First attempt at porting.

DeadPixel

DeadPixel

Member
#21
#21
"So if you read my earlier post you can calculate the approximate maximum flow something is capable by first finding the MCSA in Sq inches then multiplying it by 137. If the stock carb is approx. 625 in diameter and max carb flow is around 40CFM at 28 inches."

Well ole4 this changes my view on my carb choices. Need to hurry and get a Mikuni sooner than planned. Even my .650" carb is going to hold be back. I think my BSP is only .610" :( Is there any power to be had or noticed from a person porting a head on a totally stock motor? Say if a person was taking the motor apart to install a billet rod during a governor removal?
 
ole4

ole4

#22
#22
Here is a thread where I flowed some stock carbs and the best one was 43CFM. Post #22
https://www.oldminibikes.com/forum/mini-bike-discussion/139109-mikuni-chikuni-comparison-3.html
As for your question I don't know but If you had two identical engines and one had the sharp edges removed in the port and SSR radiused perfectly that it would perform better but that is just my opinion, not worth much. Here is a webpage from someone at bobs that shows what the areas to smooth and radius are in a cutaway head. Keep in mind there is a lot of this kind of info on bobs 4 cycle because any slight advantage in karts helps. But if you are talking about riding your mini down the street the seat of the pants increase probably won't be noticed.
Photos - Dyno Don Kart Engines
 
DeadPixel

DeadPixel

Member
#24
#24
I don't know if it is a good idea or not but I used a thin strip of emery cloth that I pulled back and forth like if sanding a shaft to round out the short side. It worked pretty good and was a lot easier than trying to fit the grinder in there.
 
K

Kleyny

New Member
#26
#26
I was able to get a dremel bit through the port to get to the short side. But I wasn't sure how to smooth it out. Thin emery tape makes sense
 
DeadPixel

DeadPixel

Member
#27
#27
I found if it is too wide it cups on the sides and dose not apply even pressure. I use a thin piece about 1/4" thick or just a little thinner. The solder idea is a killer idea. Will have to dig the solder out now :glare:
 
DeadPixel

DeadPixel

Member
#29
#29
I know this is a little off topic and don't mean to thread jack but have any one tried stream lining the throttle shaft and screw of there carbs? I have modified the throttle shaft of 2 of my carbs a .610" and a .650 I think there both Ruxing's. I have not tried them out yet as the billet rod is not installed in my motor yet. Is there any other easy machine work we could be doing to these motors that's worth wile besides porting and filing the timing key to advance timing?
 
K

Kleyny

New Member
#30
#30
It's all good deadpixel. I haven't even started on the carb yet. Slow and steady wins the race lol. I'm way too new on these little engines to jump in too deep lol.
I definitely interested in what I at home can do after porting, filing key way to get more ponies.
I like the idea of tinkering to get hp not throwing huge amount of money at it. I find it more rewarding.
 
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