Triumphrat

LukeMac · 10-27-2006

Just when I thought things were finally squared away! I've been tinkering with my 1979 Bonneville Special for about a year now. I've been in no hurry just getting a part here and there. Finally got it running well, got new tires, new ignition parts, new susupension...etc. My birthday rolled around and my dad and I decided to hit the road for a ride.

Just moved to the Charlotte area this summer. I've heard good things about a section of pavement known as the "Tail of the Dragon" in eastern NC. It was fun and we put in about 600 miles in a couple days.

Riding was great except for the fact that my beloved Bonnie burned roughly 2 quarts of oil in 600 miles. I'd ridden it around town for about 500 miles without any significant oil usage, but when we got on the highway the smoke started. Any time the engine was under load, the left cylinder smoked. We checked the oil regularly every 100 miles or so and had to add some at every stop. Looks like I'm in need of a top end rebuild. Just hit 12,000 miles but I think some damage must have been done in the 15 years of being parked in a garage.

All that said, is there anything special I should look out for when I'm getting the motor apart? I'm hoping I can get away with honing the cylinder, new rings, re-seating the valves and sealing things back up. I'll check the clearances to make sure I don't need to have the cylinder bored out. If anyone has done this before, I'm looking for any advice you've got. I've got some friends that have done similar work on cars and other bikes, but I've never done it myself. Should be an adventure...I just don't want to get in over my head.

daveforty · 10-27-2006

My T140 burns oil, always has done, and I have to top it up frequently. I tend to look upon it as a 'rolling oil change'. :blush: Still do a complete change every 1500 even though its continually being fed fresh oil.

Getting the top end off is pretty straightforward, a Haynes manual describes it well enough. It can be done with the engine in the frame. Make sure you get the correct type of oil seals for the pushrod tubes, there were several types of O rings used on them.

The only 'trick' tools you will need is a 3/8 hex key with a 1/2" square drive to re-torque the head bolts, and a 'flat' ring spanner to undo some of the nuts around the base of the cylinders.

Each rocker box has two long 1/4" screws on the outer edges, make sure they are not overtightend when re-assembling.

The hardest part will be separating the exhaust pipes from the balance pipe and the exhaust stubs in the cylinder head, I suggest you give it a good soak with penetrating oil before starting work, I find 'Plus Gas' works well.

Before you lift the cylinder barrels, wrap an elastic band around the tops of the tappets (cam followers) to prevent them falling out of the tappet block, otherwise they could drop into the crankcase and that would make you unhappy.

When it is all done you will need several re-torque-ings of the cylinder head bolts and re-setting the valve clearances as it settles down.

TRI-AL · 10-28-2006

Why is it that 9 times out of 10 it's the LEFT cylinder that "acts up"???? I park mine on the center stand, so it's NOT that the bike is "leaning" to the left, yet if a cylinder is going to smoke, it'll ALWAYS be the left one. Any thoughts on the matter? Hmmm....? :???: And yes, it goes through a lot of oil, but I know not where? Doesn't leak a "whole lot", and doesn't "visibly" burn any. What a piece of machinery! :evil:

OzBloke · 10-28-2006

LukeMac,
DaveForty is giving good advice. Also remember to get the valve stems and valve guides checked for clearances.

okiecityflash · 10-28-2006

My '79's left pipe smokes when idling on the side stand. I lean it over to the right and it quits. Valve guide most likely. I've never checked the usage as I've never taken any long trips, but I'm sure I use some, especially if I'm riding around in left hand circles.

Good luck on your project. Keep us informed. Thanks

daveforty · 10-29-2006

Whenever I have investigated the oil consumption on my bike, I have usually found it is due to wear of the inlet valves & guides. The inlet tract & the back of the valve will be covered in burnt oily gunge. The spark plugs will always be the correct 'light brown' colour, which implies (to me) that the oil isnt being burnt in the cylinder, but on the back of the valve before it is drawn in to the cylinder. Also find that high oil consumption goes with an engine that is prone to 'pinking' under load, 'cos the fuel / air mixture is contaminated with oil.

IIRC there is a line of thought that the valve geometry of these engines isnt quite what it should be and that the angle the rocker contacts the top of the valve stem causes sideways movement of the valve in its guide, hence a high rate of wear. Mushroom headed rocker pins may help, I believe Norman Hyde supplies them.

My engine (1979) didnt originally have oil seals on the inlet valve guides, later engines did and I used the sealed type of valve guide during an overhaul. They wore out just as quick. It was suggested that the oil going down the valve stems kept them lubricated and the oil consumption was just one of those things.

I remember in the mid 70s BIKE magazine road testing a T160 and a Kawa 750 2 stroke triple and finding the petrol and oil consumption of the two bikes was pretty much the same.

Mecchanica · 10-30-2006

I have just pulled down my 68 Tigerville (Bonniger?) which has been together for nearly 12 years and 85,000 miles since a complete overhaul. No notable oil burning, but leaks from the tappet block/cylinder joint left a healthy smear on the bike. I used Kibblewhite Black Diamond valves and guides, also their spring and retainer kit. Routt 750 cylinder kit with Morgo (AE) pistons. Megacycle cams. Synthetic oil for the last 55K miles, or so.
Actually, my engine is soldiering on for another month or so, since I am loaning it to a friend while rebuilding his TR7V engine.
I will be reporting on it when I get it apart.
I suspect the oiling on the left side with the OIFs is an artifact of the modified breather system instituted in 1970. Perhaps the little drain holes squirt oil onto the left side of the flywheel which then throws it onto the cylinder wall and underside of the piston.

GrandPaulZ · 10-30-2006

I don't know, but BOTH of my '79 Specials will start puffing on the Left side if left on the sidestand for a few minutes.

Clears up in a minute once righted.

panda · 10-30-2006

My 1961 5TA speed twin smoked on the left barrel from new. no noticeable oil consumption though. It still did after a rebore and high compression pistons were fitted,, but much less so. that incarnation of the motor did about 70k miles before I sold the bike.

LukeMac · 10-31-2006

Thanks for the input gentlemen! I'll keep you posted on my progress. Just picked up a hone for the cylinder walls, I'm hoping I won't need to bore it out but we'll see. I'll get the clearances checked and move on from there. I'm planning to get it apart, assess the damage, then order replacement parts.

Long-term plan is to sell the Bonnie but I want to get it in good shape and ride it once or twice first. Wife and I can't ride together on it comfortably. I love the bike, but I'm not in a financial position to have more than one motorcycle in my garage! Hoping to find a Triumph lover that will take good care of her and enjoy the bike for years to come.