Five must-haves for a good-running GL1000

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Re: Five must-haves for a good-running GL1000

#16

Post by mikenixon »

Hi, gltriker. No, no bad effects, no fallout. The experience of mechanics everywhere confirms this. Not only is not harmful, it will gain you at least 10 psi and possibly 20 psi cylinder compression per cylinder. And the carbs, as I say, will work better, because they will get a stronger signal. They actually richen slightly.
As for accelerated valve wear, no. The 0.002" is invisible vertically. It's horizontally that makes the difference.
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Re: Five must-haves for a good-running GL1000

#17

Post by gltriker »

WOW! :shock:

Thank you very much, Mike! tumb2

Can I quote your response into another already active Compression Testing topic here in the Forum, please?
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Re: Five must-haves for a good-running GL1000

#18

Post by mikenixon »

Certainly. This drawing helps explain why a 0.002" change makes no difference in valve opening distance but a remarkably effective change in valve open time. Really works.

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Re: Five must-haves for a good-running GL1000

#19

Post by gltriker »

Very Interesting, Mike, but I don't understand the illustration of horizontal effect ;)

This afternoon, I've performed a cylinder leak-down test on each of the 4 holes. The lowest leak rate was ~4% in one cylinder, to a high of 7% in another cylinder. The remaining two cylinders were , of course, in between the high and low % of leak rates.

When I get back to the job to reset all valves' clearance gap to 0.006", I'll provide my hopefully enhanced cylinder compression test numbers results.

If I understand the "stronger signal" benefits to carburetion, it is best identified by the vacuum measured during the carburetors' idle synchronization procedure, that will display at a higher value on the vacuum measuring device/s?
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Re: Five must-haves for a good-running GL1000

#20

Post by mikenixon »

gltriker wrote:Very Interesting, Mike, but I don't understand the illustration of horizontal effect ;)

This afternoon, I've performed a cylinder leak-down test on each of the 4 holes. The lowest leak rate was ~4% in one cylinder, to a high of 7% in another cylinder. The remaining two cylinders were , of course, in between the high and low % of leak rates.

When I get back to the job to reset all valves' clearance gap to 0.006", I'll provide my hopefully enhanced cylinder compression test numbers results.

If I understand the "stronger signal" benefits to carburetion, it is best identified by the vacuum measured during the carburetors' idle synchronization procedure, that will display at a higher value on the vacuum measuring device/s?

The graph depicts the intake valve's motion plotted on two axes, vertical vs. horizontal. Vertical is the valve's lift, horizontal is the valve's duration. The graph is produced by the very traditional method of positioning a dial indicator on the valve stem and affixing a degree wheel on the crankshaft. As the crankshaft is rotated, a mark every so often is made on graph paper, and the result is the half oval shown here. The red sine curve is the plot using a 0.004" clearance, the blue is the plot repeated with the clearance at 0.006" (I did only a sketch for your sake, in this case, not an actual plot, though the actual plot is easy and very commonly done...it's known as profiling and I have two bikes in my shop right now I recently did plots on). The message here is that lift is reduced by only the 0.002" clearance change and thus is even less than neglible, to the point of immaterial. However, the duration is changed much more considerably and unlike the change to lift important.

So why does reduced valve open duration increase cylinder compression? The reduction in duration increases the percentage of time in every four stroke cycle given to compression buildup. Kind of simulates an increase in stroke, in a way. It works remarkably well and is a phenom observed by thinking mechanics for many generations. And though horizontally the effect is enough to increase cylinder compression dramatically, vertically no change is effected, thus no increase in valve wear or pitting is to be anticipated.

I have written on my website several articles referring to the little considered aspects of cam and valve timing, much of it tempered through direct experience and observation. Unfortunately, my site is being rebuilt after a cyber attack, but I'll try and make some of that material available to interested folks. I'll say this: I have experimeted with tiny changes in valve timing to very good results.

Oh, one more thing. I would not expect to see a change in manometer readings when running 0.006" clearance, though to be honest I haven't looked for them, so I really don't know. There you're talking intake vacuum, so...I don't know. The effect of higher compression, however it is achieved, does observably richen carburetion though. To some it seems counterintuitive (many think a big bore kit or other increase in compression requires jetting up to compensate for resulting leanness, but that is false, it can and has been documented to require a jetting down). Carburetion richens with compression increase for the same reason it leans with compression loss: venturi signal. This isn't exactly the same as vacuum.
Last edited by mikenixon on Sun Apr 29, 2018 8:51 pm, edited 2 times in total.
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Re: Five must-haves for a good-running GL1000

#21

Post by mikenixon »

gltriker wrote:This afternoon, I've performed a cylinder leak-down test on each of the 4 holes. The lowest leak rate was ~4% in one cylinder, to a high of 7% in another cylinder. The remaining two cylinders were , of course, in between the high and low % of leak rates.

