FZR400 poor running :(

[raptor2210]

Hi guys,
haven't posted on here for a while as i've been busy enjoying the bike among other things...

Anyway, theres always been a problem with the bike since i've had it but i've never bothered to investigate before but now its really annoying me!
Basically the bike seems to 'get stuck' at around 3000rpm and 6000rpm. This is quite difficult to explain but here goes: for example, if I was to let the revs drop to around 5000rpm for a bit then open the throttle the revs will rise to around 6000rpm then they will stick there for a while and the bike makes an almost hollow roar that I would describe as intake noise. Same thing at 3000rpm. The only way to get through it is to either ride it out (eventually pulls through after a few seconds) or slip the clutch.

This makes overtaking scary and slow speed riding noisy as I have to keep the revs high to avoid getting stuck!

Apart from that the bike runs fine, you can accelerate from a standstill through the gears just fine. The problem only occurs when you've been hanging around the lower revs for a bit (starting an overtake from 4000 - 500 rpm for example).

The garage I brought it from said its caused by the 33bhp restrictor kit thats fitted (required by uk law for 2 years). For those who dont know, the kit consists of a washer that fits in the engine side of the carb that reduces the size of the hole into the engine.

Oh and my first thought was the exup valve, but that appears to be functioning correctly.

So do you guys think its the restrictors or does this sound like a different problem to you?

many thanks,
simon

[Evilchicken0]

I haven't riden a 33hp bike so it's difficult to comment.

Maybe cleaning the carbs will help

[Q007]

I've just removed my restrictor kit 2 months ago, and yes i did have the same problem, turned out the carbs have to be set up properly when the restriction kit is fitted (it's not just a case of putting the 4 washers in). Think the guy who done mine said it was way overfuelled for the small amount of air the engine is now getting. Any mechanic worth his salt should be able to adjust and re balance your carbs for you n all should be better. 2 years seems forever but trust me it's worth it, 1 for the law abiding and not risking losing the liscence you worked so hard to get. and 2. when you have it removed and set up again to run without the kit you'll think you've got a NEW BIKE.

it really flies compared to the 33Bhp restriction, not much faster top end only another 25-30 mph but now it gets there so much faster, still get the odd little wheelie now and again n shit meself for a second or 2...

Good Luck n ride safe

Q.

[wullvfr]

with whats been said it definately sounds like its running slightly rich probably due to the restriction.when you are hanging about the lower revs it starts to bog down with the overfueling.like its flooding.



wull

[raptor2210]

Hi,
I was hoping that would be all it was I shall book it in the garage for the weekend and get it sorted.
I'm not really surprised it wasnt done when the restrictors were fitted as the garage were useless... They 'forgot' to put the pins that hold the brake pads back in and i only noticed 60 miles later when I got home.

I must admit it has been very tempting to take the restrictors out but like you say Q its not really worth the risk in my opinion, only a year left this september anyway.

Anyway thank you all and i'll let you know how it goes at the garage.

cheers,
Simon

[raptor2210]

Hi again,
The bike has been to the garage and the carbs are fine, turns out the problem is the exup valve!

After taking the cover off i can see that the pully is not attached to the exhaust at all. It also appears that the valve has been removed as the hole just goes straight into the exhaust

See pic for details, the only thing removed to take that was the outside cover and the pully, which pretty much fell off.

so i'm guessing i will need new cables, valve and all of the springs washers and bolts that go with it . Anyone know where i can find these?

Also the one bolt left holding the cover on wont budge and the end is now rounded off, any ideas how to remove it?

Cheers,
Simon

[Q007]

Also the one bolt left holding the cover on wont budge and the end is now rounded off, any ideas how to remove it?



If you've got a dremmel tool use a small cutting disc and cut a slot in the head of the rounded bolt head and use an impact driver with a normal screwdriver flat head.

works for me on rounded bolts etc.


Q

[Evilchicken0]

Um ... yeah ..... well I reckon that's problem !!!

Well - have a look around on ebay and see if there's a set of headers with a working valve to fit your bike (a 3EN or 2TK SP I think). If they're in good nick then all you need are the exahaust gaskets - soak your reataining nuts in penetrating oil for a day or so before you take it off.
Once you've got them off clean the outside (scotch brite) and use some rust killer. Paint them before you put them back on.

If you're prepared to swap the exup's then you might find a racer who has the parts ... or you can buy some rusty pipes off somebody braking a bike and swap the valve out.

Getting those bolts out is a b4stard job but try heating the surrounding area with a blow torch (not to much heat) and then get a pair of molegrips on it to see if it turns. If not don't break the head off carefully drill the bolt out. If your not confident get a garage to get it out.

[raptor2210]

managed to get the bolt out with mole grips in the end and just as suspected, no valve

Just gonna have to keep my eye on ebay and see what comes up. so i'm lookin for 3en1, 3en2 or 2tk sp?

in the mean time i will plug the big hole where the end of the valve exited the exhaust, that will help a bit i'm sure!

Thinking about it, the bike is strangely loud. Not surprising considering the hole!

Well Thank You for all your help everyone.
Simon

[Evilchicken0]

Yes - basically a set of 1WG Exup down pipes.