Hey everyone,

In the latest episode of "problems with my bike", after cleaning the carbs, removing the PAIR system, and reshimming the bike, the bike will no longer start from a cold start unless I put it on its center stand. I'm not sure why this is, and why its only when its cold, but it's 100% reproducible.

Once the bike is sufficiently warm I can start it from the sidestand or sitting on the bike and holding it center.

Does anyone have any ideas about what I could check for. I've never even heard if this so I'm totally lost.

Thanks!

Heat related problems generally are electrical in nature.
Check the sidestand interlock.

Quote from: bmf on April 03, 2015, 10:29:11 AM
Heat related problems generally are electrical in nature.
Check the sidestand interlock.

Even if the bike cranks but doesn't turn over?

That's a tough one... I'd look at the right carb not getting enough fuel while on the kickstand. My thought process is this: a cold engine is tougher to fire up than a warm one, and if the right carb is only getting gas on the center stand, then the left carb is trying to run the entire engine. Maybe check the float height while on the center stand vs the kickstand?

And I'm not thinking 100% straight right now (about to go to bed), but what about the vacuum line from the carbs to the petcock? I know if that hose isn't hooked up properly, the bike struggles to start and runs on one cylinder ....

Quote from: Big Rich on April 03, 2015, 07:30:14 PM
That's a tough one... I'd look at the right carb not getting enough fuel while on the kickstand. My thought process is this: a cold engine is tougher to fire up than a warm one, and if the right carb is only getting gas on the center stand, then the left carb is trying to run the entire engine. Maybe check the float height while on the center stand vs the kickstand?

And I'm not thinking 100% straight right now (about to go to bed), but what about the vacuum line from the carbs to the petcock? I know if that hose isn't hooked up properly, the bike struggles to start and runs on one cylinder ....

Ill take a look at the petcock tomorrow and report in. Do you know of a diagram for It on a 2006 gs500f?

Also, if its not getting enough fuel on the center stand,  then once its warm and I place it back on the center stand it should bog and die right? It runs like a champ after it starts. Even during warm up I can leave it on the side stand. I just cant start it.when its cold the engine will crank like it has no fuel until I center stand it.  It's REALLY weird I know. But I think you may be on to something with float height anyway since the bike is more forward on the center stand. That would cause the floats to lift a little in theory...hmm...

Did not realise it was cranking. I agree that it might be fuel. Have you tried to start on prime while on side stand. Maybe a vacuume problem to the petcock at startup?
Are you sure choke is working properly? Might be that steering is straighter on centre stand and that properly opens choke.

In cold conditions its harder to start a bike. Lets agree on that.

I think it might be a clutch issue. IF your clutch slips even a little, you won't notice. it with a notmal start. Howeverm in harder starting conditions, the slippage could just provide the resistance needed for it not to start.

I say, try to turn your clutchcable in a bit, at the clutch handle, so you make sure that its fully retracted when you start.

One should start in neutral, clutch will then have no effect.

Quote from: bmf on April 04, 2015, 09:48:34 AM
One should start in neutral, clutch will then have no effect.

Yes this is correct.

Update:

So I decided to start it in ON instead of RES and it seem to want to start from the side stand. I'm wondering if I'm having fuel feeding issues from the reserve side. Is there any way to confirm the reserve system is broken before I order a new gas tank petcock?

Weird.
to test the tank petcock:
Pull the tank off, hold it with the petcock over a rag or container, open the petcock and make sure fuel flows from both nipples.

did you try pri?

Errrm. .. the res/on thing a couple posts up. ... why was it on reserve? And turned to on?  Then it started!? ... how much fuel actually in tank? ... something reversed in the system possibly? ..

These bikes often 'have plenty of gas in the tank cos I can see it/hear it sloshing ' .. while really being at reserve level. .. it's a 5litre reserve!...

This theory does not explain the side/centre stand starting position though. . Cos side stand should increase fuel level on petcock side of tank....

