Topic: Highest HP - UNDER 750cc & Stock compression

[PeWe]

Another dyno of almost stock CB750 K2. K7 pistons and cam, K6 head and K6 carbs.
Flat torque curve from 3500 to 8000 rpm.  Not that bad response with stock carbs, airfilter and Yamiya no numbers 4-4 without wool.
Max Power = 57,85 Hp Max Torque = 56,67 Nm

No A/F since diffusers are in and carbs runs OK, no need to change.
Maybe ignition disturbances at higher rpms...?

[dragracer]

One day I want to do a comparison between my current dual shock F model with the 1030cc engine versus the same chassis with a bone stock  engine with the only mods being rejetted stock carbs and a sidewinder e exhaust.

[PeWe]

One extra bike is good as reference when visit the dyno

[dragracer]

One extra bike is good as reference when visit the dyno

Right. My reference point is related more to a properly set up drag race  chassis with a stock engine versus the same stock engine on a stock chassis . To make a correct comparison i would have to use tbe same stock engine in both platforms.  The original poster did explain he was after peak horsepower via dyno numbers from a midly modified engine with stock bore i believe.  He also reference a drag strip pass. I suppose I'm more focused on getting  the best out of the total package which obviously strays away from his intentions.

[Bailgang]

Who'd run a stock bike at the dragstrip or pay for dyno time?

I would and in fact did. When you have a son that has a tuned WRX, an older brother with a highly modified but normally aspirated 2000 something Mustang GT (3 valve engine) and a nephew with a small block chevy powered Corvair and they all start talking BS as to who's car is faster and decide to go to the drag strip for a showdown, you don't expect me to just set in the stands and watch do you? Hell no, me and my stock F2 had fun with them. Going to happen again sometime soon because my brother has since installed a Roush supercharger in his Mustang and my son sold his WRX and now has a Mazda Miata that he's currently stuffing a V6 from a Honda Odyssey minivan into.

Dyno time? You bet. After getting so much well intentioned but bad advice on how to tune the carbs on my F2, I got tired of chasing my tail with plug chops and instead put it on a dyno with an exhaust analyzer to tell me what was really going on rather than guessing. It was on the dyno for just one run but that's all I needed and only cost $30. The result? 46 HP which was disappointing but not surprising because the reason the bike was on the dyno in the first place was because it was running lousy and I wanted to know why. The dyno operator on the other hand was impressed because he said of all the vintage bikes he's had on the dyno, he said my 750 put out the most and was clearly capable of more once tuned correctly which by aside from it's boyer bransden ignition is stock.  It runs MUCH better now but haven't had it on a dyno to show how.much better

[scottly]

I would and in fact did. When you have a son that has a tuned WRX, an older brother with a highly modified but normally aspirated 2000 something Mustang GT (3 valve engine) and a nephew with a small block chevy powered Corvair and they all start talking BS as to who's car is faster and decide to go to the drag strip for a showdown, you don't expect me to just set in the stands and watch do you? Hell no, me and my stock F2 had fun with them.

So who won??

[Bailgang]

I would and in fact did. When you have a son that has a tuned WRX, an older brother with a highly modified but normally aspirated 2000 something Mustang GT (3 valve engine) and a nephew with a small block chevy powered Corvair and they all start talking BS as to who's car is faster and decide to go to the drag strip for a showdown, you don't expect me to just set in the stands and watch do you? Hell no, me and my stock F2 had fun with them.

So who won??

The Mustang with a 12.95 ET, the WRX Impreza nipping at its heals with a 13.02, my 750 with a dismal low 14 ET but that had more to do with me the rider than the bike. I've had the 750 for a number of years now but that was the very first time I launched the bike aggressively from a stop. Lesson learned but I had fun anyhow. The Corvair? Well the track workers were blown away by it so my nephew decided to launch it hard on his first pass giving it a shot of nitrous at the start with slicks to impress them (bad idea). The car hardly moved a few inches before its independent rear suspension snapped a half shaft effectively disabling the car for the rest of the day. He had driven the car to the track so he had a hell of a time coming up with a way to get it home.

[Alan F.]

Who'd run a stock bike at the dragstrip or pay for dyno time?

I would and in fact did. When you have a son that has a tuned WRX, an older brother with a highly modified but normally aspirated 2000 something Mustang GT (3 valve engine) and a nephew with a small block chevy powered Corvair and they all start talking BS as to who's car is faster and decide to go to the drag strip for a showdown, you don't expect me to just set in the stands and watch do you? Hell no, me and my stock F2 had fun with them. Going to happen again sometime soon because my brother has since installed a Roush supercharger in his Mustang and my son sold his WRX and now has a Mazda Miata that he's currently stuffing a V6 from a Honda Odyssey minivan into.

Dyno time? You bet. After getting so much well intentioned but bad advice on how to tune the carbs on my F2, I got tired of chasing my tail with plug chops and instead put it on a dyno with an exhaust analyzer to tell me what was really going on rather than guessing. It was on the dyno for just one run but that's all I needed and only cost $30. The result? 46 HP which was disappointing but not surprising because the reason the bike was on the dyno in the first place was because it was running lousy and I wanted to know why. The dyno operator on the other hand was impressed because he said of all the vintage bikes he's had on the dyno, he said my 750 put out the most and was clearly capable of more once tuned correctly which by aside from it's boyer bransden ignition is stock.  It runs MUCH better now but haven't had it on a dyno to show how.much better

$30 is MUCH less that I've heard of in my area. I've had friends who brought perfectly good running sportbikes to shops with the intent to make them run better, unfortunately the reverse was more often the result since they tuned only for high end not practical street riding. That was probably 20 years ago and I guess it left me cold to the idea. Besides the costs I remember them talking about were "just a few hundred dollars" which was ok for single guys but I was married with little kids so....
For $30 I'd be signing up.

[754]

It depends who you know and how many pulls..  We used to have a guy around here would bring his Dyno to bike shows and charge reasonable..
 He did my Cimatti moped for free .... a whopping 1.7 hp..!
 And then one day I get the phone call .. he said. .were were testing a Harley hi torque starter , with the plugs pulled out, and it beat your lowest HP figure...

[Bailgang]

$30 is MUCH less that I've heard of in my area. I've had friends who brought perfectly good running sportbikes to shops with the intent to make them run better, unfortunately the reverse was more often the result since they tuned only for high end not practical street riding. That was probably 20 years ago and I guess it left me cold to the idea. Besides the costs I remember them talking about were "just a few hundred dollars" which was ok for single guys but I was married with little kids so....
For $30 I'd be signing up.

It was a deal unfortunately the $30 dyno pulls are no more, the shop in question sold their dyno to make more room to work on bikes and as far as I know the only other bike shop nearby that has a dyno is wanting $100, that's been a few years ago so the price may have gone up by then.