Print
Category: Skunk Works
Hits: 2518
Star InactiveStar InactiveStar InactiveStar InactiveStar Inactive
 

Here we are with the second project in the Skunk Works area.

Going past the normal simple port/polish where you just clean up the casting flaws, I've been reading about an alternative. That alternative seems to be things like CNC porting which leaves big ridges in place to form a turbulent air layer at the walls, which allows the central air column to flow faster/better. This is similar to how a golf ball with dimples flies farther than the same size and weight of smooth ball. From what I've read, this does not require the ball to be turning, although there are other effects from the spinning ball. Anyway, since my bike is down waiting for parts, I decided to get started on the intake manifold. I'll get to the head and valves when I have time practice it on my junk ebay head, and have time to pull the valves out of my good head. Probably won't get done until I pull the cam to send it for regrinding.

 

An interesting link that I just found, it basically supports dimpling areas not only in the intake, but in the combustion chamber. And links the dimples to increased power and the possible use of less ignition advance. The last part is very significant because I'm guessing these engine have very little advance to keep them tame and long lasting. Hotrod.com airflow article

Probably going to start tearing my good head down tonight, looks like rocker arms are a far away back ordered part and I have plenty of time to try my hand at dimpling the head. A 13:1 Raptor 125 piston will be going in eventually and a BBR cam is on order as well.

Speculation is that I can find a way to dot the intake with etch resist, then etch away everything between the dots. This would be MUCH easier and more accurate, as well as safer for the other parts of the head. I'll be looking into this as time permits, grinding little dimples takes a lot of time (about an hour on the junk head and almost an hour on the intake pictured) and the etching only needs to be a few thousandths of an inch deep so it should be more than possible. Etching might also be possible with the valves installed since it should be a cleaner process, again more research needed.

 

A couple more pictures. Here's the junk TTR head and one of the junk valves. I was using a cheap diamond burr on the valve, might need to go a little deeper when I do this for real.

intake dimples

 

valve dimples

 

Got the final mods done to the KAYO head and everything put back together.

 

dimpled head

Like all the other articles on this mod, I found that I'm now running very rich. Problem is that my smaller pilot jet is clogged so I have the air screw out to 3 turns and even in the much colder temperatures that we have here at night, it's still way too rich. Have to try and clean that jet and hope it is small enough. The only other dimple work that might get done is to find spots in the combustion chamber and on the piston crown that need a little airflow management. But that will probably wait until after the 13:1 piston is installed.

On a side note, I'm pretty convinced these stock carbs. are clones because they take a different pilot jet than I have for the TM carb. which is supposed to be the same. Looking forward to ditching this stock carb. and getting my TM built and installed.

 

10/6/16 - Managed to get another of the stock smaller pilot jets installed, it is better but still way too rich. Going to go with ethanol gas and maybe some fuel system cleaner to thin the gas out for this weekend. Hopefully I'll have the manifold for the new carb built this weekend as well. But the extra rich conditions certainly make it seem like this little amount of work will pay off in big amounts. I'll have more info after the practice session. What it is suggesting is that smaller carbs that will keep the air velocity high will work better. With a good cam this will mean that more air fills the cylinder each time, and burns better each time from the more complete mixture. It should therefor make more power. The TM24 is rated up to about 20 horsepower, should be a really good fit with this engine at more than 10 horsepower (no way to know without a dyno).