Con rod bolts

[mack]

anyone put blue loctite on the con rod bolts during reassembly. I don't have new bolts and nuts. I know the manual says to use new ones but but....?

[motoman]

anyone put blue loctite on the con rod bolts during reassembly. I don't have new bolts and nuts. I know the manual says to use new ones but but....?

Sounds good in theory, but imagine those are 'dry' torgue specs.
A torque to spec. bolt/nut will stay tight.......overtorqued or undertorqued can loosen, but you already knew that.

[mack]

These

bolts are discontinued according to yamaha. I don't want to buy off ebay and just get different USED bolts. Shame to put it all back together and throw a rod later, but , it is what it is I guess. Sure is getting hard to find the basic requirements for these bikes now. Glad for this site though. I can see in the future that lack of parts will be the end of them. What a shame.

[jetmechmarty]

I wouldn't do it. Find the bolts. I've been following a CB750 build on YouTube and he had the same issue. He went with aftermarket con rods, but conceded he could get the bolts if he tried hard enough. Somebody has what you need to do this right. I wouldn't want the bike if I had any notion that it might throw a rod. I'm not a qualified machinist, but bolts that are meant to be stretched one time only, should be discarded to the circular file.

Have you tried Speed & Sport in PA? Google "Yamatopdog".

[bikerphil]

Fellas at ARP may be able to find you somthing if you contact them, JAT

[mack]

Searched

I've spent the whole day searching, but no one had any. Looks like I'm going to have to reuse mine.

[crazy steve]

anyone put blue loctite on the con rod bolts during reassembly. I don't have new bolts and nuts. I know the manual says to use new ones but but....?

Where are you finding this? I looked in the factory manual, and the only 'caution' I saw was one pertaining to torque. Nothing specific about replacing them.

Generally speaking, you'll only run into 'one time' bolts/nuts under certain conditions, none of which apply here. Self-locking nuts, nuts/bolts with a factory-applied thread locker, or bolts where a specific amount of 'stretch' is desired (where the stretch is actually measured or torqueing to a number then turning the bolt a specified amount more) should be replaced, but any 'normal' bolt in good condition should last the life of the assembly if installed right.

If it's peace of mind you're after, I suppose you could have yours magnafluxed for cracks. But if they look good and the nut/bolt thread fit is still tight, I wouldn't hesitate to reuse them.

To be honest, rod failures due to bolts are rare. Far more occur from out-of-round big ends (with the bearing bore becoming egg-shaped over time) which is why resizing the rods is nearly always a part of a normal rebuild. Unfortunately, Yamaha doesn't give specs for what's acceptable here (or even what the nominal bore size should be) so you're left with the somewhat vague service manual procedure.

[jetmechmarty]

Crazy Steve does the research and saves the day, again! Good one!

[crazy steve]

I'll expand on the 'bolt stretch' thing....

Applying a specific torque to any bolt is designed to stretch the bolt a certain amount. Due to minor differences in manufacturing, you may not get the exact same stretch on every bolt. I know some race teams and high-end engine builders use the bolt-stretch method for rod bolts, but what they do is torque the bolt to attain a given amount of stretch, then compare this to the actual torque applied. If the bolt stretches at too low a number, it's replaced. Same for too high. Low means the bolt is soft, high it's hard. They're looking for a certain 'resiliency' as well as a very accurate clamping force (think of this a spring tension). These bolts can generally be reused if they meet specs.

Locking methods are generally used in clamping applications where there's more movement than the bolt stretch can compensate for. Different expansion rates (dissimilar metals), shock loading, flexing, all can be cause for additional locking being needed. But these also introduce a larger variation in the clamping force, so installing any sort of mechanical locking device where none were is a bad idea.

[BA80]

The torque on those bolts is only 28 Ft Lbs. That's not enough to stretch the bolts significantly, it's just enough to keep them from backing off.

I've built a lot of engines, all types, and reused the rod cap bolts as well as the main cap bolts without issue. And I'm not nice to ANY engine.

With that bolt stretch theory you would be replacing case bolts and head/cylinder studs every time you took it apart.

At 28 Ft Lbs I wouldn't hesitate a second reusing rod cap bolts. After all, they've already been tested in the real world.

[mack]

reference

I believe it was Haynes I read it in but it could be the FSM. I'll check tomorrow but I have to say I'm relieved. I'll give the page and para number but if you two say it's all good, that's good enough for me.

[skids]

I believe it was Haynes I read it in but it could be the FSM. I'll check tomorrow but I have to say I'm relieved. I'll give the page and para number but if you two say it's all good, that's good enough for me.

I think that torque-tensioning is most important when you have bolts with free lengths between the threads and the heads. I would think that with a lot of heating and cooling cycles (i.e. thermal expansion) you would want those types of bolts...like for the heads. Shorter bolts seem to depend more on lock washers, but I admit that I have never rebuilt one of these engines.

[mack]

reference

Here's where my concern came from:


Your right skids, the method to apply the torque to the nut is very specific in all the manuals. Once you start to turn, you can't stop at all until you hit the 28 ft/lbs. If you do miss it then you have to back it off about half way and start again.