DTR power valve compared with DTRE power valve

[Guest MaD.VeZ]

Well, myself and OG compared Power valve operation today and it caused more confusion than we expected.

I will let you see for yourselves and see if you can tell the difference and maybe explain the whys and wtf's!

Heres mine

And heres OG's

Baffled (formally know as Vez).

[Airhead]

Another couple like mine...as in correctamundo

[Cynic]

So whats confusing?

One goes clockwise the other counterclockwise. The question is are the valves the same?

[Airhead]

So whats confusing?

One goes clockwise the other counterclockwise. The question is are the valves the same?

Yes they are the same.

You see the little hole and the 'Finger' with a u shaped cut-out on the pulley, well when the cutout and the hole are aligned the PV is fully open...Now with mine as the revs increase this begins to happen. And with VeZ's it starts off closed and then goes the wrong way with increasing revs!!!

We think he should cross over the cables but cant understand why this is so.

[Cynic]

Yes they are the same.

You see the little hole and the 'Finger' with a u shaped cut-out on the pulley, well when the cutout and the hole are aligned the PV is fully open...Now with mine as the revs increase this begins to happen. And with VeZ's it starts off closed and then goes the wrong way with increasing revs!!!

We think he should cross over the cables but cant understand why this is so.

So they both start off closed and then open, just in different directions? Or are you saying MaD's is closing up? Its just looking at the video they both move to the same point during the clean cycle. So if mad reverses the cables it will be wrong even though its right, er? The pv pulley box has 1 and 2 on yours OG, is it the same on MaDs?

[Airhead]

So they both start off closed and then open, just in different directions? Or are you saying MaD's is closing up? Its just looking at the video they both move to the same point during the clean cycle. So if mad reverses the cables it will be wrong even though its right, er? The pv pulley box has 1 and 2 on yours OG, is it the same on MaDs?

Yes 1 and 2 are the same, with the engine idling both bikes have pulleys at around 30 degrees clockwise of fully open.

With high revs mine is fully open, slot and hole aligned.

With high revs VeZ's has gone even further clockwise and is now 60 degrees away from fully open.

All of this is confusing as his bike seems to go ok though.

[Cynic]

Yes 1 and 2 are the same, with the engine idling both bikes have pulleys at around 30 degrees clockwise of fully open.

With high revs mine is fully open, slot and hole aligned.

With high revs VeZ's has gone even further clockwise and is now 60 degrees away from fully open.

All of this is confusing as his bike seems to go ok though.

So how do the 4 ositions of the pulley affect things. I looked at my TDR earlier to see how that worked but i have to take the exhaust off to see. TBH i have to take the exhaust off to do just about bloody anything.

[Airhead]

So how do the 4 ositions of the pulley affect things. I looked at my TDR earlier to see how that worked but i have to take the exhaust off to see. TBH i have to take the exhaust off to do just about bloody anything.

The four possible positions of the power valve within the pulley have no affect in this case. Both bikes are correctly set up in this regard.

With exhaust removed and the slot and hole aligned the PV can be seen to be fully open on both bikes, ie smooth and flat passage along the top of the port all the way to the cylinder / piston.

If you think about it then raising the exhaust port is what is done on a tuned engine, now when you watch the videos you can see that my exhaust port is raising with increasing revs, and VeZ's is lowering.

[Guest MaD.VeZ]

Yup mine is closing when the revs are increased, although after removing the five foot of slack from the cables the bike was defiantly running better with a bit more pace to it.

I have been thinking what would happen if i tried putting the pv in another of the 4 positions.(not sure if thats what you were getting at Cynic), then the pv would start closed at the other side of the port and open in a clockwise motion.

What i have also been wondering is if this is not intentional by Yamaha to prevent the piston hitting the pv like in the post last week, by switching the cables it would move the operation of the pv to the other side of the exhaust port and move the trailing edge away from the piston, so perhaps switching the cables is the thing to do. This would mean that mine is the right way and OG's is just outdated, that i can live with

Here's another similar year DT going the same way as mine, so its not a fault.

http://www.youtube.c...S&v=ZgQCDF3zf3E

Don't be surprised if when you check your TDR cynic that the pv goes both ways just to really confuse the matter.

Well the sherlock hat is coming out and i will be investigating tomorrow!

Vez (slightly less baffled after sleeping on it).

Edit: Also to throw more into the confusion, i have yet to earth the black green wire that may change things at the pv.

[Cynic]

The four possible positions of the power valve within the pulley have no affect in this case. Both bikes are correctly set up in this regard.

With exhaust removed and the slot and hole aligned the PV can be seen to be fully open on both bikes, ie smooth and flat passage along the top of the port all the way to the cylinder / piston.

If you think about it then raising the exhaust port is what is done on a tuned engine, now when you watch the videos you can see that my exhaust port is raising with increasing revs, and VeZ's is lowering.

Just a thought here, did either of you run the engines over 6 grand?

I'm just wondering if its not to do with emisions. We know resonance is used to keep the charge in the cyl, there is no reason why you could not use the valve to reduce the amont of material escaping into the exhaust in the first place. Then when you are past the 'green zone' (lame but what can you do). It opens up to allow the power. I take it MaDs bike is no slouch?

[Guest MaD.VeZ]

Just a thought here, did either of you run the engines over 6 grand?

I'm just wondering if its not to do with emisions. We know resonance is used to keep the charge in the cyl, there is no reason why you could not use the valve to reduce the amont of material escaping into the exhaust in the first place. Then when you are past the 'green zone' (lame but what can you do). It opens up to allow the power. I take it MaDs bike is no slouch?

Think OG went to around 8- 8 1/2, didn't look at the gauge tbh.

