Crank Free-play

[al_roethlisberger]

Well, I dropped by Moto Italiano's new shop(still not officially open) in San Jose this afternoon to see how the bike reassembly is going.

 

Duane, the service tech, had my bike's parts neatly categorized/organized, and the engine itself mostly assembled. His estimate was that the bike should be ready in a couple days.

 

 

However, he had an odd preliminary observation that concerned him, and consequently me, a bit.

 

With the engine block on the table, crank and conn-rods installed, one could grab the tail of the crank and physically move the crank forward and back about 1/16th of an inch(it seemed).

 

Although the pistons, jugs, and other components were not yet installed, this initial observation seemed unusual.

 

With that in mind, with just the crank installed into the block, how much(if any) free play should the crank exhibit... "free play" meaning front/rear(non rotating) play?

 

And if none, or neglibly none, what is the first culprit to suspect and inspect to correct the problem?

 

I don't doubt that Duane will have it figured out himself, as he seemed quite knowledgeable and conscientious, however I wanted to get an idea myself.

 

 

That being said, the shop that balanced the crank seems to have done a nice job

 

 

Also of interest is that my stock pistons seem to have been worn, especially the left piston, on the skirts. The teflon coating on both sides of my left piston had the coating worn off down to aluminum as if the piston had be moving around, or the jug had been

 

odd

 

al

[helicopterjim R.I.P.]

I'll ask Gord at Valley Moto Guzzi. He isn't an expert , he is just incredibly experienced. I value his advice over most anything.

Personally I say put it back together and ride the S%*# out of it but then I'm not the brightest bulb on the string.

Cheers and hope all is well.

[Paul Minnaert]

Al, your free play there is the result of the big end bearing play. That should be correct, and if it is, no worries. Otherwise replace the shells there, that's not expensive.

[Baldini]

Al,

 

End float? Needs some for clearance, I would think it's OK but like Jim I glow a bit dim. I had a look in the manual couldn't find any tolerances (so it's fine then!!! ).

 

KB

[jrt]

It should be fine, Al- I have about that much play (fore/aft) on the engine I am perpetually rebuilding. Once the pistons/sleeves go on, it will be held fixed.

Jason

[JuhaV]

With that in mind, with just the crank installed into the block, how much(if any) free play should the crank exhibit... "free play" meaning front/rear(non rotating) play?

 

Hi Al,

 

Do not worry. This axial free play is completely normal. It will become somewhat smaller when the chain and sprockets of the timing gear are in place, but it will not disappear completely.

 

If you study the crankshaft bearing assembly, you can see that there is no way that it could provide accurate end float. This would require some kind of axial bearing surfaces in the crank and/or use of thrust type bearings.

 

During use the crank won't feel any signifant axial forces.

 

My understanding about this issue is based on this kind of experience

 

br, JuhaV

[tomsp]

good to hear the moto italiano is now in san jose -- Al, where is it? i can't find it on the WEB...

[al_roethlisberger]

Thanks guys, great quick response on the crank That's a relief.

 

 

Tom,

 

The "new" Moto Italiano in San Jose, is on West San Carlos, just one building removed from the intersection of Meridian and WSC(Safeway, Walgreens, GE Appliance store). It is located between the new construction on the corner(across Meridian from Walgreens) that is going to have a Starbucks, etc. and the self-storage complex.

 

It is on the opposite side of the street from San Jose BMW, which is a bit further down WSC toward 880.

 

Moto Italiano is in the old two story building that used to have the custom HD shop in there(Trident Customs?), which is now in the rear BTW. They've just about got everything setup, and it's a much more spacious shop than the one was in San Mateo. I think, especially with the long windows along WSC, Moto Italiano will get a lot of exposure in this new location.

 

I'm not sure when they'll actually be open, but it looks to be soon....

 

al

[BrianG]

In that icon of modern technology, the iron small block Chev engine, one of the crankshaft main bearings has flanges that ride on the cheeks of one of the crank throws, to define axial free play. It's simple, and elegant. I wonder why it wasn't considered in this far more sophisticated design.

[pete roper]

Al, when you say just the crank and rods in the block I take it that the timing chain and sprockets weren't on???

 

The thing is that unless you have the timing gear on there is nothing to set the end float on the crank so it will move fore and aft until the web faces biff into the bearings. Once the crank sprocket is installed the crank is pulled through the sprocket as the nut is tightened up and because it is all made pretty well the end float is set by the difference between the depth of the front main bearing and the crank journal.

