[Eric Davis]

Apparently, some people have been unable to view the pictures.  Here is a new link to photobucket that shows all the pictures.  Please let me know if you can’t see them and I’ll send to you directly.

 

http://s1164.photobucket.com/user/mredavis/library/

[Eric Davis]

Thanks for the interest.  All PM’s replied to.

[Eric Davis]

All PM’s replied to.

I’ve also added more items and removed some that have sold.

[Eric Davis]

Hi Richard – I’m responding now.  Thanks.

Hi Skip – Thanks for your interest.  I’ll send a message.

 

[Eric Davis]

Available as a package or will sell select parts.   Please let me know if you’re interested.

Thanks!

[Eric Davis]

Ray,

I have experimented with using EGT to tune bottom-ends by by logging patterns in EGT temperatures under consistent weather, oil, gas, engine setup, and other conditions. .  My preference is to tune the bottom-end of 2-stroke engines based on length of stable idle, throttle response, corner acceleration(s), and overall temperature.

Focus on selecting a good combination of idle jet (or inner/outer idle jet for Dellorto), air screw adjustment, and idle speed that allows the engine to idle around 2k for 5-10 seconds. Then, you should notice the engine starting to load up on fuel, and the idle speed should start to slow down.  When you blip the throttle to clear the engine, the engine should stumble, then clear.  If you notice a pattern where the engine idles for a long period of time (e.g. 20 – 30 seconds) and/or bogs on quick throttle blips, then your bottom-end is too lean (General Rule).

The easiest way to finalize your bottom-end adjustment is to ask the local top racers what their jetting and air/idle screw adjustments are, and ONLY change the air idle screw setting to identify the best setting for you.  For example, if the local racers are using a 60 outer idle on a Dellorto, with the Air Screw at 1.5 turns, start there.  Then, adjust your air idle screw inwards 1 full turn, blip/clean the throttle, then notice the difference.  Do the same process at 2.5 turns out.  You’ll definitely notice some changes, and be able to make a more educated decision for your environment, weather, engine, etc.

You can get a good understanding of the bottom-end, its’ principles, and tuning approaches by reading A. Graham Bell’s book “Two-Stroke Performance Tuning”.  It’s one of the best books on the market, and thoroughly explains quite a few key concepts.

Also, if Riley Will is lurking around here, he’s probably forgotten more than I know. :)

[Eric Davis]

Derek, good questions, and here are my thoughts.  My experience comes from sprint racing in Formula C (Rotary ICC), Pro Mod Moto 125, ICC (Reed Valve ICC), 250 stock/sprint, and 125 spec moto.

1.  ICC is a higher horsepower engine than a spec moto, but it’s powerband can sometimes be peaky and more difficult to drive than a spec moto.  The Dellorto carb can be difficult to Race tune because you have so many variables and top level racers don’t always like to discuss the carb tuning tricks (Carb and intake are the number one places to find power advantages in ICC).  Spec moto’s carb is much more simple and has less tuning options.  Strangely enough, the fuel system on a spec moto can sometimes be Very Expensive due to Pump-Arounds vs Gravity feed, etc.
2. ICC’s parts and maintenance are always more expensive than spec moto.  The ICC’s Cranks, Cylinders, Rods, Bottom End Bearings, etc, are usually twice as expensive.  ICC Engine Run time varies significantly depending upon how high you rev the engine, what oil you use, oil mix ratio, temperatures, drive time, etc.   Generally speaking, a spec moto considerably outlasts an ICC.
3. ICC Costs More – If you’re focused on costs, buy the spec moto.  If you’re club has only spec moto drivers, and/or if you have local support for the spec moto, it’s probably an easy decision.
4. I chose the ICC as my daily practice/race engine (TM K9B/C).  The ICC has a great feel, sound, fit, finish, exhaust out the rear (no more elbow burn), etc.  I just like it better.  It has plenty of power to make me smile, and I don’t mind the additional costs vs spec motor.  On another note, one of the very best engines I’ve ever driven is the CR250 on a sprint chassis.  47hp stock, the engine ran all year on a single piston (sprint racing), and it had more power than anyone of us could handle.  You really could miss a gear in a race and still have so much torque that you’d giggle coming out of every turn.  Absolutely fast, Reliable, and the least expensive class to purchase, maintain and spec.   I thought this would have been the spec class of the future, but it never really took hold.
5. TM or Maxter – Largest parts availability and tuning knowledge.  Both are great, plenty fast, and will make you smile a ton.
6. ICC doesn’t really exist in my region.  Almost all local race classes are spec moto.

In summary, the spec moto engine is a very reliable, comparatively inexpensive (2.5k), fun, and generally easy to tune racing engine package.  The ICC costs more to purchase (4k complete), has higher maintenance costs, and is harder to tune.  Like any other engine package, if you decide to go to the national/international level, the engine costs increase significantly due to the need of hiring a solid engine builder/tuner to find every little bit of horsepower to keep you up front.   Once you go to this level, the entry costs for both types of engines are about the same to purchase (5k for a national spec moto package complete and about 5k for a national ICC package complete).  The ICC will require more maintenance ($$) than a spec moto, but it will be a bit faster.  A key point — At this level of competition, both engines will require a hired tuner/engine specialist to setup the carb, oil, etc. to maximize their engine’s power.

If you’re racing locally, buy whichever engine makes you SMILE.  You’re not doing this to make money, so go find whichever engine you prefer (and chassis/brake setup), and just enjoy your time driving.  You’ll have a great time, and really learn about driving.

Overall, I much prefer the ICC even with the increased costs, carb, etc. and  I hope to be driving my TM’s and Maxter’s for many more years.  :)

[Eric Davis]

Hi Richard,

PM Sent.

[Author]

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