Whoa- this CB1100 dropped a valve seat-

[PowerDubs_imp]

Check the pics-

https://www.ebay.com/itm/266449287588


Very strange failure... doesn't appear to be over heated.

[PowerDubs_imp]

Actually- I think it is the exact opposite.

These bikes are ridden like a 1970's Cadillac- low throttle- and slow RPM.

Every picture of the insides I've ever seen are carbon covered.

A hot head looks completely different...even if burning oil.

[PowerDubs_imp]

I'd be concerned with structural issues in the head and would be leery of dropping another seat.

It's def a cheap buy- but other heads with no issues aren't that much more once any seat repair is taken into consideration.

[max]

I'd be concerned with structural issues in the head and would be leery of dropping another seat.

It's def a cheap buy- but other heads with no issues aren't that much more once any seat repair is taken into consideration.

And al this after 10 years and 13.000 mls, agreed on the carbon buildup and slow riding.
Guilty of this myself, and we have a question; how can we prevent/remedy this situation?

Since we are limited to 100 km/h speed limit here what kind of riding could be adopted for this?

Is it possible that a manufacturing defect somehow caused this?
The other guides seem still unaffected at a casual look.

Don't have the experience to judge these situations but would like it if you could provide some tips Dubs, thanks in advance.

[PowerDubs_imp]

My guess is just a fluke / casting gap flaw... but until the seat is pulled and casing examined- who knows.

I would hope that there was a visual inspection during assembly...but these days of cost cutting / expedience - who knows.

Anyone have any idea where our bikes were actually produced? (not assembled)

For the last 20 years or more it is not uncommon- 'built in' country- of foreign components of just about anything.

As for your 60mph limit- that doesn't stop you from winding it out from a stop fairly often- and even at 'speed' you can drop it down gears for a higher rev and more heat.

Yea - I can hear the haters now- won't work, no need...tons of miles with no issues, etc... but I prefer to not only relate to many decades of other vehicles...but again as mentioned above- look at any inside pictures available of these bikes- and they are always carbon black buildup gunk!

Even the recent post from someone about sparkplugs...saying they look good for more miles...I thought to myself, no they look like they need to be 2 heat ranges hotter for that persons riding style.

I grew up on 2-stroke dirtbikes as many other have here- and given countless modifications / tuning on many many bikes in the woods...fueling / heat was MUCH more of something we paid attention to / learned - often by trial and error.

Sometimes hotter / colder plug... or even something as simple as- in slow sections pull in the clutch and rave the engine a few times before it loads up...and you need to pull over to clean / replace a plug.

[max]

Appreciate the response, good to know.

The listing actually states the valve guide, not the seat as i understand, but still...

On occasion i have a look inside the cylinder with a simple bore scope just because i'm curious, can only look at the piston and sidewalls but that is still better than nothing with my limited knowledge of these things.
What we do notice is truck diesel engines at 1 million miles on inspection before a rebuild look very clean and well run, they are build to accept a good load and keep going, my cb1100 does not have a hitch plate so i'm out but it makes for an interesting observation.

When i bought my first bike, a Yamaha 250 twin it burnt out the top of one piston, the previous owner repaired it and put in cooler spark plugs; the problem never re-appeared, so yes, thanks Dubs.

[the Ferret]

Probably an outlier issue with that cylinder head. Things that are manufactured by humans and assembled by humans sometimes break. The number of CBs on this forum with WAY more than 14,000 miles would suggest so.

Max, I think there is a whole lot of difference between what goes on in the cylinder head of a 1960s-70s auto lube or premix 2 stroke and a modern computer controlled four stroke with oxygen sensors, fuel injectors, fuel pumps and pressure regulators.

Haven't we been led to believe that due to having to meet emissions restrictions, that our bikes tend to run lean, particularly at low rpms, and not rich? I believe that's what we've been told for the last 20 years and why the aftermarket makes electronic boxes which are sold to enrichen the mixture at low rpms.

I know my automatic transmission Honda cars ran hundreds of thousands of miles, never exceeding 3500 rpms and rarely exceeding 2500 rpms. I used mine for over the road sales and at freeway speeds where mine spent the majority of their lives, they never exceeded 1500 rpms. My DCT Honda motorcycle is programmed by Honda to run in the 2500-3000 rpm range, above that it will automatically shift to the next higher gear.

Could there be carbon build up in the cylinder heads of those vehicles? Probably I suppose, but not enough to inhibit noticible performance, gas mileage or engine longevity.

Ride more, worry less.

[max]

Ferret thanks for the reply, as usual you are correct.

Not having any issues with our bikes but i was just interested in Dub's opinion since i did not have enough experience with carbon buildup, other people usually know more about mechanical things than myself and i'm always up for more experienced advice to add to the mix.

Threw in the two stroke story as an example in reply to Dub's experience, not in comparison to our cb's and i know there are a lot more experienced riders out there with knowledge they wish to share in the group, i've learned quite a bit since joining here and appreciate hanging out with you guys!

[Tev62]

I'd be concerned with structural issues in the head and would be leery of dropping another seat.

It's def a cheap buy- but other heads with no issues aren't that much more once any seat repair is taken into consideration.

And al this after 10 years and 13.000 mls, agreed on the carbon buildup and slow riding.
Guilty of this myself, and we have a question; how can we prevent/remedy this situation?

Since we are limited to 100 km/h speed limit here what kind of riding could be adopted for this?

Is it possible that a manufacturing defect somehow caused this?
The other guides seem still unaffected at a casual look.

Don't have the experience to judge these situations but would like it if you could provide some tips Dubs, thanks in advance.

Finding a good twisty road and riding the bike for an extended period in no more than second & third allowing you to stay sub 100km/hr but give the engine a good high rev run. Most of us (on any bike) use far too few revs as it is. On a country road I would hardly be out of 3rd or 4th, it gives you great speed modulation and bike control without resorting to the use of brakes.

[GoldOxide_imp]

Sounds about right Tev. In agreement, especially too if road elevation is variable and curvy.