Yet another TDM900 swap question...

[MC-Chase]

Before I start - I can imagine what people are thinking when they see a new member's first post being about a topic that's been talked about 100 times already; I can only apologise! I have used the search function many times over the last month and found a great amount of info on the topic, I'm just after conformation on a few little details.

I'm looking to swap my tired old 850 engine for a TDM900 unit - I have sourced a full engine for £500 with only 9k miles on it. I understand the TDM engine bolts (more or less) straight in with some minor changes required to the oil tank and sprocket. Really I'd just like conformation that I'm correct on the below assumptions;

* I'll need to buy an adaptor plate to use the TRX850 oil tank on the TDM900 engine as the TDM900 tank won't fit. Any ideas where I may find someone fabricating and selling these?

* The front sprocket will be 5mm off on a YZF750 swingarm - what's the best/easiest way to sort this? Is there anyone that sells a sprocket that lines up for this conversion?

* I'm not after astronomic power - reliability is key for me. That being said I'm hoping to do some minor modifications to the cylinderhead along the way including a mild port and polish and a cam regrind by Kent Cams - what cylinderhead would it be best for me to use? The TRX850 or the TDM900 one?

* I have a friend who works as a calibration engineer for a UK motorcycle manufacturer who's happy to fit a megasquirt system to whatever I ultimately choose for the price of a few beers, so dealing with the loom is not really an issue for me. That being said - what else have I missed from this list? Or is it really as simple as adapter plate for the oil tank and sourcing a sprocket to sort the allignment?

Many thanks in advance,

[Killerwhale]

Before I start - I can imagine what people are thinking when they see a new member's first post being about a topic that's been talked about 100 times already; I can only apologise! I have used the search function many times over the last month and found a great amount of info on the topic, I'm just after conformation on a few little details.

I'm looking to swap my tired old 850 engine for a TDM900 unit - I have sourced a full engine for £500 with only 9k miles on it. I understand the TDM engine bolts (more or less) straight in with some minor changes required to the oil tank and sprocket. Really I'd just like conformation that I'm correct on the below assumptions;

* I'll need to buy an adaptor plate to use the TRX850 oil tank on the TDM900 engine as the TDM900 tank won't fit. Any ideas where I may find someone fabricating and selling these?

http://www.moto-twins.de/product_info.p ... ltank.html

* The front sprocket will be 5mm off on a YZF750 swingarm - what's the best/easiest way to sort this? Is there anyone that sells a sprocket that lines up for this conversion?

Nah you need to source a one-off, especially as it´s going inwards

* I'm not after astronomic power - reliability is key for me. That being said I'm hoping to do some minor modifications to the cylinderhead along the way including a mild port and polish and a cam regrind by Kent Cams - what cylinderhead would it be best for me to use? The TRX850 or the TDM900 one?

If as me using carbs and TRX head you need to do a lot of other stuff....900 uses sensor on cams...(And Kent dont have them in parts)
You need to use the TRX stator etc. I guess youll be better off using the entire 900 with injection....didnt someone make the 900 oiltank to fit??

* I have a friend who works as a calibration engineer for a UK motorcycle manufacturer who's happy to fit a megasquirt system to whatever I ultimately choose for the price of a few beers, so dealing with the loom is not really an issue for me. That being said - what else have I missed from this list? Or is it really as simple as adapter plate for the oil tank and sourcing a sprocket to sort the allignment?

Yeah, go with all 900 stuff. Chuck the JE 937cc pistons in there and a megasquirt and youll be set me thinks. Ohh, rear sprock needs to get 4mm out as well....but covered in here....

Many thanks in advance,

[MC-Chase]

Before I start - I can imagine what people are thinking when they see a new member's first post being about a topic that's been talked about 100 times already; I can only apologise! I have used the search function many times over the last month and found a great amount of info on the topic, I'm just after conformation on a few little details.

I'm looking to swap my tired old 850 engine for a TDM900 unit - I have sourced a full engine for £500 with only 9k miles on it. I understand the TDM engine bolts (more or less) straight in with some minor changes required to the oil tank and sprocket. Really I'd just like conformation that I'm correct on the below assumptions;

* I'll need to buy an adaptor plate to use the TRX850 oil tank on the TDM900 engine as the TDM900 tank won't fit. Any ideas where I may find someone fabricating and selling these?

http://www.moto-twins.de/product_info.p ... ltank.html

Cheers!

* The front sprocket will be 5mm off on a YZF750 swingarm - what's the best/easiest way to sort this? Is there anyone that sells a sprocket that lines up for this conversion?

Nah you need to source a one-off, especially as it´s going inwards

Shame, I imagine the most common approach is to space out the rear sprocket then?

* I'm not after astronomic power - reliability is key for me. That being said I'm hoping to do some minor modifications to the cylinderhead along the way including a mild port and polish and a cam regrind by Kent Cams - what cylinderhead would it be best for me to use? The TRX850 or the TDM900 one?

If as me using carbs and TRX head you need to do a lot of other stuff....900 uses sensor on cams...(And Kent dont have them in parts)
You need to use the TRX stator etc. I guess youll be better off using the entire 900 with injection....didnt someone make the 900 oiltank to fit??

Starting to get a little out of my knowledge zone here. Megasquirt can run a wasted spark/injection function as far as I'm aware so potentially I could use the TRX head could I not? I'd be very happy to just use the TDM head as compression is similar but from my understanding of what you have written Kent Cams may not be able to regrind the cams?

