check your cylinder head bolts

[fjbiker84]

This was a while back but thought I'd mention it.  If you haven't checked the torque on your cylinder head bolts lately I would recommend you do so.  I was not aware of this until seeing something about it on a website by a guy who builds engines for one of the race series that the FJ engine is used in.  So I checked mine and all were below the required 25 ft lbs.  After running the bike a 1000 or so miles I checked the torque and found a few a little loose again.  So this is something that should be done often.  Don't know - mine is an 84 - maybe Yamaha addressed this in later models. 

[ribbert]

This was a while back but thought I'd mention it.  If you haven't checked the torque on your cylinder head bolts lately I would recommend you do so.  I was not aware of this until seeing something about it on a website by a guy who builds engines for one of the race series that the FJ engine is used in.  So I checked mine and all were below the required 25 ft lbs.  After running the bike a 1000 or so miles I checked the torque and found a few a little loose again.  So this is something that should be done often.  Don't know - mine is an 84 - maybe Yamaha addressed this in later models. 

Just make sure you loosen (not with the tension wrench) and re tension them one at a time, tighten them in one continuous flowing movement until you reach the required torque and DO NOT re check once you have done this.

IMO

Noel

[fjbiker84]

The video I saw on this engine builder's site show that you started in an X pattern with the center nuts, then worked your way out to the next two on each side, then to the outside bolts on each side.  I did this to all the nuts bringing them up to 20 and then repeated the same procedure to bring them all up to 25.  Everything seems to be OK.

[CutterBill]

If the head studs keep loosening, there is one other disturbing possibility... the studs are slowly pulling out of the case.  The early Porsche 911's were notorious for this.  Expensive fix, that... 

Or... somehow... the studs have lost their temper and they are stretching. 
Bill

[fjbiker84]

That is a concern... you are exactly correct.  The reason I have the bike in the first place is because the original owner had one of the studs in the engine give out.  He went through the process of removing the engine, taking it to a bike shop and having a new one installed, but then never put the engine back together.  Instead, he bought a new motorcycle and left everything in its state of disassembly in his basement for seven years before we put it all back together and I bought it. But while tightening one of the center bolts beyond 20 ft lbs it had an almost rubbery feel as if the stud was stretching (none of the others felt like this).  I even stopped and called the guy I bought it from to see if this was how he ran into the original problem.  He said no, that he discovered it had given out while changing the spark plugs one day.  Anyway, I went back and got it to 25 ft lbs and it's been OK ever since - and this was several years ago.  But it does cause me to wonder if there was a quality control problem with studs used in the first engines. 

[CutterBill]

Hmmm... I'm gonna take a guess and say the studs are pulling out of the case. Some knucklehead in the past either over-torqued the nuts or seriously over-heated the case. Cast aluminum isn't very strong to start with, and it doesn't take much heat to make it lose it's strength.  But an easy fix...

Remove the engine, head, cylinder block, pistons and all the studs. Then install Heli-coils or Time-serts in all of the stud holes. I say all of them because, if one is bad, they're all bad. You can either take the engine to a machine shop or do it yourself, depending on your aptitude and finances.

And your torque wrench has been calibrated within the last few years, yes?  In that regard, the old bending-beam wrenches are the best.  Hard to read but they never go out of cal.  Good luck.
Bill

[FJ_Hooligan]

I don't recall this being a common problem?

In fact, this is probably the first I've read of it on this forum.

[fjbiker84]

I'll check the torque again next time the tank is off the bike. I don't think I'll worry about it unless one of the studs does pull loose.  According to this engine builder FJ engines do need these bolts checked periodically and I do remember him saying that race engines had to be re-torqued after each race.  So maybe it's not anything to be alarmed about. 

[fjbiker84]

This is the website where the instructional video on tightening your cylinder head bolts was.  That video doesn't appear to still be available although there is a comment on it.

http://www.rrcperformanceengines.com/info.html

[Pat Conlon]

If you do them one at a time, you don't have to worry about a tightening pattern.

Randy strongly suggested checking the head nuts for 25ft.lbs on the new RPM 1380 cc engine at 1,000 mile mark and I'm glad I did...
Using a beam style torque wrench I noted that several head nuts broke free at less than 10ft.lbs.
This engine has a bit more compression @ 10.5-1 than the oem FJ engine.

After the initial 1k mile retightening, the head nuts seem fine in my follow up torque inspections.
I'll still keep an eye on them.