Motor in bad shape - is there hope?

[machiasmort]

I got my motor from BGF (who burnt me), and had to totally redo it. I used three layers of rolled gasket for Advanced auto parts (cut my own) for the base gasket and didn't replace the head gasket at all!

The motor is super high compression. Really nasty in a short lived power band...

 

[AussieSteve]

Generally, if the old gudgeon circlips are a little loose, there's nothing wrong with bending them outwards a bit before fitting them.

 

[machiasmort]

You just don't want to overstress the steel!

 

[Molotov256]

Woot for all the discussion over a $0.50 part! Heheheh... it's entirely too easy to overlook the simple stuff.

Just to set the record straight, I am going to replace the "G" clips with new ones when I put it back together. Now that I know I could possibly reuse the old ones, I'll hold on to them and add them to my pack rat stash in case I need them down the road, but I guess there's no sense risking a loose one popping out when new ones are available for so cheap. I found a set through Pirate Cycles, and they've been good to both myself and a local MBer I know, so I also ordered my piston rings through them as well as a few other odds and ends. Just waiting for the magical world of shipping to do it's thing and hopefully I'll be up and running again soon.

 

[Molotov256]

Minor complications

Well, I received my package from Pirate Cycles in record time, but the replacement engine bolts did not fit properly, and I managed to break BOTH piston rings trying to slide them back into the cylinder. So, needless to say, I'm not riding anywhere in the immediate future.

For the record, the engine bolts Pirate Cycles sells individually right now on their website are stock Grubee studs - they are a 8mm 1.25 thread pitch and are not necessarily made from an upgraded steel as I assumed they were (stupid assumption on my part, their site did not indicate they were a higher grade). They do also sell a stainless steel hardware upgrade kit, and the engine studs in that kit are a 8mm 1.00 thread pitch. According to Justin at Pirate Cycles, the Grubee "80"cc engines use the 1.25 thread ptich, and the PK-80 motors (like mine) use the 1.00.

On the bright side, Pirate Cycles has been beyond awesome to deal with. Justin has answered every email quickly, and he even told me he will send me some of the stainless engine studs at no charge. As if that wasn't enough, he even offered to send me a replacement ring set at no charge, even though it's probably my fault they broke during installation. Can't ask for much more than that. I don't know if Pirate Cycles makes a habit of treating their customers with such reverence, but rest assured, they will be my first stop for parts and accessory shopping in the future!

 

[retromike3]

stainless steel

I checked at my local hardware store and they told me that stainless is not any stronger than the stock parts I had. I was having problems with the mounting hardware so I upgraded to a metric grade 8 and its held so far.

mike

 

[GearNut]

Both piston rings broke on you? Ouch! What did you use for lubrication? I recommend a light coating of pre mix oil in the cylinder. Did you line up the locating dowels in the ring grooves with the end gaps of the rings? Also, when you install the rings on the piston, be careful to not open them up too much. They are cast iron and very brittle. If you do not have a ring spreader handy, "walk" them on the piston by carefully spiraling them onto the piston. Be careful to align them with the locating dowels as you install them , and do the bottom ring first. Never try to install a ring from the bottom of the piston, always from the top down.

 

[Al.Fisherman]

Both piston rings broke on you? Ouch! What did you use for lubrication? I recommend a light coating of pre mix oil in the cylinder. Did you line up the locating dowels in the ring grooves with the end gaps of the rings? Also, when you install the rings on the piston, be careful to not open them up too much. They are cast iron and very brittle. If you do not have a ring spreader handy, "walk" them on the piston by carefully spiraling them onto the piston. Be careful to align them with the locating dowels as you install them , and do the bottom ring first. Never try to install a ring from the bottom of the piston, always from the top down.

Also BEFORE installing the rings onto the piston, slide one of the rings into the cylinder, follow it with the piston so the piston will push it in place. Now look and see how much clearance there is between the ends of the rings. You are installing the rings on a piston that is removed from the rod...right??

 

[Molotov256]

I didn't have much trouble at all getting the rings onto the piston. As GearNut mentioned, I essentially slid one side of the rings into the topmost groove in the piston, and did a kinda spiral/walk motion to get the other side to come down into the groove. Then I would repeat the process to move the ring from the top groove to the bottom groove. I don't know if I am stretching them more than they should be stretched, but I can't think of any other way to get them onto the piston that would take any less bending motion.

The rings broke while I was trying to compress them and slide them into the cylinder. I had used a little 2 stroke oil for lubrication in the cylinder (and a little on the piston while I was sliding the rings on). I got the top ring to go in just fine, but I couldn't get the bottom one to go in. Both rings that broke were in the bottom slot when they snapped.

I'm assuming they broke on account of the rings rotating to the point that the ring ends overlapped the positioning pins on the piston. I was very careful to make sure that the pins were properly located between the ring ends after installation and before sliding the piston into the cylinder, but the rings are big enough that they could rotate over the pins pretty easily, and it's near impossible to monitor ring rotation while trying to compress them, guide the piston, and guide the cylinder all together with 2 hands. I guess I just have to be more careful.

Fisherman - you asked if i am installing rings on a cylinder that is removed from the rod. The first time, yes, the piston was removed from the rod and sitting on a workbench. Then, after breaking a ring, I moved 1 and installed an old one while the piston was on the rod. I'm not sure it made any difference for me...

Anyhow, just waiting on a package again, and I guess I'll give it another go. Thanks for the tips and tricks - I think I'm already following most of the guidance, so hopefully I'll meet some better results next time. Of course, any other suggestions are always welcome as I'm not looking forward to any more broken rings!

 

[Al.Fisherman]

I find it easier to ring a HT piston on a work bench. Try this on the next set. Remove piston from rod, install rings onto the piston, now insert the piston into the cylinder from the bottom of the cylinder (lay cylinder gasket surface down on the bench). You can monitor the progress through the cut out on the cylinder bottom.
The bottom of the cylinder has a outward taper (larger then the bore), This will make it easier to get the rings started into the cylinder and you can see the position of the ring to the ring alignment pin. Once done the cylinder and piston can be slid down the cylinder studs, the wrist pin inserted and the wrist pin keepers installed. It is also easier to start with 1 keeper installed. Once the first ring is in the cylinder, rotate the piston so you can see the ring alignment pin in the bottom grove through the piston cut out.