Zenoah G260 Piston Mods


I want to publicly thank Larry Broman known as fastratfink and Michael Tyson known as Mike T on the Boat Dock Forum for their help with getting my engine modified. Michael made the mandrels for me and tried to tutor me in modifing my first engine. The first piston I tried to do I made a total mess of it. Wanting to run my boat for my vacation, Larry bailed me out with one of his pistons, which I will use as a guide to do others from here on out. Thanks to both of you for your patience and unyielding help. Below are some pictures of the mandrels and the piston. You can email Larry at fastratporting@msn.com and Mike at t-modracing@comcast.net if you have any questions for them. Or you can get a hold of them at Jim's RC Boat Dock


This shows from left to right, the cylinder mandrel, the piston plug and the piston mandrel for the lathe and lastly the piston itself. To use the piston plug you hold the cylinder upside down in a vise and drop the plug into the cylinder bore and use it to gauge the amount you cut off the top of the exhaust port. Leave it in the piston while you use your dremel and cut down to it. It gives an exhaust timing of around 175-177 degrees, and prevents you from cutting and opening it up too much. Click on the picture to the left for a bigger view.

 


This shows the piston attached to the piston mandrel. It's held together by tightening the bolt that the piston pin runs through and pulling the piston onto the mandrel. Works real slick. Click on the picture to the left for a bigger view.


 


This picture shows the modified piston when finished. Also shows a good view of the dual boost ports. Click on the picture to the left for a bigger view.

 

 


A better view of the dimple work which helps retain some oil for better lubrication. Click on the picture to the left for a bigger view.

 

 


And finally lightening of the piston by removing of some material and smoothing of the inside. Click on the picture to the left for a bigger view.

 

 


Zenoah G260 Clyinder Mods


This shows the stock cylinder with the piston spacer installed. You can see there is about a 1/16" or so of metal to remove to get down to the spacer. This will give me an exhaust timing of 175*. Click on the picture to the left for a bigger view.

 

 


This shows the finished modded exhaust port. The lower (upper in picture) corners need to be squared yet.

 

 


This is showing the exhaust port looking from the outside in. The inside lower (upper in picture) corners have been somewhat squared. Click on the picture to the left for a bigger view.

 

 


I've been building boats for about 15 years now, but just getting into the modding of the engine stuff. I've got a lot to learn. If you have any specific questions you think I might be able to answer then please email me here manross@martysrcboats.com otherwise you'll probably get a lot better info out of the experts Larry and Mike. Their emails are above.

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