 

As Keith sez there are no tollerances listed in the manual, never have been. If you ensure something is made right you presumably don't need to list a tollerance <_ . anyway i always check it and use the standard figure for end float from a datsun if good enough sophistcated work of art like daddo gotta guzzi src="%7B___base_url___%7D/uploads/emoticons/default_biggrin.png" alt=":D"> . 4 to 8 thou, 0.1 to 0.2mm is IMHO fine, you can go a thou or two bigger but no lower.

 

Also, for the benefit of JuhaV, there *IS* a thrust face on the front bearing. If you pull it out and look at it you'll see that the back where it faces the crank isn't flat, there are two, *channels* machined in it and it's through these that lubrication gets to the thrust faces. It is very important that the crank doesn't *float* too much, there is a strictly limited amount of side play in the rods on the crank-pin and in the little ends on the gudgeons. If the crank was able to lurch back and foward under the influence of acceleration and/or braking enormous side loadings would be imposed on rods, pistons and bores and believe me, they wouldn't last long!!!!!

 

Generally speaking, because the design is so simple, people tend to think that it's manufacture is also slapdash and inaccurate. In fact Guzzis are, generally, very well and accurately machined compared to many products and a lot of thought went into ensuring that by accuracy of manufacture repair and maintenance would be simple and easy. Setting the end float by doing up a nut on the end of the crank is a fine and splendid thing, it's common to most cars and many modern motorbikes but when the Guzzi motor was concieved most motorbike engines were still running rolling ellement cranks and some, like the appalling Ducati designs were so poorly made you had to shim absolutely everything to get it even roughly the right size!!!!

 

The Guzzi motor may well be a box with a couple of sticks in it, but they're well made sticks!!!!!

 

Pete

[Guest robbrugg]

"Also of interest is that my stock pistons seem to have been worn, especially the left piston, on the skirts. The teflon coating on both sides of my left piston had the coating worn off down to aluminum as if the piston had be moving around, or the jug had been"

 

Al - I would ask them to measure the cylinder walls (x and y axis, in 3 depths) and measure the pistons (180 degrees from the boss) - I am assuming that's where they are wearing. The cylinders may be out of round - I hope they are checking all that anyway...

 

 

As a side note: is there a resource that would tell us the Service Limits/Specs on our Guzzis? I haven't been able to get ahold of a "Guzzi-ology" book to save my life.

[al_roethlisberger]

I'll ask about the cylinders......

 

In the meantime, for Guzziology, contact http://www.motointernational.com/

 

....Dave Richardson, the owner of the shop, literally wrote the book.

 

 

There are also a few used ones on Amazon, which sells them new when in stock:

 

http://www.amazon.com/exec/obidos/tg/detai...=books&n=507846

 

 

al

[pete roper]

I have a set of RAM barrels and pistons in my little hot-rod. They too have a teflon coating on the pistons. Will I expect any of it to be there on the thrust sides after a few thousand KM???? Probably not <_>

 

I can understand the thinking, low friction material, used in racers, etc. etc. but people forget that racers, *real* racers are designed to get maximum power etc. for a very brief period of time. After they are over the finish line it doesn't matter a toss if they fall into a billion tiny pieces!!!

 

Much though most of us would like to think of our bikes as 'Racers on the Road' they ain't, and I tend to think that teflon coatings and the like are a load of old wank in normal, everyday, applications. I'm not fussed that my pistons have a teflon coating, my engine is adequately protected from it by an oil filter and a sludge trap, but to be honest I'd prefer it not to be there. Your opinion may vary but things like teflon coatings, asbestos exhaust windings, sodium filled valves and all the rest of the crap, (Dare I say Desmodromics???? ) are just a stupid waste of money. I haven't noticed reputable piston manufacturers like Wiseco rushing onto the bandwagon? Look at the FBF pistons for the V11, as far as I can remember no silly teflon coating there.

 

Pete.

 

(PS. I did a 1,200KM run oa Albury and back up through the Snowy Mountains opn my shitty old 44 BHP 'Vert over the last two days. My speed NEVER exceeded 85MPH and it was the best fun I've had in a fair old while! Then I found out the Race Bike has dropped a valve seat! Talk about a downer )

 

Pete