RX-1 extremely low compression-(30 psi) Help!

[WesPower]

I just bought a 2003 RX-1. The kid I bought it from said he got 150 psi on all cylinders (which I now know is lower than spec, but I’m used to 2 strokes).

It has a really hard time starting when cold. I tried everything to fix the starting issue—nothing worked—so I went and bought a compression tester today. I found that cylinders 1–3 measured 30 psi, and cylinder 4 measured 90 psi (cold). I then warmed it up for a couple of minutes at idle and got 60 psi on cylinders 1–3 and 105 psi on cylinder 4.

It seems to run well when warm. It starts right up with a bump of the key and will do 100 mph (no more). The other thing is that it burned a whole tank of oil after 150 miles of riding.

I don’t know the best option. Should I check the valves and try some Sea Foam, rebuild it myself, buy a used engine with 2,700 miles on it for $500, or try to sell it cheap?

I already have $2,500 into this thing, and I don’t really want to keep it, but I also don’t want to lose much more money.
+It was sitting for awhile before I bought it

 

[RobX-1]

Those low compression numbers don't look good and when you state you burned a whole tank of oil, did you mean the oil tank reservoir you fill when changing oil was empty? The some RX-1's were known to burn oil but more like a quart every 500 miles but keep in mind these aren't two strokes where they are suppose to burn oil. As for cold starting, you are using the choke, correct?

Also, during the startup, there a temp light used to indicate the engine is warm and can be ran that will come on and then turn off automatically.

 

[Srxspec]

If it used a whole tank of oil in 150 miles the rings are shot, so you're looking at a full rebuild at least if you use the current motor.

 

[maim]

how many miles on the sled? you could get lucky and just have some tight valves.

 

[WesPower]

Those low compression numbers don't look good and when you state you burned a whole tank of oil, did you mean the oil tank reservoir you fill when changing oil was empty? The some RX-1's were known to burn oil but more like a quart every 500 miles but keep in mind these aren't two strokes where they are suppose to burn oil. As for cold starting, you are using the choke, correct?

View attachment 180276

Also, during the startup, there a temp light used to indicate the engine is warm and can be ran that will come on and then turn off automatically.

Correct the whole oil reservoir. I am using the choke correctly I would say the hard starting is the very low compression when it is cold. I think it cranks till the rings get hot enough to seat a little better then it fires.

 

[WesPower]

how many miles on the sled? you could get lucky and just have some tight valves.

2500 miles (I would say its definitely got some ring damage)

 

[WesPower]

If it used a whole tank of oil in 150 miles the rings are shot, so you're looking at a full rebuild at least if you use the current motor.

Do you thinks it's better to buy a used engine on fb marketplace with 2700 miles on it for 500$ or do a rebuild on the one I have (I would be doing the rebuild) I have no idea what it would cost

 

[maim]

With that low miles, I would pull the valve cover and make sure no valves are stuck as they will stick a bit on one that has sat for the summer.

 

[Srxspec]

Low compression can be caused by a valve that's slightly sticking open due to corrosion on the valve sealing surface, but burning oil is not a valve sticking issue, that's a piston ring issue.

 

[STAIN]

Did anyone have any success with the Yamaha Ring Free shock treatment when these first starting burning oil back in the day?
If i remember correctly, it was the oil control rings on these early Rx's that where sticking, correct?
I know that ring free stuff is pretty nasty stuff, I still have some on my shelf. I think Yamaha still recommends this treatment in some outboards.
if it was mine, I would give it a shot.......

 

[Srxspec]

Did anyone have any success with the Yamaha Ring Free shock treatment when these first starting burning oil back in the day?
If i remember correctly, it was the oil control rings on these early Rx's that where sticking, correct?
I know that ring free stuff is pretty nasty stuff, I still have some on my shelf. I think Yamaha still recommends this treatment in some outboards.
if it was mine, I would give it a shot.......

I used it occasionally, but if a motor is using over a quart of oil in a couple hundred miles, it's likely not going to help.

 

[STAIN]

I think the other thing to make sure of is that the oil is not contaminated with fuel. If fuel has gotten into the crankcase and contaminated the oil, it will give you low compression numbers and burn oil, no matter how many times you add oil.
The P.O. could have flooded the sled once or more or if the sled was stored improperly fuel gets forced past the needle/seat into the engine.
Start with a fresh oil change with a quality oil and track oil usage from there.
Again, just something to try and consider before going full teardown.