Gear Ratio Question

[bluedog59]

There's a couple of things about dynos and HP.

1. The final figure is not the important one. It's the difference between what you started with and what you've now got.

2. It needs to to be the right type of horses and importantly, torque. Don't build the engine you "want" chasing the top line, build the torque and power curve you ( and the bike ) needs. 

Do you like to ride it like a race bike or use mid range "grunt" ?

[Neveragain55]

2 hours ago, clivegto said:

I am going to use 14/43 on one of my bikes with a big bore kit. According to gear commander with my set up speed will be 141mph at 8500 revs, so I recon top speed will be about 146mph.

Please let me know where you actually top out at when you do your first shake-down-runs....

I'd be curious to know.

 

[clivegto]

Will do. 

[Neveragain55]

1 hour ago, bluedog59 said:

There's a couple of things about dynos and HP.

1. The final figure is not the important one. It's the difference between what you started with and what you've now got.

2. It needs to to be the right type of horses and importantly, torque. Don't build the engine you "want" chasing the top line, build the torque and power curve you ( and the bike ) needs. 

Do you like to ride it like a race bike or use mid range "grunt" ?

Great points....

When I started this project, the builder asked me similar questions.

Here's what I explained to him:

"I want this motor to produce a bit more power (HP) than stock, but I'm not looking to go nuts and wind up with a motor that will overheat in daily traffic, or be temperamental and constantly shut off, or require race fuel to run properly. It has to behave like a stock (no issues) motor, but it needs to embarrass the "kids" pulling up to me on their modern bikes thinking they're about to blow away an old man on his old bike. I need/want a decent top speed somewhere near 150 (or above), but I also need enough midrange punch to blast around the slow-pokes out for their Sunday cruises."

He told me that he completely understood, and that he's built hundreds of motors producing exactly what I was looking for, that's when he suggested the 1186 kit instead of anything larger.

The engine was completely disassembled, the castings were sent out to be acid cleaned, and everything was re-assembled correctly.

Take a look:

 

Also, the transmission was rebuilt, and the gears are "straight cut", we have Carrillo rods, APE studs & springs, APE cam chain tension adjuster, etc., etc., etc.

You have to trust me when I tell you this motor was built correctly, it's actually sick.  We're going to run Keihin 39mm FCR's 

So, the build is all behind me now, what she puts out is what she'll be putting out, and I'm pretty confident that I'll never be able to open her up and let her run all the way out until she's got nothing left to give based on the fact that anything above 130 to 140 on such an old frame (braced or not) is going to feel like 250 mph. and scare me to death.......if I'm being honest.

Edited February 13, 2021 by Neveragain55

[bluedog59]

I would concentrate on the torque curve if you plan on being the old guy on the "sleeper". With a fat mid range you can kick their ass while they're winding it up then roll it off before speeds gets silly ( because you're a "sensible old guy" and your chassis is going to start struggling soon anyway).

Hit them in their weak spot. Lack of mid range.

[Neveragain55]

1 hour ago, bluedog59 said:

I would concentrate on the torque curve if you plan on being the old guy on the "sleeper". With a fat mid range you can kick their ass while they're winding it up then roll it off before speeds gets silly ( because you're a "sensible old guy" and your chassis is going to start struggling soon anyway).

Hit them in their weak spot. Lack of mid range.

Love it, and yes, you understand and get where I'm coming from...

[george 1100]

Crank looks lightened too? Oversized valves? What cams?

[Captain Chaos]

9 hours ago, Neveragain55 said:

this motor was built correctly,

except for those "cam to cam" oil link thingies.

All they do is add weight, reduce oil pressure and look stupid.

[MeanBean49]

1 hour ago, Captain Chaos said:

except for those "cam to cam" oil link thingies.

All they do is add weight, reduce oil pressure and look stupid.

Beat me to it. 

[Gixer1460]

Some interesting parts used for that particular spec. and intended output! And BTW most bike g/boxes are straight cut - maybe you confused 'under cut' on the dogs?

[Reinhoud]

I did not read any post...

 

My experience, stock ratio is usually the best.

Best way to check if the ratio is ok, but this is my personal opinion; the vehicle should make just, or just not the maximum rpm in top gear..

[dupersunc]

Nice build.

Torque is never an issue on these motors.  If you need more torque, you have that little lever under your left toes.

I don't think you'll have an issue with this motor hitting your goals and scaring the shit out of yourself.

[Joseph]

Looks like a fait bit went in

And indeed, these lumps had all the power and torque a reasonable roadrider would ever need, even brought to today, the figures are well enough. 

Todays Chassis technology has beat them fair and square but apart from that

[Reinhoud]

14 hours ago, Neveragain55 said:

Great points....

When I started this project, the builder asked me similar questions.

Here's what I explained to him:

"I want this motor to produce a bit more power (HP) than stock, but I'm not looking to go nuts and wind up with a motor that will overheat in daily traffic, or be temperamental and constantly shut off, or require race fuel to run properly. It has to behave like a stock (no issues) motor, but it needs to embarrass the "kids" pulling up to me on their modern bikes thinking they're about to blow away an old man on his old bike. I need/want a decent top speed somewhere near 150 (or above), but I also need enough midrange punch to blast around the slow-pokes out for their Sunday cruises."

