Yz444 Tuning: Building a Monster Torque Curve

Masterphil

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This thread will be an attempt to take all of the information regarding 444 engines that have been aquired thus far, as well as some new things to test, and build a yzf444 with the biggest fattest torque curve ever. I have read every thread that I could find about yzf tuning and yzf444 specifics that I can find, so bear with me if I ask a question that I may have not read the answer to.

The plans:
1) 97mm bored replated cyl
2) 13.5:1 97mm wiesco
3) ported head by Rich @ EG
4)a custom oversize headpipe that feeds a custom reverse meg
5)stock intake cam LCA 104 ( 5 degree advance)
6)stock 450F exh cam
7) 4-stroke specific race fuel
8) stock valvetrain

Now the plans in detail.

1) The 97mm Cyl. is a done deal, no questions about that. :yeehaw:

2) I think that Rich was previously lightening pistons for the yz444 to within a couple of grams of the stock piston weight, if that is correct, I will be using a lightened Hi-Comp piston.

3) How much will the flow of the intake and exhaust charges benefit from a reshaping of the combustion chamber given that the head how has an extra mm of material that isint doing anything but being flat? I am guessing that an unshrouding of the valves would make the charges more willing to flow smoothly into/out of the cyl head. How much is there to be gained on the exhaust side of the head? (if it were to flow directly into an oversize header that matches the exit diamater of the exh. port)

4) I have e-mailed Rich about meg design specs and will post his reply, as well as my questions, when I get the response back. I was thinking that a headpipe with a minimum ID of 1.75" would flow very well with the big bore. The meg will be designed first and foremost to produce a huge torque curve and flow well up into high revs. This will make it very loud and I might not be able to silence it very much, if at all, but that is not the goal of this project. :p

5) I am going to have a local machine shop (that I trust) advance my stock intake cam by 5 degrees. That makes the lobe center angle (LCA) 104, according to my research, this seems to be the best Intake timing for a motor such as the 444..

6) I have been using a 450F auto-decompressor cam in my 426 for over a year now and it shows no more wear to any part of the sprocket or cam than my stock 02 cam does. I Will be using this cam in the 444, but possibly with a different LCA. I dont know what the LCA is with this cam. Should the exhaust cam be advanced like the intake cam will be, or should the exhaust cam be retarted? The way I picture it in my mind is that after adjusting the intake LCA to 104, I now have 5 MORE degrees of valve overlap, but if the exhaust cam were anvanced by 5 degrees to make up for that, how would that effect the combustion?(since the valve would be opening 5 degrees earlier) Basically I dont know what I need to do to the exhaust cam to make it correctly compliment the Intake 104LCA with the 97mm piston. I need help on this one.

7) The search continues for a race fuel that will work well in a high-comp, ultra-short-intake tract thumper, that will not require me spending a fortune on race fuel for the season. What are everyone's best opinions, in cluding our resident fuel guru Rich, on using VP U4, which seems to be the bext Oxy fuel for it's price. But if another fuel is significantly better than U4, the wallet will just have to take the hit.

8) For the valve train I plan on using either all stock parts (they are so cheap, who cares if i have to replace them). I will not be using the Ti-Valves when they need replacing, instead I will be installing steel valves from a pre-02 426f. This choice is based purely on cost, since the steel valves should last as long as the Ti valves and I doubt that a measurable power loss will be had by using the slightly heavier steel valves vs the Ti valves. I may upgrade the springs and retainers using the kibblewhite spring kit though, it comes with Ti retainers :aj: BTW, what would oversize valves combined with the above setup do the the torque/HP curve? I hear that the 97mm piston creates a sweet spot with the stock valve size and intake flow velocity... :think: Rich said that didnt he?

I'm sure that I have forgotten something, and am open to any other mods that will help me reach my goals. Time to go eat some food and do some more thinking on this one...
 

YZ165

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Cold winters in Indiana eh!
 

Masterphil

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They do get cold. I did a teardown to check all of the engine specs and found my piston to be out of clearance and in need of replacing, therefore; I decided to start my winter tinkering a little sooner than I wanted. I hope to get at least the 444 cyl and piston installed very soon so I can still take advantage of some october and early december riding weather. The serious building, or the head, exhaust, cam timing, etc is projected for late december-about the end of febuary.
 

Masterphil

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I'm sorry, what was I thinking?!?!?! I guess the discussion of a 5-valve head’s portflow characteristics, camshaft LCA, and design specs of a good 4-stroke meg system WOULD NOT qualify this thread as an ADVANCED TOPIC!!!!!!!!!
 

