426 rod ?

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#1
Just started taking apart my blown-up 444, and the rod is broken in half,and did most of the damage.I had bought a new crank from Yamaha, and had it balanced for the 97mm piston, and welded. I would like to put this motor back together with a better/stronger rod, but I'm having no luck finding such a thing. So far,Carillo and Falicon both told me they don't make a rod for this motor.Anybody have any ideas where else to look or who to call ? Any help is most appreciated, thanks
 
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#3
Bill (SFO) and I looked into the rod thing but it seemed cost prohibitive at the time. Carrillo will do a custom rod but you need to buy 40 or 50 of them. Crower would do a single rod but I think Bill got a quote in the 400-500 range for Ti.
The stock rod isn't a bad design but the piston needs to be lighter if you plan on revving it hard. I did the math and found the extra 60 or so grams of piston weight translate into some serious load differences.
 
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#4
Mike, Falicon said the only rod they had for the 426 was for a stroker crank.Foreward Motion did the cylinder/head work for me.Rich, I do plan on revving it, I blew it up road racing it. Didn't you guys take some weight off the wiseco piston? Where/how much material did you remove ?
 
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#5
Bill - Managed to get 40+ grams off the Wiseco 97mm piston. He was working with Eric to supply him with lightened pistons done on CNC machines, but Bill's SuperMoto work with Doug Henry has put that on hold indefintely. Wiseco has a new forging process that allows them to build big bore pistons that are as light as the OEM pieces. The 250F and CRF450 pistons use this process but I don't know if they have plans to do the 97mm YZF pistons this way. Eric has some good contacts at Wiseco I'll ask him to get an update from them.
 
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Rich, I've got a local guy who can make me a titanium rod, would the lighter rod make up for the heavier piston, or would that make it worse?I'm not too concerned with price at this point, I've already spent way too much on this bike and I've still gotta buy cases, cylinder,etc.Thanks again.
 
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#9
Originally posted by pursang262
Rich, I've got a local guy who can make me a titanium rod, would the lighter rod make up for the heavier piston, or would that make it worse?I'm
It would depend on the design of the Ti rod. The failures I've seen are usually near the top of the rod below the small end by about 20-40mm. They always look like elastic failures. Given the location of the failure and the type I would hazzard a guess and say a lighter rod would have a minimal effect if the weight of the piston stayed the same. The Young's modulus for Ti alloys is usually about half that of steel so if the Ti rod was made as an exact copy of the OEM rod then the Ti rod wouldn't last long in that environment. But if the lighter weight of the alloy were put to use making the rod stronger then it might be an advantage. It would take some development either way.

It makes more sense to use a lighter piston or lower the rev limit to keep the loads with the heavier piston in line with the original oem loads. The 97mm bore engines usually have torque peaks around 8000 rpm and don't make any real power above 9500 so revving them to the OEM limiter is a waste in most cases anyway.
 
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#10
Mike, I race at Loudon, the YZ is competitive in supersingles and GP singles classes,and can be entered in about a half dozen other classes.
Rich, I like the idea of lowering the rev limit, is there a readily available way to do this electronicly ? When I built this motor I used the 12:1 piston instead of the 13:1 to get more revs, this time I'll use more compression.
 
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#11
You can get the Vortex ignition system programmed to use any rev limit you want. If you need a source for the Vortex ignition let me know. I built my 444 with 13.85:1 compression and SFO did his the same way. I really like the higher compression versions of these engines.

Here's a link to the dyno runs SFO did on his YZF444
http://www.superttr.com/Dyno_runs/SFO_index.htm
 
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#12
Yes please,more info on the Vortex would be appreciated. Looking at their website, the "new" updated x10 lists rev limiter where required, instead of an adjustable rev limit. It appears from those dyno charts that you could limit the motor to somewhere around 9500-10000 rpm and still have some over-rev,where does the extra weight of the big piston become critical ? Sorry for all the questions ,but this 4-stroke technology is new to me, and I'm really happy with the way this thing ran before it exploed. Thank you again.
 

SFO

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#13
Hey guys, just got back from Vegas and am still vibrating from 10 hr drive.

Have Falicon put a stroker rod for a CR-F on your 426 crank.

It is .060" longer than the oem rod and has a bushed small end.

That is just two base gaskets and a stock cylinder deck height for your application.

I use the oem wrist pin with the wiseco piston to save about 20 grams.

OR, you can taper bore the wiseco tool steel wrist pin at 7 degrees on each end to make it lighter than the oe wrist pin.

 

 
 
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#14
Originally posted by SFO
am still vibrating from 10 hr drive.
... and a GREAT showing by the Rocket Science boys. :thumb: :yeehaw: