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Nuances

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mikenixon
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Nuances

#1

Post by mikenixon »

I don't think most folks appreciate the level of skill and understanding good mechanics possess. It is probably assumed they are not very sophisticated. When a votech instructor I taught mechanics in the use of laptop computer vehicle diagnostics, quite a common thing now as I am sure many of you know. If fact we dealt with a wide range of computer utilization, including shop management software, manufacture online vehicle database use, and manufacturer training web use. Mechanics aren't dummies.

Further, the awareness of subtlties is not foreign to the mechanic's world. Boat prop rebuilders have to straighten their power shafts on a cloudy day because otherwise the sun brightening and dimming as it does on many ordinary days heats the shaft unevenly and makes straightening within 0.002" impossible. Similarly, I have to wait to bore cylinders til midday when the temperature in the shop is constant. With all the measuring tools changing dimension from morning to afternoon, even in a heated shop, not to mention the pistons growing due to temperature also, it's a challenge. Thus with the gnat's whisker piston-to-cylinder spec Japanese engines are assembled to, it just doesn't do to do this task first thing in the morning.

While carburetors are a little more crude than either of the above things, they too have subtlties that folks are unaware of or do not believe in. I showed you one in a recent article that pointed out the float pivot pins on GL1000 carburetors and their directional bias. There are actually many areas in carburetors that inattention will turn into gotchas. And one that lingers in my thougths right now is carburetor bracketry.

Most carburetor joining brackets for play a larger role than is commonly thought. Owners of V4 Honda carbs seem to not realize that fooling around with the steady plate on the tops of these carbs affects the whole carb set and ruins the careful alignment of the set, making the linkages inoperable and even causing breakage of the delicate carburetors. In fact, carb set bracketry not only provides stability, it also exerts forces on the carb castings that demand very careful assembly to avoid misalignment. I once had a customer insist that one of his brackets being bent, which I apprised him of during the rebuild, could not possibly be the problem he was experiencing with his choke linkage hanging up. But it was, and it happens more often than you might think, especially when someone previously has handled them roughly or worked on them inexpertly.

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The brackets on a set of Honda CBX1000 carburetors. Note the massiveness.

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Here is a bent bracket. Not very bent though is it?

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But it is bent enough that installing it throws off the sensitive alignment of the carb rack.

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This causes the choke linkage to bind and malfunction.

Take care and enjoy the holidays!
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pidjones
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Re: Nuances

#2

Post by pidjones »

'79 CB750F rack. You had to be very careful to avoid binding as the stays were tightened. I follow guidance that I've read (perhaps on the motorcycleproject) to reattach the garnish on GL1000 carbs before removing from the plenum. I don't have enough hands to reassemble those linkages between adjoining carbs.

Good mechanics have the correct tools or will buy/make correct tools before attempting the job. I expect to see good JIS screwdrivers in a dealership mechanic's set.

They also keep an organized work area, and if the tools are out of their normal storage location, they are exactly where he knows he placed them. I look at this as a primary reason to keep customers out of the shop. Safety concerns are primarily for liability, but provide a stronger argument tp the public.

When I was learning mechanical skills working on dirt track cars in my early teens, one of my first tasks was learning where the two mechanics kept each tool so that I could put them up when a job was complete. These two master mechanics took the time to show me how to apply counter-torque, which side of a nut was designed to be placed against the clamped part, and many other details. I in turn demonstrated by dojng exactly as they taught and thus earned their trust. Their cars were perennial champs in our area.
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Re: Nuances

#3

Post by JSBail »

My youngest sons first sport bike was an 80 something Honda VF500 interceptor, it was the first generation of the V4's and we quickly found out how hard it was to get parts for it. Well anyhow the tank was full of bad gas and the carbs needed to come off for a good cleaning, up to that time my only experience with motorcycles was a 75 cb550 that I brought back from the dead (literally) and the carbs and linkage on the VF500 were WAY more complex than the carbs on my cb550 but I dove in head first anyhow removing the carbs. I removed the box from the carbs which I'm assuming is the steady plate you refer to and had a nightmare of a time getting the carbs off. I eventually got them off but it wasn't until afterwards that I realized I should of left that plate intact, it also dawned on me just how lucky I was that I didn't damage any of the complex linkage when I removed the carbs without that steady plate in place.
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Re: Nuances

#4

Post by mikenixon »

JSBail wrote: Thu Dec 24, 2020 7:14 am My youngest sons first sport bike was an 80 something Honda VF500 interceptor, it was the first generation of the V4's and we quickly found out how hard it was to get parts for it. Well anyhow the tank was full of bad gas and the carbs needed to come off for a good cleaning, up to that time my only experience with motorcycles was a 75 cb550 that I brought back from the dead (literally) and the carbs and linkage on the VF500 were WAY more complex than the carbs on my cb550 but I dove in head first anyhow removing the carbs. I removed the box from the carbs which I'm assuming is the steady plate you refer to and had a nightmare of a time getting the carbs off. I eventually got them off but it wasn't until afterwards that I realized I should of left that plate intact, it also dawned on me just how lucky I was that I didn't damage any of the complex linkage when I removed the carbs without that steady plate in place.
Yes, you *were* lucky. A goodly percentage of the first-gen V4 Honda carbs on ebay are broken because of removal of that plate during carb removal, either at the plastic (yes, plastic) fuel tees or pipes or at the ultra-thin carb castings themselves, both of which are extremely delicate. It seems to be intuitive for many folks to remove that plate during carb removal from the bike, but as you know, it's a bad idea. I even had a customer complain his carbs were leaking after I rebuilt them. I looked at them for him, and he had unbolted the steady plate during install of the carbs (and admitted it) and fractured one of the plastic fuel pipes, which are hard to find for some models (though aluminum aftermarket ones are available for the more common V4 models). It was after that that I added the caveat about carb partial disassembly to my customer invoice template. :)

You are very smart and observant for figuring this out, and even more to be commended for sucessfully fettling VF500 carbs, the most difficult to remove and replace on/off the bike and so excruciatingly compact that even the float bowls are barely removable on the workbench.
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Re: Nuances

#5

Post by JSBail »

mikenixon wrote: Thu Dec 24, 2020 11:34 pm

Yes, you *were* lucky. A goodly percentage of the first-gen V4 Honda carbs on ebay are broken because of removal of that plate during carb removal,
During that time i was on a V4 forum and saw pics of a set of VF500 carbs where the the complex throttle linkage was absolutely mangled, I couldn't help but laugh because I knew exactly what the owner did wrong. How on earth I was able to do it without suffering the same consequences, I can't answer but I quickly learned how NOT to remove/install them. They had to come off a couple more times for tuning issues but having learned my lesson the first time I actually got proficient at it. The complexity and compactness of the engine still made it a pain to work on though
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Re: Nuances

#6

Post by mikenixon »

:)
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Re: Nuances

#7

Post by 5speed »

it's why I watched Randakks video on rebuilding the gl1000 carbs before I laid a wrench on the bike and why I had it playing on my laptop on the bench as I went step by step rebuilding them.
The bike fired right up when it came time to start it.
I failed miserably on syncing them because I didn't understand what I was trying to accomplish and was trying to get all the needles on the same spot on the 4 gauges..in the green. :oops: :drool
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Re: Nuances

#8

Post by mikenixon »

:)
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