Yamaha TRX850 Enthusiasts Forum

Hi

Does anyone know what the cam timing is for a stock TDM 900 at 0.040'' lift ?

I have Yamaha figures of 30/50 for the inlets and vice versa for the exhausts, BUT this is seat to seat

just trying to ascertain how much more duration a set of KENT YAM-09 cams is than the stock TDM 900 items. I have used them before on my TDM850, which became and 870 with cams, 2:1 ex, and bigger valves from Sand-Dune

In case anyone has a 900 TRX I changed the length of the intake snorkels in the TDM900 airbox and picked up 4 hp between 4200-7300rpm

thanks

Howard

interesting - did you fit 2 of the shorter snorkels instead of the stock one long one short setup?

coxylaad wrote:interesting - did you fit 2 of the shorter snorkels instead of the stock one long one short setup?

I fitted two long snorkels, but attached a pair of 5 degree internal tapered aluminium velocity stacks with a 270 degree roll back to each snorkel
one snorkel is exactly the same tuned length as stock, the other slightly longer by about 10mm.

it was an experiment, a cheap one. the goal was to try and reduce the 3500rpm dip in the torque curve,

the snorkels seemed to add torque from 4500-6500 BUT made the trough at 3500rpm worse. I have a pair of the shorter ones too, and this coming winter I will do some more testing

The tuned inlet length effect is only really at WOT, at part throttle the tuned effects are reduced a lot, mostly by the throttle flap/slide.

I am focused on the compression pressure currently, Yamaha claim a maximum of 239psi which is very high, higher than all the 2 valve stuff I have ever worked on ( my Buell with Hammer performance heads and CP pistons is at 215psi) the higher pressure will give superb response, and part throttle performance. good squish , maybe extra projected nose spark plugs and perfect AFR will all help. I am going to see if the latest 12 hole Denso injectors bring anything more to the fuel injection system, Yamaha are running 12 hole on all the bikes now, so a cheap set can be easily sourced.

And maybe bore the stock throttle bodies a little bit, the venture has the same area as the bore where the throttle plate is located taking into account the restriction of the shaft. IF the throttle plate size is increased, so the venture will need to be too. its not to hard on the CNC I have access to, but first I want to data log it and see how often I really use WOT on the road

Howard