My Winter Project

About a month ago I read an article on RevZilla Common Thread by Andy Greaser about bringing an EX-500 back to life for the purpose of riding it at something called the Reliability Rally. The Reliability Rally is a weekend event of people who have spent less than $1,000 on their bikes. The article was interesting enough but I didn't think about it any further. Until 2 weeks ago. Andy posted a follow-up story about the Reliability Rally itself. I read the article and said to myself "these are my people". I immediately started a quest to find a bike that would fit in (my current customs fit the description, but their expensive modifications don't seem in keeping with the spirit of the event). I'll put a link to the articles below.

I started looking on Craigslist and FB Marketplace, as well as a few of the auction sites where you can get rideable wrecks with salvage titles. I didn't have anything in particular in mind, but as I saw bikes in the sub $1,000 (or near enough to it) I thought to myself "would I want to spend a weekend on that thing". That eliminated every bike that put my legs/feet in the birthing position. I was kind of thinking Bandit or Katana 600, air cooled Honda or maybe an early Hurricane 600. I did see an FZ6 with impact damaged forks and thought "R6 conversion"...but I thought the frame might have some hidden problems. Then Friday night I saw on Craigslist a bike that I would never want to own in a thousand years - but it looked so right. It spoke to me.

The bike is an '81 Honda CB900C. The CB900 was Honda's first DOHC engine (also released at the same time were the CB750 & 1100 DOHC bikes) and replaced the decade old design that started with the CB750 SOHC. But the CB900C is an oddity. It was designed specifically for the American market, and was intended to compete with factory "customs" from Suzuki and Yamaha (GS850 & XS850). These bikes had shaft drive and Honda too felt that it's new air-cooled flagship should have shaft drive. But Honda didn't want to invest too much into the design because the water cooled CBR's were already in design. So they cobbled together a system that would provide a shaft drive...to the right side of the bike. In doing so they also created a hi/low gear box that could be shifted on the fly - essentially giving the bike a 10-speed gearbox. The system proved to be robust, and it allowed the bike to have a significant mpg advantage over its competition. It also added 100 pounds to the bike. Also odd are front & rear air suspension (sharred with the GL). At 600 pounds it's a big bike...and it's long too. Anyway, the photo's caused me to click into the ad.

The ad stated that the bike only had 35,000 miles, but noted that the front brakes were inoperative, that the engine smoked and that the air suspension didn't hold air for long. Sounds good to me. Also a big plus, the bike was just 3 miles from me. On inspection I saw a bike that had lived an easy life, but maintenance wasn't the owners forte'. Yes, the front master cylinder was indeed inoperative. The rear tire was the wrong size (it was rubbing on the right side swingarm/driveshaft cover). It started and ran great - even on old fuel. I didn't note any smoke on start-up, but I did hear a cam chain that was in need of adjustment. "Would you take $500?" “Sure”. I told the owner that I needed a day to think about it and to look up how to resolve the issues I observed. I was most concerned about the unobserved smoke. Doing some research showed that these engines smoke for the same reason as any other engine; a head gasket leak or stuck rings. Since there was absolutely no smoke on start-up, that eliminated a valve seal. Also, the engine ran so smoothly that I couldn't believe that one or more of the cylinders wasn't firing. I'd rather swap a head gasket then rebuild a head...so I'm thinking "yes".

I went back Sunday afternoon to pick-up the bike. I made sure that I started it myself, and it started even better after being run the day before. No smoke. I let it fully warm up and didn't observe any smoke. Great. So I handed the gentleman my money and off I went. Given that I knew I didn't have front brakes I had my son (who drove me there) follow about 100 feet behind. I was gonna take my time getting home. The three roads I would need to ride on are sparsely traveled with 35 mph limits. The rear tire was rubbing so badly that brakes weren't necessary. Every time I let off the throttle the bike came to an intimidate stop. After a mile of riding I could smell smoke. I looked in the mirror and I could see smoke. I thought it might be from the rear tire. I had to give this (smooth running) engine quite a bit of throttle to keep it moving. Just a mile from home I turned on to my street. A quick check of the mirror showed a cloud of smoke like I had never seen before. Holy smokes, this thing smokes. I made it up my driveway and pulled right into the garage. Oil was pouring onto my garage floor...not dripping. The head was dry, but the #1 cylinder was drenched in oil. Clearly, this bike needs a head gasket. The rear tire was in fact smoking too. Also smoking was the rear brake - which was also locked-up. And I'm ok with all of it - these are all simple (but involved) fixes. For the 10 seconds this bike was running in my garage, the fog was think and breathing was not possible. I actually had to go take a shower.

