Power loss?

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Joelaman
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Bike owned: VFR 400 NC30(current)
Location: South Africa
Power loss?

Post by Joelaman » Tue Aug 16, 2016 1:41 pm

Hi guys,

New user here looking for some advice,

Recently bought me a VFR400 NC30.
Tyga fairings the works. but there seems to be a problem with it, i have almost no power until the revs hit 7k... then it goes like a bat out of hell up to 11k... then its dead again.

I also have the problem of it gettin stuck on 140kmph(86 MPH)
I know the bike is limited at 180(112)

The previous owner blamed the airfilter(he cut a piece of sponge and used it as such)i replaced all the filters on the bike and i havent touched it since(throttle cable snapped as well).

I was hoping someone can possibly give me some advice because i feel like i payed a big amount for a project bike at the moment. :cry:

Thanks guys
Joel

magg
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Bike owned: VFR400
Location: Blue Mountain NSW Australia
Re: Power loss?

Post by magg » Tue Aug 16, 2016 2:00 pm

You might want to check that all the OEM air intake parts are fitted, carbies are clean and std jetting fitted and what other non-OEM changes have been made to the engine. The library on this website can provide info.

Joelaman
Settled in member
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Posts: 18
Joined: Tue Aug 16, 2016 1:31 pm
Bike owned: VFR 400 NC30(current)
Location: South Africa
Re: Power loss?

Post by Joelaman » Tue Aug 16, 2016 2:03 pm

As far as i know a previous owner also made a small hole in the airbox as "it made a better sound" I just wish we had some decent V4 mechanics in SA but most places just say "we dont touch those things"

I'm planning on having the carbs cleaned end of the month(don't touch them myself)
do you think a small hole in the airbox will make that big a difference?

Joelaman
Settled in member
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Posts: 18
Joined: Tue Aug 16, 2016 1:31 pm
Bike owned: VFR 400 NC30(current)
Location: South Africa
Re: Power loss?

Post by Joelaman » Tue Aug 16, 2016 2:13 pm

Also i am really disappointed in the previous owner, the sponge airfilter is small to the other backyard mechanics ive seen on this bike, the fuel line is literally a piece of hosepipe, the T section where the fuel filter goes in was blocked by a piece of a metal nail.

I would like to replace things and fix things myself but i am afraid of breaking or fixing the wrong thing.
how hard is it to clean carbs yourself on the v4? should i attempt it as someone who has never really touched an engine?

I would like to learn more and fix things myself but i know that will take time.

magg
Senior Member
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Posts: 1910
Joined: Mon Sep 20, 2010 11:55 pm
Bike owned: VFR400
Location: Blue Mountain NSW Australia
Re: Power loss?

Post by magg » Wed Aug 17, 2016 12:23 am

The fuel filter is in the tank, what T section are you referring to? Other than limited working space, a problem with all modern bikes, the NC30 is a straight forward engine from a maintenance perspective. There is a carby setup document in the library and other members on this site have documented their carby cleaning procedures. A Haynes manual and the OEM service manual from this site library should provide the info needed.

From your description of the state of the bike, I would assume nothing and start at one end of the bike and work towards the other end checking everything.

Joelaman
Settled in member
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Posts: 18
Joined: Tue Aug 16, 2016 1:31 pm
Bike owned: VFR 400 NC30(current)
Location: South Africa
Re: Power loss?

Post by Joelaman » Wed Aug 17, 2016 10:49 am

Thanks, will be a costly process but worth it. I've heard only good things about the VFR.

Kinda do miss my CBR NC29 though

magg
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Posts: 1910
Joined: Mon Sep 20, 2010 11:55 pm
Bike owned: VFR400
Location: Blue Mountain NSW Australia
Re: Power loss?

Post by magg » Wed Aug 17, 2016 12:05 pm

May not be so much costly, just time consuming and annoying if Honda's good engineering has been compromised for no good reason.

Joelaman
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Posts: 18
Joined: Tue Aug 16, 2016 1:31 pm
Bike owned: VFR 400 NC30(current)
Location: South Africa
Re: Power loss?

Post by Joelaman » Wed Aug 17, 2016 1:38 pm

Time is something i have lots of, where would you advise i start?

magg
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Bike owned: VFR400
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Re: Power loss?

Post by magg » Fri Aug 19, 2016 6:15 am

Airbox should have an intake duct and an associated rubber heat guard that fits over the top of the radiator. If missing it can affect the performance.

Check that you are getting good fuel flow from the tap when vacuum applied, you did not explain the nail head/T piece/fuel filter comment in your first post.

If the performance is still poor then you should remove carbies and clean the internals and restore the jetting to OEM if it has been changed. Does the engine start easily and idle smoothly at 1200-1500 rpm?

Joelaman
Settled in member
Reactions:
Posts: 18
Joined: Tue Aug 16, 2016 1:31 pm
Bike owned: VFR 400 NC30(current)
Location: South Africa
Re: Power loss?

Post by Joelaman » Fri Aug 19, 2016 10:12 am

nail head t piece is not in the main fuel line, out of the tank there are two pipes, a 10mm(i think) main fuel line and a much thinner pipe, the thinner pipe has a t section that is blocked off(I honestly now have no idea what that is for).

It does start quite easily, I have started it a few times early morning in the cold and remember being quite surprised as to how easy it starts compared to my old NC29, the idle range is usually between 1500 and 2000, if i set it to anything lower than 1500 it seems to want to die.

how do i check good fuel flow?

Also the 10mm pipe is replaced by a piece of hosepipe that doesn't sit very tight, will be replacing that tomorrow, do you think that could make a difference? note there is no leakage out of the hosepipe but it sits very loose.


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