Tired Engine: Low Compression

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.

Joined
Nov 5, 2003
Threads
73
Messages
292
Location
Just north of here
Here’s my compression for 75 2F.

Compression Test Results
Cylinder Pressure
1 50 / 45
2 110
3 65
4 120
5 105
6 105

These were dry tests with the engine warm. The valves have not been adjusted in 3 (+?) years.

I know the next step should be putting oil in the cylinders to see how the compression readings change (which I haven't done). Then the next step should be a leak down test. (which I haven't done)

So what’s my question?

My hunch is the engine is tired… I think the 105 compression readings gave that away. So new rings, pistons, or even further --> rebuild? I guess nobody can answer that without more info, but isn't that a logical diagnosis?


My problem is that the Cruiser is now 600 miles away, and the next time I'll work on it is in August. I am reluctantly getting professional help, due to the location of the Cruiser and the fact I will be 3000 miles away from it this summer. The area which it is located doesn't have Cruiser specific mechanics. I assume this can be okay, as long as the mechanic is knowledgeable.


My question:

Once a diagnosis is reached, assuming the worse, that the engine needs rebuilt (which I think is most likely) should I rebuild for $$$ or put a bandaid on the problem and swap out for another 2F? Ultimately this will be decided based on the real problem. Or maybe I can replacing the piston rings and bearings, do a valve job on the cylinder head and other basic stuff... I just want to get some ideas figured out so that when I talk with the mechanic, I'll know my options.


Thanks for the help! :crybaby:
 
I think you should reserve a full rebuild for a later date.

Your engine issue looks to me to be poor maybe even burnt valves. and I'll venture a four dollar bet that a new valve job, mill the head a bit and a head gasket will make it run like new again...

That engine is based on a superbly designed adn awesomely reliable engine that often exceeded 200K miles as daily drivers back in the 60's when most engines were worn out and needing rebuilds by 85K miles.

Think on spending the $200 bucks for the valve job adn the $25 bucks for the gaskets and coolant, and do the work then if it don't improove things rebuild the whole thing, but I think you'll find it unnecessary.


FE
 
How does it run ? Does it smoke? Stall? Does it have power? Usually the telltale sign of rings, etc is smoke and excessive oil consumption. If not, valves, etc could be the problem.
 
Reviving an old thread here.

I still am having problems. I had a mechanic look at it. He adjusted the carb. and made the thing worse.

When I am driving it, it won't idle. I can drive it, but not well.

I am weighing my options:

I don't have a good place to work on it, so work would have to be done at a shop. I am trying to make a list of the problems and find out what needs done.


I am going to get a leak down test done to see the problem is the rings.


So hopefully, it isn't a fully rebuild maybe the following "spruce up"
1. Hone cylinders and put new rings in
2. Grind valves
3. Recut valve seats
4. Check head for true and surface as needed, new gaskets
5. Main and rod bearings could be done at a later date if oil pressure is low.
6. Check tolerances on the oil pump (FSM)
Thanks for the help
 
Last edited:
Reviving an old thread here.

I still am having problems. I had a mechanic look at it. He adjusted the carb. and made the thing worse.

When I am driving it, it won't idle. I can drive it, but not well.

I am weighing my options:

I don't have a good place to work on it, so work would have to be done at a shop. I am trying to make a list of the problems and find out what needs done.


I am going to get a leak down test done to see the problem is the rings.


So hopefully, it isn't a fully rebuild maybe the following "spruce up"
1. Hone cylinders and put new rings in
2. Grind valves
3. Recut valve seats
4. Check head for true and surface as needed, new gaskets
5. Main and rod bearings could be done at a later date if oil pressure is low.
6. Check tolerances on the oil pump (FSM)
Thanks for the help


Sounds like you want to rebuild that motor. Go ahead, it's only money.

I agree with the above posts, if it's not smoking or using oil it's most likely bad valves. A head job is alot cheaper than a rebuild, especially if you don't need it.

I'm sure there is other places on that 40 you can throw money at.

By the way...that guy that screwed up your carb. Did he make good on that?



:beer:
 
I've seen a few of your other posts. Where are you going to school in WA? Why don't you try to hook up with some cruiserheads in your area. Maybe they could recommend a shop or even help out with a dry place to work on your rig.

Good luck! :cheers:
 
If it's not running, and won't idle, it may be the sign of other problems (i.e. vacuum leak).

I'm not saying your engine doesn't need either a valve job or a rebuild, but youi may want to get it runnning as well as you can befroe you go throwing a bunch of money at the problem.

The best advice is to hook up with others who can help you diagnose the immediate problem, and then make educated decisions.

Good Luck

Rocky

Can you take a general engine repair class (auto shop) at your college? Bring in your cruiser and make it into a project vehicle!
 

Users who are viewing this thread

Back
Top Bottom