Summary
This swap probably isn't a good idea.
I was doing a top end rebuild including light porting (gasket matching really), and a 1.5mm oversize piston. Decided to do the YFM660R Raptor carb swap as I had heard it is easy to tune and can be quite powerful.
Setup
The airbox is chopped in half, and two intake runners made from silicone tube and aluminium pipe. A flexible black cyanoacrylate glue is compatible. (Chopping the intake box maintains battery holder, all original fixing points, mud protection for the rear tyre. You only lose maybe 2 inches of water clearance but who's fording that deep regularly....?)
Pod filters on the end.
I used intake boots from a raptor but cut and shut to change their angle and make then shorter. Wrapped in vulcanising tape just in case. This way the carbs sit nicely in the frame and they point roughly horizontally rearwards.
Final picture to follow...
A modified Tenere cable (new soldered ends) works well and the action was light and used a little less rotation for full throttle.
Losing the second cable is obviously a disadvantage though. I had to remove the corner of the cooling fins on the block to fit the cable.
The Result
I tried pilot jet combos and tried to get the new piston run in. The bike got warm and ran well at idle. But ANY throttle and it died. Needle clip position did nothing, piltot jets did nothing.
Air Circuit
I assumed it was an air circuit problem with the CV diaphragms not doing what they should, I tried different spring stiffnesses, a homemade resevoir to mimic an airbox... nothing. Back to the Tenere carb.
Tenere Carb - Another data point for everyone
With podfilters, 1.5mm oversize piston, light porting, stock exhaust:
Pilot 52.5 (+2), LH Main 125 (+1), RH Main 165 (stock), LH needle clip 2nd from bottom (1 richer)
This runs really nicely. Maybe a slight hesitation at low RPM when hot.
I have a few more thoughts on this swap:
Area
Raptor carb is 2 off 33mm bodies totalling 6842mm2
Tenere is 1 off 33mm (LH) and a larger size (RH) - I can't measure at the moment maybe someone can add this info. So the Tenere has a larger overall area, and lower relative wall area. The RH feeds two valves so surely should be larger? The raptor carb setup makes no sense.
Cam The raptor cam is different to the tenere cam (according to their forums). Perhaps there is a mismatch. Again, you'd be combining things that haven't been designed together.
Genuine It's possible my raptor carb was not genuine mikuni which would have screwed me anyway. Not easy to find a real one...
Tuning Tuning the Tenere carb is easy enough if you stop and think about it. It's harder to get in and out of the bike but now I've modded the airbox it's much easier.
Also the Tenere carb has effectively a flatslide left carb so you get immediate throttle response, plus the smoothing of the CV.
Power/Torque It's so hard to tell the difference after rebuilding. Until I see dyno numbers back to back between a Raptor and Tenere carb with nothing else changed, no one could convince me the Raptor swap is sensible. My Tenere feels epic after the work described above.
