Inconsequential ramblings of an Old Git

[mangocrazy]

Well, it's a case of one step forward, several steps back I'm afraid...

Yesterday Mrs Mango and I set off on the LC for a little ring-ding-ding around the Peak district. I'd modified the carburation over the winter to richen up at idle and lean off the top end, and the mid range/top end now felt a lot crisper and more responsive, but I'd obviously overdone it on the pilot jets as if it didn't fire first kick on the choke, I had to knock the choke off to get it to fire. But all in all, an improvement.

I'd done the first 280 miles of running in on premix, but over winter had converted back to the Autolube pump, having first bled all the delivery lines. So off we went, cleared the urban sprawl and were just about to start on the twisty bits of the A621 on the way to Bakewell when - guess what?

The bloody thing seized solid halfway round a bend - that's what.

Fortunately some vestige of muscle memory had kept my left hand hovering over the clutch lever, and we managed to avoid a painful, expensive and unpleasant meeting with the tarmac (or a car coming in the opposite direction.) It's hard to put in words just how pissed off I was, after spending most of 2020 restoring and rebuilding the bike, only to have the bike's first outing of 2021 end so unceremoniously.

Today I had another look at the bike and fairly quickly spotted what had caused the seizure. Basically the LH cylinder (why is it always the LH cylinder?) was starved of oil because the oil delivery pipe for that cylinder had come into contact with the hot exhaust and had been cut in two. The photo below shows it more eloquently than I can explain.

All this was because I have always been annoyed by how little slack Yamaha provided on their delivery pipe. It only ever JUST fitted. Now I know why. By providing a lot more slack in the oil pipe I became the unwitting architect of my own downfall.

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I won't know the extent of the damage until I open the top end up, but I'm also concerned that the crank bearings on the LH side might have suffered oil starvation, or that the seizure might have caused the crank or rod to twist. But right now I really can't be arsed. It can sit in the shed for a few days...

[Supermofo]

Bugger

[Le_Fromage_Grande]

That's shit, I doubt if you've damaged the crank though, they're pretty strong, you might even get away with just a melted piston, but I think it's going to be rebore time, hopefully you've got plenty of liner left, don't go 375 big bore unless you have to, long term you'd be better off getting the cylinders relined - PJME can do this

[Skub]

Bummer is what that is.

Still,every day's a school day and I'm glad you and the missus aren't dead.

[mangocrazy]

Yeah, it was definitely an 'oh shit!' moment, especially with it being mid-corner. It felt like a highside wasn't very far away, but once the clutch was in it sorted itself out. Didn't really have time to soil me keks...

I'm resigned to a rebore and new pistons. It's +0.75mm at present so still a bit of meat left. But really annoying, especially as it was self-inflicted.

[Le_Fromage_Grande]

Yeah, it was definitely an 'oh shit!' moment, especially with it being mid-corner. It felt like a highside wasn't very far away, but once the clutch was in it sorted itself out. Didn't really have time to soil me keks...

I'm resigned to a rebore and new pistons. It's +0.75mm at present so still a bit of meat left. But really annoying, especially as it was self-inflicted.

At least with an LC you can go to 2mm over, on a YPVS 1mm is a definite maximum anymore and the piston will hit the power valve.

I'm going to get mine rebored as it shows evidence of having either seized or a ring snapped.

[mangocrazy]

Yes, small mercies. But I do feel like a cat using up my 'lives'...

[Tricky]

That's a real bummer, but as others have said, I'll be surprised if you have anything other than piston, and possibly bore damage- assuming that it will turn over now its cooled down , all being well it'll just be a piston and a light hone to remove any ally deposits, and of course a new oil pipe and you'll be away

[mangocrazy]

The pipes were moved out of their 'normal' place for the purposes of taking the photo, which has confused matters, But there was enough slack for the pipe to make contact with the hot exhaust flange. When I replace it I'll use the old OE pipe I removed as a guide to length and just add 15-20mm to aid fitting.

I was advised not to use clear plastic piping by the guy who overhauled the pump, but take your point.

And I may pluck up the courage to look inside the bore today. The motor does turn over now it's cooled down.

[Le_Fromage_Grande]

Btw if you can get the crank out yourself and send it off with the cylinders for the rebore then Grampian will measure it and let you know if it's ok.
They'll also match a new set of pistons to the rebored barrels and you can just bolt it all back together and bobs your uncle.

You probably know that already but I thought I'd mention it.

It's pretty easy to get the crank out, especially as he's owned it from new and it won't have been abused by an idiot with a hammer and chisel.

[Yorick]

Btw if you can get the crank out yourself and send it off with the cylinders for the rebore then Grampian will measure it and let you know if it's ok.
They'll also match a new set of pistons to the rebored barrels and you can just bolt it all back together and bobs your uncle.

You probably know that already but I thought I'd mention it.

It's pretty easy to get the crank out, especially as he's owned it from new and it won't have been abused by an idiot with a hammer and chisel.

*waves*

[MingtheMerciless]

That's really boring, good luck with the rebuild and hope the damage is minor.

[Le_Fromage_Grande]

Btw if you can get the crank out yourself and send it off with the cylinders for the rebore then Grampian will measure it and let you know if it's ok.
They'll also match a new set of pistons to the rebored barrels and you can just bolt it all back together and bobs your uncle.

You probably know that already but I thought I'd mention it.

It's pretty easy to get the crank out, especially as he's owned it from new and it won't have been abused by an idiot with a hammer and chisel.

*waves*

I think my YPVS is too old to have been yours

[mangocrazy]

Both barrels are off and there are some pretty nasty marks on the LH barrel. The LH piston is toast. I'm going to take it for a second and third opinion to a couple of guys I know; one has probably worked on as many LCs as I've had hot dinners, and the other one runs a bike shop not too far from me and is proper 'old skool' . He doesn't sell bikes, he just fixes them and sells spares. Here are some pictures that may make for unpleasant viewing...

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[mangocrazy]

And a couple more...

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[mangocrazy]

And finally, if you have the time and fancy a trip over then Dave (Muttsnuts) is the man for setting your bike up on his dyno so it's running better than it did when it left the factory. He's a perfectionist and my bike runs like a sewing machine after he had it for a day.

I am absolutely going to do this.

[mangocrazy]

I was advised not to use clear plastic piping by the guy who overhauled the pump, but take your point.

IIRC Gary (Arrow) told me the same thing, I can't remember why, I think he said it was the quality of the clear pipe many people use. I bought good quality proper clear stuff and it hasn't let me down in the years I've had it on. I think Norbo sells the clear oil line and loads of people use it.

It was Gary (Arrow) that told me this. I think you're exactly right as to his reasons. I've just gone with standard black rubber, as it's original.

[Le_Fromage_Grande]

I think your going to have to have a rebore, it's hard to see whether the barrel is scored or there's melted piston smeared up it

I've just discovered the frame I bought at the weekend has some damage where the bottom steering bearing goes in the frame, so that'll be a bit more money spent getting the frame repaired

[mangocrazy]

Yeah, I reckon it will need a rebore. A seizure from lack of oil has to cause a bad outcome. Looking at the state of the piston, how can that not have caused damage to the bore? It's a pisser but doing half a job would just be storing up problems for later.

Every thing you buy of that era will have history, there's just no way around it. Finding even halfway decent stuff is getting to be a real challenge.

[mangocrazy]

That looks like someone has been at it with a die grinder and carbide burr...