V7 Sport conrod play

[Phang]

I am replacing the old jugs with gilardoni on my 1973 V7 Sport.

All is well until I pulled the right cylinder.

I took a self explanatory video as follow.

https://youtu.be/XvUxEDz8ZNc

Please feel free to comment,  thank you in advance.

Phang

[Peter from Sch'dy]

To measure is to know?...If the chrome was bad on cylinders you are replacing you'll need to clean out the sludge trap as well. When you do this you will need to disassemble the rods and then you can inspect the shells and journals for proper size.
Best,
Peter

[huub]

hard to say anything from the play at the end of the rods,
it would be a good idea to at least change the bearing shells while you are in there, just as a precaution. 
even better would be to clean out the sludge trap , but that means a engine stripdown.

[canuck750]

Hi Phang,

I just finished assembling the bottom end on my 750S, the crank mains were ground but the rod journal was within spec, new standard size shells were fitted, new rod bolts and nuts, The rod is designed with lateral float on the crank, the piston maintains the rod position so you should see lateral movement of both rods once the pistons are removed.

It appears that the rod is rocking more than sliding laterally, that said I would remove the oil pan and unbolt a rod, mic the crank journal to see if it is within spec. As others have said the job is best done with the motor removed and the crank pulled, then all journals can be measured and sludge trap cleaned. If the bike is on original chrome cylinders you may be looking at a crank grind and new bearings.

Jim

[JoeW]

It's hard to tell from the video what direction the rod is moving. Con rod side clearance  is .3 to .5 mm or .0118-.0196" which is rather loose compared to the bearing to crank pin clearance .011 to .061 mm .000433-.0024". so some movement there is normal. But, Jim is correct in dropping the pan and having a look. If the pan hasn't been cleaned recently and there was flaking on the cylinder walls, there will be chrome flakes in the pan. If the bearings are damaged, you'll also find bearing material, it'll be dull compared to the chrome. To determine whether you need a crank regrind would require complete tear down and inspection. Remember, Guzzi cranks are very hard. I did a T3 motor last spring that had serious bearing wear and the crank looked so bad I ordered undersize bearings before sending it to the machine shop. Bob, my crank guy, called me a few days later and said the crank cleaned up in the acid bath and was well within spec, no grinding needed.

[Phang]

thanks for the replies.

both the original chrome bores didn't flake, almost like new except some light "starry nights" under strong lights.

the engine sounded normal before this, no big end knocking sound.

today I recheck the play, both left and right conrod move axially,  total play is about 0.5mm, the right conrod in the video has no radial play and won't rock along the  crank.

I have a new questions.

when I  installed the left gilardoni cylinder,  it needed some persuasion from a soft face mallet to enter the crankcase, so much so that I think I  will have problem if I need to pull it again in the future but the right side drop right in with only a light push from my palm.

I think the resistance was from the frction between the cylinder outer surface and the crankcase as I can easily move the piston with the rear wheel after the installation.

Do I need to worry?

[JoeW]

I have had snug cylinders before, nothing to worry about as long as the piston moves easily in the cylinder.

[Dick]

I think the resistance was from the frction between the cylinder outer surface and the crankcase as I can easily move the piston with the rear wheel after the installation.

Do I need to worry?

I would be concerned if block/spigot clearance is incorrect. No room for the cylinder spigot to expand, possibly causing piston seizure, (assuming the cylinder will expand more and sooner than the block). JMO. Good luck.

[Phang]

Thanks for the prompt reply Joe, it's reassuring to hear that from you.

Hi Dick, it make sense. I think I'll take the risk to fire it up and see what happens.

By the way, I tapped the cylinder in squarely and it seated nicely on the crankcase too, confirmed by uniform base gasket line around the perimeter.

[Phang]

I left the heat gun in the cylinder this way to heat up the piston so that I could push in the pin by finger.

I think it also expanded the jug.

I did the same for the right side but spent a while with the bloody circlip, more time for things to cool down I guess.

[canuck750]

Sounds like you are good to go with the new cylinders.

[Phang]

some updates.

I pulled the tight fitted left jug today.

piston, rings and Nikasil surface all fine, nothing unusual.

there were two spots on the spigot outer surface showing interference mark. coincide with the 10 o'clock and 12 o'clock studs. the corresponding spots on the crankcase look and feel normal.

I sanded the spots lightly with sandpaper and it dropped right in like the right jug.

I also dropped the engine sump, nothing unusual except a layer of sludge at the bottom.

and yes, the left conrod slide axially along the crank and no detectable axial movement.

[Chuck in Indiana]

I sanded the spots lightly with sandpaper and it dropped right in like the right jug.

I feel much better now.  A little too much clearance on the spigot is much better than a little too little.

[Kiwi_Roy]

I checked my big end shells with Plastigauge they were right at the limit for maximum wear so I slipped in a new set of standard ones with new rod bolts, they are cheap.