Here's my theory on the head gasket leak. The rear tire should be a round profile 130/90. This bike has a square profile 140/90 (Engager by Kenda). It has obviously rubbed on the swingarm since the day it was installed. This tire looks well used, so I'm thinking that under light loads, the engine is fine. But the way this tire rubs, it has to overcome significant drag - imagine if the bike was pulling a 3,000 pound trailer (I'm not kidding it's that much drag) - requiring 1/2 throttle just to go 30 mph. That's what blew this head gasket.

I will disassemble the body parts, degrease and powerwash the engine and frame, and then begin tear down of the engine. My Clymer manual will be here tomorrow. So that's my winter project.

That's a GREAT fixer upper!

And a keeper too

I would read weekly updates of this story. Great opening chapter!

I didn't even look at the bike for a few days. I found out that replacing the head gasket requires that the engine come out of the frame. Not such a big deal, but the engine weighs 260 pounds. So it would take a hydraulic lift and an engine stand. I went on line to see how others supported the engine hoping to find a cool cradle made of wood. I was also watching how-to videos on YouTube to see what was involved in replacing a head gasket. Somewhere in those videos someone mentioned that head gasket leaks do not result in external oil leaks, and he suggested to look elsewhere, like the valve cover gasket, the cam chain adjuster, the tach drive...And then I started thinking...

The reason the #1 cylinder was wet was probably because I put the bike on it's side stand. Hot oil is gonna flow.
Also, if it was the #1 cylinder, then why did I see smoke from all 4 exhaust pipes?
And, this bike was clearly firing on all cylinders. The engine is silky smooth.

So maybe the two problems aren't related. Here is what the front of the engine looked like this morning:









Today I felt like I had given the potential problems the right amount of thought. The first order of business was getting the bike so I could push it. The rear tire is supposed to be a 130/90 and have a maximum width of 5.15 inches. At this width there is about 1/4" of space between the tire and swingarm. The installed tire is a 140/90 with a width of 5.85. It rubs badly. It also has a date code of 2003 - so it's getting changed. I took a utility knife to it so it would no longer rub.



The rear caliper was also locked up. So I removed the pins and tapped the caliper off with a dead blow hammer.

With the bike now able to be rolled I pushed the bike outside and grabbed two cans of engine degreaser and soaked down the engine and carbs. While that was doing its thing awaiting a wash down I emptied the fuel tank. The fuel that came out looked like your pee would if you slept for 16 hours - dehydrated. It was pure varnish (the bike was last on the road in 2013). I can't believe I was able to start and ride this bike home on that stuff - it says a lot about those old Hondas.

With the tank empty I power washed the engine and then hand cleaned as much oil as I could off the engine. This was clean enough to see an oil leak:







I put the battery on a charger, and then removed the spark plugs. Finding number one; the plugs showed no signs of burning oil. Nice and clean. Interesting.

With the plugs back in and the fuel tank installed I put a few gallons of AvGas (100LL) into the tank. After the engine lit off I let it run for about two minutes and shut it down. This is what I found:





There it is - finding number two. That bolt was loose, by almost 1/4 turn. I snugged it up and ran the engine for another two minutes - no leak.

And what I perceived as oil being burned by the engine, was actually oil flowing down the exhaust pipes and burning off.

This engine runs great. It will run even better after I clean the carbs.

Onto the brakes....

That's not an automatic oil changing set up? Just add oil?

You got real lucky on that leak!

It's still leaking. After another round of cleaning and observing, I have found the location of the leak.



If you look at the right threaded stud, it's wet. Whereas the left is dry...and dirty. Not good. So, I did a compression check on the engine and all 4 cylinders are at the factory spec of 170 psi (not bad for a 40 year old bike with 35k miles). I don't have a blown head gasket, just one leaking at a stud. What has probably happened here is that the stud has stretched, and now it is under torqued. I was going to open the valve cover anyway to check/adjust the valves (shims on this engine) so what I'm going to do is back-off each of the head nuts (in the tightening order) half a turn - one at a time, and then retorque them at +10%. This should ensure all are properly torqued at the same vale, and it should reseat the copper/steel crush washers.

