Yamaha TRX850 Enthusiasts Forum

Has this ever been attempted?

My mate mentioned it the other day and it got me thinking.

Get a half a set of throttles and injectors off a 4 cyl bike, and a standalone engine managent system like megasquirt or something (Motec or Autronic would be too expensive for this application I'd have thought), fit an elctric fuel pump.

OBviously not as easy as that, but in theiry, is it possible and more to the point, Is there any point?

This falls under the 'can be done but not cheaply' category.

Can't see the point myself but then that has never stopped me before

so where is the expense?

surely second hand throttles and injectors can't be that expensive, I guess a fuelling sytem could be robbed off a more modern bike too.

and you can make megasquirt yourself! it's only about £250

TDM 900 throttle bodies are 38mm.......too small?????? they should fit straight onto the TRX head

so where is the expense?

surely second hand throttles and injectors can't be that expensive, I guess a fuelling sytem could be robbed off a more modern bike too.

and you can make megasquirt yourself! it's only about £250

The expense is in getting the fueling right. Look at the abuse Triumph got when they launched the TT600 about low rev snatchiness etc. and more recently bikes like the Suzuki GSR600 have been slagged off for needing a PCIII to sort the fueling.

What makes you think that throwing second hand injectors and a home made engine management will give you perfect fuelling when huge motorcycle manufacturers with limitless budgets can't get it right? (By the way, I'm not having a go but I am genuinly interested in why you would want to do this and if you believe that the results will be better than a well set up pair of carbs)

As an asside, That is the avenue I have been considering for my 23 year old Jaguar XJ6, as the standard Bosch Jettronic injection is rather primative.
Been reading a bit about the megasquirt. Sounds interesting.
I don't think that injection for the TRX would be so great from a performance point of view. I can't immagine it being any better than a well set up pair of FCRs.
But for a "just out of interest" project it would be interesting. As you say, second hand parts (throttle bodies, injectors and O2 sensors) are plentiful.

megasquirt is sequential only, meaning, all injectors fire at same time (last time i checked) which isnt an issue, but staged is better obviously..

Throttle body from a TDM would be prefered as its "ready made" to fit between your cylinder head and your air-box. Computer would obviously be a benefit to use stock from donor bike / engine and its POSSIBLY a direct bolt-in conversion (altho it COULD be different with all the wiring harness, so be careful on that one.)

Fuel system should be salvageable from just about anything (fuel lines and pump) altho im not sure you would bother, as you can prolly get this and O2 sensor from donor bike.

All in all you are up for the price of:
Throttle bodies / inlet runners (some ppl call it inlet manifolds)
Wiring harness / ECU
fuel pump and some hoses
O2 sensor
misc wires / connectors
Dyno / tune time

Add all those up, and tell me waht its worth.. Then price some FCR41's and see how much difference EFI and carbies produce.