I want to get an inside micrometer to measure my cylinder bores, but I don't want to spend hundreds of dollars, and I don't want to buy useless junk either. I won't be doing any machining myself, I just want to get an idea of what's what with my engine before making decisions on what should be done.
The cheapest name-brand set I could find was a Fowler's for $112.
Even cheaper are telescoping bore gauges that you measure with an outside mic or calipers. I already have a Fowler's vernier calipers. Would these bore gauges be suitable for my purposes?
Telescoping bore gauges are fine. You want measurements in three locations down the bores, and each with a corresponding measurement taken at 90 degrees. The calipers will be close enough for measuring the gauges. These measurements are FYI only, not a final. HTH
Hugh: Proof the Dodo is not extinct 1964 Bonneville A couple others
I just take the barrel(s)to the local machine shop where I get the boring done. Was recently offered an Atlas barrel that was still at standard bore and had the guys measure it down the bore and would have had to go to 40 over( unless I could find some plus 30 pistons) so wasn't such a good deal after all. Cheers, Wilf
Engines that give out internal noises described as "banging under moderate load" should be be considered problematic. This is not a sign of anything good!
I recently received a pm where the owner was showing me where the top half inch off the rod came of freeing the wrist pin and piston. This would be something that would have a symptom of banging under moderate load.
As far as expanding bore gages go you get what you pay for. The inexpensive ones sold from China are all but useless!!!! Don't be temped to buy them. They will ruin your experience and turn you away from using a expanding gage. Its the difference between a Ford Focus and a Ferrari.
I have a set of Starret I bought over 50 years ago that I keep locked away. With only a little experience you can get very accurate readings. I have tenth reading bore gages for cylinders and reclaiming Vincent connecting rods. I can come within a couple of tenths using an expanding bore gage as compared to the very expensive bore gages.
John, I'm pretty sure this is piston slap. I've put between one and two thousand miles on the bike with this noise, and although it's gotten a little louder, the engine runs very good. I think if it were anything such as what you described, it would have grenaded by now. To clarify a bit, there is always a "chuffing" noise, even at idle. As I accelerate to a certain rpm, the chuffing morphs into a metallic banging. The banging is persistent at moderate cruising speed, say, 55 mph. Then if I get on the throttle hard, it quiets down. Likewise, if I let off the throttle, it stops.
How does a Fowler 2"-12" inside micrometer set for $79 sound?
This isn't the classic symptom for piston slap. T140's with about .006 inch piston clearance exhibits the classic piston slap. Starting from cold the you get a distinctive metallic rhythmic clack. It is easily picked out from all of the other clacks and whirs with a screwdriver held to your ear held against the cylinder. The key to the symptom is the noise decreases or just goes away completely as the engine warms and the piston grows in the bore. I have a GMC Envoy that has had pistons slap for years. It is worse in the Winter. Once the engine warms you have no sense that there is anything wrong.
Now, take a loose (internal clearance) drive side main bearing. It will give you a banging noise that will make you think the crankshaft is about to jump out of the cases. Pull up a slight grade keeping a load on the engine. At the top of the hill roll the throttle back unloading the engine and be prepared to hear sounds. Expensive sounds.
Triumph has always had a problem with the timing side crankshaft ball bearing. In storage condensation will collect in the outer ball track of the timing side ball bearing. In under 1,000 miles after the bike is put into service you will get a loud rumbling sound from the rear of the primary cover. You swear that there is a problem with the clutch. A screwdriver held against the timing crankcase above the timing bearing area, or around the oil pressure relief area, will illicit a distinct rumbling sound.
Rod bearing/wrist pin problems will typically come and go with load and will not change appreciably as the engine warms. While noises are inevitable as parts wear or start to deteriorate how they manifest themselves can be different with different engines. This where a mechanic with brand experience can give you better advice than a text-book definition.