When I get back to the job to reset all valves' clearance gap to 0.006", I'll provide my hopefully enhanced cylinder compression test numbers results.
That's very good leakdown and surprising for an older engine. Typical is 10-15%. On the compression comment, I have posted on my website's customer testimonials page a customer's results.
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Re: Five must-haves for a good-running GL1000

#22

Post by desertrefugee »

mikenixon wrote: So why does reduced valve open duration increase cylinder compression? The reduction in duration increases the percentage of time in every four stroke cycle given to compression buildup. Kind of simulates an increase in stroke, in a way. It works remarkably well and is a phenom observed by thinking mechanics for many generations. And though horizontally the effect is enough to increase cylinder compression dramatically, vertically no change is effected, thus no increase in valve wear or pitting is to be anticipated.
Uh oh. Now I'm left wondering why, after getting into hi-po cars and bikes over 40 years ago, and finding the nirvana of high-lift, longer duration camshafts as solid performance enhancers, how this plays out. Does your counsel above suggest that, in some cases, higher compression isn't the "trump" card in a particular application - that optimal intake charge and efficient exhaust stroke are more important?

If that's not the case, I may have to take up knitting. Seriously, this revelation has me a bit gobsmacked. Problem is, I have no doubt you're right, just trying to get my head around it.
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Re: Five must-haves for a good-running GL1000

#23

Post by gltriker »

Yes, Mike, the first time I performed the cylinder leakdown testing, Summer 2016, the leakdown % numbers were so low on my 1975 GL1000's cylinder #1 that I was suspicious whether my tester, a regulated single pressure gauge unit that Kohler Engines sold from their Service Tools catalog, was still working correctly. 20ish years ago, its accuracy tested surprisingly close to a dual gauge Snap-On leakdown tester. ( ~5% leak rate consistently displayed, 2 years ago, in all 4 cylinders was quite surprising.)

Enough so, that I nudged the kick start lever to rotate the crankshaft sufficiently to allow the applied air pressure (100psi, regulated ) to dynamically force the piston towards bottom dead center. When the T1 timing mark suddenly disappeared from the "window", I was relieved when the exposed left side camshaft pulley closest to me displayed continuing rotation, and the tester's pressure gauge reading immediately dropped to zero, expelling the still flowing air supply into the exhaust system.. I know there will always be, even at the very best internal conditions, air leakage into the crankcase past the piston ring end gaps, but have no idea what those ring end gap dimensions are. Apparently very small!

Since I became so invested in the "Yet another Compression Testing topic", and as a consequence, this one, too, my interest in having the best equipment for this investigation purpose has increased. Even though I have a Snap-On 250psi maximum cylinder compression tester gauge set-up, it's old, and I don't have complete confidence that the sealing oring on the 12mm adaptor is up to snuff, nor adequate for testing accuracy. I'm working on producing an adaptor, made from a 12mm NGK spark plug, that can be tightened with a wrench, to seal against the cylinder head with its already compressed, metallic gasket.
With the wealth of information I'm gleaning here, my being satisfied with fairly consistent 140ish psi cylinder compression tested numbers no longer suffices when trying to make my trike's engine perform as well as it should.

Several months ago, I was the old cat (68 ;) ) that had expressed that I would like you to ride my trike and tell me how the engine behaved in your estimation. With a "modified" exhaust system. Simply, a slightly angled, 1 3/4" OD straight pipe off the header outlet, into a 1 3/4" inlet H-D Softail muffler.
But, we're 3,000 miles distant. Exhaust constipation, has always been a concern, but how can I get best overall engine performance AND fuel mileage numbers, without deafening myself and unduly annoying others? The tip of the twin mufflers extends beyond the rear axle centerline. Why so long? I found from previous experience with my CB900 Custom trike with a Slipstreamer windshield installed, that the air circulation off the fairing, draws exhaust gas back into my riding space.
CO headaches are a very real threat.

Last week, before my first time out this year, I had removed the H-D Softail catalyst mufflers, and installed a set of new Rush 1.75" baffle mufflers. Overwhelmingly loud, but seemingly better engine performance behavior was presenting. Surprisingly, the Route 81 Interstate speeds' fuel consumption rate, averaged over 330 miles, at 4,300-4,900 rpm range, ~65-75 GPS confirmed mph, when compared to similar operating speeds last Fall with the catalyst mufflers installed, has actually increased, 3-4 mpg to ~31 mpg. The very best fuel mileage average had never exceeded 30mpg , at an average speed of 60mph, at 4,000 rpms, prior to that change of mufflers this first time out. A GPS displayed 80mph, at 5,200rpm, shows the stock GL1000 speedometer, itself, displays ~2-3 mph, fast. Difficult to hold my cell phone and compare numbers.
I have to get trike weighed sometime, but would estimate that, conservatively, 850 lbs with sporting a Pacifico fairing, too, reduces averaged fuel mileage expectations, drastically. Plus, my 220 lbs, in addition puts it and I over 1,000 lbs.... :shock:

BTW, The trike's GM 8.5 inch rear axle ratio is 3.73 to one.
The Continental 215/60-16 tire diameter, 26.1 inches is close to the standard tire dimension that was previously installed sometime before I bought the original configuration '75 GL1000, with 7,831 on the odometer. What appeared to be Jardine downturn mufflers were in place, too. NOISY!
Another 25,333 miles has been accumulated on the odometer since trikification, in 2012.

