Valve clatter wasn't due to maladjustment, but gas in oil!

[brand new bike zealot]

I had a thread about how my bike started running weird after being on the highway for a while and it seems my initial diagnosis of valves out of adjustment was mostly wrong. Here are some of my clues that hopefully other people can use to diagnose their issues properly..

After being right warmed up, lotsa valve noise through midrange, mild tick off the line.

Running REALLY hot after highway run.

Just ran half bottle of stp carb cleaner through the tank. Too much at a time?

Anyway, I haven't changed the oil in 2500 km's or about 3 months, so it's due and it seems I have a slow oil leak (was aware of seemingly tiny amount of drip from kickstart and clutch thrust rod) that was being replaced with gas keeping the oil window in exactly the same position, duping me into thinking everything was ok. What made me think to bend down and sniff the filler cap was a sudden increase in oil loss, and noticing oil in the intake.

I know the carbs are worn, and it runs a little rich, but I've been told that it's very expensive to replace the needles and to just clean the plugs regularily and not worry about it too much.

My petcock is fine, although I assume 30 years old. The fuel leaking seems to be in the carb. I assume the floats are slowly dumping the gas into the motor when it's off?

Anyway, I hope I haven't done too much damage to the motor with the laughably thin oil/gas in the crankcase. I think I'll stick to changing it based on a timeline rather than a distance measure. That, and maybe use less carb cleaner.... or get the carbs fixed properly

[renobruce]

Needle valves are cheap.

http://www.z1enterprises.com/detail.aspx?ID=310

Buy those and some bowl gaskets, (13 bucks for 4), and an oring kit from www.cycleorings.com (cheap), and rebuild your carbs. You may also need a new petcock (don't buy the rebuild kit) which will set you back about 40 bucks. So for about 40-90 bucks and some of your labor, you should be good to go.

[tkent02]

Needle valves are cheap.

http://www.z1enterprises.com/detail.aspx?ID=310

Buy those and some bowl gaskets, (13 bucks for 4), and an oring kit from www.cycleorings.com (cheap), and rebuild your carbs. You may also need a new petcock (don't buy the rebuild kit) which will set you back about 40 bucks. So for about 40-90 bucks and some of your labor, you should be good to go.

You most likely don't even need the gaskets, or the needle valves. O rings yes, surely.
Take it apart, see what's wrong, put it back together, adjust.
It's all simple stuff...

[SqDancerLynn1]

78 doesn't have float O rings, You should replace the float needles if they are leaking AND replace the petcock. TO get fuel into the motor two things go wrong -- petcock leaking, not shutting off & float valve worn/dirty

[tkent02]

78 doesn't have float O rings, You should replace the float needles if they are leaking AND replace the petcock. TO get fuel into the motor two things go wrong -- petcock leaking, not shutting off & float valve worn/dirty

If it's a '78 it should have float bowl overflow tubes? And these overflows must be blocked? Or the gas would just **** out harmlessly on the ground?
I thought the gas leaking into the engine thing started when the EPA made the overflows go away on the CV carbs?

[gearhead13]

Correct me if I am wrong, but, if your fuel inlet needles are leaking, the overflow should go into the overflow lines and down the back of the engine before it gets high enough to get into the engine

[tkent02]

The only path that makes sense with VM carbs is for the fuel to run down the hose from a bad petcock diaphram into the vacuum port on carb number three, and into the engine from there...

[TheCafeKid]

78 doesn't have float O rings, You should replace the float needles if they are leaking AND replace the petcock. TO get fuel into the motor two things go wrong -- petcock leaking, not shutting off & float valve worn/dirty

They dont have Orings, but they do have those lil red/pink washers that need replaced now and then. Most times you can reuse them, though. And yes, they SHOULD vent overflow to air, unless the overflows are pluged up with crap (often happens) or you are dealing with so much gas it cant vent fast enough. The diaphram leaking thru the vac line is also a problem possibly. You are aware that the vac line on the VM carbs is on the THIRD carb correct?

[brand new bike zealot]

I'm pretty chicken when it comes to carbs, I think I did the gearhead's math homework in exchange for the carb rebuild in high skool shop... but, I've taken the tank off and left it with a line into a container on run, and no real fuel leaks could be measured. I have an o ring kit I bought from cyclorings, yet to be installed. I think I'm going to have to knuckle down and learn... you just wait guys.. more questions coming....

[brand new bike zealot]

If it's a '78 it should have float bowl overflow tubes? And these overflows must be blocked? Or the gas would just **** out harmlessly on the ground?
I thought the gas leaking into the engine thing started when the EPA made the overflows go away on the CV carbs?

I've had that happen too. Something jammed the float open, and fuel came madly flying out the overflow, except I didn't have any lines connected so it poured all over the motor I solved it by disconnecting the vacuum to the petcock until the motor stalled out. Whatever it was plugging the valve is now floating around at the bottom of the float bowl...