1975 850t

[850brian]

Hello there, I am starting a new thread about restoring a 75 850t. I have changed out the cylinders thanks to this forum however I am trying to diagnose a problem I noticed before I swapped the cylinders. The engine is only firing on the right cylinder and nothing on thr left. I am getting spark on the left. Any ideas on what could be going on?

[bigbikerrick]

Have you looked at the plugs, are they wet with fuel?  Have you popped the float bowls off the carbs to check for gunk in the jets?  If you have spark, which you do, and fuel, and compression, it should fire up.
Rick D.

[John A]

The first thing I would do, especially not knowing the history of any work on the engine is verify the timing. What confused me years ago was the left cylinder is called #2. It’s because they are numbered front to back, not left to right. The engine is timed off #2. With the covers off and plugs out, roll the engine over and watch the valves opening. When the intake opens on the left and starts to close put a finger over the plug hole and as you keep turning the engine over you will feel pressure. That is compression and you are on compression stroke. The spark should fire a few degrees before the piston gets to the top, top dead center. There should be a line visible on the flywheel marking the fixed advance as well as one for tdc . Check the distributor to see if it is in a position to have the points open for the left side. If not, that is the problem.

[n3303j]

My T3 is timed off both cylinders.

D for Right
S for Left

Set the cylinder connected to fixed points to its correct timing first.
Then touch up the movable point set to get second cylinder in sync.

[John A]

My T3 is timed off both cylinders.

D for Right
S for Left

Set the cylinder connected to fixed points to its correct timing first.
Then touch up the movable point set to get second cylinder in sync.

Sure it is, I meant in the deeper sense like timing valve events. As you look at the engine from the front and observe the timing marks on the crank and cam wheels, they line up when the engine is on #2 compression stroke tdc.

[850brian]

The first thing I would do, especially not knowing the history of any work on the engine is verify the timing. What confused me years ago was the left cylinder is called #2. It’s because they are numbered front to back, not left to right. The engine is timed off #2. With the covers off and plugs out, roll the engine over and watch the valves opening. When the intake opens on the left and starts to close put a finger over the plug hole and as you keep turning the engine over you will feel pressure. That is compression and you are on compression stroke. The spark should fire a few degrees before the piston gets to the top, top dead center. There should be a line visible on the flywheel marking the fixed advance as well as one for tdc . Check the distributor to see if it is in a position to have the points open for the left side. If not, that is the problem.

Looks like this newbie has some researching to do. Thank you for the info. I head too that having a bent valve could be the cause? Would I bent valve still move?

[John A]

Looks like this newbie has some researching to do. Thank you for the info. I head too that having a bent valve could be the cause? Would I bent valve still move?

Yep, depending on where it’s bent. The easiest one to bend is the exhaust for it chases the piston when it opens. It only takes a touch to bend one as you are experimenting with cam timing. Don’t ask how I learned that. Didn’t expect the crank has enough weight that it will roll after the weight passes a point. I suspect the distributor is installed 180 out and as you roll it over and look at stuff you should be able to determine that as well as feel the compression which will not be there or reduced from the other side if a valve is bent and not seating

[Shiny Hat]

I wouldn’t think a valve was bent but the valves should have been checked when you did the other engine work.
At a minimum when the heads were off you could turn them upside down with a plug installed and pour some liquid over the valves (if you’re in your house preferably nothing highly flammable, this rules out acetone) and blow some air in the intake and exhaust ports. If the valves aren’t sealing you will see air bubbles showing around the valve and seat.

The old saying is you need three things, air, fuel, spark. You have spark (if it’s there at the right time is another thing)  you’ll have air but it needs to compress, check compression. Fuel, add some in the carb inlet, and see if it fires. I do not recommend starting fluid, it can cause severe damage.

Chip away and find out what you have and let the members know, they will tailor their advice based on what you can tell them.

[jrt]

I don't recall who it was...maybe Pat Hayes?  who was having an issue of not firing on one cylinder.  Whoever it was figured out that it was a weak coil; compressed (cylinder) gasses require more energy to spark.  The coil was good enough for ambient pressure, but not able to spark at compression. 