Without having a stock configuration exhaust system to install and have an exhaust sound/engine performance standard to compare my modified system to, I feel that I'm getting to the point where the realistic expectations are getting closer to optimal for my trike, and me, too! tumb2

Thank you, VERY MUCH, Mike! action1
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Re: Five must-haves for a good-running GL1000

#24

Post by mikenixon »

desertrefugee wrote:
mikenixon wrote: So why does reduced valve open duration increase cylinder compression? The reduction in duration increases the percentage of time in every four stroke cycle given to compression buildup. Kind of simulates an increase in stroke, in a way. It works remarkably well and is a phenom observed by thinking mechanics for many generations. And though horizontally the effect is enough to increase cylinder compression dramatically, vertically no change is effected, thus no increase in valve wear or pitting is to be anticipated.
Uh oh. Now I'm left wondering why, after getting into hi-po cars and bikes over 40 years ago, and finding the nirvana of high-lift, longer duration camshafts as solid performance enhancers, how this plays out. Does your counsel above suggest that, in some cases, higher compression isn't the "trump" card in a particular application - that optimal intake charge and efficient exhaust stroke are more important?

If that's not the case, I may have to take up knitting. Seriously, this revelation has me a bit gobsmacked. Problem is, I have no doubt you're right, just trying to get my head around it.
It's not too mysterious. However, note that modern production engines of all kinds are currently employing .45 and .50 L/D valve trains. That is, their valves are lifted much more aggressively than in decades past. An emphasis on lift vs. duration (consequently resulting in reduced duration comparatively) in other words.

www.motorcycleproject.com/text/camshafts.html
www.motorcycleproject.com/text/secrets.html
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Re: Five must-haves for a good-running GL1000

#25

Post by gltriker »

mikenixon wrote:
gltriker wrote:This afternoon, I've performed a cylinder leak-down test on each of the 4 holes. The lowest leak rate was ~4% in one cylinder, to a high of 7% in another cylinder. The remaining two cylinders were , of course, in between the high and low % of leak rates.

When I get back to the job to reset all valves' clearance gap to 0.006", I'll provide my hopefully enhanced cylinder compression test numbers results.
That's very good leakdown and surprising for an older engine. Typical is 10-15%. On the compression comment, I have posted on my website's customer testimonials page a customer's results.


Ah, yes, I finally located that particular customer's testimonial, Mike. Very Interesting!! tumb2

snip:
"Mike, I readjusted the valves on my CBX to 0.006" as you suggested and wow, it tracks just like you described! Just like you said, everything improved! Here is what I got, before and after:

BEFORE AFTER
140.........160
135.........165
130.........160
150.........175
125.........155
140.........170
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Re: Five must-haves for a good-running GL1000

#26

Post by gltriker »

Hello Mike.
I have realized that I'm going to need a new battery before I try to perform any further compression testing!
Was thinking about how you described that the effect of increasing the Valve gap clearance could be likened to an increase in stroke. Keeping in mind that comparison, suddenly it hit me this morning, if there was a significant increase in cranking compression readings, will that require me to go to a higher octane fuel to prevent knocking?
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Re: Five must-haves for a good-running GL1000

#27

Post by gltriker »

I just thought about what I had just asked you, and remembered that Honda spec 4 cylinder compression test figure is 171 PSI. And that 87 octane gasoline is what works with that compression number. So, with that in mind I think that I've answered my own question! :lol:
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Re: Five must-haves for a good-running GL1000

#28

Post by mikenixon »

:)

Compression ratio and compression values are not directly related, neither are compression values and required octane, and neither are compression ratio and required octane. In each case, a couple more factors are in the mix. For example, modern sportbikes run compression ratios over 12:1, yet they are content on 87 octane. What are the missing factors there? One of them is combustion chamber shape, another is squish, still another is swirl.

More to the point of your situation and question, all you are doing with looser valve clearances is recovering some of the lost compression your engine was designed with and had when new. You are not creating a compression scenario above normal, in other words.
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Re: Five must-haves for a good-running GL1000

#29

Post by gltriker »

Did I ever tell you that my 1953 Servi-Car's 45" sidevalve engine came with cast iron heads? No, of course not....

A year or so later I spotted a go-cart with an Army Surplus 45" engine perched on it, with cast aluminum heads. :shock:

I thought that was the secret ( I knew NOTHING about engines back then) to making a stronger :lol: engine, along with the 4 Weber Cams, modified camshafts ($100 ish dollars in 1969) and a small SU carburetor, that I believe came from a small Jaguar sedan. Plus, Super Shell gasoline was less 40 cents a gallon.

Eventually, I discovered the cast iron heads were 4.5 to 1 compression ratio. But those aluminum heads, oh those aluminum heads, were a 6 to 1 compression ratio component. :-?
But,.......side valve Lawn Mower engines didn't utilize roller camshaft followers! ;) lolol
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Re: Five must-haves for a good-running GL1000

#30

Post by mikenixon »

Took this reading today on the CBX engine I am fettling. Corrected for altitude it becomes 213 psi. Complete top end repair including Wiseco 1147 kit.

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