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Back in the saddle again!

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  • Back in the saddle again!

    Sup lasses and lads! I have been cruising this forum as a lurker for a little and I'm finally into posting because I plan on getting my ped out of retirement and really going full resto/heavy mod. Many years back I was ripping on a GSR25 and decided 23cc wasn't enough. Got the rattle snake pipe and a velocity stack and had loads of fun with my other ped buddies. Soon after my need for speed led to burning out 2 (that's right 2!) gp460s without breaking them in properly and mixing my oil well. Soon after high school started we all got cars and thus the ped gathered dust in the corner of the garage. Still have everything laying around and i'm thinking of getting the stock engine running first (gzn25n23) then moving to to the remains of the 2 gp460s. I miss the tinkering days and the simplicity of 2 stroke engines. probably sourcing most parts through DDM since they were always my go to. Any thoughts on other parts suppliers or big no-no situations are much appreciated. whole point of posting this long winded bit is because I WANT TO RUN CORN!!! looking at a high compression head kit for the gp460 but really gotta research the pros/cons in using e85 in small displacement 2 stroke. PLEEEZZZ HALP!!!

  • #2
    Hmmm interesting. No experience with peds. But some with cars, I’ve been running a straight e85 in my Evo ix for about 2 years, and in LS motors since 2013. It’s 33.3% less efficient, so first step would probably get a carb which will flow more fuel. Next is the oil, you’ll need something that will mix well with the ethanol. From there your benefits are timing and compression. E85 has the burn rate equivalent close to 116 octane, but runs way cooler since you’re flowing more fuel. I’ve heard that ethanol (like alcohol) has horrible lubricating properties and will accelerate your engine wear but I haven’t had any issues. But also we are talking about race motors, which don’t go too long anyway without being blown/rebuilt.

    On another note. Im curious as to how you’ve toasted so many 460s? What oil ratio are you running? Could they have been running lean? I’ve personally never fried a larger bore goped motor. Just pulled apart my 40 cylinder from 15 years ago and it looked mint. My 460 I’m sure looks the same.

    i guess upon rereading your post, you said the oil wasn’t mixed well. That’s 2 stroke 101 right there. Also you want to run a ratio of 24:1.
    Last edited by dsport; 08-27-2019, 11:48 PM.


    • #3
      Hey dsport! Thanks for the input. I've heard lots about engine wear due to poor lubrication with e85 but that it can be mitigated with a lower ratio like 20:1 instead of 32:1. I've also heard that castor oil will bond well with ethanol to provide proper lubrication. Not 100% confident on those two statements but seems theoretically correct with some of the research I've done.

      As far as toasting the 460s well it's a combo of a few factors I'm guessing. Back when they began producing the 460s CY was using a plating on their pistons that would eventually break down and began to deposit on the walls of the cylinder head, specifically on/around the exhaust port and eventually the entire piston and head would lose compression basically rendering it useless. Now I did read a proper break in cycle with those engines was necessary for reliable operating but that people were still experience the plating decomposition even after proper break in. Now don't quote me on this but I think CY wanted people running their gas 50:1 back then because it was a "HP engine." At the time I was running more like 40:1 in my previous engine and had no apparent issues with the stock Zenoah besides minor carbon build up. So I could have been running too rich or even too lean of a mixture but I know for a fact I did not break the engines in properly, because well at 12 years old patience was nowhere to be found. So with that said I have learned that the smaller the engine the less tolerance they have with extremes, particularly with temperature and lubrication.

      knowing that ethanol runs cooler gives me a little hope that the plating issue may never occur again. Plus I plan on picking up the ADA high compression head kit for the gp460 which may actually negate that problem. My thought is to start at the 15:1 compression ratio and run it on 115 octane for awhile as break in and just see how it is. Once I'm confident the engine will handle e85 I'll begin the tuning transition.

      Also thinking of making a little documentary on the whole thing to post here for all the ped-heads!


      • #4
        Here's a little look at one of the pistons...
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        This gallery has 2 photos.