Are symtoms related to vacuum petcock??

[Windsmile]

I have noticed a pattern related to difficult starting on my GS750T. What's happening is if I haven't started it in a week or two, it takes a long time to lite up the engine. After 3 or 4 attempts that last for 15 or 20 seconds I get get a few muffled coughs and then after a try or two more it fires up.

If I use the bike again within a few days, it fires up instantly. I'm wondering if this could be related to a problem with the petcock's internals such as a sticky diaphram or other internal part of the petcock. The vacuum line to the petcock is in good shape and solidly attached at each end.

If the scenario of the difficult starts followed by easy starts a day or two later is a classic problem, I'm hoping that someone out there has a classic answer to help me out. I've already figured out a simple solution which is to ride the bike every day or two but life has a way of interferring with that fix.
Thank you.

[sedelen]

I believe this is probably normal, I have the same problem with both my bikes, I think the gas depletes, evaporates, or what have you in the carbs.
If I go a week or so without running it, it'll take awhile for the fuel to get
where it'll fire. But if I put it in Prime, it'll start right up.

[TheCafeKid]

Correct.

Let sit for a week or two, the gas will evaporate. The carbs are not air tight.
It will evaporate even quicker in certain circumstances, such as carbs with individual filters, on a hot summers week. I've, in the same situation, had the gas evaporate in a couple days to the point that I need to switch it to prime.

Switch it to prime, wait about 5-10seconds and give it a crank.
Make sure however you never leave it on prime, as in that setting fuel flows freely.

[keman]

Yep, if my bike sets more than a day or two, I automatically switch it to prime, give it about ten heartbeats and back to on. Starts right up everytime.

[Windsmile]

Thank you Cafekid and sedelen for your advice...

Both of you have had the problem I described and offered the same advice. I'll start switching to prime from now on when I haven't ridden the GS in awhile.

Not being familiar with vacuum operated petcocks lead me to persuade myself that the three positions were "on", "off" and "reserve".
Best to you both for being so kind to respond.

[sedelen]

Please make sure that once you get it up and running to switch it from Prime to ON, otherwise your carbs could overflow if left in Prime with engine off and possibly fill your crankcase with gasoline .

[Steve]

Not being familiar with vacuum operated petcocks lead me to persuade myself that the three positions were "on", "off" and "reserve".

Nope.

Rotated fully clockwise (tab pointing forward), it is in REServe.
Rotated so tab is pointing down, it is in ON.
Rotated fully anti-clockwise (tab pointing rearward), it is in PRIme.

As mentioned, DO NOT LEAVE IT IN PRIME. Put it there while you are putting on your helmet and gloves, turn it back to ON, start the bike.

.