I need some help with my latest GS1000 dilema

[terry]

I just finished fitting a 1980 GS1000ET engine and 34mm CV carbs to my 1981 GS1000ST, and of course, I don't have a manual that covers the carb settings for the CV's. (my ST has 33mm slide carbs standard)

I've cleaned the carbs, blown out the jets and checked the diaphrams, every thing seems in order, and I wound all the air (mixture?) screws in until they seated, then wound them back out 1.5 turns. This was a bit of a ball park figure based on how they were set when I checked them, am I close?

Anyway, if you can help me out with some techo info I'd appreciate it. No real rush though, I rode it, but it ran like *@%^$*@%^$*@%^$*@%^$, lots of popping and very rough idle, so I did a compression check, results as follows:

#1 cyl 140 psi
#2 cyl 135 psi (so far so good)
#3 cyl 20 psi (crap)
#4 cyl 140 psi.

I tipped oil into #3 and tried the compression check again, it made next to no difference, so I'm guessing that I've got a buggared valve, I did the shims yesterday and the clearances are all fine, all on the looser side of the accepted tolerance (0.08mm) so unless there was some carbon build-up that has now gone and I just need to re-shim it, I'm guessing I've got a burned valve, or a stuffed head gasket. (there appears to be a slight weep at the front of the engine)

Ah well, it fills my days..................

[Anonymous]

If you suspect you have a holed valve you can do a simple leak down test, no equipment necessary.

Put that cylinder at top dead centre so valves are closed.
Take off the exhaust pipe.
Take out the spark plug.
Get some plastic tube (I lied when I said no equipment)
Put the tube to the plug hole so it seals,
- blow into the tube,
- listen for air coming out through the valve.

You only ever burn out exhaust valves from running too lean and hot. A typical hole is about a quarter inch diameter half circle. You've got some compression, so it might be smaller. These motors are too good at helping along an ailing cylinder, until the damage is very evident.

Kim

[terry]

If you suspect you have a holed valve you can do a simple leak down test, no equipment necessary.

Put that cylinder at top dead centre so valves are closed.
Take off the exhaust pipe.
Take out the spark plug.
Get some plastic tube (I lied when I said no equipment)
Put the tube to the plug hole so it seals,
- blow into the tube,
- listen for air coming out through the valve.

You only ever burn out exhaust valves from running too lean and hot. A typical hole is about a quarter inch diameter half circle. You've got some compression, so it might be smaller. These motors are too good at helping along an ailing cylinder, until the damage is very evident.

Kim

You were dead right Kim, it was #3 exhaust valve, I've replaced it and lapped the new one in, and the bike is now back together again, starts and runs well, but I suspect the new head gasket isn't sealing, (I've re-torqued it to no avail) as now I'm down to about 70-80 psi in each cylinder.

I'll take it for a ride on Saturday anyway, (only got it back together Tuesday night) but I suspect the head will have to come off again.........

[daveo]

[ but I suspect the new head gasket isn't sealing, (I've re-torqued it to no avail) as now I'm down to about 70-80 psi in each cylinder.

I'll take it for a ride on Saturday anyway, (only got it back together Tuesday night) but I suspect the head will have to come off again.........

check your valve clearances again before you rip into it, may save some effort