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Pile of junk connecting rods.
#563345 09/15/14 12:29 pm
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I've been sorting through my pile of parts for the ongoing T120/750 build...I can't believe in this whole pile of connecting rods that every big end is out of round by .0015 to 0025. I checked them twice and even had the machine shop check them..
I have a set of Carrillo steel rods but don't want to go that path...
Anyone got a got set of good 70-9525 rods? grin


79 T140D, 96 900M Ducati ....On a bike you can out run the demons..
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Re: Pile of junk connecting rods.
Hillbilly bike #563357 09/15/14 1:34 pm
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Just for giggles which torque figure were you using?
The rod bolts with UNF threads should be 24 ft/lbs and the CEI should be 28 ft/lbs.

Re: Pile of junk connecting rods.
John Healy #563361 09/15/14 1:43 pm
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22 ft pounds...UNF


79 T140D, 96 900M Ducati ....On a bike you can out run the demons..
Re: Pile of junk connecting rods.
Hillbilly bike #563373 09/15/14 4:02 pm
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22 ft-lbs (dry) is right, or 0.004"-0.005" elastic extension of the bolts.

Re: Pile of junk connecting rods.
Hillbilly bike #563397 09/15/14 5:57 pm
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...somehow I torque mine (UNF)with 4kgs because that was the only way that the conrods moved perfectly free on the crank.

Re: Pile of junk connecting rods.
Hillbilly bike #563402 09/15/14 6:16 pm
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Why can't the machine shop true up the big end? I would think .001" would be OK.

Re: Pile of junk connecting rods.
reverb #563403 09/15/14 6:17 pm
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Why not just get a pair of those rods resized in the bigend bores, common enough operation.

davy

Re: Pile of junk connecting rods.
Hillbilly bike #563411 09/15/14 6:40 pm
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Aluminum only gives you one "tap on the shoulder" that the load has exceeded the material's modulus of elasticity. It means that the stress stretched the material past the point where it would normally spring back. While you can do this with steel and resize the rods, aluminum is a different story.

I have never bought an aftermarket rod to go racing with. I always have used stock rods, and bolts, racing. That said I measure, and record, the rod and bolt dimensions before and after I use them. Any variation and the rods are thrown away. In some 30 plus years of racing I never broke a stock rod, even running the 500s between 9,000 and 10,000 rpm. Can't say the same about stock and Nourish crankshafts, especially the 500. The 750 broke its share of Nourish crankshafts until I switch to the Nourish large journal. That was problem solved.


Re: Pile of junk connecting rods.
John Healy #563424 09/15/14 7:45 pm
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I'm aware of "one warning " before the crankcases get sawed in half by a broken rod...

So here's how the rod big ends measure, I believe the are scrap...
Holding the rod with the small end straight up and measuring straight up and down is 1.7695 . Measuring across from left to right just above and below the parting line is 1.7710 .Out of round by .0015 across the parting line, both rods measure within a few 10 thousands of each other. The rods look nice and the small end not covered in burnt oil.

I run after market aluminum rods in my race 650 for lack of good used rods and not wanting to pay 400 bucks for NOS rods.


79 T140D, 96 900M Ducati ....On a bike you can out run the demons..
Re: Pile of junk connecting rods.
Hillbilly bike #563458 09/16/14 1:41 am
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Hey Hillbilly, when you say aftermarket do you mean cheap rods? I am hoping to button up a set of 500 cases with a set of rods that won't mind the occasional spin to 8k rpm on the dirt track. I thought the Carillo rods were the only way.

Jon, do you mean stock Triumph bolts or replacements. Does a company like APR get into this stuff?


Full time classic motorcycle mechanic and enthusiast to a fault
Re: Pile of junk connecting rods.
Hillbilly bike #563487 09/16/14 9:41 am
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HB: Here comes the conundrum. The Triumph specification for the big end bore dimension is 1.770". So the problem is where did this rod start out. Also it is a bit odd is that it is oval side to side rather than top to bottom.

Did you oil the threads before tightening? Did you face the threaded end of the rod bolt in a valve stem grinder so you could get an accurate reading on bolt stretch?

Re: Pile of junk connecting rods.
John Healy #563519 09/16/14 1:18 pm
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The threads are dry.I thought about spot facing the bolts but from the odd measurement I think it's a bit late for that..Yes,it's strange the way the big end is stretched. I also had my retired machinist friend come over with an assortment of measuring tools so the measurements are accurate.


79 T140D, 96 900M Ducati ....On a bike you can out run the demons..
Re: Pile of junk connecting rods.
Hillbilly bike #563523 09/16/14 1:47 pm
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Threads dry- good! In the future you might look at facing the rod bolts and take some notes for future reference.

