TZR125 YPVS Valve Setup

[looey]

Anyone here an expert on setting up the YPVS on the TZR125 ?.

I've got a 1989 2RK (UK restricted) TZR125 that has has a full YPVS system fitted.

I've done some research and apparently the only restriction on these bikes was the Valve pegged in the closed position and no Servo etc. fitted.

This bike has nice low down power but it just doesn't have the power it should have up in the revs.

I've checked the valve and cable settings and they look spot-on, i.e. does the cleaning cycle and sits in the fully open position with the ignition on and the bike not running, and when you start the bike the valve moves to the closed position and when you rev it it moves towards the open position.

Problem is..... the valve doesn't get to the fully open position until the revs get to about 10,000rpm, which is obviously far too late.

If I remove the cables and peg the valve in the fully open position I get exactly what you'd expect, no bottom end power whatsoever, then good power between 6,000 - 8,000rpm, then it goes ballistic from 8,000 - 10.500rpm.

I've looked at the pulley housing and that has 29L on it which I thought was a 350 YPVS part, or were they the same part numbers used on the TZR125 ?.

The problem I see is the fixed movement of the servo, so if I adjust the valve so it is fully open at lower revs then when the revs get higher the valve will continue past the fully open position and start to block the outlet track ?.

Anyone got any ideas on how to get it setup so the valve is fully open at lower revs ?.

And does anyone know what revs the valve should be open on the TZR125 ?. I have a Haynes manual but it doesn't cover the valve assembly cos it shouldn't have one fitted !!!.

Cheers

[midlifecrisisrd]

Not got a TZR but had some problems with my DT one.

The pulley on mine is a 29L one so think they are all the same. You would be surprised how high the max opening is, the F2 YPVS is 10200 before fully open which it will never reach.

I did find the pv motors have different pulleys on them as mine was from a DTR and was impossible to adjust till I worked this out. The pulley seems the same other than the locating bolt through the shaft is in a different place. I just marked where it needed to be and drilled another hole and tapped it.

Hope that helps,
Steve

[looey]

Yeah cheers for that.

When you ride this bike with the valve set as per the book it never gets to rev high enough to get the valve fully open.

Maybe I just need to ignore lining the pulley hole with the hole in the block and set it further round ?.

Like I said, if I pin it manually in the fully open position (where it stops after the clean cycle) it absolutely flies from 8,000rpm onwards but it's as flat as sh*t with the valve working and never gets to the redline

The valve is deffo working, it's just like it opens too late

[Deleted]

the way I set up the one on my dt125ypvs was to have the valve open ie completely lined up flat to the top of the exhaust port, then connect everything up and while setting up making sure the adjusters for the cables kept the valve in that position, then just turned the key and it worked.
As for opening right up or any of that I couldn't tell you, it just went like shit of a shovel (esp in the 80lc rolling chassis lol)

[looey]

Yeah that's exactly as it's setup.

It's almost as if it's all adjusted correctly but the servo just isn't moving it around far enough as the revs rise

When you rev it in neutral, the valve doesn't get to the fully open position until beyond the revs it will pull in the gears when you're riding it !!!

Peg it in the open position and at 8,000 it goes bonkers.....

[looey]

Well I've come to the conclusion that sommit must be up with either the Control Unit or the Servo itself, or they're just not talking to each other properly.

With it set correctly it can't pull enough revs when being ridden to get to the revs the valve fully opens !. And if I adjust it so it's fully open at around 8,000rpm, it is better but when you get to 10,000rpm the valve has gone past the fully open point, so must be starting to block the lower portion of the outlet track.

I could do with trying replacements but they are as rare as hens teeth so not likely me thinks.

Does anyone know if the YPVS Control unit will be harmed if I run the bike with it disconnected from the the servo at the multi-plug near the Control Unit ? (behind right hand side panel).

Cheers

[midlifecrisisrd]

Aug 27, 2013 14:49:54 GMT 1 looey said:

Well I've come to the conclusion that sommit must be up with either the Control Unit or the Servo itself, or they're just not talking to each other properly.

With it set correctly it can't pull enough revs when being ridden to get to the revs the valve fully opens !. And if I adjust it so it's fully open at around 8,000rpm, it is better but when you get to 10,000rpm the valve has gone past the fully open point, so must be starting to block the lower portion of the outlet track.

I could do with trying replacements but they are as rare as hens teeth so not likely me thinks.

Does anyone know if the YPVS Control unit will be harmed if I run the bike with it disconnected from the the servo at the multi-plug near the Control Unit ? (behind right hand side panel).

Cheers

Something just occured to me.

Are you using the separate controller and servo? I thought this was for the early bikes like the RD and the DT lc and the later ran a combined servo that had the electronics in it and the 3 wires simply plugged straight in the loom. Mot 5 wires from the servo plugging into the controller and the 3 wires from the controller to the loom.

Maybe you have the wrong set up

Steve

[AndyYam]

Not sure how much help this will be but I've done a fair bit with the DT125R models and the the servos.

The 3 Wire type servos have the YPVS control unit built inside the servo and were used on the 1997-1999 DT125R's, TDR125's and Italian import TZR125's.
The 5 wire type servo do not and need a seperate control unit to operate them.
They also used the 5 wire on 1999 onwards DT125R models which took its control straight from the CDI.