Bonneville America Forums Forums General Motorcycle Forums Other Bikes T120 from He!! update

So I finally found a crankshaft for my 1972 Triumph T120, after going through a couple. Could'nt get sludge plug out. Took to Vintage Brit Bike shop, he could'nt get it out either (first one in his career). The guy I bought the crank from called last night, said he would find another crank, take to Atlanta (about 65 miles) and take care of it for me. These people are the kindest, most considerate people I've had the opportunity to meet...they are bending over backwards for me in an effort to get this bike ready for the Rally in June...

Sounds like you are in luck. Keep us updated

Acquired serviceable crankshaft, had to be turned down .020, but that's okay...I already have the big end shells for that...Purchased "Pazon" electronic ignition also, slowly going back together with her...

Rods torqued, crank installed, case halves bolted together..Pazon arrived...

Cylinder on and torqued, new primary chain and hardware installed (NICE), engine installed into frame, cylinder head installed and torqued, PAZON installed....Ordering Tympanium regulator tomorrow...rocker arms and boxxes next, then exhaust and drive chain...Having a blast...Should be ready to fire up next weekend..

We need pictures Mark

Progress! Lots of work, but satisfying I bet. Let us know when we have lift off.

Did you replace the Phillips head bolts on the engine side covers with Allen head bolts? I always did on my 120s and 140s, it makes it easier to tighten after a ride when the engine is hot. The only place my 76 leaks is the ****** OIF filter gasket, the engine doesn't. Let us know when she is on the road, well after you calm down from the excitement!

My 69 TR6C didn't leak but my 72 T120V always leaked at the final drive sprocket. I did everything I could think of and it always leaked. I even ran 90W gear oil in the tranny and it still leaked. Never had a mechanical issue just that one leak. Now all my old bikes leaked here and there with age but most, once I rebuilt them, didn't at first. When ever anyone told me one of my antiques was leaking I would tell them, good I'm glad since if it wasn't it meant there was no oil in it! Since they all left a little on the ground when parked due to the crank breather blowing a little on the chain.

They are just Alpha bikes marking their territory!

Carbs installed, gas tank installed, Tympanium (electronic regulator) installed, all fluids topped off, wiring harness re-wrapped and ty-wrapped, Prop clear, switch on, KA-BAM! She started on the first kick! No oil pressure though. After 7 or 8 seconds, shut her off, swapped oil lines, re-started, now 50 psi. Took her up the road through all 5 gears, test ride satisfactory. Topped her off with fresh gas. Still a little ways to go, but at least she's up and running again!

Congratulations, I'm jealous.

Mark, I should just bring my 64 motor to you so I can tour and the sludge trap work will get done...

Absolutely welcome anytime Ed, we're only about an hour or so away from you....Let me know, and we'll meet you somewhere with your crankshaft...You CAN get a bonneville crankshaft in you saddlebags, ask me how I know...

I gotta tell ya, she just keeps getting sweeter and sweeter. She starts very first kick everytime, and if your not ready, she'll throw you back over the seat when she fires...Leaks have started to show now on the garage floor, but I did everything right, so Im convinced theres no sense in pursuing the minor leaks...I am somewhat concerned about the oil pressure. I installed a analog, rather cheesy oil pressure gauge, and on first start, it indicated about 50 psi. Now after 15 or so miles, the highest I can get her to show is around 25 psi, and well below 10 psi at idle. Will pull side cover again for inspection....

If that gauge is right that is extremely low for those bikes. I would look into that before you really do any running of that engine.

Of course it is...remember, this IS the T120 from ******...The most difficult problems at the most inconvenient time!

was the seal in the timing cover that seals to the end of the crank replaced? If I remember right you said the old crank was mushroomed.

WHEW...45 mile road trip today on the old Bonny...She performed flawlessly, as my son, Brad, rode beside me on my America. We got to the Cartersville airport to watch planes do touch and goes, trying to get someone to take Brad for a ride, but no takers...we kept trying to wave them down to no avail. Anyway, got back on the bike, nothing...acting like theres no fire to the plugs, and of course we have zero tools...Finally got her to fire, and rode the 25 miles back to Hiram, then again, no fire...Fuse blown, too tired to fool with her anymore...She runs strong, and really fun to ride...will fix her tomorrow...

