In a foul mood....

[Dodgyiti]

The float needle (fuel cut off) was 'scuffed' on the rubber tip so i replaced it with a used spare in better condition (old coots never throw anything out)

tight b'stard

Next I will order a new needle and needle valve (prob $30 or so) and continue to tinker...

STEADY ON!

[Paul in NZ]

So how come the pre ignition with unleaded? You'd think running cooler there would be no problems.None of my old cars (Falcons,Escorts,BMC's etc) would run on unleaded without octane boosters....or retarded timing.

I think the lower octane is the answer and yes - I will knock the ignition back a couple of degrees as well ;-) I'm only going 1 grade hotter...

[Paul in NZ]

tight b'stard

Hey - enough of the 'tight' business - I'm very loose...

[Paul in NZ]

Well - I've been mucking about with old gas tanks rather than attending to the rich low speed running like I should.. But I have been thinking and asking questions and developed a cunning plan..

Carb - I will strip it again and fit a new air filter, float needle jet and a No4 slide as I believe the main issue (engine dies when coming to a stop) is richness when riding at 30mph in 4th - this is just where the slide is coming into play so it's worth a crack.

Plugs - I have gone 1 grade hotter with a little improvement so the next step is to go to an extended tip plug. There is enough clearance and local 'experts' assure me they stay cleaner and run slightly hotter.

Observation - I need to verify this as it's just something I was told thus far but I believe Triumph themselves went 2 grades hotter in plugs when electronic ignition was fitted? If so - thats quite interesting.

QUESTION - Did Triumph ever specify an idle speed? I can't find one so I suspect not. What do others use as a rough guide? 1,200 rpm?? stuffed if I know

So today - test ride to Otaki for a bike thing...

Bike runs well at first at town speeds, but 1/2 way to Otaki the throttle jams and its pinking like a bastard... argh! NO - before you ask I have NOT overtightened it and warped it OK - when the engine cools down it is just rideable so we limp home with my tail between my legs in a foul mood...

The extended tip plugs came out dangerously white (gulp) which indicated that the No 4 slide and the extended tip plugs was a probably a bad combination.

The NEW slide stuck because it was such a crappy fit (I possibly could have hammered it in to start with) and I didn't relieve it enough last night. It got hot (its a stinker here today) and gauled the alloy sticking in the bore so I've relieved it more and now it falls out when inverted.

So - while the tools were out I rebuilt the original slogged out carb (its a left handed one of some old bonnie) with new gaskets and a reasonable No 3 slide from the pile of half worn junk. This carb was old when I got it and I've done 50,000 miles on it. Re fitted the B7ES's and guess what - bike idles 100% better. Even, crisp and reliable...... GAH.....

My guess is the new carbs pilot jet is miles too big. Sweet - hours and $$ wasted.... I think I'll have a beer now... and another cold beer and cooled down.... (its darn muggy here today) and twiddled a few bits and set the idle
again.

I picked some of the red doris plums which are just coming on and the child bride whipped up a rhubarb and red plum crumble which put me in a very fine state of mind and filled my belly so we thought we would pootle up the coast on a test run and maybe a fancy coffee... so.... off we go...

Feck - it's running like a sweetheart.... Hot damn...

Out to Raumati beach and up to Paraparaumu and through Otiahanga, on to Waikanae and out to the beach there where I nearly die with shock and fall off - the engine keeps running at the roundabout... Good grief - is it possible???

Delirious with joy we head for Peka Peka along the coast road where all the noice people are building beach houses through the twisty bids - beautiful...

Get to the open road and open the tap and........ eh?? Wheres the power gorn and why is it banging on the over run?? Fine up to 60mph in the old money but sluggish and then the door slams shut, gurgle splutter cough wheeze - roll the throttle closed and she picks up again... hmm - this sounds awfully familiar (text book lean main jet) but awfully dramatic and waaaay to low in the rev range..... but awfully familiar...

So we cruise home on a whiff of gas at 60mph, roll into the shed - idling like a trooper (at least THATS fixed)

Pull the bung from the float bowl and the main jet falls out... gah.... I guess I didn't tighten it enough when I was cleaning the old carb up...