In the mean time it was time to assess the brakes on this bike because, it doesn't have any. The front lever is frozen and so is the rear caliper. This "might" be the reason for the frozen master cylinder:



I was able to score an entire (working?) front brake system on eBay for the cost of a rebuild kit. Bonus - the left front caliper is the same as the rear, so in buying the front system I got what I needed for the rear. My front calipers work fine and so does the rear master.

With the parts bagged and tagged I was curious about the chrome on this bike. It’s showing it’s age, but it looks ok. The before and after photos below are after just 30 seconds of 400 grit (wet with WD-40) and 30 seconds of 00 steel wool. Not bad. After a bit of Noxon polish the chrome on this bike will look as good as new.









I’m starting to bond with my machine.

Gollllly! I ain't NEVER seen no one use puddin' in the brake fluid reservoir!

trepetti said:

Gollllly! I ain't NEVER seen no one use puddin' in the brake fluid reservoir!

Click to expand...

And whipped cream too.

Just for fun, I shot it with brake cleaner and then placed it in boiling water. DOT 3 is water soluble, so it actually cleaned up quite nice.

I have been up and down with this oil leak problem. I removed the valve cover gasket and retorqued the head bolts. While in there I decided to check the valve lash. Like the FZ, this is a shim on bucket setup. I had to wait a week for shims...and after the shims arrived I had two valves that were still a little tight...so a week later I was ready to button it all up and see my leak free engine. One last step...adjust the timing chain. In this engine the exhaust cam gets the chain from the engine, and there is a second chain that drives the intake cam. It's simple, loosen the holding nuts for each cam chain tensioner (one in the front of the head, two behind the cylinder) and the springs on the tensioner removes the slack. WIth that done I installed the valve cover gasket and started it up.

My first thought was "damn, that cam chain is noisy" and then about two minutes later oil began rapidly dripping into the pan I placed under the bike. My next thought was F**K!

It clearly isn't the head gasket that is leaking. But it could be one of the washers under the #2 cylinder stud. I also decided to check the condition of the o-ring under the cam adjuster. I didn't check this originally because 1) it's over by the #3 cylinder and 2) I don't see a visible path of oil. But I checked it anyway and here is what the o-ring looks like:



As you can see, it's no longer an o-ring - it's a broken piece of plastic. Pretty sure that's the source of the oil...even though I can't see how it gets all the way over to #2.

I removed the valve cover gasket to make sure that the cam chain tensioners are actually moving when the holding nuts are removed. On the CB900 forum it suggests giving them a nudge to get them to move. Now knowing what to look for I looked at the primary CCT and could see that it is at the end of its travel:



That circled item is what is known as the blade. That inner part is supposed to be 1/4" to 3/8" above the outer part. When the inner part is even with the outer you should consider changing the CCT and when it's below, your done. I pushed on it hoping to gain a 1/16 of an inch...but got nothing. It's done.

Now what? Button it up and try to unload it? Button it up and ride it until it dies? I went through the common stages when confronted with such a reality; denial, anger, bargaining, depression, and finally acceptance - this needs to be done right, or I need to cut my losses. I'm not one to walk away from a problem, and I feel comfortable getting the head and cylinder bank off - but splitting the case scares the hell out of me. But I'm gonna do it anyway. I've watched a number of videos of people tearing down and building up these engines. I feel confident doing this...until something snaps or breaks.

My other justification is this gives me a good opportunity to get EVERYTHING cleaned and polished. I'll start disassembling the bike this weekend.

I just looked on Partzilla and none of those chains are available..
Did you already check around and see if the parts you need are available?

Interesting set up re the chains, guides and tensioner:
https://www.partzilla.com/catalog/honda/motorcycle/1981/cb900c-a-900-custom/cam-chain-tensioner

There are plenty of crappy reproductions everywhere. But there is a company in New Zealand by the name of Vince and Hyde that makes performance parts for the CB750 & CB900 DOHC engines. Their CCT is an improvement over the OEM as it removed the harmonic oscillation from the system, providing more accurate cam timing and longer chain life. They also sell a chain that is made by the same manufacturer that Honda used in Japan. The owner (Brent Mopar) is a former CB750 racer. Anyway, those parts are expensive, but if I'm going that deep into the engine, I'm only going in once.

