hi this my first post an my first yamaha tzr 125. well the problem is wen i ride the bike its got no power till 7000 revs an then the power will kick in. i find my self holdin in the clutch till 7000 revs an then lettin it out to get power [only done it a few times no more than 5]only had the bike 1 week to this date 17/03\10 ride it once. so can any one help or give me some info i think its got some thing to do with the power valve [correct me if im rong] i think its stayin open or something my m8 who i got it off has had the head an barrel skimed an new pistion an rings be for i got it an i think thats wen the prob started. its a 1990 model any help i will be very greatfull thank you kris

Hi and welcome,

You are right about the powervalve staying open. Its not a problem its a feature and how they are. Dead before 7k rpm then like a rocket after. You have to ride the powerband like a nutter to get results.

Has it got a servo motor to turn the PV ?

http://www.youtube.c...h?v=ZgQCDF3zf3E (I know its a DTR but they are the same engine.)

Don't think they had servos as standard on 90 TZR's. So it is probably pinned open for full power as they suck when pinned closed. You could strike a balance and pin it half way open though. Or you could go down the route of fitting a servo but its no small task.

Vez.

Hi and welcome,

You are right about the powervalve staying open. Its not a problem its a feature and how they are. Dead before 7k rpm then like a rocket after. You have to ride the powerband like a nutter to get results.

Has it got a servo motor to turn the PV ? 

http://www.youtube.c...h?v=ZgQCDF3zf3E (I know its a DTR but they are the same engine.)

Don't think they had servos as standard on 90 TZR's.  So it is probably pinned open for full power as they suck when pinned closed. You could strike a balance and pin it half way open though. Or you could go down the route of fitting a servo but its no small task.

Vez.

hi thanks for replying

yeah thats right 7000 an then its like a rockit i dont no if its got 1 of them wats on that vid so wat could i do just set the power valve cuz it needs alot of work allready if u no wat i mean so the simple way is better 4 me lol is it wat my m8 done wen he done the head an barrel

I don't think your bike has a servo motor fitted because of its age. This being the case, people tend to pin the PV so it is fully open to get the most power at full revs, but this leaves very little power low down in the revs. You can reposition the PV to get a more steady flow of power by fixing it half way open. 

I will post a description of how to do this when i get home unless someone else does before i do. 

Vez.

yeah thanx that well be great nice one

Completely forgot to post last night.

DISCLAIMER. I am not responsible for any damage, destruction, explosions, fires or anything else caused by following my advice. You should be aware I am not a trained mechanic, everything i know i have been taught by experience, friends or books. By following my advice you do so at your own risk! 

Ok to start you will possibly need to remove the fairing (if it has 1). You will need access to the left hand side of the cylinder and the exhaust port.(left and right as looking from the rear to the front of the bike)

Then remove the exhaust, so you can see inside the exhaust port on the front of the cylinder and take a mental note or picture with a camera/phone of the position of the power valve in-case you want to reverse the process later.

Now on each side of the cylinder head there will be a circular end cap about 40mm diameter, remove the left hand end cap by removing the 2 allen bolts and the 10mm bolt in the center then pull the end cap out.

You will then see a diamond shape with a bolt hole in the center, this is what needs to be rotated to change the position of the PV. Also note there should be a brass sleeve holding this in place with a hole or dowel at one point of the edge. The sleeve sometimes remains stuck to the end cap when removed.

You then need to rotate the PV towards you until it slopes slightly(lower edge to the front) and closes the port off a little. If you rotate the pv around you will see the difference between fully open and fully closed by looking up the exhaust port, you are aiming to make the exhaust port size somewhere between the two.

The next part may be tricky, If you examine the end cap and brass sleeve you will see a pin and a slot that stop the sleeve rotating thus holding the pv in place. When the pv is in the place you want, you need to pin it in place either by cutting a new slot in the brass sleeve or removing the sleeve all together and hoping the bolt in the end will hold it in place(i recommend the former), you could try loctite on the thread and around the end of the bolt, but it may cause trouble in the future(seen it done but wouldn't really recommend it).

There may be other/better ways to do this, i have only done the fully open or closed setup on my bikes. I've seen a couple of mates try the half closed bit and it seemed to work for them.

Hope this helps

Vez. 

hi

ok thats birll so i dont need to take the head an barrel off then i thought i would of.

i got a manaul comeing so i should be ok if i need to put it back as standard.

ok i will be busy the weekend i will put a new post on next week.

just 1 thing be for i go [servo] will i need to change the barrel or just the loom at most?

my manuals just come

oh an thank you again for your info at least now i understand it all a bit better

Hard to say what you will need to change for a servo, could be a simple plug and play a servo or you may have to replace the cdi and the loom. Would need investigation, probably the easy fix for fitting a servo would be to get the complete loom, cdi, servo and maybe even the stator plate and coil etc. from a TZR that has the servo fitted.