So - refit the jet - restart and off for a raaack to McKays Crossing and back - faaark - shes flying again, and idling... So - I've ditched the expensive new carb - how long before the electronic ignition and oil filter follow? Blasted modern rubbish

[Sensei]

Mate has to run 2 hotter plugs in his T150 from standard , it has neally sorted out the same trouble you are having . Avgas just hides the problem .

[James Deuce]

Blasted modern rubbish

That'll learn ya

[Paul in NZ]

That'll learn ya

According to Vicki I don't....

Thanks Sesei - I'm running 1 grade hotter now - std tips and I'll see how it goes. I think those new amals have some 'issues'...

[Ixion]

Was the new carb one of them Concentric things with the fixed pilot jet?

They don't work they don't , stick with good old Monoblocs. Or the type 5 or 6. They work

Settle an argument, that'll put you in a good mood.

Did the pre unit Tbird , alternator version come ex factory ever with magneto ignition. An old geezer at the Classic races today says no (there was a 1960 6T there with a Lucas Mag). I say yes, cos I had a 62 with a mag. Motu agrees with the geezer, but then mumbles and equivicates and tries to change the subject to SU carbs - HEY -- THERE'S YOUR ANSWER ! (we all agree that the dyno model came with mag)

[Motu]

I did have a concentric that ran rich at idle - strange,it was good as a single carb,but was way off when run as one of twin carbs.If it was a Mikuni you could change the primary jet......so how can you do that on an Amal...?...?

Told ya so!

I set the points and timing on the TL125,set the tappets and lowered the float level waaaay down on the spec level....did my turn off the fuel trick until it was right.Now I have a good idle and throttle response....but is still rich just off idle.Now,if I had an Amal I could fit a leaner slide.Oh,it's a cruel world int it?

[Paul in NZ]

Was the new carb one of them Concentric things with the fixed pilot jet?

They don't work they don't , stick with good old Monoblocs. Or the type 5 or 6. They work

Settle an argument, that'll put you in a good mood.

Did the pre unit Tbird , alternator version come ex factory ever with magneto ignition. An old geezer at the Classic races today says no (there was a 1960 6T there with a Lucas Mag). I say yes, cos I had a 62 with a mag. Motu agrees with the geezer, but then mumbles and equivicates and tries to change the subject to SU carbs - HEY -- THERE'S YOUR ANSWER ! (we all agree that the dyno model came with mag)

Meh - concentric of course but theyre not so bad really.

Re the T'bird... Oh gawd - can of worms time. According to the 'book' no. In real life - yes. Prior to the TR6P many police depts used 6T's and 5t's and I think that the mag could be specified so the alternator could be used for the radio etc and frankly lots of people didn't like the whole distributor thing on them (me included)... I had a 57 Speed Twin with alternator (6V) and a magneto so.... (mind you it was a real pile of poo by the time I purchased it for $190)

Then there is the kiwi I can do it attitude.. Change everything etc. Originality is a wierd thing. I have people telling me 'that aint right for that year' all the time with mine. The usually spot about half the things and are wrong half the time....

[Motu]

As far as mags went I preferred the BTH,they were a bit more quality than a Lucas,apart from the competition model with the red screw in pickups.But did any twins of any make come with a BTH? Some mags were specific to makes - the AMC twins all had a kill button on the end cap,Norton twin mags were slotted for chain adjustment....but I've seen both types on Triumphs,obvious retro from people who didn't know.

But I prefered a dizzy,because mags had terrible discrepancies in timing between cyls,the distributors were more accurate in that regard.I fitted a Morris 8 distributor to my alternator T110 powered Triton.Don't you hate bastards who bastardies bikes?

Long live twin points.

[Paul in NZ]

This from the archives

It is surprising just how far into throttle ranges some things have an influence. For example, I would not have suspected that the pilot jet would have an influence up to 7/16 throttle, or the main jet as low as 1/4 throttle.

