1986 gsxr750 problem

[riversbikes]

An email from a buddy -- been trying to get him to join this forum but he's a bit of a luddite.  Aside from compression, or perhaps a timing issue, or way too much fuel to 1 cylinder, I'm stumped -- any ideas?:

The #1 cylinder on my GSXR is not firing.  It is getting fuel because the plug is wet.The spark plug is sparking.The coil’s primary and secondary resistance are within spec.

Looking at the top of the piston through the spark plug hole it appears black and wet.Now that I write this it is pointing ominously toward low or no compression.

I cannot test the compression because my compression tester does not have a small enough end to screw into the plug hole.

Annoyingly, the bike ran well last fall. What could have happened while it sat in the garage for a few months?

What do you think?

[wsn03]

Needle jets failing / sticking and flooding the carb. Compression doesnt go by doing nothing. I'd bet my life its a floodong carb

[banoffee]

I’d be looking at the carbs next too.

[yyt]

8 hours ago, riversbikes said:

Annoyingly, the bike ran well last fall. What could have happened while it sat in the garage for a few months?

What do you think?

If all was well before, best to check the 2 things that make it tick - fuel & ignition.

You can check the electrical system by starting the engine with the plugs out and looking to see if there is a spark on each plug.

With the fuel system, first check bowel fuel level, with the choke fully opened the engine should give some life indication.

Tell us how it goes..

[fatblokeonbandit]

10 hours ago, riversbikes said:

An email from a buddy -- been trying to get him to join this forum but he's a bit of a luddite.  Aside from compression, or perhaps a timing issue, or way too much fuel to 1 cylinder, I'm stumped -- any ideas?:

The #1 cylinder on my GSXR is not firing.  It is getting fuel because the plug is wet.The spark plug is sparking.The coil’s primary and secondary resistance are within spec.

Looking at the top of the piston through the spark plug hole it appears black and wet.Now that I write this it is pointing ominously toward low or no compression.

I cannot test the compression because my compression tester does not have a small enough end to screw into the plug hole.

Annoyingly, the bike ran well last fall. What could have happened while it sat in the garage for a few months?

What do you think?

Duff plug, once soaked in petrol they do give up

[wsn03]

1 hour ago, fatblokeonbandit said:

Duff plug, once soaked in petrol they do give up

Had a 1200 v low mileage that ran like a pig. All it needed was new plugs, the ones in it were barely touched but had got wet. Odd. Very sensitive to plugs.

 

However flooding carb would make the plug wet.

 

Take carbs out, connect to a remote tank, let them fill up. If fuel starts pissing out its needle floats sticking or shagged (they go in the end). Floats should be fine because they don't adjust themselves.

OEM is a good way to not have problems. Anything else good luck.

[billd]

Pull the valve cover off and just make sure there is not a valve hung up on #1 cylinder. If there is this will cause low compression. A valve can stick open simply from sitting as your bike has. Let us know how you proceed.

[wsn03]

12 hours ago, billd said:

Pull the valve cover off and just make sure there is not a valve hung up on #1 cylinder. If there is this will cause low compression. A valve can stick open simply from sitting as your bike has. Let us know how you proceed.

Is this a common occurence? After what sort of time sitting does it usually happen?

[Crass]

Surely if he's turned the engine over a stuck valve would have been clouted shut by the piston?

[billd]

The valve can be stuck in place by dried out carbon formation and inactivity when the motor has  not been running for a while. With respect to the piston slapping the valve closed the valve may only be stuck .020 open and the piston would not touch it yet it is enough to cause lose of compression. I'm not saying this is the case but is a possibility and very easy to check, simply remove the valve cover and check the valve clearances. If one valve is stuck open slightly the clearance will be excessive.