The International CBX Owners Association

I sent my bike to have the carbs tuned on a dyno with a sniffer, and while the power number looked quite good, the dyno room was filled with blue smoke. Compression looked OK, but a leakdown test showed problems with some of the valves and most of the rings.

So, this winter it's coming apart for a refresh.

I contacted the last person to have that engine apart, and he said that when he rebuilt it, the head had damage in the lifter bores - caused by a ham-handed Honda tech who worked on the engine earlier.

What I want is to do this work once. I like the idea of sending the whole engine to Bill at TIMS and getting back something that looks & works like brand new, but while I think it's absolutely worth every penny he charges, that's more pennies than I have to throw at the engine of this bike. It's a rider, and I can live with the visual imperfections on the outside as long as I get the inside taken care of. So I'm planning to compromise - have the rings & cylinders (hopefully not pistons & rebore) done locally, and have the whole head assembly redone by Bill. I'll know more when the engine comes apart, which should be soon before my local mechanic closes for Christmas.

This thread will document what is found in the engine, and the decisions I make in getting it to the same standard as the rest of the bike (which is working very well overall these days). I'll also solicit some advice about what to reuse, what to replace, and what to upgrade.

My goals are rideability and dependability, so I intend to stay as close to stock as possible. If this engine can be built to go another 20 years / 80,000 kms (with regular careful riding and maintenance), that would be awesome.

With that said, I can tell you that it is taking a physical effort on my part to keep from going to shim under bucket and a hotter set of cams. But that's Stupid Phil just messing with Rational Phil. Stupid Phil usually wins some battles here and there, I'm just trying to keep him from winning the war so Rational Phil has some money left for gas when all this is done.

While the head is off and being tended to, are there any mods or upgrades that should be done? I'm thinking Viton seals for sure, maybe new valve guides, possibly new valves. The bit of research I've done suggests that there's not much to be gained from porting, and I don't really want to bump compression - but I'm open to suggestions on this stuff.

What can be done to a head, that you cannot do yourself? If you don't want it ported and flowed, all it will need is a thorough cleaning off of the carbon deposits, new valve stem seals and the valves lapped for seating. All DIY stuff. If you are concerned about the lifter bores - if a ham-fisted guy was at them, I would assume the lifter buckets are not matched to the bores as they should be - I would buy a good used head for $300.- and do above work on that. The only thing to add to it could be a bit of planning to make sure it is flat. Be aware of any claims that s.o. is doing "performance work" on the head. You may get taken. I had a head ported and flowed by a friend who did heads for a race team and he told me the job would have cost me $1,000.-

Thanks Mike. I want to send the head to someone experienced with the CBX. Even if there's very little with the head that's specific to the CBX, I want it done by someone who's done it a bunch of times before and who knows what looks/feels right and what doesn't.

I am assuming that I'll want a replacement head & buckets, but want confirmation of the current condition first.

I rode the bike for the first time since the diagnosis and in retrospect the signs of bad rings were there for a while - it's very hard to start when cold, and smokes on startup. I used to attribute both issues to carbs as I thought I was tending to flood it when getting it started from cold, and I thought that it was black smoke on startup, not blue. By luck, when I started it last week I happened to have a tailwind and there was no doubt that it was blue/oil smoke. Now I'm embarrassed about not noticing it before.

It's funny, I've always wanted an RG500 but my conscience wouldn't let me get one. It seems like I could have had one for the last few years and not been a worse polluter.

Anyhow, it should be going into my regular shop later this week so that they can get it opened up before they take their Christmas break.

How many miles are on your engine?

cross wrote:How many miles are on your engine?

According to the seller, it had about 100,000 km on it when it needed a rebuild due to the cylinders being out of round. At that time, it got 0.5mm over OEM pistons and the cams were degreed. Sometime before that is when the lifter bores were supposedly damaged by a Honda tech.

That rebuild was done almost 20 years ago, and it's had plenty of time sitting still since then, plus about 19,000 km from the previous owner and an embarrassingly low 5-6000 km from me.

I suspect that the problems are more a result of sitting than usage. If there was some corrosion on the cylinder walls, that would cause problems with the rings. I believe that the valves may be sensitive to similar kinds of issues.

I bought my bike with 22k and it was also sitting about 7 years. It was smoking when started it first time but now I have about 28k and it only smokes when revved cold. I was thinking of pulling head and block off and checks things last winter but bike runs great, it doesn't burn very much oil and compression is 140 on all so I'm rethinking that idea. I know that valve seals are probably dry but once I decide to do things I'll do the whole thing.
This winter I'll be checking my steering and swingarm bearings and change my brake hoses to braided ones and at the same time rebuild calipers and master cflinders and perhaps gold valve emulators in forks, plenty work for short california winter season
Good luck on your project
Sasha

cross wrote:I bought my bike with 22k and it was also sitting about 7 years. It was smoking when started it first time but now I have about 28k and it only smokes when revved cold. I was thinking of pulling head and block off and checks things last winter but bike runs great, it doesn't burn very much oil and compression is 140 on all so I'm rethinking that idea. I know that valve seals are probably dry but once I decide to do things I'll do the whole thing.
This winter I'll be checking my steering and swingarm bearings and change my brake hoses to braided ones and at the same time rebuild calipers and master cflinders and perhaps gold valve emulators in forks, plenty work for short california winter season
Good luck on your project
Sasha

I'm in the same boat Sasha, my bike smokes on startup and when cold, runs great, but uses very little oil in fact. Compression is north of 150. I'm leaving it alone .

