'86 250 YPVS Restore

[Gavin]

Hi,
Not sure if I'm supposed to post workshop questions here. If not, feel free to move.

1st job is to find why the engine is seized. I pulled off the heads and found this:



Not sure what the silver crescent is, visible around the edge of the piston. Looks like a ring but didn't think you should see it.

Can anyone shed some light on this for me pls?

[JonW]

I think its a ring, the cyls are worn and the ring may well have moved in the piston, its not easy to tell from the pic tho... is this whats stopping the engine tunring over, if so then you have found the issue...

[Gavin]

So a quick update with some pics on the 250.
The engine is out, and I can turn the flywheel mostly by hand. Cylinders are not seized but there is a few sticking points around the cycle where more force is needed. A friend suggested that the crank may have rust.


I also have an awkward nut stopping me from removing the 2nd bore. Before I strip it with a ring spanner, does anyone have any suggestions like heat, or maybe a chisel to get it off?



I'll now need a gasket set. Without upsetting any vendors, who is a recommended supplier for a kit? Is Ebay quality OK or can you suggest an alternative. I read a few differing opinions on this.

Finally, if it is a rusty crank, is there a one stop shop I can send this to have the case split and rebuilt? It's now getting beyond my comfort zone. Happy to stick with the top end work.
Speaking of which, do I polish up the pistons, or get new?

Thanks all

[JonW]

bang a socket on that nut and you should be able to turn it, if not then you will have to try and masacre it. heat will help loosen it, as will a decent penetrating oil, but the flat is holding i not the thread i suspect. chisel = last resort.

pistsons... new.

crank and bottom end... its really simple. use your manual, honest its an easy one.

crank... probbaly time for a new one or revuild with one of the forum advertisers. Ive used Link before, top guy.

gaskets... oem for base and head, rest can be aftermarket... just buy a kit of em from ebay. exhuast gaskets are best from wicked or oem tho.

[Gavin]

Cheers Jon,
I tried hammering a ring spanner - can't get the socket on due to the exhaust flange. I'll clean it up and try again. Either way I'll need a couple of spare bolts from somewhere.

I've read some forum post about Link. Will follow that up.

Quite a learning curve but I'm enjoying it. Would be good to hear the engine running once again.
Where do you buy your grommets from? Surely there's a local source that costs less than 5 quid per pair of rubber rings?

G



I

[JonW]

oh ok, the spanner should so, defo use one with flats not multipoints, even better one that grips the flats not the points.

spare nuts and bolts... simples... lots of options.

which gromets? I buy from partzilla, norbo and others, but not sure which ones youre lloking for...

[hybrid]

Worst case, you could use a small set of stillsons on it. That should get it off.

[Greasemeup]

Looks like you would have better access after removing that stud, use some heat.


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[L.B.]

Put the other 3 nuts back on & nip up before you try undoing the problem one,heat the area & try an imperial size ring spanner to get a tighter fit.Failing that buy a nut splitter & split it.
Link is your man for crank rebuild.Or Roger in US can do you brand new crank plus most of the parts you'll need,pistons,seals (o rings/gromet,not the dog) new studs & nuts etc.You'll need someone to look at your head too,or just run it as is....

[Gavin]

Another update followed by a few questions for the group.
The problem nut is no more. No damage to the rest of the engine but fair to say that the nut can't be used again for similar purposes
The engine moves freely now, and when the piston rings arrive I'll put it back together and back in the bike.
While the engine is out I've been having a clean up of the interior frame. I've dropped the bike weight 2 kilos by removing the dirt. The question here is the welds on the lower frame mid point. Is that normal or do I have a 'stitch together' frame?



If you look closely something looks amiss:



It doesn't look as per design so the question is, can I pull it apart and re-use the rubber washer / bush / thingy or order new. If new - what is the part? I can't tell from the exploded views as none of the items list a 'rubber' anything.

Next issue, the gear selector shaft has splines on the end which appear worn. Is this condition re-usable as I don't want the extra cost and time to replace if I really don't have to:


And finally, I'd like to spruce the bore casings up a bit before putting them back in. Do they need sand blasting or will a can of paint stripper and Knights Engine paint do a suitable job?. Was the original a silver or shiny / matt black?





Thanks again for any input. As always it's very much appreciated.

[Greasemeup]

Hey Gav,

The standard YPVS swingarm pivot width is 207mm with thrustcovers installed, its a tidy fit into the frame when assembeled.

See the picture below shows no rubber part like whats sticking out in your picture, just a washer (Item 7) and the thrust cover (Item 4). The thrust cover has bonded rubber liner but shouldnt stick out at all. I am even confident that there should be only 1x washer (item 7) on the nut side, outside the frame, the parts fische seems to lie about the assembly order, unless the later bikes are different?

Its possible if your frame is wider that the space was made biger to accomodate a different arm?

I am under the impression that the welds at the bottom mid point of the frame with the gussets are where the factory tube joint is.



Just a grip for your gear leaver, should be OK.

How did you get the nut sorted???

[hybrid]

Yes, that join in the frame is normal. No issue there.
As GMU said, don't worry about those splines on the gear lever. It will be fine as long as the clamp is done up tight enough.

The barrels would originally have been satin black.
Just give them a good de-grease and scrub before you paint them. You can use a soft wire brush if you need.

[JonW]

What they all said

clean the barrels with some degreaser / cleaner... some even use the dishwasher (i dont), but a run with a small wire brush and maybe some paint stripper will work wonders to clean em up. then decide if you like the look or want em black...

the swingarm looks bizarre, ive never seen that happen.... could even be the wrong seals...

gear lever, pretty mornal, but a new one is cheap as chips from the usa... banshee is the same. I always change em on all my bikes now...

[Gavin]

Before cleaning I've tried to remove the power valve as they don't turn much anyway so a clean is in order. Is there a trick to getting them out?
I've removed the locking plate, removed the centre bolt and orange seals, then tried pulling - nothing.
I've got them turning full circle now in situ but would like them cleaned on the bench if possible.
Any tips on cleaning coke build up??
Does that oil seal (orange or ring) need replacing. if so, is there a quicker way of getting them without ordering another shipment from the UK? Each part takes ages and adds to the overall rebuild time.

Ta muchly

[JonW]

Hmm if youve removed the bolt it should come apart, so long as youve also pulled the bushes out... have you? they will probably come when you pull the PVs now, just douse the area in fluid to give it a chance. you will need new o rings for them as well as orange seals when you refit.

cleaning... the usual. gentle scraping and then something like a pot scourer.

I had a bunch of those PV seal kits that i sold locally, someone may not have used theirs, worth asking in the wanted section... dont pay yam aus prices... eeek!

In case youve not see this... Have a look on the partzilla website, OEM parts, Yamaha, 1984 RZ350, as it shows an exploded view. Always worth a look on any part of these bikes, it shows the shape of the PV and you can see it wont come out of the end without the bushes coming out first. you can gently tap the PV as well, but no hard hits...

http://www.partzilla.com/parts/search/Y ... parts.html