I am a DTR fan, so after the engine my knowledge is limited regarding the rest of the TZR.

Vez.

ok thanks.

i will lookin to it a bit more about fittin a servo. sounds like the best option but only if i need to.

your info as bin helpfull an i understand that you are not a trained machanic i will use info at my on risk an do not hold you or anyone else responsible.

ok thanks.

i will lookin to it a bit more about fittin a servo. sounds like the best option but only if i need to.

your info as bin helpfull an i understand that you are not a trained machanic i will use info at my on risk an do not hold you or anyone else responsible.

I'm not worth suing anyway its just a standard paragraph i copy n paste when posting guides/how too's .

Post back with anything you find out about the servo kris, i'm always keen to learn more

lol.

i was going to lookin to a servo a bit more but i ended up lookin in to the cdi because the yamaha tzr125 has two sourse coil.

cuz ive got a new ignition coil [spark plug part] so wen i found out about the cdi is part of the ignition system it got me thinking

my cdi could be at fault but the only way to find out for sure is to buy a new or used cdi used one is much better cuz new they cost doe.

but if i get a used one must make sure it works. then theres the cdi control box i can do a test on that [thats the easy bit].

now back to the pv if i need to fit the servo an at most i would need is cdi an loom [or new barral but not sure yet]an the servo its self

an pv cables. 2 birds with one stone if my cdi is faulty cuz i would or think i would need to change cdi anyway if i go down the servo rote.

i have taken off my exhaust an i cant really tell if the pv is open or closed but a can seen my pistion an i can feel the valve so it sounds

like its open?

so do you think i should go down the cdi rote 1st dont think it would do any harm i can get a used cdi £30 an he says it works an he seems ok

but wen i told him about no power till 7000revs he talked about power valve he did or dose want £45 for it but he sed he would take £30 so he sed

the same about some people pin open the pv for more power but you lose power low revs.

but my m8 tells me its the cdi or the spark plug coil.

so not sure on wot way to go first£

so wen the spark plug coil comes i could fit it test it if its still the same then do a check on cdi control box an then if its not the control

box.an then cdi or pv ?

Nothing wrong with that mate, rode one myself for a couple of weeks after my bike was nicked years ago, well one of the early RD's with the ALL NEW powervalve motor. Dead as a dodo till just under 7 grand then bang, lean foreward and hello captain Kirk, "warp speed Mr Sulu".

The later powervalve servo stuff will retro fit if you swap the loom in from a later bike, probably not all that cheap, but you will need the later cdi and servo controller and the PV motor to go with it. You can see the mountings for the black box, or should under the pillion seat.

I recall that 350 ypvs stuff can work quite well, i believe its the same stuff (Yam are pretty lazy like that). Trouble with that is finding good kit to begin with.

A couple of TZR's were converted using old fasioned car choke cables and a 350pv cable box (the bit that fits on the barrel)Back in the day. When you want low grunt pull one cable, when you want fast pull the other. With gradients in between. Not all that sophisticated but its not all that dear either. And can be opperated going down the road if you fix the top of the cables on the top yolk.

I recall that 350 ypvs stuff can work quite well, i believe its the same stuff (Yam are pretty lazy like that). Trouble with that is finding good kit to begin with.

A couple of TZR's were converted using old fasioned car choke cables and a 350pv cable box (the bit that fits on the barrel)Back in the day. When you want low grunt pull one cable, when you want fast pull the other. With gradients in between. Not all that sophisticated but its not all that dear either. And can be opperated going down the road if you fix the top of the cables on the top yolk.

Thanks for that, i just spat coffee all over my monitor

Does sound like a simple fix, if not a little crazy.

Kris. if your cdi or coil were goosed you would now about it mate. I did see the price of a servo from Yamaha £399 ish iirc so £40 doesn't sound bad.

Vez

thanks for your info lads.

i brought a cdi for my model an year [1990] for £1.20p off ebay just in case mine is faulty at that price it was

worth the risk.

im still waiting for the ignition coil so when they come at least i can c if that is the prob or not. mean time i

will buy some bits an bobs for a servo off ebay. what year would i need? a 1995 tzr for the loom i might get a

dt barrel as i will need one that should work enit? or is it best to stick to tzr everythink.

The DTR barrel should fit, i have never tried it myself but have real elsewhere its possible.

