My evolution tps has developed some play in the connecting rod, crank bushing. I have it torn down, purchased parts, and it's ready for reassembly.

how do you remove the wrist pin from the piston? Should I clean the piston and sleeve? With what? What about lube during reassembly. Any other insights would be nice.


Thanks, David

I recomend not cleaning it unless it was 3 feet in the ground or really dirty in the future as for the sleeve, run some toilet paper or paper towel to clean it. I wouldn't remove it.

Dave Trimmer

not sure how the wrist pin is held in place,but there are the following ways.
1. pressed in will need special fixture to press it out without deforming piston[fox engines ise this method]
2.just slide it out but watch the teflon or brass pads on the ends[veco,webra,os and others use this on some engines.
3.remove the wire circlips that hold the wrist pin recessed in the piston.these clips are in a groove inside the wrist pin bore of the piston.

Dave Trimmer and aerowoof have offered helpful advice. If you want more detailed information than what is already provided, try checking out the glow engine forum:

http://www.rcuniverse.com/forum/forumid_114/tt.htm

There are a number of engine experts who post there quite regularly.

I have rebuilt quite a few engines . I can tell you often it is more economical just to buy a new one if heavy damage has occured or its worn out.sometimes it pays if only one or two parts need replacing.if nothing else ,its an education. you must pay very close attention to how things are aligned& placed so it goes back EXACTLY the same way. normally, I would not recommend disassembly of the piston& liner for crash damaged motors . flushing the engine with the head removed , backplate removed& carb removed usually works. 3 in one oil works for assembly oil

... and when you get it rebuilt, stick to 15% or less nitro and at least 16% oil and ballance your props. Lack of lubrication and vibration will cause play in the conrod bushing as well as the front bearring. - Just a thought -

I don't know the Evolution but almost certainly it'll have either one or two circlips holding the wrist pin in place. If there's only one then the other end has a step in the piston so it can't move in that direction so take out the circlip and push the wristpin out that way. If there are two circlips then just take one of them out.

But that's getting ahead of things because there's something you'll have to do first seeing you've already got the piston/rod out of the engine. Assuming you haven't marked anything to know which way to put it all back together the same way (and you want the piston to go back in the liner the same way it's been running) then all is not lost, hopefully .

Almost all conrods only fit one way on the crankshaft so you'll have to look carefully at the bottom bush in your rod. One end of the rod will have a chamfer in the bush like in the first photo below and that goes up against the crankweb, in other words it faces to the front of the engine. The other end of the bush will be machined flat to the rod as in the second photo and that's the end you see when you take off the backplate. Find that chamfer and you'll know which way the piston should be so make a mark on top of the piston pointing to the front or maybe to the exhaust, whichever suits and that you'll remember. To the front is probably better because that's going to be the way the chamfer in the new rod will have to point.

Now you can take out one of the circlips using tweezers or very fine pointed pliers. I use tweezers with an angled end to get inside the wristpin hole more easily. But be careful because if it springs loose then you'll probably never find it again. Some guys take the circlip out with everything in a large plastic bag to catch it if it springs loose.

Push the wristpin through far enough to come out of the rod and then you can fit the new rod (put some oil in the rod bush first) making sure the chamfer goes the right way. Fit the circlip back into the groove with the tang pointing the same as it was originally but make dead certain it's right down in the groove.

Pistons and liners generally don't need to be cleaned other than a wipe with a very clean rag and some fuel just to make sure it hasn't picked up any dirt in the meantime. Rod bushes usually last quite a long time with the right oil so I'd suggest using a fuel that's got quite a bit of castor in it. There's no better lubricant for plain bearings or bushes than castor.

Repair finished. The wrist pin had a small, white plastic piece holding it in. It tapped right out. For cleaning I used a tissue and a can of compressed air, the kind used for electronics.

I richened the high needle two clicks, hope this helps it last a little longer. Before it was turning a APC 10 7 at 13500. Don't know rpm's now as I don't own a tach, I borrow one at the field.

Thanks for all the advise, I didn't want to send it in for repair. I want to learn to repair my own stuff. Cost 15 dollars. Experience priceless.

thanks again, David

The white plastic pieces are actually teflon pads to protect the cylinder walls. Can we assume you remembered to put them back in?

Yes I put it back in. There was only one as the wrist pin will only come out one way. The pad went to back of the engine so it went back the same direction.

Thanks David