Never ride that old Bonnie with no tools. I never had anything big happen that was fixable along the road but there will be minor hiccups. I always carried tools and some parts I knew I might need.

Good idea, but nowhere to store tools on her...will have to come up with something..Problem seems to be with fuse holder.

Isn't there a tray molded into the left side cover for a tool pouch? Or is that only on the earlier models?

I had a problem with my old bonnie due to the handlebar control kill switch. Took her apart and cleaned the contacts and had no more issues.... at least with that.

If I remember right the tools went under the seat on those. I have a couple but I used a leather tool bag.

Short test run tonight, accelerating out of Dallas, Ga on highway 61 in 5th gear, started losing power, with distinctive "tap tap tap". Shut down engine and pulled off side of highway. Got her unloaded from the truck into the garage, compression reads 150 on the right, a little over 30 psi on the left. Removed valve covers, all valves operating normal, with proper clearance on all...sounds like the left rod has either came loose, or burnt a bearing again...very frustrated, contemplating selling the whole thing for what I can get out of it....

I really don't understand all the problems you are having. I rebuild those once and run them for 35,000 to 40,000 miles before checking to see if it's time for a top end and in most cases it's a quick hone and fresh rings and off I go again for a while until it's time to bore. Reseat the valves with fresh guides if it had bronze guides but not if it had iron. Bottom end usually went through several top ends. Done right the bottom end on those bikes was tough. Tap tap and 30 psi tends to tell me maybe a ring was broken on installation. Possibly a burned piston if not timed right but more likely the ring I think. could be a clip came out of the piston too causing compression to drop as the wrist pin wears into the cyl. wall. That would damage the rod if you are sure it's a rod knock. Sorry to hear you are having so much trouble with such a fun bike.

ouch!

What is the piston to cylinder wall clearance supposed to be? Scuffing is usually due to overheating, lack of lube, tight clearances, overreving when cold, lugging the engine down, etc etc.

Man, that sucks.

Wow. Looks like a case of first degree felony assault upon a motorcycle engine with intent to commit boat anchor

http://www.youtube.com/watch?v=-feif-Q6Kok

Clearances are all good, this is the result of way too far advanced timing. Haven't decided whether Im gonna split the cases yet, but the crankshaft, rods, and cylinder head are all undamaged. Found a little metal in sump plug screen, and main oil filter, flushed engine thoroughly, trying to decide whether to split the case or not. Got new Pistons and rings (thanks Lowell), cylinder was saved by a hone job for $20 (thanks to Will's machine shop). $140 worth of damage, ready to go back together with her...

What do ya'll think? Trying to decide whether or not to split the engine open again, something tells me it'll be okay, as there was very little metal in sump plug and main filter, from what I can see of the crankcase, pretty darn clean, crankshaft turns super smooth, and all oil lines clean...what would ya'll do? Got new pistons, rings, gaskets, ready to install cylinder and head...Honest opinions please, cause I can't make up my mind...

Are you using the timing plunger? I never liked the electronic ignition for those bikes. I always ran the dual points. Lucas makes a really nice replacement for the breaker plate, better than the OEM and the points for it are better too. The crank is drilled for TDC and fully advanced firing position.Set the left cyl on the compression stroke, the plunger should lock the crank in the adv. spot and the hold the cam lobe to fully advanced then rotate the breaker plate until the left point just opens with the cam lobe still held in the fully advanced position. Do the same for the 2nd cyl. except move the point holder on the breaker plate instead of the whole plate. Very simple, can't tell you the procedure for the electronic ignition you have.

You can remove the small round cover on the front of the primary and use a timing light to check the timing with a timing light. Always get power from a seperate battery for the timing light NOT the battery in the bike , the battery in the bike could give you a false reading. There is a pointer under that small round cover and marks for each cyl, on the alternator rotor.

Engine split, crankshaft out, no damage to crankshaft, bearings and journals still like new...Cleaned thoroughly, will re-assemble over the weekend...

don't forget to use assembly lube and clock the rings. Take a good look at the wrist pin bushings.