Scrambler 800 Tuning

[koko64]

A customer has a Scrambler 800 similar to mine and wants it freed up for trackdays.  I notice that my own bike gets breathless pretty quickly with an airbox and intake architecture that looks like it was designed to promote sleep apnoea or asthma! It makes the airbox of the Sports classic and air cooled Hypermotard look like high performance kit!

A mate has a Scrambler 800 with a WASP kit (which are no longer available). The WASP kit gives a major mid range boost in torque and hp but with no top end increase. I rode my mates bike and it felt like a well tuned carby M900 with great torque.

The customer bike will be tuned with various parts available to emulate a poor mans WASP kit. The ingredients for this tune include major intake mods as it will be a track bike (an unusual  choice for a track bike). The local race track complex has various dirt tracks and an asphalt circuit and has a Supermoto layout available, so maybe the bike choice makes perfect sense.


I got inspiration from a Scrambler 850 big bore built by KAMNA and decided on the following.

1.K&N pod filter
2. PCVI
3. Powercommander O2 emulator
4. Smart Moto PAIR delete kit and device
5. Free flowing exhaust of customer choice
6. Dyno tune
7. Airbox delete
8. Mini K&N filter for the breather.


Brad Black informed me that the Scrambler 800 has long duration cams (I'm guessing to compensate for the single throttle body). The compression is at least 11:1 and the valve sizes appear large enough if I can confirm them based on the 796 models. I've seen dyno charts with a 10hp increase in peak power with similar mods.

So I'm hopeful.

[koko64]

 20240101_195829 by Tony Kokonis, on Flickr

Intake is very close to ceiling of the airbox. The cut away is for the filter which is fed through a small hole. The air filters via the walls of the cylindrical filter, travels upwards then has to flow over the small gap down into the throttle body. A torturous route.

[koko64]

20240101_195939 by Tony Kokonis, on Flickr     



The pod filter has a nice velocity stack inner radius.

[koko64]

The airbox incidently severely blocks airflow to the rear cylinder. With it removed the substantial cylinder cooling fins get a good shot of air. Important for a track bike.

[stopintime]

Cool 

My 800 got new 44mm intake valves (stock exhaust valves). That was enough for my 99bhp (Kämna calculation). I have more mods than the Scramblers you're talking about and working on. Compression equal. 900i cams.

IMO for any kind of performance improvement on this budget bike; the geometry, suspension and brakes are MUCH more important.

[koko64]

Very true, but the motor is very restricted. Its not too bad street riding as there is strong low rpm torque, but when making demands of the motor, it is very noticeable and frustrating. With my bike stock is ok as the speed limits are 50-60 mph or 80-100 kph. I have my Gixxer for the track. Both my mate and the customer note how the motor struggles . I suspect the rear cylinder over heats in our summers with a drop in power. When I rode a Scrambler around Chianti, I was surprised how restricted the motor was.

Suspension upgrades are very likely. My mate with the other Scrambler has fitted an Ohlins shock and complete fork cartridge upgrade kit. Most people also fit lower bars.

[koko64]

Cool 

My 800 got new 44mm intake valves (stock exhaust valves). That was enough for my 99bhp (Kämna calculation). I have more mods than the Scramblers you're talking about and working on. Compression equal. 900i cams.
 

That's great power. A good outcome!

I still have to confirm the Scrambler valve sizes if they are 796 sizes or older 800/900 sizes.

[ungeheuer]

 

A mate has a Scrambler 800 with a WASP kit (which are no longer available). The WASP kit gives a major mid range boost in torque and hp but with no top end increase.

Where'd he source the WASP kit?

[koko64]

From WA, but they stopped making them when I inquired, so I looked at Kamna for ideas.

[koko64]

IMG_3692 by Tony Kokonis, on Flickr  


20230822_001531 by Tony Kokonis, on Flickr 

Front cylinder exposed for easier servicing and top cooling fins get airflow.. Rear cylinder has exposure to air cooling with the airbox removed. A mate with a WASP kit reports cooler operating temps of the rear cylinder. Half the valve cover is normally covered by the lower airbox which completely blocks airflow over the motor.

[koko64]

  IMG_3691 by Tony Kokonis, on Flickr



What lurks high under the tank.

[koko64]

    IMG_3690 by Tony Kokonis, on Flickr  


This track bike gets PAIR block off plates for accurate dyno tuning with AFR meter. Also removes items to declutter for easier trackside work and better airflow to the motor.

[koko64]

Cool 

My 800 got new 44mm intake valves (stock exhaust valves). That was enough for my 99bhp (Kämna calculation). I have more mods than the Scramblers you're talking about and working on. Compression equal. 900i cams.

IMO for any kind of performance improvement on this budget bike; the geometry, suspension and brakes are MUCH more important.

Brad informed me that the SC800 has 44mm inlet valves and 38.5 exhaust valves, so I'm happy about that.

[koko64]

Dyno session this week to tune the PCVI. An O2 Optimiser controls closed loop tuning and a Smart Moto emulator covers the PAIR removal. The bike will be a heavy weight supermoto/track bike for the local track that covers a range of disciplines.

[koko64]

Bike had an initial dyno run to get it going. Runs like an M900 with open airbox, jet kit and light flywheel.
Will finish off the dyno tuning when we settle on an exhaust configuration. Haven't tuned the front cylinder yet or fine tuned both pots as yet to decide on  2 into 1 (doubt it), 2 into 1 into 2 like an 1100 Evo style or 2 into 1 into 2 like a 900 Monster.
There is a Zard low mount pipe that has two outlets I'm considering. I tried to graft a set of Termis on from an 1100Evo but the lack of ground clearance is an issue and a fair bit of friggin' around.
Open to any suggestions.