No acceleration passed 3rd

[850brian]

Hello all, I have a 1975 850t that I am restoring. I thought I had it road ready; however, it seems something is not quite right. Just got back from a test drive and it has decent power up until about 40mph and about 3rd gear and then it seems that no matter how high the rpms are there is no acceleration like at all. Any thoughts?

[Dave Swanson]

Were the carbs cleaned thoroughly?  Did you set the ignition timing with a strobe?

[850brian]

I did not set the timing with a strobe and the carbs were cleaned rather thoroughly.  Additionally I have noticed a rather significant oil leak coming from the hole just above the oil drain plug. Any ideas?

[Tkelly]

Clutch slipping?

[Dave Swanson]

I did not set the timing with a strobe and the carbs were cleaned rather thoroughly.  Additionally I have noticed a rather significant oil leak coming from the hole just above the oil drain plug. Any ideas?

Of course it is either the front seal of the transmission leaking, the rear main engine seal, or both.  There are no easy fixes.  I think you know what the next steps will be.

Tkelly's question is valid.  Is the clutch slipping?  Could be oil soaked plates.   

[Tom H]

Rear main seal leak. Rear main bearing carrier gasket. Front trans seal. Oil on the clutch plates can cause them to slip? Leak can also come from the breather hoses if the clamps are not tight or the hoses are bad.

Tom

[850brian]

Thank you for the reply, it doesn't seem that the clutch is slipping. I will take a look at the breather hoses with fingers crossed.

[850brian]

Unfortunately it looks like I also have oil leaking out of the inspection plug

[Antietam Classic Cycle]

Time for:
https://www.thisoldtractor.com/moto_guzzi_loopframe_transmission_out__check_these_things.html
https://www.thisoldtractor.com/moto_guzzi_loopframe_engine_out__check_these_things.html

[850brian]

Yeah just had to trailer it home. It lost all acceleration at any gear at any rpm. Wish me luck

[guzzisteve]

I would check your timing, maybe it moved. I remember you asking about timing last.

[pehayes]

After you set the ignition timing correctly, I would also check for proper centrifugal advance of the spark under higher rpm.  If the advancer gets dirty/stuck, it will start and idle just fine.  It will accelerate at low rpm just fine.  It will feel like hitting a wall when  you get to higher speed and higher rpm.

Patrick Hayes
Fremont CA

[Scout63]

It sounds like two separate problems.

Oil in the clutch housing could be rear mail seal, maybe the crank vent tube came loose?  If it is gear oil leaking then front trans input seal. Either way a crab is coming.

Loss of power would be spark or fuel. If it were just high rpm then maybe jetting.  But there is a total loss.  I would check power and ground wiring to the coils and distributor. Put a voltmeter on them and start wiggling wires all the way back to the fuses and switches.

[850brian]

After you set the ignition timing correctly, I would also check for proper centrifugal advance of the spark under higher rpm.  If the advancer gets dirty/stuck, it will start and idle just fine.  It will accelerate at low rpm just fine.  It will feel like hitting a wall when  you get to higher speed and higher rpm.

Patrick Hayes
Fremont CA

I will look into this. Seems exactly like my symptoms.

[John A]

If you are in third about 4500 rpm and go to wide open and the rpms increase without acceleration, it’s due for some clutch work. Once they start to slip, they are done for.

[brider]

I agree with John A, symptoms say clutch slipping.

[850brian]

If you are in third about 4500 rpm and go to wide open and the rpms increase without acceleration, it’s due for some clutch work. Once they start to slip, they are done for.

So I need to get a new clutch and probably replace the main seal?

[brider]

So I need to get a new clutch and probably replace the main seal?

I would think new friction plates and a fix to whatever is leaking to contaminate the clutch. Might not know fer sher until you pull the tranny.