Connecting rod to crankshaft clearanceConnecting rod to crankshaft clearanceI have removed the cylinders and pistons (had been bored to 0.75 already) which means I am going to need to resleeve the cylinder. However today's question - how much play should there be between the connecting rods and crankshaft? It seems like I have more than I would have expected. Thanks for any advice.
Liners can be bored up to 3mm o/s if you can find a larger set or pistons. 1.0mm used to be available and there were 2mm and 3mm O/S sets on the market for a while.
64mm needs new liners though... I can't remember teh crank side play but it's a lot of play sideways and even rock is more than you might expect, but basically zero radial play is allowed. Do you know a practical way to check out a used crank Teazer? The CB77 Shop Manual says for the Lower end con rod Axial clearance .0027 - .012" as standard with .0196" as the repairing limit and for Diagonal clearance .0002 - .0006" as standard and .00196" as the repairing limit. I'm looking for a good used crank and don't know how to use that info or if it's even practical.
Hi,
One way to do it if you're unexperienced is measuring. Lay down the crank in V blocks, put your 1/100 mm clock at the back of the conrod (big end) and try to move the conrod back and forth in a straight radial direction. The movement of your clock gives the play. One way to do it when you have the experience : Lay down the crank on flat surface, grab the conrod with one hand (your thumb and finger) and point the conrod to the ceiling, and push it up, but not so hard that you lift the crank. Use your thumb from the other hand to tap it gently straight down. If you feel play / hear play, measure it to see how much it is, but if you feel (and hear) nothing, it's good. You have to practice this one with a good and bad crank to get the feeling. Jensen
assembly of Japanese motorcycles requires great peace of mind (Pirsig)
"One way to do it when you have the experience :
Lay down the crank on flat surface, grab the conrod with one hand (your thumb and finger) and point the conrod to the ceiling, and push it up, but not so hard that you lift the crank. Use your thumb from the other hand to tap it gently straight down. If you feel play / hear play, measure it to see how much it is, but if you feel (and hear) nothing, it's good. " -------------- Thanks Jensen, that's similar to the way I used to check my cranks back in the day. I would alternately push and pull on the rods while lightly tapping on the small end with a ballpeen hammer and listen for a change in the tone of the taps. What I don't remember is how much of a tone change indicated good or bad. I don't have a meter like the one in your picture and I don't think my digital calipers would give me accurate measurements in this situation. I guess I'll play a little marimba music on my questionable crank and see if I have a deja' vu moment.
Hi Hotshoe,
Important but logical note : The big end bearing should be clean and dry, absolutely no oil. Jensen btw, the costs of a low cost meter is around 40 Euro or 50 USD. The clock meter is a relative measurement tool, not absolute, so a cheap one will do the job. assembly of Japanese motorcycles requires great peace of mind (Pirsig)
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