By the way, this is how I do it, others do other things.....

On this page you can see some stock and modded engines to see what are the differences,
http://www.first-racing.eu/html/steuerzeiten.html[/QUOTE]

Roelof:

That link is also in Dutch, but I can understand it though. The OS TZ-18 has an additional 17 degrees of timing when modded?!! Stock (204) and Modded (221). That's a nice increase in duration. Where are you cutting this particular crank, (opening, closing or both) and how do they run after your modifications?

It is German, you can use Google language tools to translate a site:

http://translate.google.com/translat...n&hl=&ie=UTF-8

School is never out here I see; beautiful! How quick are your modified OS TZ-18 engines? Based on that chart, there isn't many engines with that much (221) duration when modified.

That is not my site, that is a German company doing pinching, mods, coating and other stuff mostly offroad based.

Some of my projecs can be found here:
http://www.euronet.nl/users/tooms/
(also some onroad timings)

What tool (bit type) do you use to cut fangs in the sleeve, and how to you raise the exhaust port without destroying it? Also, I want to open up the crankshaft (where the carb send fuel into the case) about 2mm. have you tried this, and does it increase power?

For the sleeve I use this:
http://www.amazon.com/Pro-Quality-20.../dp/B000MOI9G6

And I must say the Dremel wall tile cutter is also an awesome tool for the sleeve:
http://www.dremel.com/en-us/Accessor...aspx?pid=TR562

For the crankshaft I use simple grinding stones for a Dremel tool.

For raising the ports you can also try to modify an headshim so it will fit over the sleeve. When placed under the upper edge of the sleeve you will raise all the ports. But what you add to raise the sleeve must be taken away from the head to be sure the combustion chamber will stay at the same height.

This is done a lot, for some brands they are even available:
http://www.capricornrc.com/capricorn...d_product=1320

For the most part, there are two types of 2 stroke engines... reed valve, and rotory valve. Our little nitro engines are rotory valve.

These engines have a two stage intake tract. First stage, piston is on its way up transfer ports are closed, vacuum is created in the crankcase. Then the rotory valve opens (crank window)... and the fuel mix is drawn into the crankcase.

Second stage. Rotory valve closes (crank window), piston is on its way down.. pressure builds in the crankcase, the transfer ports open.. and the mix is pushed up into the cylinder.

This is all happening at extreme speed ... in these little engines.

If you get crazy grinding on that crank window... that pressure thats building in the crankcase will take the path of least resistance... and blow back out the carb... instead of filling the cylinder.

The red silicon filling is mainly there to fill the bore of a drilled out crank.
Tuned cranks are drilled hollow to save weight.

There are engines that have that ramp simply milled into the steel.

So, first you have to drill the crank on a lathe with a damn good HSS drill. (cranks are usually hardened)
Then you find some Aerexon Motorsil D (or something similar), fill the hole and fix the crank in the correct position to let it level and dry for at least 24 hours.

I have seen someone to pour silicon into a crank that was not drilled. You only get a thin layer of silicon in their which will not hold, so don't try that.
It wouldn't improve performance anyways.

Hope this helps.

Yes, that does help. Thank you for the feedback. Although I have been at this for quite some time, it is amazing how much I "don't" know about these little engines. Just picked up a new cheap engine that I am about to do some serious experimenting on based on Roelof's and your information. Thanks.

Okay!! So that is why I have seen fuel blowing up and out of the carb. However, the strangest thing happened; I put a larger (9mm) carb on the motor (TZ-18) and a home-made pipe (similar to a true two-stroke expansion chamber found on race bikes) and the reversion stopped, and the little sucker now run like a bat out of hell! Any ideals why?

Roelof:

I ordered everything, and can't wait to start experimenting. I have been using the wrong tools for years!! Thanks.

I tried it on an OS 15RX that I've had for a while. I ordered the pro-quality 20 piece diamond bit set, and at low speed, I slightly opened the exhaust port in the corners (up and out) and the same for the intake ports, but not as much or on both sides, just on the side of the port of the direction of the flow. I also fanged, tapered and lightly sanded the roughness out of the sleeve. Further, I cut .5mm off the opening side of the crank and 1mm of the closing side of the crank. I put this motor in one of my on road cars (NTC3) and its quick/fast as hell! A partner of mine with a Traxxas 4-Tech (3.3), that he is so proud of, couldn't wait to race me. That little 15 is all over that 3.3 from start to finish! He wants me to do his motor now, but I don't want to be responsible for messing up his motor. It's amazing what you can learn and do based on shared information within race forums. Thanks!

Be very careful messing with the tops of intake ports. The angles are absolutely CRITICAL. Mess it up and you can "short circuit" and engine as Gordon Jennings calls it, destroying its fuel mileage and hurting power. Plus for onroad use, you really don't need to. Exhaust and crank timing are more key.

Winggracer:

Thanks for the knowledge, and I guess I got lucky in the power department and unlucky in the fuel mileage. It runs like hell but goes through fuel like an old hot rod!!

Yep, normally the intake does not need any change in timing unles you gonna work with shims to raise the sleeve.

But be sure when you have grinded into the pots you have to smoothen the sharp edges, if you do not do that you will get scratches on the piston.