Ol'89r

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Masterphil said:
I'm sorry, what was I thinking?!?!?! I guess the discussion of a 5-valve head’s portflow characteristics, camshaft LCA, and design specs of a good 4-stroke meg system WOULD NOT qualify this thread as an ADVANCED TOPIC!!!!!!!!!

Oops. Sorry Masterphil, I guess we didn't jump on this one fast enough for ya. :ohmy: Just kiddin. ;)

What do you plan to use the engine for? Is it a race bike or are you just gonna pull tree stumps out of your back yard. Possibily a yz444 trials bike or a 1/10 mile drag bike??? Just wondering.

By having two seperate cams in your engine you are able to change the torque curve without regrinding your cam.
In my experience, building a torque engine requires narrowing the spread of the two cams. This packs the most charge into the combustion chamber. The amount of spread used is limited by mechanical clearances. (Valve to piston, or valve to valve.) Valve to valve is not a big factor in your engine due to the valve angles. Also, decreasing the spread too much will result in less working vaccum in the engine and it will not want to idle or carburate very well.

The 104 degree center is a good place to start. I use a 105 center as a reference point to degree most cams in depending on what the engine is used for. Rather than use the stock cams, you may want to have a set ground. This way you can change the lift and duration and still have the ability to advance or retard each individual cam. Best of both worlds. Check with Web Cam, Hot Cams or Megacycle Cams for a regrind.

Port design also plays a big factor in torque. A deep pocket port is best for a torque engine. In most modern engines there is not enough material in the port to reshape it very much. Your engine has a fairly straight port design. The problem with a deep pocket port is, the motor will stop pulling at a very low rpm. A straight port does not disrupt the flow and will rev to a much higher rpm.

Usually a smaller diameter exhaust pipe will add to torque, but you need not go there until you have the engine built. IMO, exhaust tuning should be done on a dyno. Pipe diameter and length are both a factor. Doing it any other way is just guesswork. Intake manifold length is also a factor and that is also determined on a dyno.

I would recommend using the Kibblewhite stainless valves. They will outlast the stock valves and you can get them in oversize and definitly use the ti collar and spring kit.

Rich would be the guy to answer your fuel question. You might want to pm him if he doesn't respond to this thread.

Hope this answered a few of your questions. :cool:

Ol'89r
 
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Masterphil

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I guess I neglected the most important part of this thread: The intended use for this engine! It will be used for MX, exclusively. By what I can tell from other 444 dyno graphs that Bill and the like have posted, the torque peak is at approx 7k RPM and the HP peak is about 9k RPM. I basically want the torque and HP curves to look stock, just with more power everywhere. But, I feel that if the HP peak was about 9000 RPM, I would be able to use it more effectively.
 

Ol'89r

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Masterphil said:
I basically want the torque and HP curves to look stock, just with more power everywhere. But, I feel that if the HP peak was about 9000 RPM, I would be able to use it more effectively.


Phil.

If that's the case, you may want to look into getting a high performance cam, (torque grind.). By changing the stock cam too much from its intended settings it could make the bike hard to ride. By changing the lift and duration on the cam itself and maintaining close to stock degree settings, you should be able to increase power while maintaining stock curves. Tell the cam grinder what you want to do and they should be able to set you up.

My experience in this comes from racing the old Triumph twin engines on flat track and TT. The Triumph is a twin cam engine and the cams are adjustable by broaching new keyways in the cam sprockets.

On the TT, we set our engines up for max torque. TT tracks are similar to MX tracks in the way that you have short straight-aways and tight turns. Usually a jump or two with a short run to it coming out of a turn. Normally only one big turn and one long straight-away, so top end performance is not a big factor. The biggest factor was low end torque and good carburation coming off of the corners.

We used the same engine for half mile and mile also. On the mile tracks we ran about 130 to 135 mph on the straight-aways and slowed down to 90 to 100 in the corners. So carburation was not a big factor since we ran a very high rpm and the engines never really fell off of the cam, (Power band), in the corners.

Although we used the same engine for both types of racing they were set up completly different as far as cams, degreeing, port design, valve sizes, pipes, flywheel weight, balance factor, etc, etc.

Good luck. :cool:

Ol'89r
 

Masterphil

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My research(searching almost every YZF thread ever written) has lead me to the conclusion that stock yzf cams have more than enough lift and duration to provide flow to a 444. I am going to use the 104 LCA starting point on the intake side, but I am not sure what to use on the exhaust as a good starting point. At this point I am interested in seeing what can be done with the stock cams. Hot cams or custom grind cams may come later. Does anyone know the LCA for the stock exhaust cam, and what a good starting LCA would be given the intake at 104LCA(5 degree advance)? That is what I really want to know regarding cams.
 