But the bolt stretch of .004" to .005" is a good way to approach this especially when using lock nuts on the rod bolts. It is hard, without a bunch of experience, to get a meaningful torque reading.

Using lock nuts also precludes the multiple tightening recommended by ARP in an effort to seat the threads in the nut and bolt.

Re: Pile of junk connecting rods.
John Healy #563530 09/16/14 2:29 pm
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I got a deal on a new set of Harris made in UK rods...


79 T140D, 96 900M Ducati ....On a bike you can out run the demons..
Re: Pile of junk connecting rods.
John Healy #563615 09/17/14 12:54 am
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So which "STD" rods and bolts does John Healy use with large journal cranks ?


'74 T140V,'83 XR1000, C&J FLATTRACKER T140,
Re: Pile of junk connecting rods.
Hillbilly bike #563642 09/17/14 8:24 am
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The Nourish crank is the exception as TSS rods are like hens teeth. We have used alloy rods, and modified rod bearings, supplied by Nourish. I am not sure they still supply these rods.

Re: Pile of junk connecting rods.
Hillbilly bike #563783 09/18/14 9:41 am
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'77 T140J
"Vintage Bike". What's in your garage?

"The paying customer is always right."

Fitting round pegs into square holes since 1961...
Re: Pile of junk connecting rods.
Hillbilly bike #565479 09/29/14 3:47 pm
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Denis J: I use thunder engineering rods. They are aluminium and beautifully made. Extremely strong. Personal experience I think they are superior to carillo rods but no denying they are at least equal. We had a crank bolt let go and wizz around inside, it gouged the rod and it took it in its stride. Highly recommend

Re: Pile of junk connecting rods.
Hillbilly bike #565480 09/29/14 3:49 pm
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All race use for my usage of them

Re: Pile of junk connecting rods.
PatrickMcG #565484 09/29/14 4:45 pm
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The Harris OEM type rods didn't meet my quality inspection...I had talked to Marino at MAP cycle about his forged steel lightweight rods. I also considered another set of R&R aluminum rods...
The steel rods from MAP arrived a few days ago.. On my triple beam scale they weigh 429 grams.A stock late T120 rod is 405 grams.The Carrillo rod I have weigh 505 grams....The R&R rods about 415 grams.
The MAP rods look like aircraft quality,a very impressive piece...I also bought a set of MAP 750 "Routt" pistons so the cylinders can be honed to get a proper fit. The forged MAP pistons weight 10 grams less than a standard bore Hepolite 650 piston.
I sold the Carrillos on eBay. I have a set of nice used TRW Routt 750 6.5 inch rod forged pistons to fit a 3.012 bore if anyone is interested...


79 T140D, 96 900M Ducati ....On a bike you can out run the demons..
Re: Pile of junk connecting rods.
Hillbilly bike #565514 09/29/14 7:41 pm
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I highly recommend the MAP steel rods. After searching high and low for a good set of alloy rods, I used them in my last 650 project. I returned 2 sets of stock rods and 2 sets of R&R rods for bad quality. I check them with mandrels on a CNC set up and I can tell you the MAP rods are really precision parts. I was measuring as much as .02" out of straight over 6" on some of the junk rods I sent back. The scary thing is these will probably be sold to someone else...
Also, I sent the crank to John Healy's guy for ballancing.The MAP rods are really light so he had to remove very little material from the flywheel.

Re: Pile of junk connecting rods.
DMiller #565622 09/30/14 12:37 pm
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I remember your problems with the R&R rods.To be honest I never checked my set of R&R's other than bearing crush but the race bike runs great so they must be fine grin


79 T140D, 96 900M Ducati ....On a bike you can out run the demons..
Re: Pile of junk connecting rods.
John Healy #666108 09/01/16 1:05 pm
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Originally Posted by John Healy
HB: Here comes the conundrum. The Triumph specification for the big end bore dimension is 1.770". So the problem is where did this rod start out. Also it is a bit odd is that it is oval side to side rather than top to bottom.?


old thread, I know Chevrolet found that the rods pinch in at
the parting line and wipe oil off the crank so they had more
clearance at the parting line either on rod or bearing

when I've checked rods on engines i've built, verticle
measurement then 45 degrees each side of verticle to get
correct out of round

Re: Pile of junk connecting rods.
Hillbilly bike #666113 09/01/16 2:06 pm
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Quote
I know Chevrolet found that the rods pinch in at
the parting line and wipe oil off the crank so they had more
clearance at the parting line either on rod or bearing


All rods are torqued and finished honed perfectly ROUND during production. Rod bearing shells are NOT manufactured perfectly round. They have more clearance designed in at the split.

Re: Pile of junk connecting rods.
Hillbilly bike #666165 09/02/16 12:58 am
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yeah,i didn't know if the rods were being measured with out bearings
which is the norm -didn't want good rods being chucked out if they
were still allright

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