Engine Woes - Less than 300 Miles (smaal end bushing)

[Kielohawk]

I snapped some pics of the damage from running the engine with a bad upper arm bushing.

Here is the engine after I punched out the bad bushing (what was left of it) This shows the upper (wrist?) arm where the bushing gets pressed into...

Here is what's left of the bushing that I punched out. Lots of metal missing

Here is the Piston. Lots of damage on upper part, the rings have some scoring also.

And the upper engine.. Not too damaged.

The wrist pin and clips are Ok

Thatsdax is supposed to be adding some bushings to his site so we can buy them. Looks like I will be purchasing a new piston, rings, and bushing at least. Do you guys think I should replace the cylinder?

Dan

 

[Kielohawk]

Oh yeah, does anyone know if the Dax 70/80 parts will work inside the Power King 80 engine?

 

[OldPete]

Fact: The bike should have been pushed or pedaled home as soon as this noise/vibration started. I post that for others as well as the OP.

Piston pin to bushing fit must be very close as I noted above. Nothing over .001" will really do. If pin fit is .003", the repair will do for selling to a non-friend.

The bushing must be pressed into the rod and not all rods will have the same press fit, that will alter the bushings inside diameter, then the bushing must be precision reamed for fit. With the rod off the crank the bushing would be reamed close to fit, then finished with a Sunnon honing machine. I have done this work, allbeit 40 years ago.

Two things about the cylinder bore will be considered.
Are the scratches deep enough to catch a finger nail? If yes, it will need a proper honing. Are there aluminum deposits on the cylinder wall? If yes, these MUST be removed by honing or the piston will start to seize after a few hours of operation at best.

Like it of not, the con-rod just might have bent from this internal activity. If it is bent too much the piston will drag, over heat and seize. If it is bent just a tad, the motor will work but in a labored state. Power output will take a real hit.

Like it or not, there will be debris in the crankcase that MUST be removed, otherwise it will find a home on the cylinder wall. True, some will be blown out but the gamble to my work would force me to split the case and clean it out properly.
The real debis of this failure are hidden behind the flywheels of the crankshaft around or in the crank's ball main bearings.

My intent is to be honest not mean. Take it for what its worth.

 

[Guest]

Put some butter on it, 'cause that jug is toast!

Nikasil lined cylinders with that much (or virtually any) damage are goners.

 

[OldPete]

Put some butter on it, 'cause that jug is toast!

Nikasil lined cylinders with that much (or virtually any) damage are goners.

Opps! Thought it was a cast iron bore.

 

[Egor]

Sorry to say that I think you will have to put most of those parts in the dust bin. I have put a Kings top end on a Dax engine, I had to drill out the 6mm head bolts to 8mm. I am not sure about the Gudgeon pin bush. On a Hodaka one of the only motorcycle engines I can think of that came with a bushing, we had to ream it out after install, but it was not made to use as made. The bushing for the china engine is a large thick bushing it might make the press fit, anyone know? I have taken these cranks apart, but you need a special tool, if you like I will make a drawing of one, it is not hard to make. I have never found a proper place to get the small parts for these engines, I need the big end rollers and cage, with a new rod. A few outfits have the complete crank but I have never used a new crank unless I had to, just me. Some of these engines seem to go forever and others last a few days, I will not say who failed, but everyone is good about the replacements as a general rule. I rode a Whizzer as a kid and never got over it, I would have one now if not for the cost. Have fun, Dave

 

[Kielohawk]

Thanks man. I have been talking to Thatsdax (Duane) a lot in emails. I had ordered a cylinder, piston, rings, and new upper wrist bushing (bearing) to fix my PK80 engine. I asked him if the dax engine parts were interchangeable with the PK80. He told me that his engine came with 8mm engine studs instead of 6mm and that his parts might not work on the PK80 engines especially the cylinder. So we cancelled the cylinder, and he is sending me a grab bag used engine that a customer had sent back for some minor issue. I am going to tear the upper half down on his Dax 70, upgrade the piston and rings, check the upper bearing for wear (replace if needed) and now I will be a user with a Dax70 instead of the PK80. I should have just ordered a Dax first.
My fault as a rider was not knowing what particular vibration and noise came from the engine when the upper bearing goes out. While it was happening, I thought it sounded like the muffler baffle rattling inside the muffler body. I know now. And knowing is half the battle!! G.I. JOE!!!

 

[Egor]

My every day rider is a Dax engine. A friend of mine was the original owner, and Duane replaced the first engine, I like there engine, it has a built up crank shaft. It uses hidden balance holes as not to increase the volume of the crankcase, that is important in a 2 stroke. It is smother running also. Have fun, Dave

 

[locoWelder]

Put some butter on it, 'cause that jug is toast!

Nikasil lined cylinders with that much (or virtually any) damage are goners.

I agree, unless you can have it rebored, time to get a new one.....now handa70 hop up rings and pistons will work but they take alot of work to piston and jug to get them to match

 

[Kielohawk]

FYI everyone. I ordered this kit from EBAY. Its a Power King 80 from seller POWERKINGSHOP. I got an email from them after I told them what happened and if they could do anything about it. They pretty much told me, Sorry bout your luck. Sold brand new as is. I paid $188 usd total.
Oh they do cover "dead on arrival" from shipment or manufacturing damage or defects up to 7 Days from receipt of item.

Dan