Bad Crank?

[quadman21]

What would a bad crank sound like? I was told by the mechanic that installed my 440 that the wrist pin to small end of my connecting rod was going. It does have a small knok but nothing like a deep serious sounding knock. I am skeptic because I just measured the wrist pin to connecting rod clearence when I changed my cam chain back last summer. It was knocking then but my cam chain had stretched from the increased torque of the 425 11:1 I had at the time. It fixed the knock then. So? How indesructable is a Honda crank? Is the guy trying to get more cash out of me? What about the knock?

[Blackguywithouta400]

I have the same kind of knock, and so does the other 425 engine my buddy has. its just like at idle it has a knock that sounds like its comming from the bottom end i havent had a problem with the motor yet at all so i wonder whats going ot happen it runs really strong right now. I guess ill keep riding it, and winning on it.

[MIKE400EX]

First, the wrist pin goes thru the piston and the small end of the connecting rod. You may have to replace the connecting rod, but for that problem not the crank. However, since the rod and crank assembly are pressed together, the crank would have to be taken apart and re-assembled to replace the rod. Second, the added torque of the 425 is not transmitted thru the cam chain, so that's not the reason why it stretched. The chain probably stretched from the added thrashing you gave the motor with all that new found "go-power". Honda cranks are pretty tough, chances are you just need a con-rod. But...If you take it apart and the wrist pin/rod/piston look good, check that the bore isn't a couple thou big. It doesn't take much to create some piston slap.
Does the knock get better or worse as the engine heats up?

[quadman21]

The mechanic that worked on it said it got worse as it heated up but I haven't noticed it. I raced a harescamble last sunday and It ran great. I didn't think that the knock got worse at all. I did however notced tueday evening that my head gasket was bad, That was a different noise all togehter. Like an exhaust leak. I'm gonna install a new one tomorrow. I wish I could be more desciptive through words but I can't. It's just a knock that I can only compare to a ping. When my cam chain stretched it made a much worse knock that what I have now. I have priced a crank and bearings. The best price I have found so far is $241 for the crank assembly and $78 for both crank bearings through Planet Honda. I don't want to replace the crank and spend all that money if I don't have to.

[MIKE400EX]

While you're replacing the head gasket, go a little further, and check out the piston pin area. See if it's the pin, piston pin bore, or the small end bearing. If it's the rod you don't have to replace the whole crank assembly - just get a new rod (maybe an upgraded one). You will have to take everything apart to change the rod.:(

[Blackguywithouta400]

I think mine is all piston slap, i know the guy that did the bores on the motors i built does wisco pistons too and i know they have differnt tolerences for the two so it might have been since he bored out so many that day and mine was a JE and he didnt bore them that often he could have done the wrong tolerences. I guess thats it cause the bike was only 4 months old when i did the work and i know everything was sounding perfect before.