Suddenly hot starting very difficult and low stationairy rpm.

Klikoo · Tuesday at 7:31 AM

Dear FJR riders.

I have a 2015 FJR type RP23 with almost 32,000 km on the clock for 4 years now without any problems. At this moment I suddenly got the problem of difficult warm start. The engine runs smoothly and cold start is good. However, after refueling, for example, the warm start is very difficult. I myself suspect the mixture is too rich, I have to keep giving some gas to keep the engine running. But i am not sure about this. The battery voltage during starting varies around 11-12 volts, the starter motor runs very well. So, i think its not the battery. If I read codes according to the manual, then diagnosis code 67 was on 02. According to the manual, this must be reset, which I did. There were no other error codes. This has no effect, the situation may have become even worse. Sync adjustment was done about 10,000 km ago, it was good then. Not checked yet. The engine drives fine, only that the idle speed varies when the engine is warm and the engine has a strong tendency to stall. I have to keep giving it some gas. I can upload a video of all diagnostic codes, but code 67 is now 01. Does anyone know a possible cause?

RossKean · Tuesday at 7:57 AM

For the hard starting problem when hot, does the engine turn over at normal speed or is it sluggish. If slow to turn over, it may be either the starter or battery. Best check is to use a clamp-on DC ammeter to check starting current. If excessive (i.e. over 100A), the starter motor may be failing. If it is turning at normal speed, I wouldn't suspect starter or battery.

I can't help you with the diagnosis code issues - I have a Gen II which is different. Sometimes a random code may be generated when you have a failed start so these might not mean anything. Still should investigate.

I doubt it has anything to do with throttle body sync.

harper · Tuesday at 8:33 AM

It appears you are not the first owner. Did the previous owner install a Power Commander or other fuel mapping device? I have an '08 which developed a similar problem (always requiring a wide open throttle to start when warm) and removing the Power Commander immediately fixed the issue. The mixture was too rich while starting.

RossKean · Tuesday at 8:51 AM

Just occurred to me that there were some reports of problems with throttle position sensors for some Gen III bikes. You might do a little searching on the forum for this. (I thought it was earlier Gen III such as 2013-14, but may have included later bikes.) It could certainly cause starting problems (especially when hot) and uneven idle. Another thought is to check out your O2 sensor and MAP sensor.

Edit: Have a very close look for vacuum leaks...

Klikoo · Tuesday at 10:39 AM

Thanks for the answers. Its a generation 3 bike, 2015. I am the second owner for 4 years. The bike has run 1500 Km at the moment when a bought it almost 4 years ago. So almost new. It was, and still is in excelent condidion and complete original. At startingmoment the motor turns at normal speed, accuvoltage between 11 to 12 volts. When it starts, i have to keep some gas to keep the motor running. There is no power commander and there is no fuel mapping done or something like that. Everything is factory original and the problem suddenly arose. Driving and cold start is perfect. I am going to look for vacuumleaks and contamination of the throttelvalves? And as a wrote, there are no errorcodes in the diagnostic screen except number 67 was 02. It should be 01. The manual says idle speed control and must be reset. I have done that according the manual, but now its seems worse. The code on number 67 stays now on 01.

RossKean · Tuesday at 11:02 AM

Vacuum leaks, yes. Unlikely dirty throttle valves. Throttle position sensor is suspect. Same with manifold pressure sensors.

vzhq16 · Wednesday at 8:41 AM

Sounds like classic vacuum leak. Look to make sure the port plugs are still there and sealing properly. They can crack and still look fine but leak.

Wizard37 · Wednesday at 10:34 AM

I had the same problem on my 2007. I cleaned the negative pressure hoses (8) page 7-7 in the manual. Seemed to clear up the issue. Got a lot of crud out of the lines. Then balance the throttle bodies. I think I changed the air pressure sensor not long after that along with new by-pass (12) and negative pressure hoses (8). That was around the 50,000 mile mark. No problems until its untimely demise.

