engine rebuild

[Andrewsteward]

The time has come (and ive found some time) to freshen up my 81 model and any advice would be helpful.

The compression is down 110 each side and although still runs fine, the fuel consumption is down and just that general feeling in need of a overhaul.

As im going to do a more major overhaul in a couple of years, I was wondering if I could get away with just a set of rings ?( I know this is impossible to tell until its pulled down but generally speaking). its got about 120k on the clock.

I was hoping just to lift the compression a bit and do a proper overhaul later.

or

Do I just order complete piston kits and then its done. Im only asking this so I can pre order parts as I only have a week or so as this is my daily ride.

thanks

[Bob_Roller]

You should have Nikasil cylinders, so there is only one size for replacement piston rings .

If you can get a good look at the valve faces to see what they look like, the '81 model year bikes, were the worst for valve recession, especially the exhaust .

[montmil]

With the Nikasil cylinder bores, you will use the soft iron piston rings.

Besides ordering the new rings, add in the required O-rings that go between the crankcase and the cylinder base. One large and two small o-rings each side. New head gaskets and maybe fresh rocker cover gaskets.

As the cylinders must come off, this will also be an excellent time to replace the pushrod tube seals. If yours are OEM vintage 1981, you'll be happy to freshen them.

Many Airhead owners will use just the lightest little smear of a gasket sealer such as Yamabond or the Suzuki equivalent on the crankcase base, avoiding getting any sealant in the upper cylinder studs as this is the oil passage for lubricating the rocker assembly.

Consult your shop manual for the proper sequence for snugging down the six nuts -4 cylinder and 2 rocker arm- and use a torque wrench. Something like 8 /11/23 lb/ft but nothing over 23 as you'll risk pulling a stud from the case. That's big $$$$ repairs. Re-check torque after the first 100 miles or so.

Keep the left n' right components together. No mix n' match wash and wear.

Ask question here before you get in a difficult spot. Digital photos during disassembly are gold.

I've probably forgotten a few items. Read the workshop manual. If you don't have one, buy it.

[Justin B.]

Pay attention to push-rod tube seal orientation (there is an "up" side) and I put synthetic motor oil on the tube, slide on the seal, and a light coat of gasket sealer where the seals contact the block.

[Mike V]

Andrew,

Here's a few photos of my 81 top end job to familiarize yourself with what to expect.  I would refresh the entire top end if you can, and if it's needed. $$$ I would definitely have the valve seats updated and replaced along with valves, guides and springs. Our 81's as mentioned are very susceptible to valve seat recession.

Disassembly;
http://tinyurl.com/p87byb7

Assembly (Rt);
http://tinyurl.com/kdme3ue

Assembly (Lt);
http://tinyurl.com/k8qdhlt

[Bengt_Phorqs]

Great photo series Mike.  Your work area is so pristine.  How did you get the cases and cylinders to spotlessly clean?

[clonmore1]

Hi Mike,

Looks like the OR, not a garage!

Brilliant series of photos, every time I look at them I get inspired...

Great job.

Chris

[Andrewsteward]

wow, Mike that photo sequence is insane. Thanks so much. How did you get the components so damn clean?

Appreciate the tips guys. Will be taking them all on and certainly have a close look at the heads.

Ive got a full gasket kit already so will indeed change out all gaskets n seals.

[Mike V]

Thanks for all the kind comments. I'm very pleased the way the bike turned out.  Cleaning the cases on our bikes is no secret.  It takes a lot of time and labor.  I spent more time than I want to admit getting the cases looking nice.  I started with a pretty miserable conditioned bike.  This bike was stored at the water's edge unprotected and uncovered at the San Diego Yacht club for many years before I obtained it so you can imagine the rust and corrosion that had built up.  I tried a pickup full of chemicals and processes - with little joy.  To make a long story short ... what seemed to work best in my case was to fully clean and degrease the aluminum with Brake Cleaner then work small areas with moderate pressure scrubbing with SS and brass brushes, and scotch brite pads, rinsing often with Brake Cleaner.

I considered paint, and coating with Rubb'N'Buff but didn't want interfere with the natural finish.  My big objective was not to "polish" the natural porous finish of the casting.

