Help RVF400 Won't Rev Out

[MrB]

Hi All,

Hope someone can help please. Had a running problem with my RVF400 so I sent the carbs off to be ultrasonically cleaned. Carbs came back, refitted and bike would run and rev lovely but only when using an auxiliary fuel tank i.e. a funnel connected to the pipe. When I install the fuel tank the bike refuses to rev cleanly, any ideas? The fuel tank has fresh fuel and from what I can see none of the hoses are blocked. I must be missing something??

Thanks all, I love this bike but now it's starting to annoy me and hope to get it sorted for the Summer.

Matt.

[samace]

I had sam problem and rust is getting into carbs from tank. I flushed it out 6 times and fitted a small fuel filter. It still takes a little while for the fuel to get through the carbs and always seem to fire on 2 cylinders only for a little while when starting.

[Cammo]

Hi mate, sounds like your fuel tap vacuum operated diaphram is shagged, fuel tap problems are pretty common. Could also be a split vacuum line that opens the tap diaphram, you should replace this hose regardless, even if you can't see any splits it can collapse in when hot, blocking vacuum which opens the fuel tap.

The vacuum line runs from the right rear cylinder (under the carbs) to the fuel tap spigot - check it!

Easy fix. This thread might assist:

viewtopic.php?f=22&t=24110


You've come to the right place for advice!

[MrB]

Blimey that was quick, excellent will have a look into both suggestions thanks a lot. If I can get this sorted I'll owe you a drink. I've spent a fortune on this bike now only for this to happen when I thought it was sorted, you can imagine my frustration.

Thank you.

[Cammo]

You need to take the carbs off (I think?) to remove/replace the fuel tap vacuum line at the cylinder intake. The line is part #7 in this diagram:
http://www.akhara.com/nc30/nc30parts/files/33.htm

Full parts manual here:
http://www.akhara.com/nc30/nc30parts/index.htm

Many people do the 'hrc' fuel tap mod to the fuel tap, which removes the vacuum operation (will then work just via gravity). Danger of this is that if your carb float valves don't seat correctly you'll end up with: a) a tank of fuel in your engine's sump, b) a cylinder full of fuel which will bend a rod on start up. I wouldn't recommend doing this for a roadbike, just something else which can be forgotten at the end of a ride.

I have the fuel tap mod on my race bike, it's fine if you use a dry break line connector in conjunction with it. A better option for a roadie would probably be a fuel tap rebuild kit and new thick-walled fuel tap vacuum line from Rick Oliver (member here , search for his details).

If I can get this sorted I'll owe you a drink.

No worries, sent by air mail wil be fine!

[MrB]

Great ! Carbs off again then, oh well I'm a dab hand at that now glad I replaced the carb rubbers.

Trying to keep the bike as standard as possible so will look into rebuilding the fuel tap, may as well do it now while the bikes still in bits. If I don't it's bound to be something else that needs doing in the near future. And to think I thought I bought a good one ! My carb floats stuck which was one of the original reasons why I thought I would get them off and cleaned properly.

The wife was hoping the fairings wouldn't be in the front room for much longer but hey at least they are well polished now.

Thanks again.

[CMSMJ1]

Have you definitely got the vacuum hose ont he right spigot? You want the furthest out not the middle one.

You cna test the tap with a piece of hose and a helper. Stick the vacuum on, turn the tap on...and suck the vacuum hose while your helper tries not to get fuelsplashed on them (if it works)

[MrB]

Thanks, will double check. Having looked at the vacuum hose it does look a bit "shagged" so will replace. Just wondering whether to strip out the fuel cock and replace the diaphragm whilst I'm at it.

I am going to be over the moon when I can get this bike sorted.

Cheers.

[MrB]

Finally got round to looking at the bike again and replaced the vacuum hose, fitted the tank and all is good. Only thing left is to actually ride it and see if all the hard work and expense has been worth it.



Thanks a lot for the help, beers on the way. Will let you know how she rides

[Cammo]

Hope it's fixed your problem mate.

It's a fine looking bike you have (seen in new members post), it would be a pity not to be able to get out on it and enjoy it.