You might want to give Scott Miller from Fast a shout. My friend worked with him for years building motors for the CBSK. He told me he'd be the guy to send the motor to if I ever wanted to pony it up. He knows all about the CBX motor. He's a local guy too. For the amount our dollar has taken a shit kicking, it might be a good call.

Let us Ontarioans know if you do contact him.

http://www.fast-company.ca/the-company.html

akinz wrote:You might want to give Scott Miller from Fast a shout. My friend worked with him for years building motors for the CBSK. He told me he'd be the guy to send the motor to if I ever wanted to pony it up. He knows all about the CBX motor. He's a local guy too. For the amount our dollar has taken a shit kicking, it might be a good call.

Let us Ontarioans know if you do contact him.

http://www.fast-company.ca/the-company.html

Yes, I've talked to Scott - he's the person I referenced in my first post as "the last person to have that engine apart". I believe that both he and Zaid at Z1 are top-class engine builders. Both have CBX experience, and Scott has experience with this specific engine. But what I've decided to do is have the project run by Cyclewerx in Toronto - they've been my primary shop since they opened about 10 years ago and I have a good relationship with them. They take care of me, so I want to keep taking care of them. But I want the head looked at and prepared by someone who only does CBX stuff. This will mean extra expense in terms of shipping and exchange rate, but I don't want to have lingering questions about the state of the head or valvetrain (including the Oldham couplers) after this winter.

For my own reference and any reader interest, here are the compression & leakdown numbers:

Cyl 1: 145, 14%
Cyl 2: 150, 5%
Cyl 3: 150, 7%
Cyl 4: 160, 4%
Cyl 5: 145, 15%
Cyl 6: 150, 15%

I was told the breakdown between intake, exhaust, and rings on the leakdown on the phone, but just remembered the conclusion that it needs rings and valve work. The written notes on my bill just had the above.

The compression #'s are consistent with an earlier compression test done by a different shop, and they don't look so bad on their own. I think that this is also consistent with the decent power numbers it made on the dyno. But half of the cylinders leaking down at ~15% is concerning and also consistent with the hard starting and excessive oil consumption.

Today Perry hit the shop - I managed to ride until Dec 10 without ever putting on my heated gear - although my frozen fingers were unhappy by the end of this morning's short ride...

Next week the head will come off and I'll ship the whole head assembly to Bill at TIMS. The local shop will pull the cylinder block and figure out if it needs a rebore or if a hone & new rings are enough.

In addition to addressing the rings, valves, and lifter bores, the items on the agenda this winter include:

1. Ceramic coating of the ratty-looking but solid exhaust.
2. Another cleaning of the carbs, might also send them to TIMS or Mike Nixon.
3. Some rerouting & tidying of the wires.
4. Dyno tune with sniffer in the spring.

Yesterday I went and picked up the head assembly and brought it home to pack & ship it. It was a tough call between lugging it home on the subway vs. trying to hail a cab and ride across Toronto during the height of rush hour. Since I like physical exertion and hate paying money to sit in traffic, I opted for the subway - which meant carrying that heavy bastard about 1km in total - at least it was boxed so I didn't get filthy. There's a lesson here - sitting at a computer all day every day makes you about as strong as you might think.

Visual inspection of the cylinders with only the head off suggests that it'll probably be OK with just a hone and new rings, but of course it'll be measured to see if an overbore is required. I'd rather not spend the money on an overbore, but I'll admit that the thought of getting a bunch of shiny new pistons is kind of exciting. The mechanic reported that there was some carbon in the combustion chambers, but not necessarily a problematic amount. I'll take some pics before I pack it for shipping to TIMS.

Note that none of the numbers are really concerning on their own, but taken together with some hard starting when cold, the excessive oil consumption, and the blue smoke observed from the tailpipe during the dyno test, I'm proceeding with this refresh in the hopes of having a better & cleaner-running engine.

Head assembly is on its way to TIMS. Here are some shots of the head:

Combustion Chamber:



Exhaust Port:



Exhaust Valves:



And one semi-artsy photo just because we all love these things:



I'm no expert, but to me this looks consistent with the oil consumption. Thoughts?

I just got off the phone with Roger Twito, Bill's machinist & engine guy. He said that from visual inspection the head doesn't show any obvious signs of trouble, except the white exhaust valves suggest some lean running - which is consistent with the sniffer results.

He's gonna get it apart and see where we're at with the valve seals, guides, seats, and lifter bores.

Well, that head's not coming home. The guides and seats are in such rough shape that he recommends replacing the head. He said that the lifters look OK and there's some galling in 4 of the lifter bores, but the big concern is the guides & seats.

If I had some emotional attachment to the head, or had invested in porting or skimming it already I'd go with repairing the current head, but as it stands, we're gonna start from a fresher assembly.