1999 5th Gen VFR800 hard to start after sitting for a week

Hello, new member here with a tech question.

I have a 1999 5th gen VFR800 which is very hard to start after sitting for about a week. So much so that my battery eventually runs down every so often requiring a recharge. I always set the fast idle switch to full when starting cold. Once the bike is started it works fine. The ride is great. Throttle is great. I can even leave the bike for a few hours and fire it back up again without problems.

I recently changed out the fuel filter since the bike is so old but that didn't seem to do anything.

Any help is much appreciated!

Thanks

 

On a fuel injected engine long cranking time is a likely indication that you're having to re-fill and/or re-pressurize the fuel delivery. The fact that you say the bike runs fine after it finally starts is further indication of this. How old is your VFR's fuel pressure regulator? Is it 21 years old? If it is 21 years old, how long do you think Honda intended it to last?

 

Interesting... I am not very familiar with the operation of the fuel pressure regulator. I took a look at it and there is a vacuum line and fuel tank return line coming out of it. I recently had the throttle body off the bike so I am wondering if I might have inadvertently messed something up with the vacuum lines.

 

So I changed out the fuel pressure regulator and that didn't seem to do anything. Vacuum lines seem OK.

After reading a couple of other threads, I was going to look into

• the regulator/rectifier/stator
• starter valve sync

Is there anything else?

 

You might want to have a read of my recent findings on starter valve sync.
https://www.vfrdiscussion.com/index...ct-for-22-years/&tab=comments#comment-1112224

However, that doesn't necessarily mean you don't have starting issues for some other reason... a bit of it is the cold-bloodedness somewhat, but why not try a re-sync. It does idle way smoother and much of the "lumpy" V4 characteristic is way less.

 

Just to give an update and possibly help out others. I went through the service manual and found the troubleshooting steps for a no start/hard start scenario.

One of the steps was to check the spark on all 4 cylinders. I noticed that cylinder 3 had a fractured plug from its coil pack. After testing the spark on all 4 cylinders, cylinder 3 had a very weak spark comparatively. I replaced it and the bike now starts up fine from cold. I will test it out again in a week just to make sure but I am confident that the issue is resolved.