Rich Rohrich

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Masterphil said:
My research(searching almost every YZF thread ever written) has lead me to the conclusion that stock yzf cams have more than enough lift and duration to provide flow to a 444.

Phil - That's true unless you want the engine to peak at higher revs than the one SFO built (see the link below for dyno charts). If you want the power peak at the higher rpm you are taking about, the Hot Cams intake and exhaust set with intake LCA at 105-107 will do it nicely without doing any drastic harm to the bottom end power. If anything it will probably be easier to get the bike to hook up with the power shifted up a bit from the cams.


SFO's YZF444 dyno charts : http://www.four-stroke.com/Dyno_runs/SFO_index.htm
 

mxmatt426

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Winters are not that cold in Southern Indiana, I live there too. We go to Sturgis, KY and race arena cross. It never snows or rains inside...
 

Masterphil

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I have decided that, if the funds allow, I will use the hotcams autodecompressor exhaust cam and intake cam. If I am unable to afford theese cams before I get the 444cyl and piston, then it will be installed with the stock cams at stock settings until I can get the hotcams.

I have been playing with different meg and headpipe dimensions and here is what I think I will begin testing with. I have arrived at theese numbers simply because of packaging issues. I am going to start with a 1.75OD 18 guage header of stock legnth. The actual ID of the header is 1.654". I will begin the megaphone as early as the airbox, shock and frame will let me. The meg will be about 12" long with a 3.5"ID at the largest part. Then a reverse cone with legnth of 3" will taper down to a 2.5" exit. This will allow me to make about 8" of silencer without the pipe being too prone to crash damage. I doubt that the silencer will do much good since the exit of it will still be 2.5". Does anyone know the exit diamater of the Jemco pipe? I would like to at least base my numbers off of something. All these numbers have been chosen based on a thunder alley pipe, only larger, and being pulled out of thin air.
 

Rich Rohrich

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Phil - If the money isn't there for the cams initially you can retard the cam timing LCA a bit by having the base of the barrel machined a bit. If you are building a serious YZF engine the squish should be brought into the .045" range anyway so setting the deck can have the two-fold effect of improving combustion efficiency and making the cam timing a bit more favorable in terms of IVC timing.

On the meg a couple of rules of thumb that I have found useful over the years. Shoot for an 8 degree (16 included) angle on the meg for maximum efficiency, and keep in mind that the engine will see about 1/3 of the meg length as pipe tuned length so make sure and take that into consideration as you are determining your final lengths.

If you haven't already done it do a DRN Search on the posts by Swiss. Jim Schneider (aka Swiss as in Swiss Cheese Factory Racing) is a really sharp guy and has probably forgotten more about building pipes than most of us will ever know.
 
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Masterphil

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What should the stock squish clearance be? Also, when closing the squish down to .045" am I going to have problems with PV clearance? Is the good ol' playdough-in-the-valve-pockets method going to be good enough for checking PV clearance? Is there a better way besides using a piece of lead solder through the spark plug hole to test squish? How much would changing the squish to .045 affect LCA's?(I need to just buy one of those hotcams installation kits...a shim kit would be nice too...)

What do you think about using the oversize headpipe? My calculations tell me that using a meg with the dimentions I previously listed, It would be a 4.40 degree diffuser. I read a post on TT where you said that yzf's, especially 444's, like to use short headpipes with long shallow taperd megs attached. I think I also read a post of Swiss's where he said that a 24-26" primary would be a good starting point for tuning the HP peak, or something like that. I think this would classify as a long shallow meg, but am I going too extreme on making it shallow? And since I will eventually be using the Hotcams, I would like to tune the pipe to fit the other parts of the system instead of just throwing a bunch of parts together to see what happens.

If I were to use the hotcams, where would I see an increase in power using oversize intake valves? Would I see a decrease anywhere?

Rich, What fuel do you think would work best for my engine? I would prefer to use VP as the midwest distributer is local for me.

The modified 444 spec list(as much feedback here as possible is wanted)

97mm bore
lightened 97mm 13.5:1 Wiseco
Ported head????Big valves????
Hot cams 105/105LCA's
.045 squish clearance (this combined with the 105LCA would give me close to 14:1CR maybe?? :aj: )

Custom meg whose dimensions will best fit the above engine system. (Great!!! Another variable to change!!!!)

