cylinder, lots of bad stuff. A slipped timing chain might just be a little off and keep it from running and the valves may or may not be hitting the piston

You need to pull the head off and have a look. You might also have bttom end problems.

So if you would like to ride it I would suggest pulling the motor out and taking it all apart. Find and fix whatever is broken.

[gluttonforpunishment]

Just to let you know, I've never taken apart an engine before. so for me, this is a big learning and exploring process!

so, I got off the head, the cylinder,and the piston head (HC&P). Remember, the original problem was that as I rotated the engine, I would hit a spot of greater resistance, and then it would rotate easy once through the "friction zone".

With the HC&P off, I rotated the engine again. Hmmmmmm, same "friction zone". Looking at the the connecting rod as I rotate the engine (after I fished out the timing chain), the friction came as the connecting rod (CR) was coming out (kind of like when you stick out your tongue). So what I did was spray some WD40 right at the point where the CR is attached to the crankshaft.

Wow, BIG difference! No friction!

Now, before you ask, the engine oil level is full, according to the screw in plug. But there is ONE more interesting thing (for me).

When I rotate the engine, sometimes the cams on the crankshaft get a coating of oil on them, but sometimes not. When it does get oil on it, it only covers about half of the bottom of the cams.

BTW, the crankcase seems to have been apart by someone else b/c there's red silicone sealer there.

Well, what do you think???

[Rebel]

Sounds like you have a bad rod bearing. You should look for a new crank/rod to install. You also may have a bad oil pump that can not generate enough pressure to properly lube everything. Really, a total rebuild would probably be called for. I don't know what you could just buy a motor for but I doubt it is economical.
Making a vid and posting on youtube would be helpful, posting photos would also help.

[jmkjr72]

NewcrYep toasted big end bearing

Not fun when they fail at speed
And oil
New crank bearings and oil pump at thee least

[glutton4punishment]

I'm so screwed..........

[Rebel]

It is not that hard to fix if you want to give it a try.

[arcanum70]

Glutton, there are videos on youtube on changing and connecting big end bearings. You got the motor apart (something you've never done before), you can do this too. I look forward to reading about how great she rides when you finish this fix, I know you can do it.

I can certainly feel for you, tasks like this can be daunting, however, look what you have accomplished so far. You're in the home stretch.