75 850t Cylinder

[850brian]

Hello all, I have recently acquired a 1975 850t that was my Grandfather's. I have been in the process of getting it back up and running for the past week or so since it has been sitting for 15ish years. I was unaware of the chrome cylinder issue and have started thr motor a handful of times while tuning the carbs and doubt they have been changed to another material. All of that being said, what should I look for in the motor to determine the amount of damage If any I have done by starting the motor and where can I find some resources or tutorials on changing the cylinders using a kit. Thank you.

[moto-uno]

  I think we'd be pretty surprised if there wasn't any damage in the cylinders . If you had access to a bore scope you'd probably
be able to see , but since you only need 4 or 5 tools to take the top end off ~ . And it's pretty much a given that cylinder damage
will be there ,either now or very soon . Not an "if", but a "when" kinda thing . Good luck, Peter

[850brian]

I guess what I meant to ask was would i be able to determine if me starting the motor a handful of times did any damage elsewhere in the motor. I fully intend on replacing the cylinders.

[cliffrod]

If there’s missing chrome, it went somewhere and probably did something along the way.  Whatever it did won’t be good…

You can check it all and fix it now -aka spend the money once- and know it’s properly fixed so you can enjoy the bike without any angst.  Or you can do the minimum now, cross your fingers hoping everything unknown is ok and see what happens.  It may be fine or you may learn that you should have left no stone unturned in the first place.  It won’t be any cheaper to fix properly in the future.

[Antietam Classic Cycle]

I doubt that you've done any damage just starting it a few times. But, there could be damage from 15 + years ago. The good news is the chrome usually flakes at the tops of the cylinders first, so a lot of it may have been blown out the exhaust port. Being a '75, your 850-T may have an oil filter, which will help catch flakes that do get into the oil.

[Don G]

Damage likely already done, buy a Haynes, Clymer if you have to  a Chilton's manual as well as down loading a free factory manual and a copy of Guzziology(not free) these will show you the way to repair your cycle. Also consider changing out the rod bearings if required, timing chain and spring loaded tensioner and an overhaul on the cylinder heads if required according to condition and mileage, if it is high mileage expect to remove the engine and do an in-depth re-furb as well as the whole drive train as its old and used and nearly 50! Sometimes its not as simple as just getting it going cheap, my motto is: just cuz it works, don't mean its right, riding something that needs maintenance to make it safe and correct can hurt you and your wallet.                                       
  If doing basic maintenance, check your top end oiling circuit, it may be plugged with debris, especially the rocker arms and banjos. DonG



DonG

[850brian]

Thank you for the reply! Surprisingly it only has a whopping 17000 miles on it so fingers crossed for a straight forward road to recovery! I am a fireman so I won't be able to drop the pan until Monday since im at work, but I will post an update with my findings.

[fotoguzzi]

There is a lot of real good info here,
https://www.thisoldtractor.com/moto_guzzi.html
Your T is a Tonti frame so look in that section.

I have a 1975 Loop frame,(motor nearly the same as yours) here’s what the bore might look like.. slight flaking near the top rim..I found nothing unusual in the oil/sump so assume the flaking was blown out the exhaust.. I’ve not gotten any deeper into it yet.

[Scout63]

This will sound silly, but it’s almost easier to pull the heads than the sump.  I’m kidding but not a lot.  I would lay out a clean towel on a bench and pull the heads.  Then inspect the cylinders carefully.  If no flaking of the chrome, then no worries about the bottom end. You can have your cylinders replated with Nickel Silicone or source replacement cylinders. Guzzi top ends are wonderfully simple and right there for the access.  Best of luck.  This forum talked me through my first Guzzi rebuild.

[850brian]

Thank you for the Info and picture, I will probably just pull the heads to start after sticking a magnet in there and hope I get lucky with it sticking. Anyone have the grocery list of parts that I will need for when I bite the bullet and replace the cylinders?

[chuck peterson]

MGCycle is only one source..currently out of stock

https://www.mgcycle.com/index.php?main_page=product_info&products_id=2129





Harpers Moto Guzzi

https://harpermoto.com/products/c-cyl-850-t-t3-13060162


Stein Dense (spelling?)

https://www.stein-dinse.com/en/

[850brian]

Great thank you! Has anyone heard about the knock offs from the Crusty Cycle?
https://www.crustycycle.com/products/moto-guzzi-cylinder-complete-83mm-850t-t3-eldorado-850gt

[Antietam Classic Cycle]

Great thank you! Has anyone heard about the knock offs from the Crusty Cycle?
https://www.crustycycle.com/products/moto-guzzi-cylinder-complete-83mm-850t-t3-eldorado-850gt

I wouldn't call them "knock offs" any more than I would use that to describe Gilardonis. The Crusty Cycle kits are from Stein-Dinse and the same kits old by MG Cycle I suspect. I've installed them in two customer's bikes and they work just fine, quality is on par with the Gilardonis.

[guzzisteve]

If you do some research you'll find you can send your stock cyl's to Millennium in WI for replating  in Nic, using your stock pistons. Low mileage on your pistons, they may be fine. Better than having to balance all involved.

