Running bad then good

[fredintoon]

XS650 buddy had a similar "sometimes it's a dream, other times it's a nightmare" tale to tell at last weekend's Biggar rally.
I told him, clean the carbs, clean the carbs, clean the carbs, it's easier for you, there's only two on your bike.
Meanwhile another guy was giving the bike a real close look and found the contact breaker wiring sheath was melted onto the cylinder head fins.
Intermittent short would cause the on again - off again running problem too.

[jjz28]

I think I found the problem. I was running the petcocks with the arm down. I thought it was reserve but it might be "on". I have no octi. Well I switched the to up wich is reserve I guess and its running good. Switch them back and ran poorly, back to reserve and good again. Its not something I can really tell except for in the lower RPMs so it weird. Anyway, I got the carbs cleaned for about the 5th time and the float levels set. One was WAY low. Also, I am ashamed to admit this but I have never ordered an air filter and it is bad! I took my air compressor and blew through it and could not feel a lot of air. I have never changed the filter and I has had gas in it several times. I am going to order one today. Has anyone noticed running better after putting in a new filter. I am probably the only one who ever let a filter go that bad. Just forgot to order it (several times).

[GLoweVA]

I think I found the problem. I was running the petcocks with the arm down. I thought it was reserve but it might be "on". I have no octi. Well I switched the to up wich is reserve I guess and its running good. Switch them back and ran poorly, back to reserve and good again. Its not something I can really tell except for in the lower RPMs so it weird. Anyway, I got the carbs cleaned for about the 5th time and the float levels set. One was WAY low. Also, I am ashamed to admit this but I have never ordered an air filter and it is bad! I took my air compressor and blew through it and could not feel a lot of air. I have never changed the filter and I has had gas in it several times. I am going to order one today. Has anyone noticed running better after putting in a new filter. I am probably the only one who ever let a filter go that bad. Just forgot to order it (several times).

Jeff, on the specials, up is reserve and down is on, forward is off and back is prime. Seeing that you've ditched the octy, then the prime port on the petcock should be capped.
Glad you fixed that out of spec float level, that'll help with the overall performance.
Now, get that new filter in there and see how it runs then.
Also make sure that your fuel line paths are good. (no kinks)

Another thing that might help to check is the petcock inlet screens.
IF it runs better on reserve, ie. it's getting more(better) fuel flow, then maybe the screen(s) may have some blockage. Just a thought.

[jjz28]

That's what I was thinking George. Something has to be blocked a little. I wanted to make sure everything was right for when it comes synch time. This bike pulls hard but I think it could redline faster than what it does. Would a synch help with pulling up the rpms faster? I have no trouble getting to 100 fast but I feel it could pull even harder. Maybe the air filter will help with that too, cause its not getting enough air.

[GLoweVA]

Yeah, the air filter will help a LOT. I've got a K&N in my SG (that reminds me, it's due for a cleaning too)
Once the bike can breath, then the sync will help a lot at the lower rpms.

Once those butterflies open up, it's all about the float level, fuel flow (jet size) and air breathing (filter or pods, etc).

[jjz28]

Should I get the K&N? Advance can get it for $44. By the time I pay shipping it will cost almost as much.

[GLoweVA]

Should I get the K&N? Advance can get it for $44. By the time I pay shipping it will cost almost as much.

I guess is more of a preference thing. I know that with the K&N I'll never have to replace it, EVER.
Whereas, If I got something else, I MAY have to replace it every so many miles.
When I got my G about 10 years ago, I got a K&N and havent' looked back since. When I got my SG, 2+ years ago, I searched and got a K&N off ebay for 1/2 of the cost of a new one.

(Wow, has it really been that long that I've owned my G ?!?)

[skids]

K&N washable filters are good forever... if they dont shrink due to leaking into your airbox!