.. just trying to think out loud..

I'm thinking that with the wheel on the ground, the clutch might still have a bit of resistance, and the engine a too low RPM to keep itself running.
With the center stand the rear wheel might rotate, even in neutral, giving less resistance, and allowing the bike to start.

The bike should start just fine in PRI. After it warms up, just switch over to 'on' (or res, depending on the fuel).

You might need a valve adjustment, and a carburetor cleaning if your bike isn't starting well.

Quote from: MeeLee on April 09, 2015, 09:44:12 PM
I'm thinking that with the wheel on the ground, the clutch might still have a bit of resistance, and the engine a too low RPM to keep itself running.
With the center stand the rear wheel might rotate, even in neutral, giving less resistance, and allowing the bike to start.

The bike should start just fine in PRI. After it warms up, just switch over to 'on' (or res, depending on the fuel).

You might need a valve adjustment, and a carburetor cleaning if your bike isn't starting well.

My valves were adjusted to spec 400 miles ago and my carbs were cleaned less than 100 miles ago. It's neither of those. Bike starts fine in ON with no struggling, so that throws the PRI theory out of the window. If the clutch had any resistance in neutral the idle would be choppy and low because it's not fully disengaging. After warm-up it idles so well you could set your watch by it. I've already tested all those things, which is what led me to believe the fuel tank petcock could be bad.


Janx, it was doing this ON/RES mess even with a full tank.


I will be checking the fuel petcock on the tank this weekend. If that's good, I will pull the carbs and recheck float levels. It has to be one of those two. It just doesn't make any sense otherwise.

Quote from: Dr.McNinja on April 10, 2015, 08:00:39 AM

Quote from: MeeLee on April 09, 2015, 09:44:12 PM
I'm thinking that with the wheel on the ground, the clutch might still have a bit of resistance, and the engine a too low RPM to keep itself running.
With the center stand the rear wheel might rotate, even in neutral, giving less resistance, and allowing the bike to start.

The bike should start just fine in PRI. After it warms up, just switch over to 'on' (or res, depending on the fuel).

You might need a valve adjustment, and a carburetor cleaning if your bike isn't starting well.

My valves were adjusted to spec 400 miles ago and my carbs were cleaned less than 100 miles ago. It's neither of those. Bike starts fine in ON with no struggling, so that throws the PRI theory out of the window. If the clutch had any resistance in neutral the idle would be choppy and low because it's not fully disengaging. After warm-up it idles so well you could set your watch by it. I've already tested all those things, which is what led me to believe the fuel tank petcock could be bad.


Janx, it was doing this ON/RES mess even with a full tank.


I will be checking the fuel petcock on the tank this weekend. If that's good, I will pull the carbs and recheck float levels. It has to be one of those two. It just doesn't make any sense otherwise.

Not necessarily, especially if you're running conventional oil. Ever noticed how much harder the bike "kicks" when you first put it in gear versus after you've been riding a while? It's because the clutch plates are more prone to sticking together when it's cold versus when it's warmed up.

An easy way to test this is to put the bike on the center stand and then insert a broomstick into the wheel to keep it from turning. If it starts with broomstick in...you know it's not the clutch. If it doesn't...guess what? It's the clutch.

My guess is that it probably isn't the clutch but a sticking float. The sloshing of fuel, fluctuation of fuel pressure in the lines, and the jarring motion of putting it on the center stand is sufficient to "unstick" the float(s).

Just thought of this...the sticking float theory is easy to test without disassembling anything. Do this:

• With the bike cold, connect two lines to the float bowl nipples and route it into some sort of container
• Without doing anything else, attempt to start the bike
• If the bike doesn't start, set the petcock to "PRI" and open both drains
• If the fuel drains continuously, then you know you have a solid fuel feed
• If the fuel drains and then STOPS, now put the bike on the center stand
• If the fuel starts to drain continuously...well, there's your answer. Stuck float.

Guess OP got the bike started?