Topic: Overhaul frequency for K0 CB750

[Terry in Australia]

...and then, it was knowing all the fixes for all the abovementioned CB750s, R69S gearboxes, R75/5 and /6 boxes and leaky pushrods, and saving riders' lives on the ill-fated Suzy Waterbikes that got me famous....even if was only for a few years... 

What were the problems with the Suzy GT750's Mark? I've had two, (a J and an M) and they were both brilliant bikes, and I'm about to buy a K, which will be a keeper. The only thing I'd like more would be a road going Yamaha TZ750 engined flat tracker like the one that frightened the bejeezus out of Kenny Roberts, that thing was just wicked!

[bryanj]

Delving into the age old memory Terry Only things i can remember doing to the GT's were:-

Rebuild front calipers regularly

Fork seals

Cables

Tyres

Chais n sprockets

Accident repairs

Cant ever remember pulling an engine except the one we raced----how about 5 to the gallon!!!!(UK Gallon as well!!) and an incredibable power band, can give you hints if you really want

[Jonesy]

Interesting point about maintenance mindset on the part of the owner.

I think Honda's reputation for reliability in some ways has been its downfall. I remember years ago when I worked at a Honda power equipment dealer (generators and stuff) and this guy came in hopping mad that his generator wouldn't start. He went on and on about how he wasted his money on such an expensive machine because it let him down and he expected absolutely no problems with it because "...that's why I bought a Honda!!!" It turned out he still had the service tag on it from the last time he brought it in for service- 6 years ago! He hadn't touched it since then, and the 6-year old stale gas was his problem. Further checking in the shop books indicated he brought it in 6 years back for the same issue. He felt that because it was a Honda, it didn't need maintenance as it should have been a robust machine that didn't need any "coddling" to keep it in good shape. Wrong. Any machine needs some level of care.

I think the same can be said for the CB750. Compared to other bikes of it's time it was a far cry in terms of the attention it needed to keep it in good shape. However, it still needs oil changes and occasional tuning. I remember my uncle commenting, "as long as it has gas and oil in it, you don't need to do anything else!" Errrr.. not quite. By today's standards it needs a lot of attention.

Not to discredit actual owner experiences, but this has somehow morphed into a belief over the years that Hondas (and other Japanese machines) were indestructible and infallible when compared to equipment from other regions. If a US automaker has a recall on a few cars, it's on the front page headline of every newspaper and the top story of the evening news. If an Asian carmaker has a huge recall, it maybe gets a paragraph or two in the back pages.

Bottom line is any equipment maker can have problems. Some of it is based on personal experience with that particular brand of product, while the rest is based on input from others. If you happen to talk to 5 people who love their Hondas, you'll get the impression that Honda builds a good product and is worth looking at. If you happen to talk to 5 people that had nothing but problems, you'd tend to shy away from that brand. Personal experience trumps all else, as if you had a great Honda bike and talk to 5 that hated them, you tend not to believe them, as your was good.

[HondaMan]

...and then, it was knowing all the fixes for all the abovementioned CB750s, R69S gearboxes, R75/5 and /6 boxes and leaky pushrods, and saving riders' lives on the ill-fated Suzy Waterbikes that got me famous....even if was only for a few years... 

What were the problems with the Suzy GT750's Mark? I've had two, (a J and an M) and they were both brilliant bikes, and I'm about to buy a K, which will be a keeper. The only thing I'd like more would be a road going Yamaha TZ750 engined flat tracker like the one that frightened the bejeezus out of Kenny Roberts, that thing was just wicked!

I thought they were great touring bikes, despite the 2-stroke engine. The power was always "on tap" right in the highway engine speeds, even if the smoke did get pulled up behind the Vetter during a headwind...

Aside from that, they had one nasty flaw that got them recalled in 1974: the swingarm bolt was not threaded far enough down until 1975. This would cause the assembly to not tighten up when at the specified 40 ft-lbs. of torque, and the arm's pivot was always loose and would wobble in wide, high-speed sweeping turns: one of our customers (and shop friends, a local farmer) in 1973 was killed because his bike wobbled and went down on the highway one fine day, and the semi behind him ran over him.

Suzy's immediate recall & fix was to add an extra 3mm thick washer under the nut on the swingarm bolt: the longer fix was to thread the bolt another 5mm to make sure their production tolerances stacked up to make a good assembly. The bikes were all recalled and lots of bolts were replaced, including new bikes just coming out of the crates. Be sure to check yours for this!

The next item was those crankcase suction valves, the tiny ones with the little hoses under the bottom of the crankcases. These were used to suck out any leftover oil buildup in the 2-stroke crankcases, so it would not emit big smoke clouds on freeway onramps after idling around town. At idle, these would have high suction, and would clean the lower crankcases well. Until they were stored for a while, this is: then they would gum shut, and not sweep the cases at all. You have to pull them out (they were pressed in) and clean them if the bike sat for a year or more, to make them work again. They are a tiny check valve inside. When they stop working, plugs foul and it smokes a lot.

The third item was the steering head: same problems as the other Japanese bikes of the era, with ball-and-race bearings. The frame is not terribly rigid (much worse than the CB750, for example) and it carries almost 600 pounds dry weight: the little dimples in the races would introduce speed wobbles, and IMO, started the above-mentioned scenario that the loose swingarm would then pick up and make the whole situation dangerous. This reputation for bad handling doomed them in the U.S. by about 1975, because a number of people were killed in highway accidents and it hit the AP newspapers. Their sales fell off a lot after that.

The last item I remember was rapid wear of the throttle cable(s), probably because the bike really invited a lot of throttle action with the response of that 2-stroke engine! The littler sibling, the 380 Triple, was one of my favorite want-to-have-it "toy" bikes of that era. It had the same sort of throttle feel, plus a 6 speed gearbox, lots of fun to ride!

[Terry in Australia]

Thanks Bryan and Mark, I wasn't aware of the swingarm bolt issues Mark, but I'll definitely check the "K" when I pick it up. I don't think I'll be hotting it up though Bryan, I've got plenty of fast bikes in the garage, and like you say, even a stocker had miserable fuel economy when on the throttle. I do love those big two stroke multi's though, they were just such a different animal from the rest of the Jap bikes of the era, and great fun to ride! Cheers, Terry.    

[bryanj]

I wouldnt recommend the mods i was on about unless you wanted a track bike, like I said 5 to the gallon and a 2,500 rev wide power band, but BOY did it shift till the clutch basket exploded