305 piston pin wabble305 piston pin wabbleHow much play can I have between the small end of the connceting rod and the piston pin? I have no way of putting in an overside pistion pin. I have heard that there shouldn't be any play. Please advsie, CFL
Re: 305 piston pin wabbleFor me : .0004" to .0007" if anymore then I would go with the oversize wrist pin or just replace the rods.
Tim
An old Clymer manual I have says service limit for wrist pins is 0.588 mm. Half a milli-mumble is nigh on to nothin'...if you feel lateral movement in that pin, it needs attention.
My personal experience is, any slop here and your piston will eventually cause damage of the 'oh-oh, time for a rebuild' kind. Like Tim says, probably easiest to replace the con rod. Good luck! Replacing con rodReplacing the rods on a 305 is fairly involved. There are no splines on the pieces of the crank. The 4 spots where they go together are round and pressure fit together. Re-alignment in re-assembly to make a crank that runs true is fairly involved. Unless you are an extremely adventurous sort, you will probably have to send the crank out for a professional rebuild. It will be expensive.
Another avenue is to get a used crank that is in good shape. I have gotten a couple off of ebay that seem to be alright, but I have not run any of them yet. Though there are exceptions, many 305 bikes didn't see a lot of miles and the cranks are pretty stout. Watch for rust and make sure they are "in spec" before installing. There is a risk that you will end up with a boat anchor, but if the price is right, the risk may be worth it. I was patient in buying and found them pretty cheap and I believe will work fine. You could try an oversized wrist pin, but many people are suspicious of the idea that the bushing will still be true after using a hand reamer in the small end. I have never tried it, but it would seem to me that with a little finesse a guy could get the job done since not much material is being removed. It is clear Honda thought it could be done or they wouldn't have made oversized wrist pins. Maybe your local machine shop would help out. They are not great options, but there they are. Make sure that you are checking your rods properly. Search this site. There are several posts that describe what to look for. Hope this helps.
Yoinks, I hadn't thought about how the bottom-end goes together. Interestingly, the Clymer book does not talk about how one removes the con rods, or gets at those two inner bearings on the crank. It does not talk about splitting the crank. It does mention replacing wrist pins with oversize.
Turning back to the top end, the book does suggest one possible option for you. It says the hole size for the piston pin in the piston should be max 15.05 mm (0.5925"), and the min pin diameter should be 14.95 mm (0.5856"). So, maybe you can tighten things up by replacing the piston with one that has a smaller (not worn larger) hole? It does seem possible that the softer alloy of the piston wore out first. Maybe worth a check. (I think I just convinced myself to spring for Mr. Silver's book, this old Clymer is just not complete.)
I hand reamed my rods with a 5 flute spiral expanding reamer 19/32 [they are kind of expensive 60-70 dollars] did a nice job almost made the holes round again. I can still hear pin noise with a steady speed with no load. Some day if i get energetic i will find a better crank to use. If your small ends are not wore to much it could work for you, you will also need to have your pistons reamed oversize. It's not a lot of work to only pull the top off so you could give it a try. I would just bite the bullet and do it right the first time, you only have to do it once then unless you have lots of time and enjoy working on engines.
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