Question about Cylinder Wear, Low Compression etc

[jthiessen]

I've learned a lot since owning this bike, but I am no Master yet...

My bike suffers from LCD (low compression disorder). I know this, what I'm not 100% sure on is how to fix it. I've set my valve clearances many times, I don't think this is the issue. I've been read about replacing rings, honing cylinders, lapping valves and more, but I am not sure where to start.

As soon as it warms up a bit I am going to take my motor out and open up the top end. From there I don't know what I can fix on my own, or what I need to take in to a shop.

How would you approach this situation?

 

[16VGTIDave]

I'd do a leak down test and find the cause of the "LCD" before anything else. If a leak down test isn't an option, then a series of dry and wet compression tests would be the next best (distant second place) option. A visual inspection of the bores can be accomplished with a "bore scope" through the spark plug hole, but unless one knows what they are looking at, this is probably pointless.

 

[drewpy]

maybe use one of those endoscopes for android phones, they are very cheap now and have a built in lamp

 

[XSLeo]

On your LCD, how did you check the compression?
It's best done on a warmed up engine with the throttle held wide open.
Leo

 

[jthiessen]

I'd do a leak down test and find the cause of the "LCD" before anything else. If a leak down test isn't an option, then a series of dry and wet compression tests would be the next best (distant second place) option.

I am not able to do a leak down test, but I did to wet and dry compressions. Both wet and dry were the same.

On your LCD, how did you check the compression?
It's best done on a warmed up engine with the throttle held wide open.
Leo

I drove my bike to a friends house and did the test there. So it was definitely warmed up. Compression is 95psi Right, 110psi Left.


I'm assuming one doesn't simply bring the jugs and pistons to a shop and ask them to fix it. That they need to see the engine in a more whole form? Just trying to save a buck where I can...

 

[16VGTIDave]

Since the wet and dry compression tests were the same, I'd be inclined to believe that the valves are not sealing well. The exhaust valves are the usual suspects. If you pull the head off, you can fill the combustion chamber with water and see if the valves are leaking. Adding some food colouring or something to the water to colour it (e.g. powdered drink mix) will make it easier to detect a leak.

Let us know what you find!

 

[zaphoid1801]

Just to be clear and avoid any confusion what Dave is talking about when he says to fill the combustion chamber to test for a leak, Heres a picture.