How much is a used engine worth ??

If you have ever wondered why a kart engine that costs $1,000 brand new can fetch up to 3 times as much after it is used,  here's why it is not always worth it !!

In years past when a racing class was created with only one particular model of engine allowed in that class,  the rules began in a rather simple fashion along the lines of "engines to be raced unmodified".  This was found over time to be a bit unfair as most engines changed in their manufactured specification as time went by,  and newer versions of some parts were made in varying materials and in a variety of methods that could affect their performance,  good or bad. .

So over time the rule-makers realised that a few variations had to be allowed otherwise certain engines from different years and different production runs would be faster or slower than others (  as has proven to be true ) and that changes made under a factory's normal evolution of production would render older parts obsolete - and sometimes without the possibility of the newer parts being able to be retro-fitted to the earlier engines.

Thus as all this change has occurred the variations have been noted and the rules have been altered to allow modifications to many engine parts,  but always within strict limits that in general match variations that have been seen in parts supplied by the original engine manufacturer.  What this means is that, as an example, when a different casting mould was made available with any minor changes incorporated into it, the rules were changed to allow this variation to be incorporated into all models of the engine. 

Which gets us back to where this article started  -  why should a particular engine be far more valuable after use than a brand new one ??   Well taking a known example with Australian karting,  the KT100J Yamaha engine was originally made to power a generator.  It was changed a little and then introduced as a specific model for kart racing.  Earlier versions of this engine came with serial numbers like 7G9-600xxx or 7G9-601xxx , 7G9-603xx and so on.  Each production run had minor variations to every other run,  and in the beginning,  prior to any modifications being allowed at all,  the engines with the 600 or 601 prefix were considered the faster ones.

As time has gone by two factors have made such engines less likely to be any faster than any other engine,  and indeed allow us to make almost any engine as fast as any other.  Firstly there is age,  and engines of the fancied older series like 600 or 601 are now getting on to be almost 20 years old.  And remember that they were made in the early days of the class when no modifications were allowed,  so imperfections could not be changed, nor any variations adjusted which required physical alterations.   Additionally as they have been used, raced, rebuilt and eventually worn out,  major components of these engines can no longer be considered as being original parts.  The cylinder especially wears and cannot be re-sleeved under our racing rules,  so larger bore sizes cause the cylinder to become useless and new,  later model production run versions,  now replace many of these earlier versions.  And then secondly,  and more importantly,  is that all the variations that may have been "manufactured into" these faster engines have now been noticed by the rule makers and modifications have been  allowed to be done to all other engines by the freeing-up of the rules to cover these variations.

So,  when an engine is rebuilt or "blueprinted" to race under the AKA rules today,  it can have all the good variations incorporated during this process.  Thus with a little, or sometimes a lot,  of time spent in the rebuild I am pretty confident, as are the AKA rule-makers,  that all engines can be brought up to the same standard of performance.  I especially think that if it comes to the choice of a new engine versus an old one of somewhat unknown history,  the new one must be favoured because it has not suffered through the last 5, 10 or more years of use and "mis-use" !! 

Of course there is always going to be that one driver who wins races each weekend who has an obviously very "good" engine  -  so if you choose to buy this then you should do it at the track directly after the last race.  The engine at this time may be considered to be worth up to 50% or even 100% more than a brand new one,  but be certain of what you are buying and make sure you get all of the ancilliaries - things like the CDI box and carby do make a difference !!  The engine has obviously had all the little variations ironed out,  and time spent on it to optimise all of its parts  -  and if you fail to take it there and then,  the chance is that further fiddling may go on and parts could get swapped,  or an ignition timing or some or other part is moved around and the performance might not be as good as it was. If you are buying a "winning" engine, then you really want to buy it in its exact winning form. 

Just as when buying from off the internet or over the phone,  it is always a case of buyer beware.