Tech Talk- Making Championship Dreams Come True

690 Rally Performance Camshaft

Perry first contacted us to discuss some upgrades for his bike.  He wanted a simple bolt on solution to increase the performance of the engine to give him the ‘edge’ in the final rounds of his championship in the USA.  Running a pretty stock LC4 motor, he had come to the right place.  After a few engaging conversations by phone, he soon realised the work that goes into increasing the performance of an engine system and how a complete upgrade kit works much better than just changing one single component.

Often, its not possible just to fit one of our cams, sure, we do make cams that bolt straight in with the standard piston but if you want to get the most from the motor you need more and to have more you need to change other components in order to allow these to work safely in unison.  An engine is a system and many components work together to deliver the desired results.  Before too long the question went from “I want to increase performance” to “what do you recommend for the application I am using the bike for”.  This was great as every application is different and we have many different options and configurations for different requirements from road racing to adventure riding.

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Since Perry is using his SMC for road racing and has a stock, relatively low tune motor and just 654cc, there was lots of gains to be had.  First, the choice of camshaft; because the bike is being used for road racing, it spends most of its time in the upper end of the rev range meaning that he would benefit greatly from our road racing cam which has significantly more lift and duration to stock.  With more lift and duration, you get a lot more air fuel into the engine but also require a piston designed to work with that increased lift and duration / crossover.  For this, we would have to replace his stock piston.  Now, the road racing camshaft, while increasing top end dramatically does tend to cause a compromise at the lower end of the motor and a little into mid-range which for corner exit speed can often be important.

 

To compensate for that I suggested increasing the bore and stoke of the bike, making it the very popular LPR 732cc configuration.  This means changing the crankshaft / con rod and piston / cylinder (piston already needed changing due to the camshaft upgrade). That additional capacity would not only recover but increase the bottom end and mid range power and torque.  Given that application is on the track and good quality high grade pump gas is available all the time, and that the piston was to be changed anyway, I suggested he increased the compression ratio from 11.8:1 to 12.5:1 while we are at it, this would give additional gains throughout.  The end result he could expect from this configuration is considerably more power and torque everywhere throughout the rev range with a focus on mid-top end performance.  Knowing what the result would be, I was confident his on-track performance would improve significantly as well as the size of his smile.

730 732 Cylinder Piston KTM 690
I also shared with him some reliability improvements he could make to his engine to ensure he maximised his chances of finishing events without technical issues and he opted to go with them all, a sound move.  The complete kit of parts was shipped to the United States and installed locally.  The bike was then setup on the dyno, mapped accordingly and hit the track.
A few smiley messages followed as Perry got used to the bike but the best email came months later when he confirmed he won what he set out the achieve and took the win in his championship.  As an engine tuner, nothing is more satisfying than seeing people enjoying their bikes by getting the most from them and achieving their goals.
Parts used:
Long Stroke Crank (84.5mm) with shorter rod.
Gaskets and items required for rebuild
Reliability upgrades

Best regards,

Lyndon