YPVS Valve Assy ??

[looey]

After some advice please chaps, as I've not messed with a YPVS top end before

When riding the bike, it's making a bit of a spitting noise from around the exhaust flange or inner power valve seals area and making a right oily mess around there as well.

I had planned to just leave it till after this summer's riding to do a top end rebuild, as I'm not too bothered about the oil but now after a closer look today I just can't see how the system can be working properly

I've taken a picture best I can (it's dark up there..... lol), so can any trained eyes please have a look and tell me what the crack is.

You can see from the picture that r/h bush retaining plate screw is not screwed up tight to the plate, the allen bolt is tight but there's a gap between the head and the plate and the plate just slops about, so I assume the screw that's in there must be too long and hitting the end of the hole before clamping the plate ?.

Worse is that the centre connection clamp can be moved back and forth by hand probably 30-40 degrees, so assume that will translate into the left valve moving a similar amount before it takes up the slack and starts to move the valve in the r/h cylinder. There doesn't look to be any gap in the joint halves, so can only assume that either the clamp or the valves themselves are worn ?. Is it more likely to be one over the other ?.

Looks also to me like to sort the bush clip bolt and the centre clamp that at least the radiator and exhaust flanges will have to be removed to gain enough access ?.

Thanks in advance

[looey]

Yeah I know that's the only way to get it fully sorted properly long-term but I was hoping to just get it just working correctly with no excess play for now.

Is it normally the clamp or the valves that wear, or is there no usual suspect ?.

[LC_BOTT]

Sounds like its worn on the PV shafts, which is quite common, possibly due to one seizing up slightly or getting tight, there is also a rubber damping on the flat of the joiner, so this is possibly worn or missing (mine was, so I shimmed mine)
The pic looks like the barrel is split??, I'd just get a pressure washer out for a start, and get it all cleaned up, could be exhaust gaskets just blowing, nice and simple. But definately a top end PV overhaul is due by the sound of it.

[paulo]

If you can live with it over the summer then leave it till the dark cold winter nights. Mine required new valves, bushes, seals & centre joint when I had the same problem - not a cheap job!

[looey]

Do you mean just behind the retailer clip bolt head on the right of the picture the barrel looks split ?.

I can see what you mean but just went and wiped it and it was just a lump of crud creating an optical illusion that the barrel was damaged there....phew

[looey]

Apr 21, 2013 18:38:07 GMT 1 paulo said:

If you can live with it over the summer then leave it till the dark cold winter nights. Mine required new valves, bushes, seals & centre joint when I had the same problem - not a cheap job!

Yeah that's what I was hoping to do..... just thought if it was the joint clamp creating most of the slack, then I could make it better for a while until I fully strip it but by the sounds of things it will all be fudged..... ;D

[bare]

Understand your hopes. But mechanical bits once showing wear/damage.. and.. Left unattended/ignored do far more serious collateral damage than their owners imagined.
Choice is: pay Some now or a Lot more later :-)

[midlifecrisisrd]

You could try and get the clamp off and pack it as a temporary fix just to get the valves working properly but in my experience the screws are a nightmare to get at and are often seized.

The ends of the valves can be worn badly and no new clamp will sort that.

Best get a good set of valves and new bushes, seals, joint and a top end gasket set and get it over and done with. While you are at it change the bush retainers for the thicker stainless ones from Norbo or NK. Sorted within a day.

Hopefully the barrel will not be worn from the bush moving, there should not be a groove in it. If worn it is not uncommon to use silicone to pack it.

Even with a second hand set of valves and only changing the inner bushes and seals you are looking at £150 - £200 in parts

Steve

[lb]

Id look at it asap. If pv bushes are floating around they can wear grooves into the barrels & wear pv themselves.

[looey]

Ok, cheers for the advice chaps.

I guess the centre clamp needs to be removed to get the barrels off anyway ?, so I'm going to have to do that regardless off a complete strip and rebuild or temporary packing ?.

What do people do it the screws are seized solid, drill the heads off ?.

[midlifecrisisrd]

Apr 22, 2013 9:26:17 GMT 1 looey said:

Ok, cheers for the advice chaps.

I guess the centre clamp needs to be removed to get the barrels off anyway ?, so I'm going to have to do that regardless off a complete strip and rebuild or temporary packing ?.

What do people do it the screws are seized solid, drill the heads off ?.

Drill is the only way I'm afraid.

Steve

[markhoopy]

All that crap is coming from the powervalve seals(s) so one or both of them need replacing anyway, and if you had to replace one then you would change them all while you were at it.

New powervalves are £120, centre joint piece, four O rings and three castle seals £60, gaskets £25, so if your p/vs are ok it won't cost a huge amount .. it does need doing sooner rather than later though!

[fatfastroger]

I remember mine in the 80's leaking and spraying oil over my white ankle boots everytime I rode it.

As mark says it might not be too bad, if your valves are ok then seals etc. Use genuine though !
My joint screws were seized too, the heads chewed up too. I used a hacksaw blade to cut a slot then a centre punch to knock them undone.

[cb250g5]

I'm assuming this is my old bike. Exhaust studs / bolts look familiar anyway.

They were off 3 or 4 years back, so I reckon they will come off again. It's all stainless & apparently well lubricated.

I *think* I filed the valve ends flat, took a bit off the connector block & used a bit of copper shim to get it all bolted up tight & in line at the time.

Or maybe that was my current engine - not sure. Something has worn again if you can turn the centre block without both of the valves moving. This really is a crappy design from Mr Yamaha.

[looey]

Ok thanks for all the advice and observations chap.

Yeah it is your old bike Jason, only done 100 miles since I got it !

Got a couple of other bikes in the queue for attention first then I'll get this all apart

I will have some more questions for sure