[cappisj1]

I agree with verifying the timing is as good as you can get it. To do this you really need to modify the brush plate in the distributer so it turns far enough. I think This Old Tractor site has a couple write ups. Once you are confident the timing and valves are correct and it still only runs on one side then spray some starter fluid in the carb on that side. If it runs some then it’s a carb/fuel problem if it won’t fire then it’s a spark issue and then you can take the correct trouble shooting path from there. It’s one or the other, fuel or spark, figure that out first.

Link to distributor mod needed.
https://www.thisoldtractor.com/moto_guzzi_tonti_distributor_dual_points_plate_modification_so_you_can_time_both_cylinders_properly.html

[guzzisteve]

If it were mine I'd clean points, lube dizzy & have a go at it, next would be change old plug wires.

[850brian]

Lots of good places to start. I am swamped with work this week but will post an update in a few.

[John A]

Lots of good places to start. I am swamped with work this week but will post an update in a few.

 

Take a few days off, we want to know!

[850brian]

Ordered some new condensers just in case and will be inspecting the points tomorrow. Hope to have a positive update tomorrow!

[nsmith]

what part of Ok?

[850brian]

what part of Ok?

Okc!

[850brian]

Update: put new condensers on and am definitely getting a better spark but the left cylinder is still not firing. Going to try cleaning out that carb again. Any other suggestions?

[850brian]

Update: pulled the left carb off to clean it and noticed it was dry. Followed the problem and found the fuel filter had broken and clogged the fuel line. And noticed the way the fuel line was routed, the fuel would not flow. Going to fix these issues now and will post back when it's running hopefully.

[John A]

Update: pulled the left carb off to clean it and noticed it was dry. Followed the problem and found the fuel filter had broken and clogged the fuel line. And noticed the way the fuel line was routed, the fuel would not flow. Going to fix these issues now and will post back when it's running hopefully.

Progress! I once bought a non running T and found it had two problems. One was a partially plugged idle jet and the other was the power jumper between the coils had a bare spot that would rub on the frame intermittently. Both on the same cylinder and the story was that it had stumped every one that tried to fix it. It was a good deal at a hundred bucks, around’82. I didn’t find the coil wire rub until I was parting it out. Thanks for the update!

[Turin]

When are you going to post a picture of your T ?

[850brian]

When are you going to post a picture of your T ?

Going to put some stock bars on it and get the seat redone!

[Turin]

looks better than my T did !

[850brian]

UPDATE!: I  cleaned that broken filter out of the tank and replaced the fuel lines and she started up super easy! Took her for a spin around the block and this thing rips! I need to restore my front brake caliper and for some reason the clutch wasnt working.

[Turin]

Think about upgrading the caliper? you can substitute a 4 piston caliper with an adapter.

[850brian]

want to upgrade the caliper?

Beauty! And I would like to restore the stock one if I can. It might be too far gone.

[n3303j]

Beauty! And I would like to restore the stock one if I can. It might be too far gone.

Stock caliper parts are available. Clean the castings. Replace the pucks and the seals and you have a caliper that is is good as new.

[Turin]

F08's are available and you can also get a F09 reproduction caliper.

[n3303j]

F08's are available and you can also get a F09 reproduction caliper.

Puck and seals are the only wearing parts.
https://store.bevelheaven.com/Brake-Related-Parts/Brembo-F08-Caliper-Rebuild-Kit-Special-black-pins/

[Turin]

The only thing salvageable on my T was the master cylinder. The 850T comes with a 15mm master which is huge for a single 2 piston caliper.  I tried a few different brake set ups. Here is the previous set up.



Brembo B34 caliper, stainless line, guzzipower caliper adapter. The EBC stainless rotor is pretty, but the stock cast iron unit is better if in good shape. Works well.

the 15mm master is big enough to support any pair of 4 piston or 6 piston calipers you would want to throw at it.
here is my current set up.

[850brian]

Do you all think this oil leak is coming from the oil pan seal?