Gore/Rohrich bigbore Breathes FIRE
- Thread starter SFO
- Start date
Bill - If you get the chance to run the Arrow and OEM back to back let us know what you think about the differences. With the big motor I'm sure the Arrow will have a substantial advantage, but it will be interesting to hear what you think.
SFO
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- Feb 16, 2001
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- #29
I rode Hollister with the stock pipe today.
After the Arrow, the stock pipe is louder and subdues the power delivery.
I remember opening the throttle 100% once.
Once today I was able to open the throttle all the way.
It reminds me of the old yz 490 I had.
Short shift at least one aditional gear and don't breathe on the throttle unless you mean business.
I let my 520 friends (2) ride it and they loved the power, suspension, and the fact that it turns...
After the Arrow, the stock pipe is louder and subdues the power delivery.
I remember opening the throttle 100% once.
Once today I was able to open the throttle all the way.
It reminds me of the old yz 490 I had.
Short shift at least one aditional gear and don't breathe on the throttle unless you mean business.
I let my 520 friends (2) ride it and they loved the power, suspension, and the fact that it turns...
- Jan 25, 2000
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Rocket Boosters
I already have a 426.
I've ridden my 426 and someone's 400 back-to-back, and found that the 426 romps a bit harder down low, but nothing to write home about. This is an increase of 27cc (399 to 426) and I didn't go nuts about the difference in power.
Now we have an increase of a mere 18cc (426 to 444) and suddenly we have an "oh my god, everything else is a moped, can't even open it up or it'll loop, rippin' my arms off, where's my mommy?" motorcycle.
I was wondering what differences (other than displacement) were required to create such a rocket. If you have to shoot me 'cuz you told me, got ahead and shoot.:eek:
I already have a 426.
I've ridden my 426 and someone's 400 back-to-back, and found that the 426 romps a bit harder down low, but nothing to write home about. This is an increase of 27cc (399 to 426) and I didn't go nuts about the difference in power.
Now we have an increase of a mere 18cc (426 to 444) and suddenly we have an "oh my god, everything else is a moped, can't even open it up or it'll loop, rippin' my arms off, where's my mommy?" motorcycle.
I was wondering what differences (other than displacement) were required to create such a rocket. If you have to shoot me 'cuz you told me, got ahead and shoot.:eek:
Differences from a box stock 426:
- 444cc displacement hits a sweet spot in terms of intake velocity with the OEM port shape and size. 98mm would actually be better but there are too many trade offs at this point.
- Compression ratio
- Squish clearance
- Piston crown shape and swirl/tumble changes
- Cyl head changes
- Cam timing due to deck height changes
- Jetting
- Running the CORRECT fuel
and last but not least assembly by an engine builder versus a factory line worker :)
A properly setup 417cc engine with 13.5 compression might have some advantage down low compared to a well tuned stock 426 but nothing earth shattering. Compared to a sloppy 426 the difference is much more noticeable.
Treating engines as systems rather than a random collection of parts can pay big dividends. These engines are a prime example of that. They respond very poorly to generic bolt on solutions because Yamaha did their homework.
- 444cc displacement hits a sweet spot in terms of intake velocity with the OEM port shape and size. 98mm would actually be better but there are too many trade offs at this point.
- Compression ratio
- Squish clearance
- Piston crown shape and swirl/tumble changes
- Cyl head changes
- Cam timing due to deck height changes
- Jetting
- Running the CORRECT fuel
and last but not least assembly by an engine builder versus a factory line worker :)
A properly setup 417cc engine with 13.5 compression might have some advantage down low compared to a well tuned stock 426 but nothing earth shattering. Compared to a sloppy 426 the difference is much more noticeable.
Treating engines as systems rather than a random collection of parts can pay big dividends. These engines are a prime example of that. They respond very poorly to generic bolt on solutions because Yamaha did their homework.
- May 14, 2000
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Re: Gorr/Rohrich bigbore Breathes FIRE
SFO continues to compare his hoped-up 426 to bone stock 520's.
Guess us 520 guys should take that as a compliment!
You would'nt want to compare that to Dowdy's 520,....would you? :D
Actually SFO,I dont want to burst your bubble, I'm sure the 97mm kit made great power improvements. (I was never very impressed by the power the stock yz/wr made either). I'm glad to hear you found good results with your mods. My point is that one is only limited by his resources to proper modifications. :)
SFO continues to compare his hoped-up 426 to bone stock 520's.
Guess us 520 guys should take that as a compliment!
