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TR4/4A TR4 Crankshaft bolt

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steve_sims

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Howdy All, Just bought a 63 TR4 that has been sitting since 1994. Cleaned out gas tank, replaced fuel lines, rebuilt carbs and she fired right up. Problem is crank pully wobble.When the bolt was removed, someone had added several washers to make up for either bolt being too long or old bolt broken off in crank. Hole in crank is only 1/2 inch deep. Threads on bolt are 1 inch long. Bottom of hole looks smooth, not ragged like broke bolt. Friend suggests we either cut off 1/2 inch of bolt threads or try to drill and remove old {broken} bolt. Any suggestions would be greatly appreciated. Thanks Steve
 
Steve, I just measured a good crank and the depth of the hole is 1.25-1.33(appx). If you have the dead remains of an old bolt at the bottom of your threads you may need professional help to extract it without damaging the crank.
I would suggest getting a bushing made up to guide the centering of the drillbit, getting a good easy-out and some gentle heating of the crank.(lots of heartfelt prayers too).
MD(mad dog)
 
Thanks MD, Engine was rebuilt in 1974 and not driven much since. Please forgive my ignorance but did other years have different thread depth? The bottom of the hole looks flat. Is yours flat or tapered? It is hard for me to see how the bolt could have broke off without damaging the remainding threads. Thanks Steve
 
This crank was out of a 64, and there is some crud in the bottom of the hole that has built up over the years so I cant tell if its flat or not.The depth of the hole should be the same for all, give or take some minor production variations(aka mondays)
If you only have 1/2 an inch I would suspect a broken bolt.
MD(mad dog)
 
Steve, I strongly second MD's recommendation of using a guide bushing to drill your pilot hole. Maybe start out with about a 3/16" or 1/4". Are you going to attempt this in the car? Just give yourself plenty of room. Then use a couple of incrememtal drill sizes up to the required size for the 'easy out' you choose. It's a 5/8's bolt so get the extractor as big as you dare. Maybe one that requires a 7/16" pilot hole for mechanical advantage. You'll probably have to pull the timing cover if you want to heat things to avoid seal problems. I would probably try some sort of setup using a hand type impact tool(steady light taps). Just have someone available to step on the clutch while you're driving in the extractor to take the shock load off the front thrust washers. Buy lots of nice new bits unless you own a sharpener. Just measured three cranks on the shelf and they all have 1.5"+or-0.1 thread and could not lay my hands on a bolt so am not sure how much you'll have to pull out. Keep us appraised and good luck.
 
Ya'll ain't going to believe this !!!! We drilled a pilot hole thru a bolt that fit the crank hole, unbolted the steering rack to make room and using the drilled bolt as a pilot started drilling. After getting the hole drilled , inserted the easy out and it came out by hand turning. What was amazing is what came out. There was a 1 inch long 5/16 bolt with nut on the end in the hole !!!! How in the heck it got in there , who knows but it came out and didn't screw up the threads. The crank was turned back in 74 when engine was rebuilt and we thought possibly the machinist put it in as a spacer and never took it out. The the guy who put the motor in added washers instead of trying to get the bolt out. Who knows? Who Cares? I'm just glad its out. Thanks for the help. Now on to brakes and ????? Steve
 
Either you are incredibly ingenious or incredibly lucky. I think you are ingenious. Welcome to the mad, mad world of Triumphs. TR4s are becoming very collectible, and hard to find in decent condition. Fix it right and you will have an investment that you can enjoy.
 
Hi Bill, Truth be known, i'm a tad bit insane with ingenious friends. I've been buying selling and keeping British Motorcycles and other strange bikes for years. I am down to a 75 Norton, 78 BMW r100/7, 61 Simson 425s, 56 Indian/Enfield Fire Arrow, 68 Triumph Bonneville and piles of broke bikes and parts. If that don't make you nuts , i guess this TR4 will. I found this car{looking for bikes} in a garage where it had been sitting since 94. It has a nice body, real nice interior and sounds great. I had to pay $900 for it. For an extra $100 i got a set of wire wheels and a Porsche 356 Nose Clip and fender patch panel.Sold the nose and patch panel on Ebay for $1028 so i ain't hurting too bad on the car so far. I'm sure it will soon be a money pit but iv'e wanted a TR4 for 40 years. Steve
 
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