Yamaha TRX850 Enthusiasts Forum

Hi guys, i have a couple of small problems that i need some advice on if anyone can help?,

1st- i have removed the original clocks and put in a koso digital speedos set up and all seems to be working well except for the fine tune of the digital tacho. I have set up as per instructions but it seems to lag behind on low revs but hits the max revs to easily. i have sensor on the left coil positive and earthed to the frame behind the coil, and set the speedo to P1 which i believe is 4 stroke 2 cylinder any help on set up will be most appreciated.

2nd- the radiator fan no longer seems to come on even though the speedo temp gauge shows over 100 degrees c. does the original temp gauge trigger this to come on and do i now have to do a by pass to get it to run from the thermostat?

3rd- fired up for the first time yesterday since fitting my new fcr's. they sound awesome (love the metallic ticking on tick over) but i have noticed that when i tried to do a short run up the road they bikes bogged down when winding on the throttle will i need to reset the tps as i have it connected to the carbs. can someone remind me how to reset the tps and i suppose i will need to re connect the original tacho to see where the needle sits on the test.
engine is standard except for the carbs and some beowulf cans, so would expect carbs to be ok for this.

any help with the above would be greatly appreciated.

Mark

markrennie wrote:Hi guys, i have a couple of small problems that i need some advice on if anyone can help?,

1st- i have removed the original clocks and put in a koso digital speedos set up and all seems to be working well except for the fine tune of the digital tacho. I have set up as per instructions but it seems to lag behind on low revs but hits the max revs to easily. i have sensor on the left coil positive and earthed to the frame behind the coil, and set the speedo to P1 which i believe is 4 stroke 2 cylinder any help on set up will be most appreciated.

2nd- the radiator fan no longer seems to come on even though the speedo temp gauge shows over 100 degrees c. does the original temp gauge trigger this to come on and do i now have to do a by pass to get it to run from the thermostat?

3rd- fired up for the first time yesterday since fitting my new fcr's. they sound awesome (love the metallic ticking on tick over) but i have noticed that when i tried to do a short run up the road they bikes bogged down when winding on the throttle will i need to reset the tps as i have it connected to the carbs. can someone remind me how to reset the tps and i suppose i will need to re connect the original tacho to see where the needle sits on the test.
engine is standard except for the carbs and some beowulf cans, so would expect carbs to be ok for this.

any help with the above would be greatly appreciated.

Mark

1. IIRC there are some posts in here about one need to have a long cable wound many turns on the coil cable....search for it!
2. My cuts in at approx 107 degrees...did you let it to run higher?
3. It´s cold outside, guess you got a lean bog...i run without airbox and needed 170 mains on the TRX and even bigger on the TRX900 (don´t know what size yet)

There's a 'fix' for Vapor tachos which might also work with Kosos, you need to put a 600k ohm resistor in line with the wire going to the coil otherwise the tacho goes mental. Also check that you have the spark count right, as there might be a couple of settings (four stroke, two cylinder, non-wasted spark and four stroke, two cylinder, wasted spark) which would affect the readings as well.

Is this your race bike? You don't need a fan (it's just more weight and more to go wrong!)

You can just disconnect the TPS. It defaults to full advance when you disconnect it and the tacho error won't show up on your Koso gauge

Thanks for the input guys. just a couple of things.
firstly my speedo came with the plug in coil wire not the wrap around type so have plugged in to no 1 cylinder coil. checked the settings on the speedo and it only allows for type of engine and how many pistons. i know others on this forum others have fitted a koso so please could one of them let me know what they set in.
secondly your right kayla dont really need it but i will be keeping it just road legal so will come in handy when out for a blat. also will have to run water in the system when racing so dont want it to boil over. i will try to leave for longer so see what happens.
thirdly i have heard that you need to do the tps by pass mod if you disconnect it, is this true or can i just unplug it now i dont have the original speedo?

cheers

markrennie wrote:Thanks for the input guys. just a couple of things.
firstly my speedo came with the plug in coil wire not the wrap around type so have plugged in to no 1 cylinder coil. checked the settings on the speedo and it only allows for type of engine and how many pistons. i know others on this forum others have fitted a koso so please could one of them let me know what they set in.
secondly your right kayla dont really need it but i will be keeping it just road legal so will come in handy when out for a blat. also will have to run water in the system when racing so dont want it to boil over. i will try to leave for longer so see what happens.
thirdly i have heard that you need to do the tps by pass mod if you disconnect it, is this true or can i just unplug it now i dont have the original speedo?

cheers

3. TPS bypass if not using TPS....otherwise the tacho goes haywire....

Killerwhale wrote:

markrennie wrote:Thanks for the input guys. just a couple of things.
firstly my speedo came with the plug in coil wire not the wrap around type so have plugged in to no 1 cylinder coil. checked the settings on the speedo and it only allows for type of engine and how many pistons. i know others on this forum others have fitted a koso so please could one of them let me know what they set in.
secondly your right kayla dont really need it but i will be keeping it just road legal so will come in handy when out for a blat. also will have to run water in the system when racing so dont want it to boil over. i will try to leave for longer so see what happens.
thirdly i have heard that you need to do the tps by pass mod if you disconnect it, is this true or can i just unplug it now i dont have the original speedo?

cheers

3. TPS bypass if not using TPS....otherwise the tacho goes haywire....

But there's no standard tacho so he can just unplug the TPS

Kayla wrote:

Killerwhale wrote:

markrennie wrote:Thanks for the input guys. just a couple of things.
firstly my speedo came with the plug in coil wire not the wrap around type so have plugged in to no 1 cylinder coil. checked the settings on the speedo and it only allows for type of engine and how many pistons. i know others on this forum others have fitted a koso so please could one of them let me know what they set in.
secondly your right kayla dont really need it but i will be keeping it just road legal so will come in handy when out for a blat. also will have to run water in the system when racing so dont want it to boil over. i will try to leave for longer so see what happens.
thirdly i have heard that you need to do the tps by pass mod if you disconnect it, is this true or can i just unplug it now i dont have the original speedo?

cheers

3. TPS bypass if not using TPS....otherwise the tacho goes haywire....

But there's no standard tacho so he can just unplug the TPS

Thought it was the cdi itself bla bla bla.....i had a moment!

If it comes to it, the bypass mod is on page 2 of this thread: viewtopic.php?f=6&t=811

Set the tacho to 2T, 2 cylinders - sounds odd but it will work

If you bypass TPS you will lose low to mid power - fine on trackdays but can be a pig on the road

Thanks for the help, just to update you all on a few things. 1st is the fan is NOT connected to the original temp gauge so fan will come on with an aftermarket speedo at around 107 degrees. 2nd i have been informed by jon at digital speedos that if you want a good signal from the tacho pick up wire do NOT ground the black wire out it interferes with the signal, works better but still not quite right will try the 2t, 2p set up instead as suggested.
lastly i have the full digital DB02R battery back up speedo if anyone out there goes for the same one then do not buy the mechanical to digital speedo drive converter it doesnt work with this speedo. instead use the supplied magnet pick up and connect to the rear wheel, it works a treat.

now another bit of advice please i have done the tps reset test and my old tacho always points to 3,000 rpm when i disconnect the tps! i have read elsewhere that it should point to 4,000 rpm if set correctly is this right and if so how do i adjust it to be correct?

thanks for all your help, i will post some picks of the bike when finished, will be a yamaha m1 rossi valencia rep.

Go to the downloads section (via board index) and look at the service manual pdf you`ll find there.