You would'nt want to compare that to Dowdy's 520,....would you? :D
Actually SFO,I dont want to burst your bubble, I'm sure the 97mm kit made great power improvements. (I was never very impressed by the power the stock yz/wr made either). I'm glad to hear you found good results with your mods. My point is that one is only limited by his resources to proper modifications. :)
SFO
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- Feb 16, 2001
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97mm vs 520
I should back up and say that I was motivated to change my 426 because my friend came around me so fast on his 520.
I think I will end up building a 520 as well in the future.
The 520 is the benchmark these days.
BTW, my new buddy with his 02 520 still comes around me, after riding his bike, I can't figure it out.
Maybe all those oil filters make it faster?
(maybe he is just a faster rider)
I should back up and say that I was motivated to change my 426 because my friend came around me so fast on his 520.
I think I will end up building a 520 as well in the future.
The 520 is the benchmark these days.
BTW, my new buddy with his 02 520 still comes around me, after riding his bike, I can't figure it out.
Maybe all those oil filters make it faster?
(maybe he is just a faster rider)
theMotoMan
Member
- Jan 12, 2001
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Isn't the AMA going to limit the displacement of thumpers in the 250 class to 450cc :eek: ? Seems like a 444cc mod to the 426 seems about right! But open class is another story...:p
Re: 97mm vs 520
And the 444 will be no different. The 520 has a distinct advantage in terms of absolute valve area to piston area ratio over the 444, but area under the curve is where the fun is :)
And the 444 will be no different. The 520 has a distinct advantage in terms of absolute valve area to piston area ratio over the 444, but area under the curve is where the fun is :)
SFO
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- Feb 16, 2001
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Dale just called...
I am going to run the 97mm on the dyno tommorrow.
The b03 has not shown up yet, although the receipt came in the mail.
Rich, what do you want me to do for the fuel set up, w/o bo3?
I have the b32 and the b37.
I am not going to get a lot of dyno time so it is down to running one set up.:scream:
Mounting the street tire tonight.
les' see what she'll do...:D
I am going to run the 97mm on the dyno tommorrow.
The b03 has not shown up yet, although the receipt came in the mail.
Rich, what do you want me to do for the fuel set up, w/o bo3?
I have the b32 and the b37.
I am not going to get a lot of dyno time so it is down to running one set up.:scream:
Mounting the street tire tonight.
les' see what she'll do...:D
Re: Dale just called...
On the dyno you don't have to be concerned with throttle response and you'll generate a lot of heat anyway so run the B37.
On the dyno you don't have to be concerned with throttle response and you'll generate a lot of heat anyway so run the B37.
Tony Williams
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- Mar 23, 2000
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Fun With Numbers
I like this formula for displacement of the cylinder(s):
(bore squared times .7854 times stroke times number of cylinders)
Of course, you have to use the same values throughout the formula.
9.7 * 9.7 * .7854 * 6.01 = 444.12869886 cc
Since the motorscooter linear measurements are typically in millimeters with displacements in cubic centimeters, you'll need to either divide the end result by 1000, as Rich has done below, or enter the linear measurements in centimeters.
Tony
I like this formula for displacement of the cylinder(s):
(bore squared times .7854 times stroke times number of cylinders)
Of course, you have to use the same values throughout the formula.
9.7 * 9.7 * .7854 * 6.01 = 444.12869886 cc
Since the motorscooter linear measurements are typically in millimeters with displacements in cubic centimeters, you'll need to either divide the end result by 1000, as Rich has done below, or enter the linear measurements in centimeters.
Tony
SFO
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- Feb 16, 2001
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I would love to have you ride this bike.
Everyone who has ridden it is impressed.
I am very excited about how my biuke runs, forgive me.
It is not my intention to sell anyone, anything.
I think I am going to baja for xmas.
Maybe we could hook up, holeshot?
Rich can explain the thermal aspects of blah, blah, blah...
The bike runs good and is a veru different creature.
Actually, it is more of what you love about a yz-f. Rippin'!:eek:
Everyone who has ridden it is impressed.
I am very excited about how my biuke runs, forgive me.
It is not my intention to sell anyone, anything.
I think I am going to baja for xmas.
Maybe we could hook up, holeshot?
Rich can explain the thermal aspects of blah, blah, blah...
The bike runs good and is a veru different creature.
Actually, it is more of what you love about a yz-f. Rippin'!:eek:
- Jan 25, 2000
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rippin' 444
.
