Triumphrat

jpkuhns · 01-08-2008

I just posted last night to a plethora of awesome responses about pipes but I now have another problem. I'm running a 1970 650cc T120TT that the previous owner had built for him with dual mikuni carbs. It ran fine yesterday with no problem but I tried starting it tonight to no avail. As I'm new to vintage bikes I was wondering the best way to get this bike primed and ready for riding. I had both fuel petcocks (?) down and was wondering what I should do with the chokes on the carbs and if I'm flooding the carbs by turning the throttle while i kick.

I am a noob and thanks a lot for anything you could recommend.

McQueen · 01-08-2008

Hmmm...

I'm not familiar with the Miks. Amal guy here. So hopefully others will correct any of my comments.

You won't flood by opening the throttle as the carbs don't have accelerator pumps.

Not knowing much about the condition of the bike, it could be many things:

- discharged (bad) battery (If you have electronic ignition, you need a good charge on the battery; if you have points, check the gap and inspect for corrosion)

- Check for spark (take out the spark plugs, lay them on the head so they have a good ground, turn on the ignition, and give it a few kicks to check that both plugs are sparking)

- bad/old gas

- vapor lock (go through your normal start procedure but take off the gas cap when you start it. If it fires up, get a new cork gas cap gasket)

- float adjustment

EDITED because Mecc knows a cr@pload more than I do.

Mecchanica · 01-08-2008

The factory didn't make any TTs in 1970, so it's probably just TT styled. Photos would help with identifying it.
How big are the Mikunis and are you running as a 650 or 750?
Usual is VM series 32mm miks, they don't have ticklers, do have "enricheners"....small valves that open and add fuel to the main air choke.
Lift one or both of the levers and kick being careful to not whack open the throttle. Usually, just a LITTLE throttle is enough to fire this up. Once it starts, drop the levers.

jpkuhns · 01-08-2008

I just ran the numbers for the engine online and it comes up a 1966 T120TT. It's serial is DU39XXX. And the frame is registered as a 1970 trophy. So it's a mix and match but it's my first vintage bike and I got a good deal on it. What's the best angle for pictures of the carbs?

Mecchanica · 01-08-2008

One from the left and one from the right....side on. One from each side, as if you were sitting on the rear of the seat, looking down and leaning out a little.

Good frame, decent engine. Would be good to know what is in the engine as the original TTs ran eleven to one compression and were designed to run on alcohol. Kinda like me.

Frame parts will have SAE threads and the engine will have BSF and CEI. Two sets of tools.

GrandPaulZ · 01-09-2008

I'm going to stick my skinny neck out and take a wild-haired guess.

Pull your spark plugs out. They are most likely sooty Black.

Install new plugs, the bike will start instantly.

The conglomeration bike you got a good deal on may not need much more than proper re-jetting of the Mikuni carbs, unless a set of 2-stroke carbs were installed (happened all the time in the 70s, when this one was probably built).

Personally, I recommend going back to the original, but rebuilt & sleeved Amal Monobloc carbs with modern material slides. Or maybe new Amal Concentric carbs.

If the fresh plugs don't fire you up, it's time to carefully tune it up with a timing check and proper valve adjustment. All the other suggestions, including low battery, are good ones to check.

I'm still sticking with my gut reaction. Fresh plugs, carb jetting. It happens too often for the liklihood to be any greater with any other line item.

jpkuhns · 01-09-2008

Well, I just found out that the guy that built the bike said the former owner didn't ride it that much after the carbs had been rejetted and had everything checked out. I also found out that the engine is probably a faked TT but then again I want to ride it not win trophies or put it in a glass case. I went out and bought a battery tender and got overly anxious after about an hour of slow charge and tried to start it. I cranked on the second kick and I let it idle but it fizzled out then I kicked again and it started up. But as i was riding it around it seemed like it was missing and then it stalled out at a stop sign luckily close to my house. After walking it back home I put it back on the trickle and we'll see how it goes tomorrow afternoon. The only other thing I think it could be is a bad plug. And yes it does have electronic ignition.

Emanthehorse · 01-10-2008

Could well be a bad battery/malfunctioning charging system.

Those *&$%@(*&$ Boyer ignitions will fail as soon as the voltage drops below a certain level. One of the big reasons I hate them.

If you get it going again, grab a voltmeter and check the voltage across the battery terminals at idle and at higher RPM. If you don't get at least 13.5V, you'll have to look into the charging system.

Back in the 'day' when the battery died, I used to just pull out the main fuse and go. BSA's used to have an "Emergency start" position on the keyswitch that just took the battery out of the circuit. Ahh, the good old days of points.

This is also why I love magnetos.

Mecchanica · 01-10-2008

Yep, a dead battery is a liability, not an asset. Most points equipped bikes with permanent magnet alternators will run sans battery, except for any electric starter which may have found it's way onto said bike. Fit a capacitor and go. If you have upgraded to a three phase alternator, so much the better. Even some EI systems will run sans battery with a sufficient alternator source and a good healthy filter cap. I have run all of my bikes, Nortons and Triumphs, sans battery for more than a decade now. Never spent a dollar for a battery until I picked up a Tri. 500 with EI a year ago. That will change soon.
The alternator, cap, coils and points are essentially a magneto system distributed, actually TWO magnetos, in the case of twins. Hunt and ARD mags, based on the Fairbanks-Morse mags, spin a permanent magnetic rotor and induce current into a coil directly, doing away with most of the wiring. Lucas, of course, does it backwards and spins the coil inside of the stationary magnets. FM spins a breaker cam and has stationary points, Lucas spins the points and has a stationary (more or less) breaker cam ring.
Magnetos are clunky, heavy, and have little advantage over the modern permanent magnet alternator and coil system which has few parts which need maintenance or adjustment. The alternator has no serviceable parts, the rectifier and regulator are solid state, the filter cap is kind of solid state, at least it doesn't need maintenance, other than to keep it clean. The points rarely need attention IF you start with good components and do an occasional check and lube on the moving parts of the AA unit and points. My bike put on over 90K without NEEDING points replacement. I did replace them on two occasions just to be certain....one new set of condensers. Also, I never needed to adjust the points, although there were several occasions when I did that, again, just to be sure. I did need to adjust them about a thousand miles or so after installing them, as they kind of bed in, it seems. After that, just clean and lube every couple of years. Gotta use synthetic oils and grease, though.