Swiss, I would love to discuss the meg design, specs, and construction with you in as much detail as can be at this point.

Someone in a previous post suggested that I upgrade the con-rod. Will I need to do this? I am under the impression that the 426 rods are tuff-as-hell.
 
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Ol'89r

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Masterphil said:
Also, when closing the squish down to .045" am I going to have problems with PV clearance? Is the good ol' playdough-in-the-valve-pockets method going to be good enough for checking PV clearance?

If I were to use the hotcams, where would I see an increase in power using oversize intake valves? Would I see a decrease anywhere?
QUOTE]

Phil.

The method that I use to check PV clearance is to replace the stock valve springs with a light spring, ie throttle slide return spring or something similar. Set a dial indicator up to rest on the edge of the top spring collar. Rotate your engine until the valve is closest to the piston and then push down on the valve until it hits the piston. Your dial indicator will tell you how much clearance you have. More accurate than trying to mic a piece of clay. :cool: For squish clearance I use clay.

Using bigger intake valves while maintaining stock exhaust valves should increase torque, but may decrease the ability for the engine to flow at top end.

By going to the Hot Cams, I think you are going in the right direction. Like Rich said, the bike will probably hook up better. Building an engine with stump pulling torque is one thing but, you also have to keep the bike ridable. By changing too much from the intended settings it can change the working pressures of the engine enough to make it not want to take the throttle or not want to hook up coming off the corners. It's nice to have mega power, but if you can't get all the power to the ground it doesn't do much good. Another thing you may want to consider is a flywheel weight.
 

Masterphil

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So stock valve size it is. I can see how the hotcams and oversize valves together might be too much. So you would advise AGAINST using the solder in the sparkplug hole to determine squish. I like the method that you have for PV clearance though. What is a good ammount of PV clearance to run on a motor such as this? I also noticed that SFO's 444 was setup with a .035 squish. What would be the comparison between Rich's recomended in-the-area-of .045 squish compar and the .035 squish that SFO is/was using in his 444?
 

Ol'89r

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Masterphil said:
So you would advise AGAINST using the solder in the sparkplug hole to determine squish. What is a good ammount of PV clearance to run on a motor such as this?

I also noticed that SFO's 444 was setup with a .035 squish. What would be the comparison between Rich's recomended in-the-area-of .045 squish compar and the .035 squish that SFO is/was using in his 444?

Phil.

It is just my own personal opinion that clay displaces better than solder and there is little chance of binding something with clay.

The proper amount of P to V clearance is more or less an experiment. I have run as low as .022 in a Triumph 3 cylinder road race engine. It was close enough that carbon would not form under the valve yet the valve did not touch the piston.

Rich or SFO would be better at answering that question since they have more experience with that particular engine than I do.

Keep in mind, when setting things up that close, you don't want to miss a shift. :yikes:
 

Rich Rohrich

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For piston to valve clearance .060" @ 10 ATDC and .040" radial clearance should work on the intake, and .090" Piston to valve @ 10 BTDC and .040" radial clearance on the exhaust should be plenty assuming you keep a fresh rod fresh main bearings in the motor.

Make sure and use a proper sized transfer punch or an old valve converted to a punch to mark and verify the exact center of the valve/ guide on the piston crown. You might be able to get away with less radial and P/V clearance but like 89r accurately pointed out there are no hard and fast rules so experimentation tends to drive rules of thumb, or maybe it's the other way around. :)

As to your question about squish clearance, .035" is basically zero deck and the thickness of the head gasket is the squish. This is the way I run my own YZF444 as well, BUTTTT I throw away the crank and mains on a regular basis and I tend to short shift the engine. I've never hit the rev limiter because I know where the power is and I know there isn't any point in revving it that high. SFO also set his up very carefully so he knew he could get away with running the clearance very tight. If you want to move the power peak up and run the engine in the higher rev range than I would suggest running .045"-.050" and freshen up the rod and mains on a regular basis. Loose bearings have a way of closing up clearance in a hurry at 10,000 rpm so I would do mains and a crank rebuild before you do the big bore setup.

On fuel, if you want to use VP , their oxygenated MR3 is a good choice.

Lots of people seem pretty happy with U4, but I don't have any real experience with it in these motors to say one way or the other. I use Phillips B35 (now called FirePower 324) in mine and have been very happy with the results. SFO finally standardized on Phillps B35 in his as well. .
 
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Masterphil

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How often do you replace the crank and mains in your 444?