As for the servo, it depends what you are going to change, if your only adding a servo then the closer to the age of your bike you can get the more chance of it being compatible with your loom imo.

But you need to check for extra connections on you cdi for the servo to connect too, from my manual it shows two empty blocks(brown/red - black/brown - white/black - yellow/blue wires on each block) for both models covered in it, i can only presume these are for the servo and a servo controller unit(never seen one of these) so you should probably look out for a servo controller unit as well as a servo unit if your CDI has these extra blocks.( my manual ends at 1993 for the TZR-3pc3 model btw).

If you are changing it all (cdi loom etc) then going for a later model would be best because it will have had less use.

Like i said before, i can't be 100% sure about this.

Good luck

Vez.

Thanks for that, i just spat coffee all over my monitor  

Does sound like a simple fix, if not a little crazy.

Kris. if your cdi or coil were goosed you would now about it mate. I did see the price of a servo from Yamaha £399 ish iirc so £40 doesn't sound bad.

Vez

Hey don't knock it MaD, when i was fiddling with these they were new, and there was no ebay etc. These bikes went like F seriously seriously fast when you compare it to the stuff trundling around in the early mid eighties.

Yamaha and co wanted megga bucks for any kind of servo stuff. I know people nicked bits off 350's. The powervalve controler/ servo motor and stuff. One smart arse made his own programmable PV controller. The more financially challenged like myself and my mates who put 90% of our earnings in the tank needed to use imagination.

For me and my mates pretty was far too expensive. Our bikes were fast pure and simple, no tat, trinkets or otherwise added. If it didn't make it faster it went in the bin simple. Indicators gone,mirrors,chrome swapped for plastic. Friday and Saturday nights on the 'new' bypass called the mad mile.

A roundabout at each end and 2 miles of dual carriageway inbetween in open country, now surrounded by houses and has 40 limit with 3-4 extra roundabouts in it . Speed was king.

I'll stop now.

Hey don't knock it MaD, when i was fiddling with these they were new, and there was no ebay etc. These bikes went like F seriously seriously fast when you compare it to the stuff trundling around in the early mid eighties.

Yamaha and co wanted megga bucks for any kind of servo stuff. I know people nicked bits off 350's. The powervalve controler/ servo motor and stuff. One smart arse made his own programmable PV controller. The more financially challenged like myself and my mates who put 90% of our earnings in the tank needed to use imagination.

For me and my mates pretty was far too expensive. Our bikes were fast pure and simple, no tat, trinkets or otherwise added. If it didn't make it faster it went in the bin simple. Indicators gone,mirrors,chrome swapped for plastic. Friday and Saturday nights on the 'new' bypass called the mad mile.

A roundabout at each end and 2 miles of dual carriageway inbetween in open country, now surrounded by houses and has 40 limit with 3-4 extra roundabouts in it . Speed was king.

I'll stop now.

I ain't knockin it Cynic, just didn't expect it is all, hell it even got me thinking of a way to do it with a gear lever from a mountain bike and some kind of spring return on the servo pully  

Started my biking life on the cheap, my first running bike was only £50 and that was the most that ever got spent on it in the 2-3 years i had it. Had to go round to garages scrounging used engine oil just to keep it running at one point. My first DTR was a real mess too, ask OG, i showed him a pic the other day, i had to buy bits every week for months just to get it running, which is probably why i hoard parts like i do now. 

Speed may have been king for you, but just running was all i could hope for.   

Don't get me wrong, I'm the last person to throw money at a bike when it can be done cheaper and as effective. If there is a cheaper way to do something i have probably tried it, i just wouldn't suggest it to someone on here unless i suspect they want the cheaper answer.  

anyway   and im waffling too.

back to the plot, the pv controllers on RD350's (chances are the dt's do as well) are all worked the same way, Yamaha have been their usual basic selves. The pv sevo and servo controller are fed from the taco feed from the cdi. Or what could be used as a taco feed on the early bikes with the mechanical taco.

So, that means that any pv kit with the respective servo will power up the valve so you could use the newer stuff too, so long as the pv motor and the controller match up. Bit of basic wiring to connect the 2 together and your away.

Common sence (steady) sayes the 350 kit , or TDR/TZR 250 stuff will be better as it will have been designed from the begining to give full power so no built in meddling to spoil the fun. They all go ape shit at around 6 grand so the valve must opperate at pretty much the same time and with the 250 being 2 125's (litterally it appears) it should open about right as well.

I'm not going to say absolutely it will work, but i don't see why it can't.

I've got a 2rk with 3mb barrel and 3bn head. Does anyone know if i have to use dt carb settings or stick with the tzr carb?