Repair Pistons and Cylinders Using Alumiweld/Alumaloy/HTS-2000 (Experiment)

rohmell · Sep 19, 2011

I have a piston and cylinder here that got scored by an errant needle bearing jumping up from the connecting rod's small end.

I am planning an experiment which will involve filling in the scored area with some aluminum brazing/welding rod (Alumiweld/Alumaloy/HTS-2000) and then machining the areas back to normal dimensions.

The rod melts around 730 degrees F (388 degrees C) so it should hold up in a normally running and correctly tuned engine.

I plan on taking before/after pics and posting them all here.

I know a replacement piston and cylinder are cheap, but I have a ton of these rods sitting here, so I going to give this a whirl.

rohmell · Sep 19, 2011

Will also be using a brass bushing in the connecting rod little end, instead of the prone-to-failure needle bearing in this experimental engine.

bairdco · Sep 19, 2011

good luck. i tried to fill in a stripped exhaust stud hole with alumiweld and a bernzomatic mapp gas torch, and just couldn't get the area hot enough to melt it together.

alumiweld is some tricky stuff. the area has to be super-clean, otherwise it won't stick. it still has a tendency to peel off, or just not work at all.

i've made custom intake manifolds with it, and when it works, it works awesome. but it has a very high frustration rate. i can't tell you how many flaming hot parts have been thrown around my work station in anger...

rohmell · Sep 19, 2011

Maybe the key is preheating the part using a stove or barbeque grill until it is uniformly hot, then going in with the torch and then applying the alumiweld.

The piston is small, and I think there will be little trouble getting it hot enough to melt the rod. The cylinder is another matter, it is going to be like a huge heatsink sucking away all of the heat.

biknut · Sep 20, 2011

I doubt you'll be able to get anything to stick to the chrome bore.

happycheapskate · Sep 21, 2011

Where do you get the parts cheap? I have a 48cc grubee with a busted piston, cylinder. I have been saving it for parts. The piston ring split and it locked the engine. I think the bottom end is ok though. It turns smoothly and the rod doesn't rattle around.

rohmell · Sep 21, 2011

I buy from BGF on eBay, he does combine shipping.
I don't know if his parts fit the grubby Grubee garbage engines.

happycheapskate · Sep 22, 2011

Hhaha. What do you have that is not a "garbage engine", esp since yours blew up?

rohmell · Sep 22, 2011

I buy from BGF.
I don't blame BGF for the blown needle bearing; he didn't assemble the engine, nor make the bearing in it.

happycheapskate · Sep 23, 2011

Doesn't he sell china-kits too? Does he do something different to them?

Pilotgeek · Sep 27, 2011

Alumiweld is great, but you MUST get the parts hot enough to melt the rod. NEVER melt the rods directly with the torch. They are kinda fussy, but work well for minor repairs or making small stuff. That said, I would not use it for internal engine parts.

rohmell · Oct 17, 2011

I said I was going to post before and after pics, but I didn't get the chance to take any pics, but the engine is all assembled and 50 miles so far no problem.
Also, I said I was going to use a sleeve bearing, but instead, I put in one of these:

10X14X15 shell needle bearing
2mm longer than the stock 13mm open bearing, plus 2 shims added on either side, so there is no side to side play.

Lubricating oil mist can condense and pool inside the shell rather that leaking away thru the needles, so there will always be some lubricant inside the shell casing during initial startup.

Pilotgeek · Oct 17, 2011

Ooh, I very much like that solution.

richirich · Oct 17, 2011

where did you get such a bearing, that does look like a great solution.

rohmell · Oct 17, 2011

The bearing is from here:

http://www.ebay.com/itm/HK1015-10x1...728?pt=LH_DefaultDomain_0&hash=item1e66bf9df8

richirich · Oct 17, 2011

thanks for the info, i think ill order one just in case.. i havent had the needle bearing go but it will be a possibility since i ride my motor hard. that bearing looks like it would be hard to destruct.
thanks again

rohmell · Oct 25, 2011

As an aside, this seems to be the only vendor that has the brass bushing for the older engines:

Custom Motored Bicycles - PARTS for Motorized Bikes 2,Cylinder,Slant Heads, Rings,Gaskets

Goat Herder · Oct 25, 2011

I hated these wrist pin clips.

A Long time ago I tried them there are two different styles out there. There was replies to my question in this thread a very long time ago when I had first joined. Every body that replied to my question prolly had the better clips any how I left a part number to good ones. http://motorbicycling.com/f34/piston-clips-6307.html

rohmell · Oct 25, 2011

I don't like the looks of those clips... The ones on my engines make more of a complete circle and then have the little firn going in towards the center of the cirlce..

Goat Herder · Oct 25, 2011

rohmell said:
I don't like the looks of those clips... The ones on my engines make more of a complete circle and then have the little firn going in towards the center of the cirlce..

Those are the good clips you are describing! The ones I put the picture of are lousy.. they are really bad laff

I got a small collection of the original brass bushing set ups. Got them from fellow members etc. I am not letting go of them ether!

Repair Pistons and Cylinders Using Alumiweld/Alumaloy/HTS-2000 (Experiment)

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