Triumphrat

Sykotik · 10-25-2008, 11:40 AM

Hi Guys, great site with heaps of useful info, especially from OzBloke and GrandPaulZ whose advice was very helpful in my first post here...

I'm hoping someone could help me diagnose my new issue.

I've recently been eliminating gremlins from my Dad's 750cc Morgo kitted '64 6T Thunderbird. Ive been entrusted with the old girl as he recently came off his '02 Legend and has lost his confidence on bikes, which is a bit sad. I'm 36, hes 68 yrs old.

Anyhoo... The Boyer stator wires were reversed, timing was thus impossible to set by the book. After adjusting the magnet rotor I made up a timing wheel and set it with a light to 19deg BTDC (on the cam) @5000rpm. I only had the TDC mark on the crank to go by, what a mission. The inlet valve timing was also set to the wrong mark, which I put back to the 6T setting.

This bike flies! Runs really well but it now flat spots when cruising between 90-100km/hr in top (4th) gear after about 10 minutes riding. With slow throttle applied it will power through it, otherwise just coughs and splutters. Power up through the gears and theres no flat spot. I did try a 200 main jet and same thing happens.

Velocity stacks, unbaffled exhausts, Champion N4C's, twin Amal mk1's with 220 mains, 106 needles on middle groove, 3 slides, and Ive set the floats to 2mm below top edge. I've synced the carbs the best I can.

My thought is either the needle is to rich or a coil issue. Im not sure if they're 6v or 12v (should be 6v with Boyer, I know) How do I find out? I'm learning as I go...

The bike is running rich, but Im scared of leaning it out as warned by "dear ole Dad".

Thanks for reading all that, Any ideas what would cause these symptoms? Am I on the right track?

Ride safe.

Beezer · 10-25-2008, 12:27 PM

Sounds rich to me. I would drop the needle a notch.

Sykotik · 10-25-2008, 12:41 PM

Thanks Beezer, thats +1 for the needle change.

I'll try and post a pic of her tomorrow...

edit: Dropped the needle, no more flat spot.

eagle · 10-28-2008, 04:00 PM

a blocked tank breather. Try lossening the petrol tank cap (safely on an uncongested straight road!) and see if it makes a difference. I think your bike breathes through a small hole in the cap.

Or maybe not. Might be worth checking the float levels in the carbs in case they are too low (starving fuel) or too high which might make them go overrich, esp on small throttle openings held stready.

Also pretty sure the coil is 6V - but it should be marked. Is it a single coil with two HT leads?

Sykotik · 10-29-2008, 01:29 AM

Thanks eagle, I'll try that tank cap thing next time I'm out on it. Should be this weekend if the weather holds...

I've set the floats to 2mm below the lip of the bowl, so that should be OK.

The bike has 2 seperate coils under the seat, I can't see the sides to see if theyre marked in any way, may investigate later.

Cheers.

Sykotik · 10-29-2008, 09:49 AM

Ive been staring for hours at the pic in this thread (I have it as my desktop) trying to come up with a solution to this flat spot problem I have.

Should those Amal's be on an upward angle like that?

Or has someone put the angled intakes on upside down?

Would an angle like that not play havoc with fuel levels, etc etc...

htown16 · 10-30-2008, 04:04 PM

Recommended plug for that model is N3C.