2PG performance (with math! Yay!)

[clr.R4tch3t]

I forgot to mention that I have a degree wheel on my flywheel, and my ports are mapped out, so hopefully soon we can go over some needed (or not needed) port tuning. Here are also some random pictures of TDC and BDC.

[sho305]

When I modded a yami G1 I raised the exhaust port about 1mm, cut the head but with those you can only cut so far it needed the jug cut too. I advanced the stock pickup that runs forwards and back, that made it a slug in reverse but long as it still backed up that was ok. It ran better forward. Did other usual mods to clutches and airbox/jetting and so on. It would run away from a stock cart. A better pipe would have helped a lot but could never figure out what one would work well.

The stock comp on a G1 is very low as back then some courses used sub standard fuel of very low octane.

Friend of mine back then put a larger sled carb on an ezgo like that and a sled kit in the clutch. It would rev high and pop a big wheelie taking off. It made more power alright but not long and it blew the engine.

[clr.R4tch3t]

Sorry it has been a while, life always gets in the way. I took the 1.6mm lip off of the head and re-measured my combustion chamber. We are now sitting at 26.6cc. In a .50mm over engine that gives you almost exactly 7.00:1 compression. A full point higher! Yay!

I am still not happy yet. The piston crown and head part ways too fast and I think the motor will benefit from a slightly better squish area. The good news is that we are getting closer to the sweet spot, the bad news is that there isn't much more we can do 'for free'. As of right now I have only used a wiz wheel and sand paper to get the head cut down. Easy enough anyone can do it in their garage. I will post up some pictures of my progress tomorrow.

P.s. a 20cc combustion chamber would bring compression ratio up to 8.9:1, but I don't think it will be possible to get there without shaving the jug down. For this engine build, I will not be doing that.

[clr.R4tch3t]

Here are some pictures of my ongoing head modification. The first pictures show how warped the head is in factory form. You can see the outer edges of the head were not even with where the head gasket ring sits. The last pictures show how I evened out the head so the lip was taken off. This brought the combustion chamber volume down to 26.6cc. Now I am going to take the head down all the way to where the first cooling fan is. Will post more pictures and new combustion chamber volume..

[clr.R4tch3t]

With the head shaved flush, I got the magic number I was looking for. By the grace of the golf cart gods it came up with almost an exact 20cc combustion chamber. With a .50mm over stroke volume of 159.763cc we have an 8.988:1 compression ratio. Unfortunately, due to the head casting limitations, the true squish band is limited to 8mm. Fortunately, this band is a really effective squish clearance of 1mm (0.040"). It is at least something.

Now that the head is done it is time to work the numbers for the current engine port timing efficiency and build an exhaust that best matches it.

[van the man]

Looking good! If i have to pull the head off of mine, i'll have to do that! Maybe I'll do it anyway some rainy weekend. Thats a pretty significant increase for nada.

[clr.R4tch3t]

I found best results came with sand paper taped to a machined flat surface (I used a manufactured wood laminate table). Then it is just a lot of patience. Then just work your way into fine sand paper the closer you get to your end goal. Not too shabby for the cost of some paper and determination!