[jjz28]

Good thing I didn't get one of those first. Until I found a float with a hole in it and cleaned up my needle valve seats, I probably run 1/4 tank through my airbox.lol Not really, but it did get in there a few times. I changed my oil like 4 times in the first month of having the bike cause I was afraid it had gas in it. I'm pretty sure it hasn't done that for a very long time though. I also had to trim the paper gasket cause it was catching a float.

[DGXSER]

On the petcocks, ON flows from the side with a solid portion to the lower section of the filter. ON and PRIME both flow from the side where the filter goes all the way to the bottom. As George pointed out, (provided you have all the right parts of the two petcocks together and on the correct side of the bike) Forward is OFF, up is RESERVE, back is PRIME, and down is ON.

On the Special models, the only difference between PRIME and RESERVE is that PRIME goes through the forward nipple on the petcock, bypassing the vacuum valve, while RESERVE goes through the rear nipple keeping the OCTY in the loop. So, if you have 86d the OCTY, then they are one and the same.

The only other thing to look at if your bike is running better on RESERVE than it does in ON, is how much fuel is in your tank. Trust me, you would not be the first person to think your bike was having issues only to realize, you needed some petrol product in the tank.

[jjz28]

my tank was completely full don. with the arm up it runs better than the arm down. I think after a synch it will run right.

[GLoweVA]

Thanks to BikerPhil for this photo:


There are 2 paths down the filter, one for 'on' and one for 'reserve/prime'.
The top 1/3 is the 'on' filter screen, and the rest of the filter it is for the reserve/prime position.
So, if there's an obstruction/clog near the top (or down in that filter tube), then the fuel flow will be restricted when on the 'on' position, but move the petcock to 'reserve' and you've got a WHOLE lot more surface filter area that won't restrict the fuel flow.(and a different flow path down the inside of the filter)

OR, Heck it even be something as simple as a messed up gasket like these:


Another school of thought is: on 'reserve', there's more 'height' of fuel pushing down ie. more fuel line pressure thus more fuel delivered. (Static fluid dynamics)(also why you have to pop your ears at the bottom of the pool)
That's why it's important to make sure there's no kinks and the fuel lines run okay.

[jjz28]

Thanks for that pick George. So, my top screens could be plugged. When I run this tank of gas out, I will check the petcock screens. Also, my lines are run in the loop style and one side petcock feeds the other side and circle around the air filter tubes and I have filters also. I am going to call advance and order that K&N filter right now, I think that will help a lot too.

[jjz28]

ok, just went out and its doing the same thing no matter where I put the petcock. So, I got to thinking and disconnected the vacuum line to the advance and no change that I can tell. Would that be the pickup coil wire? I revved it with it hooked up in neutral the other day and it did move a little but not much. Also, it don't feel like there is much suction on that #2 nipple, I mean it don't REALLY suck my finger on there. It does have some. How much suction is required to move that advance. I did it by mouth and it seems like more than the carb pulls. Also, I hooked the advance back up and a rode it about 55 mph at around 5k rpm in 4th I think to get a load and unhooked it while moving and no change at all. How much a difference do the advance make? Should I have noticed something? thanks.

[GLoweVA]

What's your vacuum line like? is it old and squishy?
In otherwords, could what little suction the carb is giving you be 'swallowed up' by the 'give' in the hose?
Can you suck on the vac advance and get the advance to move? (i think you said yes on this already)
Maybe your port on #2 carb is clogged. Try spraying some carb cleaner down there and see if it squirts out the little hole in the throat.

You notice the little notch in the butterfly plate? it's there so the hole isn't covered while the bike is at idle.

I'll also restate what I put in the pm so that all the other readers here can also see it:

Some ideas:
It sounds like it's starving for gas (or not firing) on at least 2.
When it happens, try spraying with some water or something on the header pipes and see if 2 of them are not as hot as the other 2. That should give us some good info as to if it's a carb/fuel or ignition problem. (Carbs are 1&2 / 3&4 and ignition is 1&4 / 2&3)