Is there a method to calculate the change in LCA that will occur by decking the cyl?

What would the compression be with a .045" squish, 13.5:1 piston, and 105LCA intake?

What are your thoughts on the idea of using an oversize headpipe?
 

Rich Rohrich

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Masterphil said:
How often do you replace the crank and mains in your 444?

Every other season.

Masterphil said:
Is there a method to calculate the change in LCA that will occur by decking the cyl?

I would imagine you can calculate it, I just measure it after I set the deck.

Masterphil said:
What would the compression be with a .045" squish, 13.5:1 piston, and 105LCA intake?

LCA has no effect on the mechanical compression ratio only the dynamic.You'll have to CC the head and the piston crown to know that for sure but I would guess it would be in the 13.5-13.8 range depending on the valve cutouts and the depth of the valves themselves. If you give me your mechanical ratio and the IVC timing you are using I can help you with the dynamic compression ratio.


Masterphil said:
What are your thoughts on the idea of using an oversize headpipe?

I've had good luck with 1.875" OD 18 guage (ID = 1.77) and 1.750" OD 18 guage (ID = 1.65) head pipes . I think the OEM sizing is a bit small for the RPM range you want to run in so going a bit bigger is worth looking at. Just don't get it too big or it won't accelerate worth a damn, and don't forget that the overlap and exhaust closing will influence what works and what doesn't size wise on the exhaust.
 

SFO

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For myself I made a fixture to carry dial indicators to determine a realistic value for the deck height to piston dome height offset that allowed me to measure the piston rock and create a real value for this dimension.
I mocked up some stud spacers to allow me to torque the barrel down as the two 6mm bolts that are on the outside of the cam tunnel cant the bore enough to skew any measurements.
Measuring clay always seemed goofy to me, although it works for a lot of guys I just want to see what I really have and using clay as a transfer medium seems to introduce a fudge factor that I can't requite, like what is the difference between .025" of clay and .030"?
I might not be able to discern this but I am pretty sure my motor knows...
Trying to build some project like this around fixed cam sprockets seems insane.
Pop the $$ for either hotcams or falicon sprockets on your cams and get the control of being able to perfectly dial your cams in.
It will pay dividends on the dyno when you have pre marked the LCA's with a scriber on your sprockets and reindexing is as quick as removing your valve cover and moving the sprocket to the new marks.
Easy to make a lot of pulls without a bunch of downtime between.
Unless your guy charges by the job and not the hour.
 

Rich Rohrich

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SFO said:
For myself I made a fixture to carry dial indicators to determine a realistic value for the deck height to piston dome height offset that allowed me to measure the piston rock and create a real value for this dimension.

I check the deck height the same way as SFO is describing. I never had any faith in the whole clay thing either.

Some folks use clay to measure piston to valve clearance as well but the method 89r describes for measuring the piston to valve clearance with light springs and a dial indicator is the way I do it and the way I think is best.. Like SFO pointed out, if you are going to the trouble to measure it you might as well go all the way and get the most accurate measurement you can. It's worth the effort.

Below is a picture of the fixture I use for measuring the deck height.
 

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PowerFiend

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Masterphil said:
Someone in a previous post suggested that I upgrade the con-rod. Will I need to do this? I am under the impression that the 426 rods are tuff-as-hell.

I have heard of a few cases of pin seizure. Try Falicon for an upgrade from stock.
 

SFO

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PowerFiend said:
I have heard of a few cases of pin seizure. Try Falicon for an upgrade from stock.


I R&R'd my 426 top end for the break in inspection and the small end bore of the rod was already showing some signs of galling on the right side.
I ran a ball hone through it and it went another 1400 miles +50dyno pulls as a 444.
The recent incarnation, or remnants thereof have included mounting a Falicon stroker cr-f rod onto the crank.
It is .060" longer than stock so cutting the barrel to establish your .04" squish might not be needed.
The Ampco 45 bush in the small end is the bees knees as far as bronze bushing material goes, the 5%nickel content makes those bushings as tough to wear out as they are to size...
If your budget allows I would vote yes, but installed it is the price of an oem crank complete so it is a geek thing that you alone can decide.
 

LJW

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SFO said:
The Ampco 45 bush in the small end is the bees knees as far as bronze bushing material goes, the 5%nickel content makes those bushings as tough to wear out as they are to size...
If your budget allows I would vote yes, but installed it is the price of an oem crank complete so it is a geek thing that you alone can decide.

Agreed!!!
I've had good results with Ampco 45 bushings in stock Honda rods.
 

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