Strange starting problem

[Jackbob]

[quote=physics-teacher;919580]I have a GS650G that ordinarily starts instantly with a slight amount of choke. However, if the bike sits for a week or more without starting (and this only happens with weather mandated situations) the bike just turns over with maybe one faint=hearted effort at firing, then nothing but empty-handed cranking.

My GS1000 does the same thing if left for a week or more. I have come to the conclusion that the fuel has evaporated from the bowls - so logically set tap to prime prior to starting after a long lay off. However - even doing this sometimes no fuel flows from the tap (set at the prime position). I then have to crank a lot, or remove the vacuum line from the tap and apply a little vacuum to it (suck on it). The tap then goes pop and fuel flows no problem. Unsure why the cranking vacuum is not enough to overcome the diaphragm spring in the tap.

FYI - the tap is near new genuine Suzuki part at an extravagant cost. Tank is an 80 with the leverless tap design.

[Jackbob]

And i meant to add yes the vac line is in good nick + connected from the tap to the correct (#3) carb.

NB Warning ;Seems logical to me but if you have to resort to sucking on the tap vac line to get fuel flow in an emergency - i use a long length of clear plastic hose attached to the tap vac port and hold it vertically in case of any fuel leakage - no sense risking a drink of petrol!!

[physics-teacher]

This thread is proving very interesting, at least to me. I was half convinced that mine was the only bike that acted up after a week of inactivity, even when in proper tune. Now I see that Suzuki probably planned it that way for a variety of models just so that we would keep riding these bikes at least weekly, come Hell or high water.

[ktp1598]

You don't have the only one....

[jbs80106]

FYI...lesson learned....

One of the posters mentioned checking the left most plug 'cause the bike sat on side stand...I was told to park on center stand if for a duration to prevent fuel from the bowls spilling over into the engine or air box. Don't know if its true but I've finally mastered getting the beeatch on the center stand on the first try....usually!

[Stefnwolf]

Gas evaporation

Just for continuity.
Yesterday I drained the leftmost bowl, [lowest cos of sidestand], and got very little out.
Today pulled the carbs and drained all of them. Even less in there, I reckon about 2 coffe scoops at most. Seeing the size of the breathers / drain pipes or whatever they are, I think evaporation is not as unlikely as it seems at first.

Checked the petcock and it works just fine. Good flow on prime, and when on normal, a very little suck on the vacuum pipe provided identical flow.
Filter was very clean too.

[physics-teacher]

Strange starting problem update

So far at least for my bike a weak battery seems to have been the problem. With a new battery installed, and after several days of sitting in miserable winter weather, the bike started right up. It looks like a weak spark could have been the culprit. The evaporated fuel issue cannot be totally dismissed, because the more energetic cranking may be pulling fresh fuel with the vacuum the way it was designed. Anyway, back on the road to work this morning in 36 degree weather. About 2 or 3 degrees for you Kiwis and Ozzies.

[open roader]

I recently started experimenting with running wife's gs750tz when it first starts with the choke only. With a clear road and second gear one can accelerate quite nicely using only the choke no throttle. The idea being the plugs are allways dry when it wont start cold with the chokes on,so I figure they are plugged and a good way of unplugging them would be increasing the pull through them. I'll report back. So far this thing is driving me nuts,not old triumph nuts but close