These are much easier to use than inside micrometers and with a short learning curve you can easily measure bores to .0005". While you should get the best telescoping gages you can afford, you will only need a decent micrometer as you are using the two as a comparator. You will be comparing the difference between the measurement you take off the piston with the measurement you take of the telescoping gage.
Thanks for the link John. I guess I'll go with the Starrett telescoping bore gauge, not too expensive. I only need the one, 2.75-3.50".
I will be measuring the bore gauge and the pistons with vernier calipers. I don't have a big outside micrometer, and can't afford one right now. Remember, I only need to see what's going on in general, precision to half a thou is sufficient. The engine WILL be going to a pro, it's just a matter of whom.
And the lower will be examined as well. At the very least, if I change pistons, the small end bushings will have to be replaced. The pistons I have now were about .002" large on the wrist pins, and the bushings were reamed to fit. (It's a long story.) But it's probably time to look at the timing side main bush again, and the sludge trap. And I'll probably go for one of those late-model cast iron oil pumps; I'm getting a little tired of the wet-sumping.
The pins fit the pistons, just not the small end bushings. I had inadvertantly received the wrong pistons, and this was not discovered until I tried to assemble the engine, a year and a half after getting the pistons and having the cylinders bored to fit (i.e., too late to return the pistons).
Anxious to get on the road, and not wanting to tear down the lower end, I convinced my engine man to try reaming the small end bushings in place. He did a superb job, using the old wrist pin and the opposite rod as a guide, and he did this free of charge (in part because he had obtained the pistons for me), warning that if it did not come out right, the lower would have to be disassembled. As well as can be determined, the job came out right. As I stated above, the engine was torn down again and measured immediately after the rebuild, because of the noise, and there was no problem with the small ends.
Here are two more reasons I think this is piston slap: First, I was told a long time ago that piston slap sounds like there's a little man inside your cylinder with a hammer - that's exactly what this sounds like. Secondly, the engine did not make this noise before the (upper-only) rebuild, and made it immediately afterward. The noise is under moderate load ONLY, which would seem to rule out valve train. Last weekend, I consulted with another experienced British engine man, who put a screwdriver to the cylinder and his ear and said the noise was "definitely upper-engine".
The only inconsistent symptom is that the noise doesn't go away when the engine warms up.
Mark: If you haven't torn down the engine yet, Check the rotor. My youngest sons' Norton had a similar knock. After Adjusting the timing chain and still hearing the knock, we opened it up again. We saw oil streaks radiating away from the rotor nut. We swapped it out with an extra rotor I had. Problem solved. The knock coming from the rotor in the primary sounded as if it was coming from the timing chest.If you mount the rotor in a vice by its center and grasp the outside you might be able to feel it move. I have 2 of them now hanging in the garage marked as loose. It won't cost much money to check, just time. Good luck frank
The only inconsistent symptom is that the noise doesn't go away when the engine warms up.
Then it is most likely not piston slap unless the clearance is extreme. As the piston warms to operating temperature it expands reducing piston to cylinder clearance. So typically the piston slap goes away, or at least the amplitude of the noise abates, as the engine warms.
There is a relatively rare condition where the wrist pin slides from side to side as the engine rotates. It happens when the wrist pin bushing is not square to the bore. Eventually it pushes past the circlip and starts to wear a couple of grooves in the bore. The pumping action of the pin doesn't change as the engine warms so the noise, or its amplitude doesn't change as teh engine warms. Once the pin reaches the cylinder it is usually accompanied by oil smoke out the exhaust..
It very well could be the rotor, this is why having a marque specialist listen to it is so helpful. As I mentioned with a failed Triumph 650-750 twin timing side main bearing the noise is most prevalent to the naked ear at the back of the primary cover.
Yeah tt and John, the lights are starting to go on.
I'm glad this all came up, and thanks for wringing it out of me. I think the engine will be coming apart sooner than planned; I'd like to save the cylinder from another bore job if it's not already too late.