SFO:
I'm sure the 444 rips, but questions have to be asked.:confused:
I can barely hang on to the 426 for more than a lap right now, but that's
probably just me. Maybe I need the 444 setup to get that roost'n feeling again.:)
I haven't been to Baja, but it sounds like a plan. Maybe you can get a group
together for the first DRN Baja ride? December is a bit far off (for me anyway), but when the time approaches, it could be posted again.:cool:
.
SFO:
I'm sure the 444 rips, but questions have to be asked.:confused:
I can barely hang on to the 426 for more than a lap right now, but that's
probably just me. Maybe I need the 444 setup to get that roost'n feeling again.:)
I haven't been to Baja, but it sounds like a plan. Maybe you can get a group
together for the first DRN Baja ride? December is a bit far off (for me anyway), but when the time approaches, it could be posted again.:cool:
Last edited:
SFO
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- Feb 16, 2001
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x-mas new years ride
How about the west coast drn faithfull make the pilgramage to Mikes Sky Ranch for the holidays?
It is never too early to start planning.
We are also going to camp at StoneyFord for turkey day.
Let me know if anyone is interested...
How about the west coast drn faithfull make the pilgramage to Mikes Sky Ranch for the holidays?
It is never too early to start planning.
We are also going to camp at StoneyFord for turkey day.
Let me know if anyone is interested...
SFO
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- Feb 16, 2001
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Dale just called...
The 97mm motor makes 52 dynojet rwhp.
The pipe will be measured for sound tommorow, when he runs the nutec through it.
He said the bike is very impressive on the dyno.
It made the best power with pump gas.
He said the motor runs out of air at 8 grand and flattens out.
He likes the way it runs and coming from a guy who builds national championship bikes this is high praise.
He also had praise for the pipe, which coming from a pipe designer is interesting...
He said that normaly he would not use a stepped header but there appears to be no trade off on the dyno. He said also that he wouldn't change anything, except that he found the bike hard to start.
He says that the engine noise is louder than the sound coming out of the tailpipe.
The 97mm motor makes 52 dynojet rwhp.
The pipe will be measured for sound tommorow, when he runs the nutec through it.
He said the bike is very impressive on the dyno.
It made the best power with pump gas.
He said the motor runs out of air at 8 grand and flattens out.
He likes the way it runs and coming from a guy who builds national championship bikes this is high praise.
He also had praise for the pipe, which coming from a pipe designer is interesting...
He said that normaly he would not use a stepped header but there appears to be no trade off on the dyno. He said also that he wouldn't change anything, except that he found the bike hard to start.
He says that the engine noise is louder than the sound coming out of the tailpipe.
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theMotoMan
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- Jan 12, 2001
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Re: Dale just called...
Best power on pump gas? How does that work? :think
By running out of air at 8 grand do you mean literally, as in it needs to breathe more on the intake side? :confused:
It would be nice to see a dyno chart or a list of RPM/HP figures so we can get a feel for the powerband.
Best power on pump gas? How does that work? :think
By running out of air at 8 grand do you mean literally, as in it needs to breathe more on the intake side? :confused:
It would be nice to see a dyno chart or a list of RPM/HP figures so we can get a feel for the powerband.
Re: Re: Dale just called...
By combining high port velocities and proper chamber and squish setup you can make these engines very tolerant of fuel.
My guess is that the pressure rise of the high lead content oxy fuel is too fast for the stock ignition curve. Less ignition advance will likely show more power across the board with the oxy fuel. If I can coordinate it quickly enough I'm going to send Dale a Vortex programmable ignition to test with so we can optimize the ignition curve to take full advantage of the fuel. Then we should see even more power especially in the upper rpm range.
This is the really fun part of engine and fuel development, taking a good combination and optimizing it for serious gains :)
By combining high port velocities and proper chamber and squish setup you can make these engines very tolerant of fuel.
My guess is that the pressure rise of the high lead content oxy fuel is too fast for the stock ignition curve. Less ignition advance will likely show more power across the board with the oxy fuel. If I can coordinate it quickly enough I'm going to send Dale a Vortex programmable ignition to test with so we can optimize the ignition curve to take full advantage of the fuel. Then we should see even more power especially in the upper rpm range.
This is the really fun part of engine and fuel development, taking a good combination and optimizing it for serious gains :)
Tony Williams
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- Mar 23, 2000
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Re: x-mas new years ride
You probably want to start a new thread, but I'd be interested in a Baja ride.:)
You probably want to start a new thread, but I'd be interested in a Baja ride.:)