He told me that he completely understood, and that he's built hundreds of motors producing exactly what I was looking for, that's when he suggested the 1186 kit instead of anything larger.

The engine was completely disassembled, the castings were sent out to be acid cleaned, and everything was re-assembled correctly.

Take a look:

 

Also, the transmission was rebuilt, and the gears are "straight cut", we have Carrillo rods, APE studs & springs, APE cam chain tension adjuster, etc., etc., etc.

You have to trust me when I tell you this motor was built correctly, it's actually sick.  We're going to run Keihin 39mm FCR's 

So, the build is all behind me now, what she puts out is what she'll be putting out, and I'm pretty confident that I'll never be able to open her up and let her run all the way out until she's got nothing left to give based on the fact that anything above 130 to 140 on such an old frame (braced or not) is going to feel like 250 mph. and scare me to death.......if I'm being honest.

I just read half of what you posted, and not many responses...

 

My opinion/preference/experience regarding a better performing engine; more displacement, slightly higher CR, cams; stage 2, or just  more lift. Now, don't pin me down on this please; I think that when you go more lift, you automaticaly change the timing. My experience is, don't go for too wild, with just a bit more  lift/timing you get a better mid/high range, most likely you get a very well performing engine from "low" down. Hopefully someone can correct me, or explain it better.

What you win at the top, you lose at the bottom, keep that in mind.

 

But personally I pefer an engine what is torquie over a lot of HP

 

[Reinhoud]

On 2/12/2021 at 3:49 AM, Neveragain55 said:

 

All of the charts I’ve seen online put the 14T / 43T set up at a ratio of 3.07

The stock set up of 15T front / 48T rear gives it a ratio of 3.20

These ratio numbers mean nothing to me and despite all of the videos I've watched and articles I've read, my thick head still doesn't get it.

 

It’s very simple:

Is the 14T / 43T setup the best in terms of getting good top end (over stock) without losing too much of the lower end and midrange punch  

(in other words, is it a good compromise)

 

                                                                                                                      As always, thanks in advance.......

 

 

 

 

Can you calculate the difference in top speed between both ratios? May be that wil give you a better understanding..

Calculate it back to the amount of revs what you're riding with at an average speed..

May be it can give you an idea in difference?

 

When you ride your bike, do you feel the need to shift up a gear? If not, I wouldn't worry about all this.

Edited February 14, 2021 by Reinhoud

[dupersunc]

Torque high up the rev range is win win. You gain power and keep the torque.

Torque low down at the expense of torque up high, loses you power and gains nothing, other than cruising in a higher gear.

 

Edited February 14, 2021 by dupersunc

[bluedog59]

43 minutes ago, dupersunc said:

Torque high up the rev range is win win. You gain power and keep the torque.

Torque low down at the expense of torque up high, loses you power and gains nothing, other than cruising in a higher gear.

 

And while you're working hard, playing tunes on your close ratio gearbox and trying to keep that peaky motor singing, wondering if you dare tap the power just yet............. The guy with a broader spread has pulled 10 bike lengths on you and going 10 mph faster.

Race engines are great on race tracks but become a pain on the road.

Look at the course before selecting your horse.

[clivegto]

The answer to more powder and torque is simple just fit a turbo. 

[dupersunc]

2 hours ago, bluedog59 said:

And while you're working hard, playing tunes on your close ratio gearbox and trying to keep that peaky motor singing, wondering if you dare tap the power just yet............. The guy with a broader spread has pulled 10 bike lengths on you and going 10 mph faster.

Race engines are great on race tracks but become a pain on the road.

Look at the course before selecting your horse.

Just make sure you're the correct gear in the first place.

Torque isn't an issue on these motors, no need to de tune them.

[bluedog59]

I wasn't suggestion "de tune"  them, just be careful not to sacrifice too much at the bottom chasing that last little bit at the top.

[TonyGee]

i would of thought a gsxr1100 motor is plenty of power to put in an old gs750 frame 

[Captain Chaos]

yeah but more power is always the solution, even if lack of power isn't the problem.

[bluedog59]

More power will never solve a lack of talent.

[Neveragain55]

1 hour ago, TonyGee said:

i would of thought a gsxr1100 motor is plenty of power to put in an old gs750 frame 

Yes............but...........

What Captain Chaos said.........

[Neveragain55]

5 minutes ago, bluedog59 said:

More power will never solve a lack of talent.

I've said my entire life one thing about both racing, in any venue, on any machine....

"It's not the machine, it's the driver/rider"

I've left tons of idiots in my rearview over the last 44 years with far less powerful equipment than what they had.

Coincidentally, I'm not a track guy, and I'm not looking to win every "spontaneous" street race that happens as much as I'm just looking to build a fast bike that will keep a grin plastered on my face the entire day, no more, no less.