KTM 690 Flowjob

  •  KTM 690 SM Head Before Flowjob
  •  KTM 690 SM Head Before Flowjob
  •  KTM 690 SM Head After Flowjob
  •  KTM 690 SM Head After Flowjob
  •  KTM 690 SM Sommer Gas Flowed Head Dyno

October 2008

We picked up our bikes after they spend a week at the health resort for KTMs, Sommer KTM in Germany. Sommer is one of the most experienced and knowledgeable KTM specialists in Europe.

Our bikes - a friends 690 SM Prestige and my 690 SMR - got the heads gas flowed, Duke/SMC cams fitted and the forks were modified.

Two bikes already had a full Akra and one a Leo Vince system. K&N airfilters and the gear restriction removed. Sommer uses a Fuchs dyno that measures power at the crank in DIN HP as most manufacturers do. Stock, the 690 SM is specified at 63 HP.

The before dyno of my SMR put out a healthy 67 HP at 7800 RPM and 70 Nm at 5500 RPM. After the flow job and Duke/SMC cam this went up to a little over 72 HP at 7600 RPM and 73 Nm at the same 5500 RPM at the crank. But these maximum figures only tell half the story. Both power and torque are up between 3 to 5 HP/Nm throughout the ENTIRE rev range between 3000 and 8000 RPM. The curves are 'simply' lifted over their full length. Impressive... and much more useful and effective on a road bike than just a top-end gain.

The Duke/SMC cam went in together with the flow job so we have no separate info for each mod. But this cam doesn't do much - if anything - for power & torque. The timing is virtually identical, only the shape of the lobes is a little different. At best it changes/improves the throttle response and feel of the engine. On its own it's certainly not worth the effort and cost to fit but the cylinder heads had to come off anyhow so...

On the road the improvements are hard to miss. Low end pickup is stronger and smoother from 3000 up with less chain snatching. There's also clearly less vibration throughout the rev range. And the 690 is already pretty good on this point. Really good! As the graphs show, the power output remained identical but there is simply more everywhere and that's what you feel too. It's obviously more powerful and faster but the engine actually feels more relaxed and effortless. But it rips to the redline like mad. Brilliant...
The extra power comes with a louder & sharper bark from the Akra's too.

The results from my mates' bike are exactly the same within 1 HP due to exemplary differences between engines. That is solid, high quality engineering. 'Heads off' to Sommer!

The before-after pics give an idea. This is the head from the SM Prestige from a friend. It has done about 13K KMs. 

Jan 2009 update: Sommer KTM has been sold to new owners and a new crew; KTM Team West

Last modified: 22-09-2009