Buy once - Cry once.

So, the engine is out and apart.



And I was able to learn exactly why I had a massive oil leak. I already knew that the previous owner wasn't big on the maintenance. It would appear as though he was down-right negligent. I'm thinking that the timing chain was never adjusted. It was slapping wildly. All of my attempts to adjust it were for naught because the CCT was broken.



The reason they break like that is because the chain is allowed to get so loose that it starts slapping the CCT. Once the CCT was broken (you can imagine how noisy this engine was) the chain went slap-happy....hitting everything in its path. Oh, it cut a nice hole in the cylinder assembly too.



Luckily the cam tunnel is not adjacent to the #2 cylinder. There are cooling passages between the two, so this hole is vented to the exact area where I saw the oiling coming from.

I'm not a big fan of JB Weld, but this is a perfect candidate for a dab (ok, a slab) of that stuff. The original formula is the best (according to Todd at Project Farm) and is good for 550F. Cylinder heads usually reach around 350F, and this is no where near a cylinder head, so it probably only gets to 200-250. I've got both grooves cleaned up and will do the repair this weekend.



Once repaired I'll split the case and replace the timing chain. I'll have to remove the crank from the engine to replace the chain, so I'll go the extra step of removing the con-rods to inspect all bearing surfaces. This chain made a lot of metal (there was a lot in the oil filter) and I suspect there might be bearing damage as well.

This is a great project - I'm learning a shit-ton...the hard way.

Gary in NJ said:

This is a great project - I'm learning a shit-ton...the hard way.

Click to expand...

That's the great thing about this forum and it's members! We're all learning a shit-ton!

I repaired the damaged cylinder assembly. I tapped off everything that I didn't want covered in epoxy and then scored it with a utility knife to give the JB Weld a good surface to bond:



Then with a gloved hand I pressed the JB Weld into the crack until I saw a nice extrusion on the other side of it, and then used some extra wide popsicle sticks to smear it and smooth it. With the goop still wet I carefully removed the tape, and voilà:





With both grooves filled I decided to give the head some love (man...that sounded weird just typing it):

Before


After


I decided not to disassemble the head. The compression is spot-on, and I didn't feel the need to potentially make things worse. Good enough is good enough. However, with that said I'm kind of torn on what to do about the upper half of the case:




I've got the gasket surface clean (but not yet polished) but the failed clear coat on the case is really bothering me. I've got three choices:

1. Do nothing and live my life like a normal person,
2. Remove the damaged clear coat and lightly polish it. It will look good, but will require maintenance polishing from time to time,
3. Remove the damaged clear coat and prime/paint the surface.

I am really fighting the urge to restore the bike. I don't want to. I just want to rehab it. I'm not intending to fully disassemble the case, just remove the conrods and bearings caps so I can inspect the bearings and slide the new timing chain into place. If I can keep it that simple, I'll probably reassemble the engine and remove the failed clear coat with 3" scotchbrite sanding discs on my diegrinder, and then sand it with 400g, then 800g and then lightly polish it (maybe 4 hours of work). I just can't look at that case and live my life as a normal person. If however I end up removing the transmission...it's getting painted and put in the oven to cure. At that point it becomes a full on restore.

I really hope that lower end needs minimal work. I'll know by the end of the week.

Once the case is split, the drivetrain is removed with minimal effort. Knowing that it would be near 70 degrees out today I stripped the old paint, tapped it up, cleaned it, shot it and baked it. This was the right thing to do.









I’m very close to reassembly. I did order some main bearing shells because four (of the 5) of the lowers were showing copper. I decided to replace them all because I’m not going back in. The piston bearings looked great.



While I’m waiting for the parts to arrive from the UK (CMS) I continue polishing the engine covers. Now that the engine is painted, it all has to look good.

Looks great but what is a "piston bearing"?

Big end connecting rod bearing perhaps?

Yup, conrod

How's the spark plug fluid, need changing?

TownsendsFJR1300 said:

How's the spark plug fluid, need changing?

Click to expand...

Silly, everyone knows it’s the blinker fluid

The lower half of the engine is reassembled and the top half is ready to install.





I used a ultrasonic cleaner to freshen up the pistons which worked great.





A little 1-minute rub with a brass brush and some WD-40 was all it took to remove the stubborn carbon.

I should have the cylinder and head reinstalled this weekend.