Its hard to tell what revs mine are at with not having a rev gauge, but i went high enough to make OG cringe and tell me off so i figure it wasn't far off full chat.

My bike is ok , but OG's is defiantly quicker, for now at least. Figure if tweeking mine doesn't work i can always stock up on cream cakes and the sort for when OG calls round and slow him down that way

[Airhead]

Just a thought here, did either of you run the engines over 6 grand?

I'm just wondering if its not to do with emisions. We know resonance is used to keep the charge in the cyl, there is no reason why you could not use the valve to reduce the amont of material escaping into the exhaust in the first place. Then when you are past the 'green zone' (lame but what can you do). It opens up to allow the power. I take it MaDs bike is no slouch?

1: Yes both bikes were revved mercilessly (almost)

2: What's all this bollocks about emissions?

3; VeZ's doesnt open up...ever

4: It's no slouch but I think i'll challenge him to a race before he fixes it

[Guest MaD.VeZ]

1: Yes both bikes were revved mercilessly   (almost)

2: What's all this bollocks about emissions?  

3; VeZ's doesnt open up...ever

4: It's no slouch but I think i'll challenge him to a race before he fixes it  

Right i'm off to the shed, and then the bakers!

[Deeteemx]

Edit: Also to throw more into the confusion, i have yet to earth the black green wire that may change things at the pv.

Earthing the green and black wire is the easiest and quickest way to derestrict the DT125RE, Vez. It has a big effect. I understand that the powervalve does close slightly at high revs on this model if the wire is not earthed, but I'm surprised it actually rotates the wrong way. I would earth the green & black wire and see what effect that has.

I did have an early (1992) DT125R which I fitted with a powervalve servo (3 wire type)and that operated backwards sometimes. In the end I diagnosed a faulty servo.

[Guest MaD.VeZ]

Earthing the green and black wire is the easiest and quickest way to derestrict the DT125RE, Vez. It has a big effect. I understand that the powervalve does close slightly at high revs on this model if the wire is not earthed, but I'm surprised it actually rotates the wrong way. I would earth the green & black wire and see what effect that has.

I did have an early (1992) DT125R which I fitted with a powervalve servo (3 wire type)and that operated backwards sometimes. In the end I diagnosed a faulty servo.

This is my second DTRE and the last time i did the black/green wire it had very little effect due to the pv being 180 out. So you need to make sure the bike is set right before it has the full effect.

I will be earthing the wire today or tomorrow, weather permitting, and will be interested to see if it does effect the direction. From what i have read/seen last night on various forums etc. this is the way the PV turns on DTRE and DTX models, but i haven't found exactly why yet.

I also saw a faulty servo, it did the dance of the sugar plum fairies and was obviously broken.

Here it is

http://www.youtube.c...feature=related

Also i believe that some DTR servos operate in a different manner as they have the PV servo cables crossed over before joining the PV.

Vez

[imager]

Nvm it is me vez just testing to see if i could post a pic in a first post

[Deeteemx]

I also saw a faulty servo, it did the dance of the sugar plum fairies and was obviously broken.

Here it is

http://www.youtube.c...feature=related

Also i believe that some DTR servos operate in a different manner as they have the PV servo cables crossed over before joining the PV.

Vez

Yep, that servo is on drugs!

A lot of owners get confused about which way to connect the powervalve cables, and some connect them the wrong way round by mistake. I don't think Mr Yamaha crosses the cables over at his factory.

[Guest MaD.VeZ]

Yep, that servo is on drugs!

A lot of owners get confused about which way to connect the powervalve cables, and some connect them the wrong way round by mistake. I don't think Mr Yamaha crosses the cables over at his factory.

I have heard more than one account of the cables being crossed and when they have been uncrossed the bike runs very poorly. To get confused and connect them crossed would be a very unnatural thing to do imo, with the easy natural thing to do being attaching them straight.

There are so many differences in DTR's from year to year and UK version to Import version etc. that I think its entirely possible for something like that to come from Yamaha. I get the feeling either someone at Yamaha likes to experiment or has a very strange sense of humor.

Vez.

[Deeteemx]

I have heard more than one account of the cables being crossed and when they have been uncrossed the bike runs very poorly. To get confused and connect them crossed would be a very unnatural thing to do imo, with the easy natural thing to do being attaching them straight.

There are so many differences in DTR's from year to year and UK version to Import version etc. that I think its entirely possible for something like that to come from Yamaha. I get the feeling either someone at Yamaha likes to experiment or has a very strange sense of humor. 

Vez.

A lot of confused owners have asked me how the cables should be fitted because there are numbers ("1" and "2") where the cables attach to the servo and the powervalve housing. People often think the cable that connects to the number "1" position on the servo must connect to "1" on the powervalve housing whereas they should connect "1" to "2" and "2" to "1".

If a powervalve is incorrectly set up (eg where the powervalve is rotated anticlockwise 45 degrees or more beyond the open position), crossing the cables over will improve performance as this will cause the powervalve to rotate clockwise as revs increase, back towards the fully open position.

[Guest MaD.VeZ]

If a powervalve is incorrectly set up (eg where the powervalve is rotated anticlockwise 45 degrees or more beyond the open position), crossing the cables over will improve performance as this will cause the powervalve to rotate clockwise as revs increase, back towards the fully open position.

This was discussed as a possibility to change the way my DT125RE opens the valve, with the servo operating the opposite way from the older DTR's, it may make a difference and improve the performance.

Worth a try i reckon

Must admit i have never seen the numbers on the servo before, but i can't say i have ever looked for them. Are they under the rubber cover?

Edit: just another thought, but the servo is a basic electrical motor, if the + and - power supply were reversed i wonder if this would make the servo work like a DTR one.