It's another VFR400 running issue....

[Callumrobin]

Hi, I'm pretty new to the forum so please be gentle :)

I have recently been working on my sisters G reg VFR400 NC30, it wasn't running right and due to her having a baby it was coming off the road anyway.

So I set about stripping the carbs down & followed the guide, fitted new plugs, it had fairly new leads on there already & fitted new race can.

Finally got it all back together & it felt great, pulled really well through the gears & sounded great!

That's where the good news end....

I then took it for MOT & was fine on the way there, whilst there the battery died & I had to jump start it (all good fun!). Got it going again then on the way home it started to bog at around 6k+.

I've stripped all the tank etc back off, checked the fuel, leads etc but can't see any problems, anyone have any ideas to what it is?? It really feels like it's holding back & so frustrating!

Thanks in advance

Callum

[oldgreyandslow]

Sounds like a battery reg rec issue to me. There's a guide in the document libary on here and I'm sure a search of forums will find another link or 2

[Andy666]

When you say checked the fuel, did you also have a look at the vacuum hose to the fuel tap? When old, it can get weak and collapse/split stopping the flow of fuel at higher revs

[Neosophist]

Have you chcked the charging system?

They fail easy, espeically if the battery is old and been standing, easy to pop the regulator.

[Callumrobin]

Cheers for the response guys, I have checked the vacuum pipe and seems in OK condition, but I will check again, I remember my friend had that problem with his pipe.

If the regulator fails would the battery not charge? What issues would that cause? I only ask as the battery hasn't been a problem since? Are they easy (inexpensive) to change?

Thanks again.

Callum

[magg]

When you say "bog down at around 6k" would it be closer to 5k and run poorly in all gears after 5k? Do the neutral and oil pressure indicator lights function?

Measure the battery voltage with the engine running, should be >13 volts at 5k rpm.

[Callumrobin]

When you say "bog down at around 6k" would it be closer to 5k and run poorly in all gears after 5k? Do the neutral and oil pressure indicator lights function?

Measure the battery voltage with the engine running, should be >13 volts at 5k rpm.

You might be right, I will check if it's at 5k in a min.... I'll see if I can borrow a volt meter also. It does bog down in all gears after 5k yes.

Neutral and oil pressure work fine and don't look dull at all.

[Callumrobin]

OK just popped the bike for re-test and it is bogging at around 5k upwards through all the gears. The initial pull off is fine, then boggs at that 5k mark. It will pull through the gears but feels like it's restricted to 33bhp or less! Haha!

Haven't got a Voltmeter handy, so will borrow one from work and check the volts.

If it is below 13 volts will that be the reg? Where's the best place to get one from as I need to get the bike sorted ASAP!

[magg]

You need to check that the speed limited unit located in the speedo is connected and functioning otherwise engine will not rev past approximately 5k rpm.

Could be a number of possibilities for a flat battery, you need a multimeter to do some testing otherwise you could just be buying parts unnecessarily.

[Callumrobin]

You need to check that the speed limited unit located in the speedo is connected and functioning otherwise engine will not rev past approximately 5k rpm.

Could be a number of possibilities for a flat battery, you need a multimeter to do some testing otherwise you could just be buying parts unnecessarily.

It revs past 5k fine, it's just flat and is holding back as soon as it gets to 5k and above.

I've got a multimeter from work, going to test tonight.

Cheers

Callum