* I have a friend who works as a calibration engineer for a UK motorcycle manufacturer who's happy to fit a megasquirt system to whatever I ultimately choose for the price of a few beers, so dealing with the loom is not really an issue for me. That being said - what else have I missed from this list? Or is it really as simple as adapter plate for the oil tank and sourcing a sprocket to sort the allignment?

Yeah, go with all 900 stuff. Chuck the JE 937cc pistons in there and a megasquirt and youll be set me thinks. Ohh, rear sprock needs to get 4mm out as well....but covered in here....

I intend to skip the big bore kit as I don't want to deal with the hassle of recoating the bores and rebalancing the balance shafts. I would like a bump in compression but hopefully I can do this with a head skim or copper gasket.

Many thanks in advance,

Thanks again!

[Rod.s]

TRX850 and TDM900 heads have different inlet ports and manifolds, the 900 has a recess for the injector and the manifold is the same, the issue is that the 900 inlet parts don't fit the 850 head....and there is one "frame to head" mount missing from the 900 head.

Just read this thread
http://www.trx850.com/phpBB_forum/viewt ... lit=tdm900

[cobbadiggabuddyblooo]

Cheapest and easiest way to get sprocket alignment is to machine down the 6mm on the rear wheel clutch hub (sprocket carrier.)
The 6 rear sprocket retaining threads unscrew, and you will see a 6mm raised section that the sprocket sits on,
Machine this down flush and problem solved and screw in the retaining threads again.
No need for special front offset sprockets to be made and you can simply use the std sprockets and if you choose to change gearing or sprocket pitch from 525 to 520 or 530, your not dictated by a one off offset front sprocket size or pitch.

[MC-Chase]

TRX850 and TDM900 heads have different inlet ports and manifolds, the 900 has a recess for the injector and the manifold is the same, the issue is that the 900 inlet parts don't fit the 850 head....and there is one "frame to head" mount missing from the 900 head.

Just read this thread
http://www.trx850.com/phpBB_forum/viewt ... lit=tdm900

That looks far more complex than I'm willing to get involved with, lots of custom fabrication, etc. TRX head it is then - I presume compression ratio isn't altered by doing this?

Thanks again for the help, I can't believe I missed that thread first time round .

[Killerwhale]

TRX850 and TDM900 heads have different inlet ports and manifolds, the 900 has a recess for the injector and the manifold is the same, the issue is that the 900 inlet parts don't fit the 850 head....and there is one "frame to head" mount missing from the 900 head.

Just read this thread
http://www.trx850.com/phpBB_forum/viewt ... lit=tdm900

That looks far more complex than I'm willing to get involved with, lots of custom fabrication, etc. TRX head it is then - I presume compression ratio isn't altered by doing this?

Thanks again for the help, I can't believe I missed that thread first time round .

Got to say the TRX head way aint really straight forward either. In your writing i got a bit confused, as if you thought TRX head is same same as 900 wich got injection!? Also from memory, front sprock inwards 6mm rear sprock outwards 4mm (so you get it right if machining your carrier)
Can´t remember doing anything special when fitting TRX stator and flywheel to the 900 enjun but you DO need to change the bottom oilpan as the 900 one is lower and then you cant use TRX exhaust.

I WILL change to the 937cc pistons this fall and then my wiseco high comp ones will go for sale if interested (new set of rings available as well)

[cobbadiggabuddyblooo]

Personally I’d keep the lower cc’s / higher compression Killer than higher CC / lower comp option and spend the money to have new gears made to optimise the power band to the rear wheel.
How often do you use 1 st gear with the higher compression???
I know I only use it taking off in the garage in the morning but can easily do it in 2nd.


TDM 900 gear ratios have a low 1st for adventure riding and a hi 6th overdrive for cruising and differs than the trx gear ratios.
Only regret I have with my motor rebuild was not having gears made.
I would make a closer ratio 5 speed with 1st gear close to std 2nd gear ratio and continuing with4 CR gears with 5th similar to std 5th.

I believe a Hi comp 870-878 with CR 5 speed would kick any 900’s arse.

[Killerwhale]

Personally I’d keep the lower cc’s / higher compression Killer than higher CC / lower comp option and spend the money to have new gears made to optimise the power band to the rear wheel.
How often do you use 1 st gear with the higher compression???
I know I only use it taking off in the garage in the morning but can easily do it in 2nd.


TDM 900 gear ratios have a low 1st for adventure riding and a hi 6th overdrive for cruising and differs than the trx gear ratios.
Only regret I have with my motor rebuild was not having gears made.
I would make a closer ratio 5 speed with 1st gear close to std 2nd gear ratio and continuing with4 CR gears with 5th similar to std 5th.

I believe a Hi comp 870-878 with CR 5 speed would kick any 900’s arse.

I use 1st a lot as i dont have standard gearing, also is the JE both bigger and even higher comp than the wiseco.
You wouldnt have a shot against mine with flatslides, it eats most sportbikes.

[cobbadiggabuddyblooo]

you gotta love a bit of banter

[MC-Chase]

Oh dear, this is turning into a far more confusing idea than I had initially thought

[Killerwhale]

you gotta love a bit of banter

[SDN]

I am putting a TRX head on a TDM900 - i have ground the TRX inlet tract to match TDM and am having the inlet mounting points on the head built up with tig welding, so I can mount the TDM inlet rubbers and use TDM injection - many ways to skin a cat.

However doing this sort of work requires good engineering skills - if you haven't got them, give the job to a professional