Idle - 100% pilot jet
1/16 throttle - 60% pilot, 40% cutaway
1/8 throttle - 46% pilot, 46% cutaway, 8% needle/needle jet
3/16 throttle - 49% cutaway, 37% pilot, 14% needle/needle jet
1/4 throttle - 45% cutaway, 27% pilot, 24% needle/needle jet, 4% main jet
5/16 throttle - 37% cutaway, 33% needle/needle jet, 21%
pilot, 9% main jet
3/8 throttle - 44% needle/needle jet, 25% cutaway, 16% pilot 15% main jet
7/16 throttle - 55% needle/needle jet, 23% main jet, 13% cutaway, 8% pilot
1/2 throttle - 63% needle/needle jet, 31% main jet, 6% cutaway
5/8 throttle - 57% needle/needle jet, 43% main jet
3/4 throttle - 55% main jet, 45% needle/needle jet
7/8 throttle - 92% main jet, 8% needle/ needle jet
Full throttle - 100% main jet

Here is some other perhaps useful information from graphs in the Haynes Carburettor manual.

- a .5 cutaway change (e.g. from a 3 slide to 3.5) changes the mixture ratio by about 9% at 1/4 throttle, and about 4.5% at 1/2 throttle
- a change of 1 needle position changes the mixture ratio by about 6.5% at 1/2 throttle, and about 3% at 3/4 throttle
- a change in needle jet by one size (e.g. 106 to 105) changes the mixture ratio by about 3.5% at 15% throttle, 6.5% at 1/4 throttle, and 1.5% at 1/2 throttle.

The latter two points suggest that the needle affects mixture for higher throttle openings than does the needle jet. This would suggest that the needle/needle jet stage mentioned by Schultz is really two stages: needle jet, and then at a higher throttle opening, needle. In other words, if your mixture problems seem to occur at throttle openings in that transition area between cutaway and needle/needle jet (3/16 to 1/2 throttle), then playing around with changes to the cutaway or needle jet may be most effective.

However, if the problem occurs in the transition area between needle/needle jet and main jet (7/16 to 3/4 throttle), then playing around with needle position may be most effective.

If you examine the two sources of information carefully, you will see that they do not entirely agree. For example, Haynes suggests that at 1/2 throttle, a cutaway change of .5 can affect mixture by 4.5%, but Schultz suggests that the cutaway only controls about 6% of the mixture at 1/2
throttle, which would mean that any change in cutaway would have minimal influence at 1/2 throttle. I am also somewhat suspicious of the Haynes claim that a change in cutaway has more effect on mixture at 1/2 throttle than a change in needle jet.

What is really quite striking though is how the different components overlap. Most other information on the components' effect on mixture tends to say something like cutaway governs mixture between 1/8 and 3/8, needle/needle
jet between 3/8 and 3/4, etc. They sometimes mention there is some overlap, but it seems to me that the degree of overlap is at least as important as the information on when a specific component has the greatest effect.

[Motu]

Thanks Paul,that's very interesting - I'll have to print that out and put it between the pages of a manual and lose it forever.....but remember that I have it all written down somewhere.....I hope the internet stays around for a few more years so I can do a search.

All the steps overlap each other much more than I thought,and the cutaway plays an important part.I always used to fiddle around with cutaways,but modern carbs don't have a selection,and tuners don't seem to change cutaways.
SU (sorry Ixion) needles are graduated every 1/8in,so you can tune them every step of the way.I always seem to have tuning problems going from idle circuit to needle....cutaway is involved here,but everything interacts.....and this is also the point where the ign starts to advance.You need to check your timing at this critical point before making mixture adjustments.

[Paul in NZ]

Settle an argument, that'll put you in a good mood.

Did the pre unit Tbird , alternator version come ex factory ever with magneto ignition. An old geezer at the Classic races today says no (there was a 1960 6T there with a Lucas Mag). I say yes, cos I had a 62 with a mag. Motu agrees with the geezer, but then mumbles and equivicates and tries to change the subject to SU carbs - HEY -- THERE'S YOUR ANSWER ! (we all agree that the dyno model came with mag)

Theres an odd thing... I was reading Classic Bike Guide and there was a picture of two duplex framed pre unit T/Birds, nicely restored and I could clearly see one of them was fitted with a magneto...

[Ixion]

I think all ther ones I've seen with mags have been duplex. You'd have to be fairly keen on a mag to retrofit one, given that they ain't cheap. I've heard of more people retrofitting dizzys in place of mags.

I wonder if Triumph, knowing that the unit 650 was coming down the pike, started fitting whatever they had excess of in the parts bins - or, more likely, whatever they had unduely large supply contracts for. The twin cylinder dizzy would have been specific to them by then, maybe didn't want to sign another contract.