[850brian]

If you do some research you'll find you can send your stock cyl's to Millennium in WI for replating  in Nic, using your stock pistons. Low mileage on your pistons, they may be fine. Better than having to balance all involved.

I will look more into it, it seemed around the same price as getting a new kit but I could be wrong. Why would you recommend that over getting the new kit or is it just for keeping it original?

[guzzisteve]

To keep motor balanced like original. Any kit should be checked for balance, weight of pistons, pins & rings. Manual will give you specs on differences allowable so as not to vibrate.

[850brian]

To keep motor balanced like original. Any kit should be checked for balance, weight of pistons, pins & rings. Manual will give you specs on differences allowable so as not to vibrate.

Great thank you! I will check the wear on the internals and post an update with which direction I plan on going with them!

[John A]

I consider it important to clean the sludge trap in the crankshaft. Unfortunately the crank has to come out for that because it is a plug facing forward that is staked and loctited in place. When it is removed it opens into the crank pin where you will find heavy black crud laying in there. Scrape it out and reinstall the plug if you haven’t butchered it when it’s removed. I smooth the threads that I can get to so it doesn’t rip the the aluminum plug threads as you wind it out. With the engine at that stage of disassembly clean and seal the cam plug on the back of the engine because the flywheel will be off. I’d replace the rear main seal and consider new clutch plates.

[850brian]

I consider it important to clean the sludge trap in the crankshaft. Unfortunately the crank has to come out for that because it is a plug facing forward that is staked and loctited in place. When it is removed it opens into the crank pin where you will find heavy black crud laying in there. Scrape it out and reinstall the plug if you haven’t butchered it when it’s removed. I smooth the threads that I can get to so it doesn’t rip the the aluminum plug threads as you wind it out. With the engine at that stage of disassembly clean and seal the cam plug on the back of the engine because the flywheel will be off. I’d replace the rear main seal and consider new clutch plates.

I will add this to the list, thank you.

[Antietam Classic Cycle]

I will look more into it, it seemed around the same price as getting a new kit but I could be wrong. Why would you recommend that over getting the new kit or is it just for keeping it original?

Millennium charges $309.95 per cylinder for replating, add rings ($132.24) and you'd spend $752.14 (and still have old pistons which may be worn) vs. $650 a pair for for kits with new pistons.

The new piston assemblies weigh within 5 grams of the original pistons, so the engine will be just as smooth as before in my experience. 

[850brian]

Millennium charges $309.95 per cylinder for replating, add rings ($132.24) and you'd spend $752.14 (and still have old pistons which may be worn) vs. $650 a pair for for kits with new pistons.

The new piston assemblies weigh within 5 grams of the original pistons, so the engine will be just as smooth as before in my experience.

Awesome, it looks like I would need the 2 gaskets and 2 o rings for the cylinders and then some for the exhaust (I already have extras for the carb intakes) any other tidbits I would need to get the cylinders back to normal?

[Antietam Classic Cycle]

Awesome, it looks like I would need the 2 gaskets and 2 o rings for the cylinders and then some for the exhaust (I already have extras for the carb intakes) any other tidbits I would need to get the cylinders back to normal?

MG Cycle sells a complete kit: https://www.mgcycle.com/index.php?main_page=product_info&cPath=284&products_id=4788

Use two intake manifold gaskets per side.

[850brian]

MG Cycle sells a complete kit: https://www.mgcycle.com/index.php?main_page=product_info&cPath=284&products_id=4788

Use two intake manifold gaskets per side.

Mgcycle looks sold out I think I found the same kit on thr crusty cycle. Thanks for the tip on the intake gaskets!

[guzzisteve]

You got your answers, unlike the other forum, not a peep. AND you need 12 orings-4 on top 2 underneath on ea side.
I had 2 sets done w/cast iron LA sleeves matched to original pistons. It all works.

[850brian]

You got your answers, unlike the other forum, not a peep. AND you need 12 orings-4 on top 2 underneath on ea side.
I had 2 sets done w/cast iron LA sleeves matched to original pistons. It all works.

Already very thankful and happy to be a part of this forum! Thank you

[John A]

You may want to do the sludge trap at a later time, it’s a good bit of added work.

[Antietam Classic Cycle]

Mgcycle looks sold out I think I found the same kit on thr crusty cycle. Thanks for the tip on the intake gaskets!

The top end gasket kit is in stock at MG Cycle.

[850brian]

The top end gasket kit is in stock at MG Cycle.

Is that all the gaskets I would be replacing during the cylinder job?

[Antietam Classic Cycle]

Is that all the gaskets I would be replacing during the cylinder job?

Yes, plus the intake manifold gaskets.

[jrt]

I'll add two more points-  one is obvious, I hope.  Label your Left/Right, Intake/Exhaust parts.  Don't mix and match.  And- when you do take out the sludge trap, use an impact driver.  It is less likely to strip out.  I suggest just buying a new plug- they are very cheap.