1988 SB50 sputters high speed

[smanke]

I found the shroud cover on ebay and I am awaiting its arrival. I really hope this ends my problems. I will let you know the results. I won't be able to work on it til Friday because I will be out of town. I really do appreciate all the help scooter gods!

[smanke]

Well I got the cylinder shroud finally and have it all put together. I drove it hoping that everything would be good. However the same problem remains. I know the thought that it was soft seizing came as a theory. Due to the fact that it was getting hot and still now with the proper shrouds it's still doing it. I assume that once the damage has been done that it will continue to soft seize even with proper cooling. So where should I go from here? Should I pull the cylinder head off and inspect the guts?

[noiseguy]

You've got another issue then. Check the compression and post back.

[smanke]

My dad brought home the compression tester for me. I will check it when I get back into town Friday. The compression should be at 142 psi correct? What possible issues could be the culprit? Could it be a leaky head gasket? Or maybe inproper spark plug?

[Bear45-70]

My dad brought home the compression tester for me. I will check it when I get back into town Friday. The compression should be at 142 psi correct? What possible issues could be the culprit? Could it be a leaky head gasket? Or maybe inproper spark plug?

142 PSI is the number speced in the manual as minimum the compression should be. Check compression with the throttle held at WOT.

Issues could be;

bad head gasket,

bad base gasket,

bad case seals,

stuck rings,

scored cylinder walls,

bad reeds (but the engine would be hard or impossible to start),

or any combination of the above.

[smanke]

The scooter starts up fine so I would say the reeds are ruled out. I will check the compression on Friday when I get home. It should be 142 psi on the button right? I have a feeling that is where my problem lies. I just hope there isn't too much damage. I would assume this came from not having the shroud cover to provide cooling? I should have known better but sometimes you learn the hard way. So where is the best place to get parts?

[smanke]

The compression test is done with the engine off though correct?

[Wheelman-111]

Greetings:

The compression test is done with the engine off though correct?

Unless you drill a second spark plug hole, it is. The compression tester fitting is screwed in where the spark plug lives, usually.

Might be interesting to see what the pressures are with with ongoing Internal Combustion, though. Get a bigger gauge...

[smanke]

Alright I admit that was a dumb question and already had posted it and it was too late. I just want to get to the bottom of this mystery. It seems that gas prices aren't going down anytime soon. Besides it's a fun scooter to ride!

[Bear45-70]

The scooter starts up fine so I would say the reeds are ruled out. I will check the compression on Friday when I get home. It should be 142 psi on the button right? I have a feeling that is where my problem lies. I just hope there isn't too much damage. I would assume this came from not having the shroud cover to provide cooling? I should have known better but sometimes you learn the hard way. So where is the best place to get parts?

No, the minimum PSI is 142. There is not much chance it will be exactly 142.

[smanke]

Do you know where a good place to get parts is when the time comes? I am assuming I will need to buy some just don't know what yet. So anything below 142 psi I can consider there is something damaged?

[noiseguy]

Honda MC shop is the best place for the parts you'd need for a ring job. But let's cross that bridge when we come to it.

[smanke]

Well I will be home tomorrow morning. I plan on working on it first thing. I just hope I don't need too much in the way of parts. I'm prepared to do whatever it takes to get this scooter in good health. So what would be your theory on what all is damaged?

[smanke]

I performed the compression test today. The result was 75 psi which is well below what it should be. So the next step is to inspect the cylinder, piston and rings? I was pretty certain that this was the next step. So where is the best place for parts? I didn't have time to tear it down already.

[noiseguy]

I performed the compression test today. The result was 75 psi which is well below what it should be. So the next step is to inspect the cylinder, piston and rings? I was pretty certain that this was the next step. So where is the best place for parts? I didn't have time to tear it down already.

Did you test with the throttle wide open?

Above is correct; you'll need to pull the cylinder and take a look.