Motorcycle wont idle when warm

[toreckman]

I've owned an 01 VFR800 since November and only driven for around 50miles (there is 31k on the clock).  The weather was pretty bad in December/early January so I wasn't out on it, but did start it a few times and ran until the cooling fan went on (around 80C) and then switched off...no problems.  I was told when I purchased the bike that the stator (or the RR, i cant actually remember which) had just been replaced.

 

One day I went out to go for a run and the back tire was flat.  So I got a new tire installed.  When I got the bike back it took awhile to start, it seemed fine though, however I only ran it for 1 minute.  I just put that down to the petrol being sloshed around a lot while the bike was being transported. That was about a week ago.

 

I went out today to go for for a ride and it started it up no problem.  As it was warming up, the revs started dropping as normal but then the engine cut out after a few minutes (after the idle went down below 1000rpm, which seems very low).  After that it would start but cut out about ~2seconds later.  If I pull back the throttle any amount it cuts out immediately. The bike was still below 50C at this stage. I let it cool down a little (few minutes) and started it up again and it started fine.  I throttled it to about 3000 for maybe 30seconds and then left it idle...no problems.  But ~1 minute later it cut out again with the same symptoms, wont stay on for more than a few seconds and increasing revs cuts it out immediately, at this stage the bike is only 60C, so it had not warmed completely.

 

I pulled off the seat and had a look around the battery/wiring etc and didn't see anything out of the ordinary.  I checked the oil level and it was fine. I've no idea what could be causing this and didnt have time to dive into it.

 

The next thing I was going to check is the FI error codes, then clear them and start the bike again to see if it generates any code.  Then check the battery voltage on idle and when around 4000rpm.  If there is no codes though I haven't a clue where to go next, as nothing has been changed on the bike except the tire and it seems fine when cold.  But as soon as it hits around 60C it will not keep ticking over.

 

TLDR: Bike wont idle when around 60C, just dies after a few seconds. Fine when cold.  Nothing done to the bike to cause this.

Any help appreciated.

[bmart]

I'd start with the basics: air, fuel, spark...and check the battery and charging system when it is running. Be methodical. 

[Grum]

Agree with bmart. 

 

- How old are the Spark Plugs? Old plugs can do strange things, just replace them. Suggest the long life  NGK Iridium CR9EHIX-9 as a replacement instead of the OEM standard type CR9EH-9

- Check the state of your airfilter

- Be sure you are working with a healthy battery, clean and tight terminals, and yes, verify your Charging Voltage at Idle and 5000rpm.(if possible with the fault you have.!) Place your battery on a charger as all the short starts and stops won't allow the battery to fully recover.

- If the ECM picks up a current diagnostic fault code your Fi Light would be flashing the code with Ignition to On and Sidestand down. Good idea to clear any old historical codes from memory then reassess.

- Check for any vacuum hose leaks around the Throttle Body area, broken, cracked or disconnected hoses.

- Check the wiring and Fuse holder for Main Fuse B 30amp, this can suffer badly from high resistance joints/contacts causing the engine to die.

- If you are smelling a lot of raw fuel from the exhaust you might have a ruptured diaphragm within the Fuel Pressure Regulator.

 

Your fan coming on at around 80degC sounds too low! Fan thermoswitch should switch on from 98-102degC. Is your coolant level ok?

[raYzerman]

Fresh fuel or perhaps some Seafoam in case there is moisture in the fuel tank....

 

One thing additional you should read is the thread about possible misinterpretation of the service manual with regards to throttle body sync.  Once I fixed mine, it runs like a charm.......

 

[toreckman]

Thanks for all the replies.

 

As Grum suspected, with all the short starts and stops the battery was low - 11.7V with ignition switched to on, but not started.  Because I don't know the history of the battery I will replace it.  I tried to get one today but no stock local.

 

I am hoping it is just the battery, but I did notice the rectifier is a SH689A-12, so possibly the original, I will inspect it after I get the battery.

 

I do have new plugs (iridium), oil & fuel filters and oil to go in, but I want to make sure it is running ok before i start doing anything.  I checked the FI codes and interestingly I got a TP sensor error (8 flashes), I cleared that, so I will see if it comes back after I get the battery. 

 

raYzerman - I will look into the TB sync, I hadn't heard about that issue before

[toreckman]

I tried a new battery today, bike still will not start.  12.4V at terminals.

 

I am going to try a battery charger and get it charged fully. 

 

Can there be issues with the auto choke on the 5th gens?

[DannoXYZ]

Most likely case of weak battery. New batteries do not come fully charged and need to be charged for 24-hrs before using. Want +13v fresh off charger. Otherwise when cranking, voltage drop is too much and ECU can't function.

 

Make 2 measurements:

 

1. battery voltage with everything OFF. volts=???

2. battery voltage during cranking with start-button pressed. volts=?? 

[Bren]

A lot of people always say they have a resting voltage of 12.8 or so, I've never had this ever with any battery. Mine are always around the 12.4 like yours after fully charged and left to rest for an hour after charging. 

 

Sorry can't help any further but I'd listen to the advice given by Bmart and Grum before you do anything else.

 

It's not your rectifier that's for sure, that would start playing up later, you cut out at 50C. There's something wrong with either your petrol feed or your air supply. You have spark because it starts easy when cold but something is clogging stopping fuel or air. Check them.

[toreckman]

1 hour ago, Bren said:

A lot of people always say they have a resting voltage of 12.8 or so, I've never had this ever with any battery. Mine are always around the 12.4 like yours after fully charged and left to rest for an hour after charging. 

 

Sorry can't help any further but I'd listen to the advice given by Bmart and Grum before you do anything else.

