Bike Hard To Start When Hot.

[Shurup]

On my recent trip to Koh Chang some strange problem with a bike developed. When hot, if let sit for 10-30 min it's very hard to start a bike. If only a few min after it's been shut off or when it cools down more, it starts in seconds.

What it might be? The bike is 2005 Yamaha XVS400 (DragStar).

Is there any reputable bike shops on the island that can look at it? I'm on Koh Chang now.

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[Neilly]

I know diddly about the XVS400...but at a guess I'd say the carbs need a clean if it's only just started. I had an XL500 which had exactly the same problem.

[apetley]

Could be vapour lock. Sometimes fuel can vapourise in the carb if it is very hot either from the engine or climate. That will definitely make it hard to start.

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[Shurup]

Could be vapour lock. Sometimes fuel can vapourise in the carb if it is very hot either from the engine or climate. That will definitely make it hard to start.

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If I don't find a bike shop to look at it here, I'll see how it runs when I get it back up North, a little cooler up there.

Regarding the vapor lock, is there a way to prevent it? Like shutting the fuel off before shutting off the engine? Anything?

And any recommendations on any bikes shop on the island?

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[Shurup]

By the way, I don't recall it doing it when I was in Phuket, hot in there also so it's something new.

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[apetley]

If it is vapour lock then look for ways to keep it cool whilst parked is the simplest solution like parking in the shade. I have also heard of guys insulating their fuel lines to stop them getting too hot. Is there an easy way to stop engine heat getting to the carb/fuel line?

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[yankee99]

If it is vapour lock then look for ways to keep it cool whilst parked is the simplest solution like parking in the shade. I have also heard of guys insulating their fuel lines to stop them getting too hot. Is there an easy way to stop engine heat getting to the carb/fuel line?Sent from my GT-I9003 using Thaivisa Connect Thailand mobile app

Do you think the designers thought about vapor lock when they originally made the bike? I assume the owner never had to park in the shade before.

What exactly is the bike doing? Without a better description off hard starting out will be hard to help the op.

Edited June 10, 2013 by yankee99

[Shurup]

Engine is turing over without starting.

Sun or no sun doesn't make a difference, first time it happened it was way past the sunset, I went to have a supper, came back and it wouldn't start...

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[thrilled]

O don't think it's vapor lock,but who am I.I would give the carb A good cleaning,or get it rebuilt.

[Shurup]

Any sort of spray can carb cleaners available in Thailand? If yes, where can I get them?

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[VocalNeal]

Is it turning at the same speed? Are you sure? Battery maybe weak, starter maybe weak when it is hot. magnets don't like heat and over time...

Does it try to fire when you let go of the starter button? This is the sign of a weak battery. All the voltage goes to the starter, not enough left for the coils.

The other alternative would be that somewhere you have a vacuum leak

or the bike is running rich all the time. So starts when cold but is too rich when hot.

Find someone/workshop with a set of jumper/booster cables and try the hot start again. This will rule out the battery or not....

[Shurup]

The starter is turning full speed and nothing happens when I let the button go, battery is fairly new and I'm sure it's not it, doesn't explain why it starts fine when let sit longer, battery wouldn't recharge itself over time.

I don't rule out the dirty carbs or vacuum leak but it's not the battery.

Didn't have this problem yesterday to that bad extent but I was shutting the fuel off when leaving the bike. Was taking a tad longer to start but nothing like the last few days.

Could it be that the fuel in tank evaporates when it gets hot and pressure pushes the fuel into the carbs flooding them?

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[VocalNeal]

doesn't explain why it starts fine when let sit longer, battery wouldn't recharge itself over time.

No but if the battery was low and the starter is weak because the magnets are hot it would crank slower and use more energy. Then when the starter is cool.. But if the battery is new...

Didn't have this problem yesterday to that bad extent but I was shutting the fuel off when leaving the bike. Was taking a tad longer to start but nothing like the last few days.

Could it be that the fuel in tank evaporates when it gets hot and pressure pushes the fuel into the carbs flooding them?

If the tank vent is plugged the bike wouldn't run for long, so the tank cannot be pressurizing the fuel system. It could be that you have a sticking float which allows the motor to flood when stopped. Then the excess evaporates when you leave it standing. Or the bike is running rich. Buy a bottle of fuel system cleaner and bung the correct proportion into the tank to clean the system out.

