How to hold crankshaft to remove Primary drive pinion nut

[BarrieC]

Hi Guys,
found damage to small end of my conrod yesterday - dropped i assume by previous owner, or one of the many while, the engine has been in dismantled state! ( I cant believe i had not spotted this earlier, I think i focused too much on the bearing conditions)

So, biting the bullett, I have to replace the Conrods.............I want to take as much off the crank as possible before handing over to a suitable mechanic/engineer.

The crank is (always has been in my hands) out of the cases - looking for some suggestions as how to hold/lock/support the crank to take the Pinion/oil pump side nut off the crank.

Many thanks

Barrie

 

[grizld1]

Ouch! The easiest way would be to clamp the crank end in a well padded vise and use a buzz gun, air or electric. Or fasten the crank down by passing hanger strap through the small ends of the rods, screwing the strap down to the bench--you'll want to replace the rods as a pair anyway. The heavy duty rods from Mike's XS and Heiden Tuning are tougher than OE, the only performance part I can recommend from those sources, and a serious bargain. Have the crank trued and tack welded; the flywheels have a nasty tendency to walk out, especially after the crank has been separated.

 

[BarrieC]

Thanks Grizld,
I do have to read up on how the crank goes together, just to get me started: I take it trueing up is ensuring the journals (flywheels) and therefore the pistons are at exactly the same position in rotation? Regarding tack welding, is this on the big end pins? and can this be done after the crank has been reassembled?
Believe I will need specs. for whichever competant person i get to split and rebuild the crank, are these the endplay/gaps with the thrust washers?
Would you have a link to the specs and any useful info. on the cranks assembly?

Unfortunately, im in the UK, so thanks to Brexit, anything from Europe can be severly delayed and postage from the US is a bit limiting due to price. Fortunatley a UK company, Yambits, has OEM standard, Japanese made ConRod kits

Sorry about all the questions

Barrie

 

[grizld1]

Good questions, Barrie. Runout is measured at the journals. It's a measure of how much jumping around the crank is doing as it spins; the more runout, the more vibration. Mama Yama was pretty crude with the crank, specs allowed up to .002" of runout, and I've seen worse. I've also measured a crank with no detectable runout. Some motors left the factory running smooth as silk, others left jumping like paint shakers.

For specs, go to www.biker.net. Specs are the same for all 447 cranks.

 

[arcticXS]

Good questions, Barrie. Runout is measured at the journals. It's a measure of how much jumping around the crank is doing as it spins; the more runout, the more vibration. Mama Yama was pretty crude with the crank, specs allowed up to .002" of runout, and I've seen worse. I've also measured a crank with no detectable runout. Some motors left the factory running smooth as silk, others left jumping like paint shakers.

For specs, go to www.biker.net. Specs are the same for all 447 cranks.

FWIW, the 2 stroke RD twin cranks, which are of the same press fit construction, have much tighter runout spec, 0.03 mm if I remember correctly. 2 thou is more than 0.05 mm. I guess the slightly higher redline, and much peakier power of the RD may be part of the reason. An RD would spend a lot of time over 6000 rpm

 

[arcticXS]

And regarding the original question, if using an electric or pneumatic impact wrench, the sheer mass and moment of inertia of an XS crank should give enough "holding force" to get the primary gear nut off.

 

[BarrieC]

Thanks Guys,

great advice! I will do my research, between watching whats happening with our Royal Family (my wife is from Ireland and fascinated by the Royal family)
Back on track: I may have already found a suitable "proper" engineer

(photo of my old XS built from bits, again, for inspiration)

Barrie

 

[Signal]

Smed Speed in the UK are worth talking to for motor parts and engine work.

http://www.smedspeed.co.uk/index.html

 

[BarrieC]

Thanks Signal,
I have sent a message to Rick at Smedspeed, I was going to get the modified Sump filter, but thats on hold for now

 

[grizld1]

Arctic, another part of the reason in spec differences is that the RD and other models were designed by Yamaha from the ground up, and the XS650 was based on an acquisition. Based on half of a Toyota DOHC motor? Pure propaganda, still being pushed. The XS650 was a price point machine--the most displacement for the dollar available, done on the cheap. The variation in crank runout straight from the factory tells the story. BTW.002"=.0508 mm. Also note that the XS650 motor is the only 4-stroke in the Yamaha lineup that lacks a mechanical balancer. It's a design out of the 1950s.

Am I bashing Yamaha and the XS650? Not at all. What's kept my interest in the XS650 alive over the years has been that there are so very many improvements to make. I hated the XS1 when it came out priced $50 higher than the Honda CB450, and I lost sales because guys thought they were getting more than $50 more motorcycle. Arguable.

 

[BarrieC]

Guys, just to go back to one of my questions:

Regarding tack welding, is this on the big end pins? and can this be done after the crank has been reassembled?

Thanks for all the help and info.
Barrie

 

[grizld1]

Yes and yes, but let the tech who does the work call the shots.

 

[BarrieC]

Good Call, your up early! it is about 5:30 where you are?

 

[grizld1]

Yep.

 

[jetmechmarty]

Mama Yama was pretty crude with the crank, specs allowed up to .002" of runout, and I've seen worse. I've also measured a crank with no detectable runout. Some motors left the factory running smooth as silk, others left jumping like paint shakers.

That explains a lot for sure. One man says the 650 shake is intolerable while another says, "What shake?" My father-in-law was a Yamaha dealer through the XS650 production run. He told me no two bikes were alike.

 

[BarrieC]

So as the runout basically measures the roundness of the journals, you are stuck with whatever it is?

I hope mine is a good one after I spend a lot of money on it!

 

[jpdevol]

So as the runout basically measures the roundness of the journals, you are stuck with whatever it is?

I hope mine is a good one after I spend a lot of money on it!

The shafts (bearing journals) themselves can be checked for roundness, but the process of truing runout involves aligning the crank flywheels, that the shafts are part of, so that all 3 shafts are aligned and have the least runout possible.

So, in the rebuilding process, a misaligned crank can be - and must be - aligned. There is more, but that's the basic point. Attached provides method of measurement.

 

[BarrieC]

Thanks JP, that really helps my understanding, the 3 parts of the crankshaft are held together by the 2 X Big End pins and if they are not correcty positioned to line everything up or those pressed pins "walk", then major issue with vibration or worse!
My understanding from the diagram is 1,2,3,4 would measure the runout tolerances
8 is the rocking movement at the small end, measuring the wear of the big end bearing
7, the side movement at the bigend i'm unsure of, is that literally the sideplay of 0.6mm?

Barrie

 

[jpdevol]

There is a splined shaft (2 roller bearings thereon) that connect the R & L halves and then, yes, the alignment is controlled by the "big end rod" crank pins and that is where alignment is achieved.

Rod side-play is to be set at .3mm (.0012") new and the service limit is .6mm: literally the distance the rod/thrust washers are allowed to slide sideways on the crank pin.

 

[jpdevol]

Old joke: Big widget manufacturer had a problem with a widget machine that staff couldn't resolve. He calls in a reputable expert. Expert proceeds to study the widget machine a bit, takes out a little brass hammer and wacks the machine's flywheel just so. Fired it up and it starts producing perfect widgets like never before. Took ten minutes. Expert writes-up an invoice and hands it to the client.

Client: "A thousand dollars!?; you expect me to pay you that much for 10 minutes work?"

Expert: "You're not paying for the time it took, you're paying that because I knew exactly where to give it the wack and also knew the size of the hammer required."