Different variations seem to work for different people.  You will hear a lot of different opinions from different folks.  My only advice is to experiment in low reveal areas to see what may be best for you. And don't be too aggressive to disturb the original finish.  I'll probably paint the next loser project I do. (seriously).

My biggest challenge was the transmission case. Our bikes have different casting materials (metallurgy) for different components, engine cases are different than transmission cases, etc.

Give us some comments on what works best for you - I'm still looking for the quick and easy way to get our castings looking like new.    

[clonmore1]

I have had mine aqua blasted once they were all apart, the finish (for the short term anyway) will look fab, just need to find a way to keep them that way...

[Mike V]

I neglected to mention any media blast procedures.  Some work very well but the only experience I have with my project regarding media blasting was what was performed on my cylinders and heads when I sent them to Ted Porter to have the valve upgrade work done.

I considered blasting but not on an assembled lower end.  I didn't want the possibility of internal contamination.  I've been hearing of some new blast processes using ice and the process Chris mentions with good results.

I did experiment with soda blasting for smaller parts such as perches and the transmission.  That turned out to be more of a post process clean-up chore than it was worth.  The soda blasting did nothing for the deep contamination I had on my casings.  It did remove grime, grease and paint effectively.  But the mess it caused in my opinion was not worth the effort without a dedicated blast cabinet.

[Andrewsteward]

And should I be ordering valve guides and seats?
I know it seems crazy to pre order parts before even pulling it down but am trying to limit time off the road.

[arvo92]

Valve guides + seats... hmm... I have had the same question.

As far as I have got the question at hand (please, correct me if I am being wrong) is that the valve seat recession appears when unleaded gasoline has been run through the system. The lead in the gasoline was what kept the valve seats happy. When they switched to unleaded is what brought problems for older R65's. I am putting lead substitute to every tank fillup and hopefully that does the trick. But the substitute is not the cheapest so if you are riding high milages, at some point getting new valve seats + getting the specialist to do the job will pay off. But that pays off for about 400 fill-ups or? That would be my rough guess.

My guide in life is not to fix things which are not broken. So if the valve seats are fine, add lead subsitute and you'll be good.

[Mike V]

Andrew,

Here's what I would suggest, you can take that with a grain of salt.  Before jumping into this I would do a Leak Down test to try and determine a better diagnosis of your compression loss.  Let me back-track a moment...
How did you perform the compression test?  Warm engine?  Carbs removed? Fully charged battery?

A Leak Down Test will tell you whether the rings, intake or exhaust valves are your problem.  If you don't have a tester - you may ask around for help nearby from someone who has the equipment.

But to answer your question I see no need to do a partial valve job if in fact you need a valve job.  If you're going to go in - I would replace valves, seat, springs, guides and keepers. I would assume you're going to farm this work out to a reputable shop who is knowledgeable for this particular work.  My experience is with Tom Cutter or Ted Porter.  There are others out there but I have no direct personal experience with anyone other than Ted or Tom.  If so I would contact the person you choose to do the work and get specifics from them regarding shipping and ordering of parts. Valve seat replacemnent and head work is a specialized job requiring knowledge I don't have. I'm unaware of your skill set but if you aren't versed in this work I would recommend finding someone who is. I normally like to send out the entire top end, including pistons, rings, cylinders and heads well marked in their original order "Left" and "Right".  This is not the cheap way by any means, while you can expect a total top end job to run in the neighborhood of $1k depending on what you have done.

But before taking the jump and getting into "mission creep" I think a Leak Down Test would answer a lot of your questions and lead you to any current problem.

Just my opinion.  Let us know how things go.

http://tinyurl.com/k8tfkph

[Andrewsteward]

Thanks Mike. The comp check was done warm but with the carbs on, so I will re-check and do a leak down check as suggested.
I am a mechanic by trade though will be out sourcing heads if they do in fact need seats and guides replaced. I am in Victoria, Oz so am looking now to find a descent shop to do this. At hits point I am thinking whilst its apart to do a proper job on the heads as theyve done quite a few K,s on ULP.
Will keep you posted.