YZF600 Fuel Pump

[SilverJS]

Hey guys,

I've actually got a YZF600 fuel pump in my basement that I got when I bought the engine (like 10 years ago!).

Anyhow - I am just wondering if anybody here is using a YZF600 pump? (Mine's a 98.) If so, does it "click" like ours when turning the ignition on? If not, anybody know how it does its thing?

Reason I ask, is I am considering switching mine to the YZF600 item. Mine seems to activate a bit more randomly than I'd like on startups (like when I turn the ignition on), and seems to take quite a while to pump fuel into the carbs (like sometimes, it'll pump for like 10-15 secs, stop, and I'll turn the ignition off and on again, and it'll do another 10-15 second cycle, and even for a third time sometimes!). Might be my petcock too, got one on the way, and I'll change the fuel filter too while I'm at it. Just looking at all options...

Cheers!

[cad600]

It might be the petcock. The YZF fuel pump works the same way as the FZR one. The only difference is how it mounts and the direction of the inlet tube (having a 90 deg. bend). It should click as the pump is priming the carbs. But if it is doing it a lot, it should mean that there is a block in the line and fuel is being restricted. I'm actually using my FZR pump with the YZF engine.

[SilverJS]

OK. That's what I thought too (wrt the pumps and differences between them). So, how about this - anybody ever compare a FZR400 and FZR600 fuel pump side-by-side? Part numbers are different, but what is the actual differences between them? Is the piping actually biggger, is the flow actually increased?

This weekend, I put the YZF600 carbs with airbox back on the 683, and noticed a very positive increase in torque all-around, and now that they're properly jetted, the bike is beautifully civilized and is lovely to ride. The ONLY problem I'm left with is due, I think, to the 400 fuel system simply being inadequate.

If I hold WOT in 3rd or 4th gear, she'll take it no problem, no stumbles, nothing. However, if I hold WOT in sixth (so, for - say, 15-20 secs or more), she'll start stumbling at higher speeds. This, to me, signals fuel starvation. She's fine at every other regime (sustained 100 mph, for example, in 6th gear).

So, I wonder if the 400 and 600 pumps are really different, and if it's worth trying to get a FZR600 one, or just trying to adapt the YZF600 one I've got? The FZR400 hose diameter looks like 1/4 ID, but the YZF ones look significantly bigger. The FZR600 pump, if it flowed more, would be the easiest fix, as it looks like it would basically bolt on.

Cheers!

[cad600]

Could be, but I'm not sure. I'm using 5/16" ID line on mine. But I know nothing about this area. Just thinking about it, can it really be fuel starvation? If it works at full throttle in 1-3 gears all the way up to redline, why would it not work in 5-6 then. The RPM is the same. The only difference is the amount of air getting into it. Are you running a RAM AIR box? I just got my YZF engine running with a 95-96 air box (no RAM AIR) and it works great. But I also haven't been above 70mph yet.

[SilverJS]

Well, the reason it would work in 3rd/4th gear but not in 5th/6th is that, in the lower gears, because of the bike's acceleration, it will only hold WOT for - what...5 seconds or so...?...whereas you need to be in 6th gear to be at WOT for longer than that. This would seem to indicate that the fuel in the fuel bowls is enough for short bursts of WOT but not sustained ones. That is my reasoning.

That being said, I am using the FZR400 airbox (adapted), so that there is no ram air, and that is a good point. However, 'fightered YZFs have been running similar setups for a while without issue.

The FZR600 fuel pump does use 5/16ths ID line, then?