Engine needs a refresh - make that a big bore!

[Mouse]

Just the sort of news I hate getting when any of my vehicles is in the shop.
Hey! those 3 scrap pile ebay CBX's for sale (see other thread) may have a good head amongst them.

[Syscrush]

Just the sort of news I hate getting when any of my vehicles is in the shop.
Hey! those 3 scrap pile ebay CBX's for sale (see other thread) may have a good head amongst them.

Bill has a supposedly good head assembly. If they find problems, Louis will hook them up.

I'm not so concerned about the head, it's not a huge additional expense - my concern is that this might mean that the bottom end needs to come apart, too. I've asked the local mechanic to pull the oil pan and do a careful visual inspection.

[Mouse]

my concern is that this might mean that the bottom end needs to come apart, too.

eeck!
I know that feeling.

[Syscrush]

The inspection of the bottom end, pistons, and cylinders all look good. Apparently the engine had +1mm Honda pistons, not +0.5. I have found some new +1mm Honda rings, but they're only $400 less than a big bore kit. So I'm a bit torn. Doing the big more would mean incurring the additional cost of boring the cylinders, plus the $300 extra for the pistons & rings. But then everything would be fresh and new, which is very appealing.

The flip side to that fresh newness is that the greater displacement and higher compression means more potential stress on the engine. The candle that burns twice as bright burns half as long... But of course I don't spend a lot of time at WFO, and I have an upgraded oil cooler, and I always run premium gas anyhow (to get the stuff with no ethanol), so that concern is mitigated somewhat.

Decisions, decisions...

[Syscrush]

OK, it seems like someone spoke too soon. During or after the honing process, it was discovered that 2 of the cylinders are not good. So I'm going the big bore route.

[steve murdoch icoa #5322]

Too bad on the engine, Phil.
Have you been able to determine when all the "damage" happened. Hard to believe it would have a been a bad install from Scott.

As you have no doubt researched, many people are happy with the Cruizinimage kits.

[EMS]

Phil: the 67.5 bore cruizinimage kit that is widely available has a compression ratio of 10.05:1. Don't believe if someone tells you it is stock compression.

[Syscrush]

I'm going with the J&E kit from TIMS - I like to support vendors that support the CBX. I'm going with the lower compression option of the 2 that are available. It's called "STD COMPRESSION", but I don't know if it has less dome than stock in order to preserve the stock compression ratio, or if it's a stock dome shape.

[Syscrush]

Have you been able to determine when all the "damage" happened. Hard to believe it would have a been a bad install from Scott.

Hey Steve. We'll never know for sure, but here's my thinking:

The valve guides are just normal wear from use - the engine had a ton of miles on it, and the guides were not replaced when the engine was rebored.

The valve seats I expect were hurt by lean running. It would go quite lean at part throttle as I had it set up, and that's after I had it fattened up a bit with a jet kit - and I put the airbox lid back on (PO ran without it).

As for the damaged cylinders, I think it was a combination of getting very hot a few times when I was stuck in stop & go traffic, and probably some oil starvation before and/or after I got the bike. There were a few times when it got so hot I really didn't like how it smelled - and the idle started racing. And as noted in another thread I had a combination of oil consumption & a variety of leaks - despite my attempts to keep the oil at a healthy level, there were times when it got lower than it should have.

[daves79x]

I'm going to make this point again - DO NOT get stuck in traffic with a CBX - big oil cooler or not. It's death for these engines. Besides the kind of damage you've seen, EVERY rubber part including carb rubbers and O-rings will be damaged. I can tell very quickly if a set of carbs I'm rebuilding has been overheated.

Especially with a newly rebuilt engine, I don't know what your options are, but just don't get caught in a traffic jam.

Dave

[Syscrush]

I'm going to make this point again - DO NOT get stuck in traffic with a CBX - big oil cooler or not. It's death for these engines. Besides the kind of damage you've seen, EVERY rubber part including carb rubbers and O-rings will be damaged. I can tell very quickly if a set of carbs I'm rebuilding has been overheated.

Especially with a newly rebuilt engine, I don't know what your options are, but just don't get caught in a traffic jam.

Thanks, Dave. I'll do my best - especially when the engine is breaking in.

These concerns are the main reason why I chose against the higher compression version of the big bore pistons - I'm not comfortable giving myself less of a safety margin when it comes to engine heat.


Speaking of break-in, can I ask your take on the Motoman break-in procedure? It makes a lot of sense to me, and I followed it for my wife's CBR125R - but that's the only new/fresh motorcycle engine I've been responsible for since learning of this approach.

[cross]

I asked my ducati engine guy that recently helped me rebuild my ducati engine on this.
He had told me that this is the way the breaks in race engines but not most street engines. According to him, sometimes when rebuilding the street engine bearings can be a little on the tight side of the spec and when that is the case, you do not won't to break-in engine like this as you are risking the damage.
This was the case with my engine and he told me not to rev it past 4000rpm's first 500 miles, he did initial break in for about 5 miles though but not the way that web site is saying to do.
Our engines cost a lot of money to rebuild and i'm not certain if we should be attempting that procedure. Maybe on a newer modern engines
Just my 2 cents

Sasha

[Syscrush]

As for managing heat, I've decided to make a further investment while this stuff is apart - I'm going to have a ceramic thermal barrier coating applied to the combustion chambers and the piston crowns, and a dry film lubrication coating applied to the piston skirts.

This is not to give myself leeway to abuse the engine, but rather to increase the margin of safety in difficult circumstances.

[Syscrush]

My box of parts (including pistons) from TIMS has cleared customs and is supposed to be on my doorstep tomorrow. The head assembly should be shipped next week.

I've found and vetted a local ceramic coating company and will run the exhaust and pistons out there early next week for treatment. Once the pistons are coated, the cylinders can be bored to the final measured size (with the dry film lubricant coating applied).

[Syscrush]

Does the "J" in "JE" stand for "jewelry"?





They're beautiful, but I want something a bit more special. They go for ceramic coating tonight.