RossKean · Wednesday at 10:44 AM

Wizard37 said:
I had the same problem on my 2007. I cleaned the negative pressure hoses (8) page 7-7 in the manual. Seemed to clear up the issue. Got a lot of crud out of the lines. Then balance the throttle bodies. I think I changed the air pressure sensor not long after that along with new by-pass (12) and negative pressure hoses (8). That was around the 50,000 mile mark. No problems until its untimely demise.

A possibility, although I haven't seen this in Gen III+ bikes. Pressure sensor is worth checking out anyway and it would make sense to check the lines for crud.
I investigated this issue on my 2007 as well and a simple swab and spritz of the lines with cleaner and all was good again. Note: Make sure any solvent is gone before connecting to pressure sensors. This issue created a Fault Code 14 on Gen II bikes. No issues on my 2011 with 160,000 km.

https://www.fjrforum.com/threads/fault-code-14-gen-ii-solved.170314/

Vacuum leak or TPS seems more likely to me, but this is easy to check once you have accessed under the tank.

Mihalis fjr · Wednesday at 1:25 PM

Another opinion,if the starter motor has a problem, such as the magnets came off of their position,or dirt or anything else,it appears when the engine is hot.Sometimes it sucks a lot of voltage and doesn't leave power for the ignition..Also a bad TPS sensor could cause a like this symptom, especially when the engine is hot..

Klikoo · Wednesday at 1:30 PM

This weekend I'm going to check for vacuum leaks and clogged hoses. The difficult warm-up idle lasts a while and then the speed stabilizes back to normal. Until then I have to give it some gas to prevent it from stalling. I'm also keeping open the option of dirty throttle valves. In the diagnostic menu I see no special features on the TPS sensor, numbers change nicely with the turning of the throttle. But I don't know if this can be explained. Apart from the deviating value for code 67 in the diagnostic menu there are no error codes at all. To be continued.

RossKean · Wednesday at 4:33 PM

An interesting on the Gen III TPS...
https://www.fjrforum.com/threads/anatomy-of-gen-iii-fly-by-wire-tps.169700/

lee stroke · 2025-02-28T18:35:58-0500

Does your bike have a charcoal filter. Some European and California bikes have one connected to their fuel tanks?

RossKean · 2025-02-28T20:59:52-0500

lee stroke said:
Does your bike have a charcoal filter. Some European and California bikes have one connected to their fuel tanks?

Charcoal canister saturated with fuel can certainly cause rough starting and initial poor idle (and smoothing out after running a few minutes) but this usually only happens when ambient temperatures are very warm - typically with a mostly full tank and parked in direct sunlight on a hot day. If these are the conditions where the OP is having problems then it is very much worth investigating.
(Had this happen on my 2007 which I bought from someone in the USA. Canadian bikes have never had the charcoal canister and (theoretically) only California bikes had it in the US. (I say theoretically because my '07 definitely had the canister and it was bought from a guy who bought it new from a dealer in Connecticut.) I think they are present at least in some years for European bikes. Seems to me that @mcatrophy had it on one of his...

Klikoo · 2025-03-01T02:25:10-0500

Thanks for the answers. My bike has no charcoal filter, and it is a original bike for the European/Dutch market. There is one connected hose between tank and injection rail. At the moment no opportunity to do further research, due to lack of time. Causes I think of are blockage of air sensor, dirty intake, or the TPS sensor. Although I doubt TPS sensor, because it is only in the beginning after warm start. Then the speed stabilizes to normal and the engine runs completely problem-free. Before I start tinkering I want to try injection cleaner first, see if this makes a difference. It is also possible that the injection is leaking, which is why the mixture is too rich during warm start? I also think about the battery sometimes, despite the starter motor turning well and the voltage is around 10 to 11 volts during starting. To rule this out I also want to connect an external 12 volt car battery in parallel.

Suddenly hot starting very difficult and low stationairy rpm.

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