 

It's not your rectifier that's for sure, that would start playing up later, you cut out at 50C. There's something wrong with either your petrol feed or your air supply. You have spark because it starts easy when cold but something is clogging stopping fuel or air. Check them.

Hi Bren.  The bike will not actually start at all now.

I bought a battery charger, I will charge it over night and test again tomorrow.

 

If that doesn't work, I'm leaning to a fueling issue. If I blip the throttle and then try starting, it seems to catch for a split setting, but them immediately back to just trying to start.

 

At least now with a charger I can rule out the battery.

[bmart]

Do you have air, fuel, and spark? 

[toreckman]

21 minutes ago, bmart said:

Do you have air, fuel, and spark? 

I will check these next.

[toreckman]

Well I think I might have found the culprit.

I checked the petrol tank and saw this:

 

 

 

 

Although the lighting is bad in the pics, there is rust inside the tank.  It makes sense that the problem manifest after transport in a van, probably knocked loose some rust particles.

 

Can a rusty tank be repaired?  Or do I have to replace it?

What else should be replaced alongside repairing the tank?

 

[bmart]

Try Google. There are a lot of options for cleaning using solutions and recoating. Evaporust is the one I may try if I ever bother with mine. 

[Bren]

Then you'll be getting your injectors cleaned.

You may be lucky and the pump and filter inside the tank are still usable, you'll have to take them out to clean them.

Bad luck but good luck getting it sorted.

[toreckman]

12 minutes ago, bmart said:

Try Google. There are a lot of options for cleaning using solutions and recoating. Evaporust is the one I may try if I ever bother with mine. 

Getting a lot of conflicting info from Google.  Some saying that there is no coating that works and they all disintegrate.

I will do some more research and see what I can find.

 

 

1 minute ago, Bren said:

Then you'll be getting your injectors cleaned.

You may be lucky and the pump and filter inside the tank are still usable, you'll have to take them out to clean them.

Bad luck but good luck getting it sorted.

Damn, that's a lot to get done.  Is that the expensive fuel filter your referring to?

[VFR750F3]

Get all the rust out first and go from there and fill it up with gas right away.   Cheapest way below.  Also blow out the fuel lines to get rust particles out and check fuel injector screens to see if they are clogged replace fuel filter and clean strainer.

 

 https://www.brooksbasics.co.uk/white-vinegar-vs-rust

 

The coating disintegrate due to poor prep.

My coating disintegrated due to using ethanol gas and sitting.  Mine probably had POR15 done a long time ago fiberglass tank.

Do not use the red coating.  Tank rusted out underneath it and had it professionally done by a radiator shop metal tank. 

I need to recoat my tank  I purchased the KBS but I watched goon glass and rubber on youtube he uses caswell.

Bill Hirsch makes a good coating because it is ethanol resistant like the KBS.

[toreckman]

I ended up purchasing the POR15 Motorcycle Bike Fuel Tank Sealer Repair Kit.  From reading online, once you follow the instructions exactly and dry out the tank completely before applying the sealer and then let dry for a few days to 1 week, it should seal ok.  I will take my time and maybe try some vinegar first to remove some of the rust.

 

I looked online for full tanks and couldn't find any that weren't either i)dented or ii)different colors to blue.  This would mean I would have to factor in repair and respray on top of the tank and shipping costs.  So repair of the current tank is the best option.

 

I'm really hoping nothing got damaged like the fuel filter or injectors, that could be quite costly.

 

On the plus side, with the tank removed I will be able to access a lot more of the bike and do some more maintenance.

 

Is it worth upgrading the fuel pump while I have it all disassembled or is an OEM one fine?

[VFR750F3]

I would just clean it no coating and see how it looks.  No change to fuel pump needed.

[toreckman]

17 minutes ago, VFR750F3 said:

I would just clean it no coating and see how it looks.  No change to fuel pump needed.

Ok, I have 20 litres of white vinegar on the way.  I will start there.

[VFR750F3]

Keep us posted  I always try the most economical first. 

[Dutchy]

If you ride the bike a lot, the fuel will never have enough time to attract water.  I tank ethanol free/low as much a possible.

 

 

[JimMoore]

15 hours ago, toreckman said:

Ok, I have 20 litres of white vinegar on the way.  I will start there.

Before you do that toss a bunch of nuts and bolts into the tank and shake it vigorously for several minutes. That will knock off the big rust pieces. 

[bmart]

And shake those loose bits out before the vinegar so the vinegar can interact with the important bits. 

[vfrgiving]

Before you proceed with the vinegar, look up a product called Evapo-rust.  It's not cheap for large volume, but it has the benefit of not being an acid so it won't attack good metal or plastic.  It works through a process called chelation.  I used it on an old Guzzi tank with great results.

[Captain 80s]

14 minutes ago, vfrgiving said:

Before you proceed with the vinegar, look up a product called Evapo-rust.  It's not cheap for large volume, but it has the benefit of not being an acid so it won't attack good metal or plastic.  It works through a process called chelation.  I used it on an old Guzzi tank with great results.

 

It does work really good, done it a few times.  Couple things I found;  You can cut it with some distilled water, it reduces how fast it woks a little, but it can help stretch your supply to fill the tank.  Related topic, if you are gonna rotate the tank around instead of filling it, do not have it upside down with your aluminum gas cap in place.  Buddy found out the hard way, the stuff is harsh on alum (and maybe plastic in the long term?), and it fucked up his vent and discolored / altered the aluminum.  His gas cap now percolates at stops.  It doesn't harm paint or clear coat, so the stress level is very low with some spillage during the process.

 

I also had some alum coolant cross over caps soaking with some rusty chrome coolant tubes.  It did it as an experiment, and the alum got super porous and they were junk.