Piston rod end caps too tight?

[mke039]

I am rebuilding two 2003 50HP Hondas. I had to replace the rings one both engines as the engines had been submerged.
I tighten the piston rod end caps to the right torque (21 lbs) and then I can't rotate the crank. When I loosen them a little the crank and pistons move freely. Why?
I don't think the starter will crank the engine like this, and I don't want to have the end cap bolts too loose.
Any suggestions?

 

[mke039]

Re: Piston rod end caps too tight?

Well I decided to DIY fix this thing. I cut small shims out of stainless flashing I had lying around the garage. I drill pressed holes to go over the end rod bolts. When I torqued down on the end nuts....the crank moved freely. I don't see why this fix won't hold, as the end caps are very tight over the shims...
If I throw a rod I will let you know!

 

[dtj]

Re: Piston rod end caps too tight?

Something is drastically wrong.

Did you install the same end caps and bearings to the same journals, in the same orientation as dis-assembled?

What are the mic'd dimensions of the crank journal o.d. and rod bearing i.d.?

 

[mke039]

Re: Piston rod end caps too tight?

Yikes...I was very careful to keep the same caps and orientation. When I put them back together they were too tight.
The rod bearings are just two halfs of metal that snap into the cape side and piston rod side. They have a grove in them for oil.
Not very high tech bearings at all, so I am not really worried about my fix. The flashing is thin gauge material and I torqued it all down to spec.

 

[dtj]

Re: Piston rod end caps too tight?

Bearing to journal clearance is normally less than .002", your flashing shims will make for a clearance of .020" or greater drastically dropping oil pressure allowing bearing to journal slap resulting in rapid bearing damage.

 

[duke33]

Re: Piston rod end caps too tight?

I'm no boat engine mech, but can't you plastiguage those too?

 

[mke039]

Re: Piston rod end caps too tight?

there could very well be too much slop between the bearings and journals. The problem is there was too little at the correct torque on the end nuts. I guess I will run it like this for a day and tear it apart to inspect the bearings. My suspicion is that they will be fine, I think I am very close to the correct clearance now.

 

[pvanv]

Re: Piston rod end caps too tight?

You are guessing, and headed for trouble. As was mentioned, something is drastically wrong. You should plastigauge the bearings. Are they used or new shells? If new, are they undersized? If so, were the journals turned down to the new specs?

 

[Star]

Re: Piston rod end caps too tight?

Mke039 Something is very wrong!!! Either you have the wrong bearings or caps reversed. Take a good look at the old and new parts. If you continue on your current path you will damage that engine. Plastic Gauge is in order!!! You could use twist ties to hold the caps on TOO!

 

[dtj]

Re: Piston rod end caps too tight?

there could very well be too much slop between the bearings and journals. The problem is there was too little at the correct torque on the end nuts. I guess I will run it like this for a day and tear it apart to inspect the bearings. My suspicion is that they will be fine, I think I am very close to the correct clearance now.

These Hondas are expensive precision motors that require the correct specs. for proper operation and longevity, time to get the factory manual for proper rebuild and maintanence instructions, otherwise you are just treating it like a cheap junkyard disposable engine. Find out why the rods are binding.

Its your motor and you can do with it as you choose but with those flashing shims dont be surprised if you end up with an expensive anchor.

 

[mke039]

Re: Piston rod end caps too tight?

I did get the engines for nothing. They came off of a capsized boat and had been submerged and then left for a year. I was able to re-ring the pistons and the bores were not corroded. The crank and cam did not show any pitting or corrosion. I rebuilt one and got it started, then tore it apart to install new gaskets. I just rebuilt the other engine, and two of the end caps torqued down properly, but the third was binding. I can see no obvious problem, but yes something is going on obviously.
I saw some used pistons on ebay, and will buy them and see if that does not solve the problem