revtothelimit - motorbike forum

Mr. Dazzle wrote: Sun Jul 16, 2023 10:51 am

I’d guess head not sufficiently retorqued.

Possibly aggravated by a skimmed head putting too much crush on the pushrod tube.

Burning oil, because the rings have not bedded in to the bore.

Kinda feels like there should be two bolts between the cylinders rather than one. I think Triumph agreed with me and went to a 10 bolt head on 750s?

Don't ask me to remember the details but I did go through quite a lot of stuff to check the pushrod crush and ISTR it's got smaller seals as a result. It's probably written down up there somewhere.

Deffo burns oil when cold though, big cloud of the stuff when first starting. Always assumed it was the stuff that had seeped down past the valve guides when sat for a while.

Can you see oil on the valve stems, back of the valve heads, or on the valve guides, if you look into the ports?

No not really, although there is a certain element of "peering down a hole" here. Inlets are sparkling clean but they get essentially vapour degreased in service anyway!

Exhausts look maybe a bit dirty but not dropping wet or anything.

You could look on this episode as another opportunity to put roadgoing pistons in it.

JackyJoll wrote: Sun Jul 16, 2023 4:02 pm You could look on this episode as another opportunity to put roadgoing pistons in it.

[/Pedant_mode_on] As the bike has travelled quite a few road miles on those pistons, they are by definition 'roadgoing pistons'. [/Pedant_mode_off]

Haha thought did occur. It would mean finding my B&Q ring compressors again though.

mangocrazy wrote: Sun Jul 16, 2023 4:34 pm [/Pedant_mode_on] As the bike has travelled quite a few road miles on those pistons, they are by definition 'roadgoing pistons'. [/Pedant_mode_off]

Except they’ve stopped.

Roadgone pistons!

JackyJoll wrote: Sun Jul 16, 2023 4:41 pm

mangocrazy wrote: Sun Jul 16, 2023 4:34 pm [/Pedant_mode_on] As the bike has travelled quite a few road miles on those pistons, they are by definition 'roadgoing pistons'. [/Pedant_mode_off]

Except they’ve stopped.

Roadgone pistons!

Schrodinger's pistons...

Maybe I should leave it parked on the street to reclaim the title.

Mr. Dazzle wrote: Mon Jul 10, 2023 9:59 pm Spoke to Boyer.

Not a huge amount of success, they suggested I test all things I've already tested (based on their website!).

Only other thing they offer is a £25 "send us the box and we'll stick it on our 'dyno'" service. Which is cheaper than £110 for a new box TBF!

After 60+ pages of you spending on the old bus, £25 isn't much more

Been pondering what to do for the last week or so.

I've apparently got an oil control problem. It appears to effect both cylinders but as JJ said it also appears to be leaking "across" the cylinders, probably due to loose bolts. I obviously need to retorque it even more than I have been!

I'll go back to the 9:1 pistons I already have and fit new rings. I've only got one of the old gudgeon pins (other one was scored/scratched) but the 11:1s came with new high strength 'superfinished' ones anyway (smaller ID) so I'll use those.

The spark plug holes kinda overlap the valves anyway cause the latter have been recut. Therefore I don't think I've for space for the full new steel insert thing, thus I'll have to try a helicoil.

All four guides and both exhaust valves are new IIRC but I'll try and see if I can see any evidence of an oil leak around there anyway.

Wiring wise...gonna have to do it from scratch I think. I'll probably do that with the head off to begin with just cause it provides more space.

I don’t think you should be sentimental about selling it, if you’re not getting much out of owning it. It hasn’t got the old guy’s soul residing in it.

Trouble is, it’ll sell best when it’s running well and that’s when you want to keep it.

Are there no places that would make you a new loom,or is that something you want to do yourself anyway?

I'm sure there are, but it's gonna be a semi custom job in any case. Loom is almost overstating it, the entirity of the wiring diagram looks like this (in fact I don't even have all of those wires, 'cause I've no horn and only a single 12v battery - I do have a few extra for the black boxes I suppose):



I wouldn't be too hard to just redo the ignition aspects of it, but it's largely a case of "well....while I'm in there...." and the wiring behind the instruments is a bloody rat's nest. Besides, if the problems are down to a dodgy earth generating spurious signals you kinda need to redo everything.

I kinda like working on it when the fancy takes me

Selling it is largely pointless, the money isn't going to make a massive difference to my life in either direction. I'm sure we'd regret it sooner or later!

Besides, I'm selling the other crap old Triumph to my uncle in law as soon as his house sale is completed

Just checked my receipts, it was actually just the exhaust valves and guides. The original problems started when the exhaust guides collapsed.

The new ones are oversized and involved machining the head.

I would say just replacing the inlets isn't that hard...which it isn't, if you have the tools...but I don't have the tools! I can probably blag a generic valve spring compressor but not the guide removal/insertion tool. And that's before you consider the inlet might need new oversized guides too.

Or they might be fine anyway!

Something else to ponder.

Valve guide extractor/fitting tools aren’t really any better than a stepped drift and a hammer, if you have hammering capability.

Either method can score the holes in the head (and let oil through) if the head is cold or the guide is dirty. It’s fairly common practice to drill or mill the top of the guide flush with the cylinder head and drive it out downwards.

If oil is leaking down between the guide and the head, but the guide is not loose, sealant under the valve spring seat stops the leak.

I think I might attempt to blag a spring compressor as above and have a look.

I suppose if the valve is snug/tight in the guide (I.e. its the guide/head interface which is leaking) then sealy goop might do the trick.

Worn valve guides are a bit of a Triumph syndrome, especially phosphor bronze guides.