Auto enrichment device is stuck? If XVS400 has one?

Edited June 11, 2013 by VocalNeal

[Shurup]

It has a starter choke but I'm not aware of any auto enrichment systems. It also has fuel heaters somewhere in carbs I believe (need to read the MOM again). Carbs were tuned not so long ago (less than 3000 km ago) with some tool, don't remember what it was, for proper AF ratio...

Didn't have problems starting it today, still keep shutting the fuel off though. Maybe it was just a bad tank of fuel and all of it is pretty much gone now as I went through 2 tanks since it first happened... will see how it goes but will buy a can of carb cleaner if I know where to buy and what to buy.

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[Shurup]

Was searching for one of my older topics, came across this one and thought I'd give an update.

It def was a tank of bad fuel, problem disappeared by itself after a number of fresh refills and bike never did that again.

Did not have to use any cleaners or anything.

Thanks for all the advice!

[AllanB]

With my NV400, it turned out to be a faulty coil and one weak plug lead (twin spark).

[AllanB]

Well despite the faulty coil, the misfire continued after the replacement was fitted. Over the past few weeks we have gone over everything I can think of.

1. Took the carbs off again and cleaned them, checked for wear and tear and nothing wrong, removed a tiny amount of dirt out of the float chamber. Set synchronisation with a 1/6" drill and mixtures screws.

2. Checked the valve clearances and guessed them to be the same as a 400 Steed .002" for inlets and .003" for exhausts, exhausts way too big, inlets just a little too loose. Engine now very quiet. Any comments about these two figures?

3. Checked operation and cleaned petcock.

4. Trimmed, tested HT leads, as I couldn't find HT cable for sale anywhere in KK. Anyone know where to buy copper core HT lead by the metre?

5. Changed the other coil for a SH unit, cleaned up HT and LT contacts. Youtube say you can get a DVM resistance reading across HT-LT, but I can get anything on any of the 5 coils I have. Comments?

6. Played around with the baffles to increase and decrease back-pressure, getting close and power/torque is better.

All this has improved the situation, but things are still not right somehow, tick-over is a little erratic too, so the next thing to do is try benzine instead of gasohol.

Any other ideas, no matter how unlikely, as despite everything, I almost have a great bike.

[yankee99]

Honestly it never ceases to amaze me how time is wasted on trial and error instead of proper troubleshooting.

[AllanB]

Oops! I posed this on the wrong topic, should have been one originally posted by me. Same subject, slightly different problem, but looks as though I wasn't paying attention in this case.

[saramsland]

Shurup.. What VocalNeal may be leading to is that if the battery is hot it builds and internal resistance... Causing a lower output to be available.. Was the battery cools again it would be like new..

[Lickey]

When you try to start it, put your hand over the air intake,

[VocalNeal]

Honestly it never ceases to amaze me how time is wasted on trial and error instead of proper troubleshooting.

Having done an Analytical Training Course myself, what would you suggest as the first question to be asked? Or even the first action to be taken?

[yankee99]

Honestly it never ceases to amaze me how time is wasted on trial and error instead of proper troubleshooting.

Having done an Analytical Training Course myself, what would you suggest as the first question to be asked? Or even the first action to be taken?

Well what i wouldn't of done is post 2, 3 and 9. I also would avoid post that suggest a redesign is needed for a bike that has run well for most of its life. I would have asked the poster some more specific questions since his op was vague.

I like to spend time troubleshooting as opposed to parts replacing. I always look at the basics Spark, fuel and compression.

[Shurup]

Not sure why this post keeps going, lol, but the problem I've had is gone now, was a bad fuel as I've mentioned in one of the latest posts here.

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[NeverSure]

I realize problem solved and I'm happy to hear it.

Only one poster suggested choke/fuel enrichener and I had that once. The choke lever would indicate that the choke was off, but it was about 1/2 on. The cable was out of adjustment. Of course it started well cold, but hot it was flooding. So just because one turns the choke clear off, it doesn't mean that it is wide open in the carb. Always worth a quick check. Harleys have an enrichener rather than a choke at least in the CV carbs, but still adjustable.

Congrats, OP.

PS For bikes with an enrichener, they have no choke but rather add more fuel to richen the mixture instead of cutting off air to do a similar thing.

Edited January 1, 2014 by NeverSure