Mark, I have telescoping gauges and they take great expertise to get consistent repeatably accurate measurements. Go with the dial bore gauge or borrow one. On piston slap I had it in 2 BSA's. Under light acceleration you hear it loud and clear with engine warm. It goes away a constant speed when you are neither accelerating or decelerating. A bore job with refitted pistons fixed the problem unequivocally. Previous clearance was .006-.008. New clearance was .0035-.004.
Mike: At .008" clearance It is probable that your pistons slap wouldn't go away, but the intensity of the sound should have decreased as the engine warmed and the piston grew in size thus reducing the piston clearance (the cause of the noise). This is an important tool when diagnosing noises coming from the cylinder area. At .008" clearance it is a wonder the pistons weren't trying to swap bores.
I invite you to google "symptoms of piston slap." The decrease of intensity of the sound when the engine warms is a classic symptom. You had so much clearance that the change in sound might be subtle, but it would be there. Also typical pistons slap is present at idle and under load.
I use both, and both require some understanding of what you are doing. Setting up a bore dial gage to read a given dimension or reading between the two measuring points of the dial bore gage requires some skill and dexterity.
If you set the telescoping gage so that it is slightly large than the bore you are measuring, and clamp the locking pin like you were making love to it rather than tightening the lug nut on a tractor trailer wheel you will find you will be much more successful.
The finger of the gage must be able to move freely with only a small bit of pressure created as you rock the gage through the bore. Tilt the gage to enter the bore and with a swinging motion slide the two faces of the gage across the bore. The action of swinging the gage will allow it to find the major diameter and is repeatable time after time. As I said above you can repeat within .0005" given your ability of using the micrometer you are using to measure it.
Because the ability to use a telescoping gage depends almost entirely upon the slot the locking pin resides, the quality of the telescoping gage is important. The pin must be free to slide along the bottom of teh slot without any restrictions AT ALL. I mentioned this above. If your experience with telescoping gages has been with a cheap import you are missing a real useful tool. The Starrett telescoping gages work!!! They are the only ones I would buy.
Because the faces of the contact points of both gages are a radius you must find the largest measurement across them no matter which gage you use. This takes some patience and dexterity. I routinely use my dial bore gage and then my telescoping gage to check myself when honing the races in Vincent rods for a new crankpin. I don't find one any easier or more accurate.
John, Don't disagree at all. It takes practice whether you use a vernier, a micrometer, a dial indicator or a yardstick. John, measuring anything takes good procedure and practice. My brother a machinist and tool maker gave me a set of Starrett telescoping gauges and showed me how to use them. I practiced a lot with the goal of getting repeatable measurements. I just don't do it enough to be sure of myself. A dial bore guage is simpler. With telescoping gaguges you have two things that introduce error: (1) The positioning and setting of the telescoping gauge and (2) measuring it. In the hands of the inexperienced thats two possibilities for measurement error.
On the piston slap, I would guess it was more likely .006-.008. Ed V bored them for me and fitted the pistons he had in hand and VIOLA no more noises.
When I was young and broke we would just reuse the old piston, slap a set of rings on it and knock the glaze offwith a hone in drill motor. I would lap the valves with a suction cup. While I could get them to run ok and get me back on the road they were never as good as a correct bore job and valve jhob. We live and we learn and it's just as much fun today as it was back then but I somehow got smarter ...and have a little more money.
Last night I purchased a Starrett 2-1/8" to 3-1/2" telescoping gauge online. I'll save and review the above posts when it comes time to use it.
I think triton and John hit the nail on the head with my reamed-in-place small end bushings, and I'll be looking for signs of that when I tear down the engine. I knew this was a risky procedure, and I was warned of that when the job was done. But I was anxious to get the bike on the road and didn't want to pull the engine. I thought the only issue was getting the correct clearance, but now I see how an out-of-square bushing would throw the piston from side to side.
If this is the problem, it would explain: 1. Why the noise started immediately after the rebuild, with the cylinders bored to fit new pistons. 2. Why the noise sounds like piston slap but doesn't change or go away when the engine warms up.