revtothelimit - motorbike forum

Whats wrong with using a flow meter or even a length of tube?

David wrote: Sun Jul 25, 2021 9:55 pm Whats wrong with using a flow meter or even a length of tube?

I didn't have either of those in my kitchen drawer

I wasn't kidding when I said it's the official Triumph method either.

I understand the synchronous lift thing...the flow meter or a tube( stick one end in each carb to a predetermined depth {keep your fingers in the same place} and shove the other end in your ear..it should sound exactly the same in each carb) is the way to assess what is going into each carb....assuming you have checked float level and jet sizes etc...yes , they need to lift the same, but there are other things that will destroy synchronicity.

It doesn't run yet, so I can't check flow.

The floats are set using the "feeler gauges and bend the tab" method. It's got the newer ethanol resistant floats with metal tabs you can bend.

Jets are a funny one. Its had what appears to be standard jetting for a 69 (220 and 106) but rich for a 70. Shes a 1970 model year built in 69 so feck knows what it's supposed to be. It's also got different cams, straight through inlet and exhaust and high comp pistons. It also has 2.5 slides which are richer than standard I believe.

Its seemed OK before but I was still getting to grips with the jetting when the valve dropped last time. I've gone a size richer on both the main and the needle for now (230 and 107) cause.of the new high comp pistons. They may well be far too rich but that's better than the opposite! Apparently it'll hole a high comp piston in 2s if its too lean.

Mr. Dazzle wrote: Sun Jul 25, 2021 10:02 pm

David wrote: Sun Jul 25, 2021 9:55 pm Whats wrong with using a flow meter or even a length of tube?

I didn't have either of those in my kitchen drawer

I wasn't kidding when I said it's the official Triumph method either.

It was Nortons’ method as well.

If you end up putting air filters on, sticking straws in it will be less convenient. You can check and adjust the synchronisation by listening to the slides hit the stops when you shut the throttle.

Most accurate way, which I think David is getting at, is a manometer attached to the balance tube stubs. It makes a good job of equalising the idle and the pull of the cables.

The original carb jets and settings can only be treated as a rough guide.

It’s unusual not to use a 106 needle jet and middle needle notch.

Last time I rode it it wasn't great. It was better than it was when I first got it, but not great. I'd fixed the ignition problems and it was revving out, but stumbling a bit and not idling.

At the time I wasn't aware that I only had about 80psi of compression and 3.5 valves. I was gonna start looking at the jets when the exhaust valve dropped.

So I fully expect the jets will need work.

If you don't want to make your own manometer you can borrow mine for a bit. Let me know if you want it and I'll get it up to Aylesbury soon.

I did the valve clearances tonight....now there's a job which is a bit fiddly if you've never done it before! Also gapped the plugs and then tightened everything up.

It's together enough now that I can plonk the tank bank on, I'll bolt it (and the fairing) on properly tomorrow and reconnect the fuel lines. Then all I need is some fresh petrol I think.

Oh and I need to put the toolbox back on, but that's 30s. It doubles as a side panel and hides the battery.

If it goes as well as it looks.......

Yeah I'm looking forward to seeing it run too

It looks better from the other side cause it doesn't have a big hole Look at the fucking state of my garage though.

When you do get it fired it, it sure ain't going to be the quietest bike on the planet.

I had it running last year, I even rode it a bit.

The noise is probably the best thing about it It sets off my neighbours car alarm when I start it and it sounds like the soundtrack to a 60's film about racing. And it's totally legal! That was before it had full compression and high comp pistons too.

Fully back together now...



I tried starting it today with fresh petrol in (£1.55/litre!) but didn't manage it. I got a few half convincing coughs, one almighty bang and a few duffs but no catch.

However while investigating to see if I still had sparks I found it only sparked very occasionally. I also realised the pistons aren't going up and down with the kicker very much. If I knew this bike better I'd have felt that on the kicker, but anyway.

It's not sparking much cause the electronic ignition only fires them above a certain minimum rpm (200 iirc) thus if the kicker isn't turning the engine over properly it won't fire the plugs.

So why is it not turning over? Gotta be clutch slip....the kicker drives "backwards" through the clutch to turn the engine over, so some adjustment is needed I think. Wished I'd figured that out before all that kicking....

I doubt if the clutch plates are involved in starting, more likely to be a primary drive issue.

Jetting - very rough guide, up two sizes for no air filter, open exhaust up another two sizes, high comp doesn't have a massive effect on mixture.

The clutch is definitely involved in starting on these bikes. The classic thing to do when starting is pull the lever and give it a couple of kicks, the second one is dead easy as the clutch comes unstuck and hence frees the kicker from the engine.

More importantly, my googling reveals that slipping clutches on start is a common problem

ANOTHER DELAY!!!!!

Are you trying to upset me?

You just wait.

If the simple clutch adjustment doesn't work I'm gonna have to break into the primary casing! Fortunately there's a little spy hole (that one in front of the rear brake pedal) to allow clutch adjustment.

I’m sure you were going to do it properly but anyway...

JackyJoll wrote: Fri Jul 30, 2021 7:49 pm I’m sure you were going to do it properly but anyway...

Just tried that. Sorta helped, but not fixed it. I'm not sure if I'm actually screwing it all the way in though, I've loosened the nut as far as I dare (don't wont to lose it in the case!) but even then I'm not sure if the screw is contacting or I'm just picking up the lock nut again.

Also had some fuel vapour go bang in the exhaust. That was a) bloody loud and b) proof that it has fuel and sparks at least some of the time.

If you put it in 4th gear you can push it along the road (with difficulty) and the engine doesn't turn over. So the clutch is not gripping really. Further proof is that it is much more "positive" on the kicker with the plugs out and hence when it's easier to turn over. But even then its not perfect.