Yamaha TRX850 Enthusiasts Forum

cobbadiggabuddyblooo wrote:I felt it only fitting to keep the name of the bike EKOJA out of respect for Ash, the previous owner since the bike entered the country in 2001 and is one of the original forum members and was 79 when I purchased the bike from him.
The bike was totally std including stock pipes and the plan was to keep it that way but....
So far it now sports the modified Thundercat forks, Modified R6 rear suspension, Over Racing Exhaust and TDMR40's.
It currently has the YEC 6 speed motor in there too and the black R6 wheels will balance things out nicely as I'm still planning in keeping it looking pretty well std from a distance including the analogue dash.
To get around not having a speed drive on the R6 front wheel, I've chosen to fit a GPS speedometer in place of the std analogue gauge.





http://www.meaningslike.com/name-stands ... learn-more

Aw shit... I don’t know what to say, really thoughtful Cobba. She still looks good ,and I miss it.
I

18 tooth front 520 R6

Sunstar 3A718

https://www.wemoto.com/parts/picture/sa-3a718

Over 6 speed Close ratio specs (modified YZF750sp) compared to with YEC TRX Close ratio 6 speed.
STD YZF750 and STD trx850
TDM 900, TDM 850 (Mk 1 & Mk 11) and XTZ750 listed also.....

Over Racing 6 speed ......... YEC TRX850 6 speed
1st.... 32/13 ... 2.462 ---——— 38/13 2.923
2nd... 33/17 ... 1.941 ---——— 35/16 2.188
3rd.... 31/19 ... 1.623 ---——— 33/18 1.778
4th.... 33/23 ... 1.435 ---——— 33/22. 1.500
5th.... 26/20 ... 1.300 ---——— 28/22 1.273
6th.... 25/21 ... 1.190 ---——— 27/24 1.125

Std YZF750 -----------------STD TRX850
------36/14 ... 2.571 ---------- (36/14) 2.571
------33/17 ... 1.941 ---------- (37/20) 1.850
----- 28/18 ... 1.555 ---------- (30/21) 1.429
------26/19 ... 1.368 ---------- (27/23) 1.174
----- 28/23 ... 1.217 ---------- (28/27) 1.037
------26/24 ... 1.083 -----

TDM 900 -------
------33/12 ... 2.750
------37/19 ... 1.947
------34/22 ... 1.545
------31/25 ... 1.240
------26/25 ... 1.040
------24/26 ... 0.923

TDM 850 Mk 1
------37/13 ... 2.846
------37/20 ... 1.850
------29/22 ... 1.318
------29/27 ... 1.074
------27/30 ... 0.900

TDM 850 Mk 11 / XTZ750 share the same gearbox ratios
------37/13 ... 2.846
------37/20 ... 1.850
------30/21 ... 1.429
------27/23 ... 1.174
------28/27 ... 1.037

TRX850 , TDM850 , TDM 900 and XTZ750 all share the same primary drive ratio of 1.718 but may differ in wheel size and final drive ratios dictated by sprocket choice.

The Over ratios you list are the same as the YZF750SP.
The YEC ratios you list have a huge spread. Where did you get them from?
You've got the same problem as me. I write stuff down and then can't find where I left the note.

I've worked out gearing for the YEC ratios you listed.
I can't find your note in any of the threads, so maybe you did actually write it down.
Have you checked down the back of the lounge?

2.923 = 38/13
2.188 = 35/16
1.778 = 32/18
1.500 = 33/22
1.273 = 28/22
1.125 = 27/24

Yes Thanks Dicky.
I got an idea I found the YEC items on the German Supertwins forum.
I know the Over gearbox is a modified YZF750 SP gearbox as I can see how they have modified the clutch hub to deal with the 6mm longer shaft. I found the same problem when I picked up an SP gearbox on the original build 5 yr ago.
The Over box definitely has some close ratios and I often short shift to higher gears so I can see how the YEC selection of gears would suit the torque characteristics of the TRX motor.
Luckily I found an R6 520 18 tooth sprocket and a selection of 38 to 41 tooth for the dymags gives me plenty of options .
I’m itching for a ride but still waiting to get the head back after having the valves and seats re cut.

I might have access to a 750SP donk. I don't think my friend has sold it yet.
The chassis is already mine, but it's got a FZR1000 EXUP donk shoe horned into it.
Getting it running again is on the list, just not sure where on the list.
Probably need to fix the garage and workshop first.

SP motor would be a worthwhile investment just to keep under the work bench Dicky as they get harder and harder to find.
Sold the gearbox for a grand a few yrs ago ...

Just recieved a msg from Over Racing and confirming YZF750 close ratio gears used on their trx boxes.

https://mostynindustries.com.au/speedo-tacho-ratios

Thanks for the link Robert

Handy hint for clutch chatter on race starts

http://www.factorypro.com/tech/clutch_y.html

Link.

https://www.peterverdone.com/archive/highspeed.htm

A little more clarification on how exhaust pulse influences the richer mixture on cylinder no.1.
As has been noted by a number of people how cylinder 2 runs a little leaner than Cylinder No1.
Some hypothesised that the cam chain galley had an influence on heat dissipation but when you look at the 270* crank and it’s impact on overlap, you will see that when cylinder no.1 is at TDC overlap Cylinder no.2 has just fired 90* earlier.
Now you will see the exhaust valve on cylinder No1 will be closing as cylinder no.2 exhaust valve is opening allowing that extra suck on overlap period as exhaust No1 is closing.
Also there is the possibility of the exhaust from no.2 opening in pulsing exhaust back into cylinder no.1 due to its velocity and corrupting the A/F mixture with exhaust gas in cylinder no.1.

Food for thought...