Difficult start when engine is hot and power problem after rejetting

[Freza]

Difficult start issue

Well I don't know who else to ask so maybe you guys could help.
I have an issue with starting my bike when engine is hot.


This is most prominent in hot weather, like now during summer, when outside conditions are: stale hot air with temps >30deg. Celsius


The issue happens only in these conditions:
1. the bike needs to be ridden hard (or long) so it warms up nicely
2. after the ride it needs to rest for at least 1hr (the more it rests the more difficult it starts later)
3. the weather conditions must be as described above


Starting it up after all 3 conditions are met is a difficulty I've been facing for the last 4-5 years. It usually takes at least 3 tries to get it started and once it starts, it does it gradually. Stutters for 2-3sec then normalizes.


4 different mechanics can't solve the problem, the last one serviced engine valves, carburetors, changed the battery, spark plugs, checked the voltage of engine electronic starter, etc.
In his own words, there's nothing wrong with the bike and it should start without problems, but it doesn't.


Since it's difficult to explain such things, I've recorded two videos.
They're both me trying to start it with above conditions met (ridden hard, rested for 3hrs, outside is summer 36deg. here)


See for yourself and tell me everything's ok:


1.





2.





Problem with power after rejetting


Besides problem with starting, now I have another problem. The above mentioned mechanic has installed a bit wider nozzles in the carburetors, because I wanted to add some power. I don't know which ones, probably the "beginner" ones, since my bike isn't tuned except for the K&N air filter and Arrow exhaust can (stock downpipes).


Now it pulls nicely through low and mid range, better than before, but after 9000rpm the problems start. It's just not explosive anymore, but it should be. As if power band now is linear instead of exponential.
Not just that, but riding it on 9-10.000rpm for a few seconds and opening the throttle now creates a brief loss of power - it halts/chokes, then opens up again, but not as powerful as before.
It lost power and explosiveness in the upper rpm.


Did you have those issues after rejetting ? Any ideas why it happens? Maybe it needs wider downpipes and more open air filter now?
In any case, I think I'll be returning the old nozzles, I'm sad enough with all this anyway 

[Frosties]

To me I'd be looking at a possible fuel vaporisation issue with high temperatures like >30 Deg C and an engine that sits in that heat after a hard run.


Does the fuel pump definitely stop clicking before you start the bike ?


Have you checked the fuel filter ?


Just my 2p after listening to the videos.

[Freza]

To me I'd be looking at a possible fuel vaporisation issue with high temperatures like >30 Deg C and an engine that sits in that heat after a hard run.


Does the fuel pump definitely stop clicking before you start the bike ?


Have you checked the fuel filter ?


Just my 2p after listening to the videos.

Hey thanks for the opinion.
I don't know anything about fuel vaporisation, but that sounds logical actually.


The fuel pump does stop clicking, but the last 2-3 clicks are very slow and almost as if it has difficulty.
The fuel filter is new.

[darrsi]

I had my bike rejetted and it hated it, it just never felt right so i took it back and had original jets put back in and it was fine straight away again.


You mention you have a K&N air filter, but have you ever cleaned it?
In a hotter country you're gonna be prone to more dust which can clog them up a bit.
I cleaned mine the other day using a bucket of warm water with some washing powder added, then just moved the filter left/right for about 10mins by hand until i could see the water getting dirty, then rinsed it off with clean water, let it totally dry naturally in the sun, and re-oiled it using the proper K&N spray.
You've not mentioned cleaning it in any of your posts before so worth a try anyway.


Also, when the bike plays up starting next time, try starting it with the side stand up, you may have a possible side stand switch problem.

[Freza]

I had my bike rejetted and it hated it, it just never felt right so i took it back and had original jets put back in and it was fine straight away again.


You mention you have a K&N air filter, but have you ever cleaned it?
In a hotter country you're gonna be prone to more dust which can clog them up a bit.
I cleaned mine the other day using a bucket of warm water with some washing powder added, then just moved the filter left/right for about 10mins by hand until i could see the water getting dirty, then rinsed it off with clean water, let it totally dry naturally in the sun, and re-oiled it using the proper K&N spray.
You've not mentioned cleaning it in any of your posts before so worth a try anyway.


Also, when the bike plays up starting next time, try starting it with the side stand up, you may have a possible side stand switch problem.

I'm probably gonna be returning original jets too.
Yes, my filter is regularly cleaned so it's not that.
Also, side stand doesn't make any difference...

[unfazed]

 
However with the kind of heat you mention fuel evaporation would not be uncommon and since you have covered most items like filters and valve clearances, put back the oem jets and with the carbs off set the pilot screws to 2.5 turns out from fully in.
There is a possibility of water in the tank which will find its way into the float bowls and since it does not evaporate as fast as fuel and will sit in the bottom of the bowl and be picked up first  by the pilot jets when restarting. Unfortunately water does not ignite with a spark
I would suggest while the tank and carbs are off to completely drain  the tank  by removing the fuel tap. Draining from the tap only will not completely drain the tank. Put in fresh fuel and that may be sufficient to solve the issue.

In Croatian you should probably be running the cooler CR9E plugs.

I had my 600 which is exactly the same model in northern Spain and Southern France in 36C and where it was slower starting after an hour in the heat after a long run, it was never as slow as yours was in the video.

[Freza]

Thank you.

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[BBROWN1664]

I have just watched the videos and it looks like you are using a slight twist of the throttle when pressing the starter button. This will potentially add to your problems when trying to start the bike.
It should start without you needing to touch the throttle.

[Freza]

It's starts even worse without a bit of throttle.

[Freza]

Today my mechanic disassembled the carbs and found out that my carbs have heating system, which was characteristic for fazers sold in colder countries, but not here.
He says that could be causing problems.

I didn't even know they produced carbs in two different versions. My bike must have been imported from some northern warehouse and sold here.
In his words, there's no way around it without some tinkering, which I'm not very fond of, tbh.

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[BBROWN1664]

The Carb heater is just coolant from the cooling system. You can just block off the pipes to remove it. In colder countries, it stops carb icing. It wont be causing your problem though.

You problem is partly heat soaking causing fuel vaporisation and partly a too rich mixture.