[Paul W]

Allowing too much water into the intake wouldn’t vapour lock the engine (I don’t understand what that means with regard to anything other than plumbing) but it might hydraulic lock it, resulting in permanent mechanical damage.

[ace.cafe]

I have used water or ATF squirted into the running engine with a misting sprayer.

[Bilgemaster]

Allowing too much water into the intake wouldn’t vapour lock the engine (I don’t understand what that means with regard to anything other than plumbing) but it might hydraulic lock it, resulting in permanent mechanical damage.

You're quite correct. I misspoke. I meant to write "hydro-lock".

"Vapor lock" (or "vapour lock", if you prefer) is something else entirely, which occurs when a fuel line, typically a metal one, gets too hot such that bubbles form in the fuel causing stalling or other power loss. It's a common enough gremlin in old British engines on really warm days, and can sometimes be cured, picturesquely enough, by the old folk remedy of attaching a bunch of wooden clothespins to the fuel line. My Amphicar's Triumph 4-banger is festooned with them--absolutely bristling like a tenement's fire escape.

Don't miss next week's Granddad's Bodges seminar, "How to cure misfires with an old sock full of mothballs" followed by Whitby Snodgrass' special presentation, "Pine tar: Not just for dressing horse's hooves--It's  a fine hair care product!"

[Paul W]

Bilgemaster, yes I’m aware of what vapour lock is, but as I wrote, only in context of plumbing/pipe work. 

I prevented it on my off road trials car (which I think you saw and commented on on my YouTube page) when it had a British engine and twin SU carbs, by replacing the potentially troublesome camshaft driven fuel pump with an electric, SU type pusher pump fitted adjacent to the fuel tank.

These days that car has a supercharged three cylinder Japanese engine and fuel injection with a fuel system running at 45 psi so it would never get fuel vapour lock. 😎

[AzCal Retred]

@ #16: My dear old Dad used ATF or water to decarbonize just like Ace says. He used to get a glass of water or ATF and get with it on the old V-8's. Don't get crazy & hydraulic it like Paul W cautions against. A spray bottle should be idiot proof.

[tooseevee]

@ #16: My dear old Dad used ATF or water to decarbonize just like Ace says. He used to get a glass of water or ATF and get with it on the old V-8's. Don't get crazy & hydraulic it like Paul W cautions against. A spray bottle should be idiot proof.

          migod you bring back good memories of me doing exactly that in the early '50s on my mom's Blue Flame 6 '47 Chevy Fleetline. Always wanted to put a '49 Olds grille in it, but the bodywork was still beyond my skills in high school. I did do a pretty good job of bullnosing the hood however. I installed a water injector also. Of course, it had twin spots, too, installed by a family friend who rode a '47 knuckle.

[ddavidv]

Yep, water or ATF gets it done. Funny how this just got posted a week ago.
https://youtu.be/JpBnLtvmO9c

[Willbrunei]

I seem to have solved the hanging idle

I stripped out the auto advance. Fitted new springs and applied grease

I then retapped  the stripped cb plate  mounting holes and put everything back together

Reset intake valve so just off slack

Started 2nd kick and idled nicely

Went for a ride around the block and it pulled nice and felt crisper and a bit more powerful. Could that just be the springs?

Got home and it did the same spit and die

Could the inlet valve be tightening up when it gets hot?

[Paul W]

The valve clearances on these engines usually open up as the engine gets hot.

Even so, it might be worth loosening the clearances very slightly, just to see if things improve.

[AzCal Retred]

Loosen them up to prove the point. You aren't going to frag it on a short mild toot around the block with sloppy valves. The whole idea here is to give them plenty of slack to make sure they aren't being held open by a high spot on the tappets. If it's clattery but idles well, and an intermittent staller when "correct",  they there likely is a low spot on the tappet.

BW trickily "resurfaced" some of his in place with a Dremel, but if that doesn't work for you there are always new extraction/install tools, tappets & guides available from H's. Mine are a bit funky but the cams are worn also, so the whole shebang needs to be fed new bits really. Anyhow - loosen them up and see if it makes a real difference, just to definitely eliminate that particular possibility.

The De-Carbon Dance is another good idea - if it's really crudded up, chunks could be flying off and holding open the exhaust for a stroke or two until the valve chews them up. Try the spritzer bottle Steam Clean routine. Peep into the plug hole before & after to see if anything changes.

Do one, then check thoroughly. You really need to know which "fix" worked. Keep after it! 

.

[Willbrunei]

Thanks all

Today I got up early and got the fantastic timing tool out and bunged it in and static timed to something like 0.8mm btdc

It turns out I was quite a bit retarded ( wife agrees) on the timing.

Buttoned it up. Started first kick and ticked over nicely.

Took it out and filled the tank with shell vpower- there highest octane at 98 plus it has cleaning agents 🤷

Did some high speed runs on the quiet dual carriageways around the edge of town to get it good and hot. It ran and pulled great - I swear I can feel the auto advance kick in now when I accelerate. I listened for pinking but am never sure what I’m hearing with primary noise air filter roar and general tappet clattering- any way seems ok with a tiny bit of popping in the silencer when I shut the throttle from high revs.

Got it home and with fingers crossed let it idle.....

Bingo! It ticked over fine.

So it seems that new auto advance springs and a proper shot at timing plus easing off the inlet valve within the clearances did the trick.

Thanks for input from everyone. I have learned so much about engines from this bike and your advice!

Hopefully some riding now.

Until the next problem...🤣