What Next? [ZXR250A 1990]

[Rusty]

I'm sort of thinking the petrol tap might be clogged. There's a screen on the inside of the tank that can get clogged up.

Also, from memory, they're a vacuum design. The diaphragm might be perforated or split which will prevent fuel flow.

[Stealthassassin]

G'day Dave#3 and Rusty,

Thanks for the replies - Hey Dave#3, did i meet you at Pie in the Sky a few weeks ago? I was the one that used to work with Cath at WM?

Anyhoo, i've been trying to get the bike running minus the tank, so i am not sure if that is a problem in itself, the way i had it set up first was No airbox, funnel into fuel line, tip fuel in and keep a small amount in the funnel to gaurantee enough fuel.
Next attempts were made with a bolt blocking the vacuum line (incase it was sucking too much air) and the last attempt was with the airbox back on, but still no tank, i had the fuel line still hanging out the side with the funnel and no changes throughout the different attempts.

It sounds as though it is quite a common problem with these bikes, but i cant find a definitive answer on what causes it.

I guess it's back to pulling the carbs out again and seeing if anything looks wrong

Cheers for the help guys.

[Rusty]

If it starts with and runs with aerostart or similar (or even a small amount of neat petrol) straight down the carbs, and you've eliminated the tank/petrol tap/vacuum leaks then the only place left is carbs. Get 'em sorted and she'll run.

They will run (with the choke) if two carbies are functioning semi-correctly. They won't idle like that, though.

[Bogan]

When I picked up my bike from QLD it broke down on the way home about 120km after the previous fuel stop. Without the long story (it's in here somewhere) the problem was with the fuel pump. The guys at the shop that fixed it said it probably gravity fed until there wasn't enough fuel (and hence pressure) in the tank to feed any more. There are a couple of little contacts like ignition contact points in the pump and they flutter to pump the fuel. You could hear it when it was working like a little ticking sound. They cleaned up the guts of the pump and it was all good then. Mine's a 1991 ZXR750J. If you have a similar pump on your bike it might pay to pull it apart and/or see what happens when you put 12V (or 6V if that's what your bike runs on) into it. I can't find listings of your bike on ronayers.com or similar to see what if any fuel pump setup you have.

As an aside with regard to hose clamps get the ones with the hex heads on the screw and use a little 6mm (or sometimes smaller) socket with a 1/4" drive screwdriver handle or other attachment. Easier and less likely to strip/slide off. Be careful though because if you hang a ratchet or t-bar off the end you'll be able to get way more force behind it than a screwdriver handle and it's bad to overtighten things.

[Stealthassassin]

If it starts with and runs with aerostart or similar (or even a small amount of neat petrol) straight down the carbs, and you've eliminated the tank/petrol tap/vacuum leaks then the only place left is carbs. Get 'em sorted and she'll run.

They will run (with the choke) if two carbies are functioning semi-correctly. They won't idle like that, though.

Sweet, well overhaul number three, here i come...

i should mention something strange that happened, but thought nothing of it (oh boy, i bet this is going to indicate the problem straight away) .

When we chucked the carbs back on the last time, when we poured some fuel down the fuel lines, a bit of fuel came out of the jets(?) that you can see through the top of the carbs, once a bit had bubbled out, it stopped, so we thought nothing of it... Reckon this could be a problem?

[Stealthassassin]

If you have a similar pump on your bike it might pay to pull it apart and/or see what happens when you put 12V (or 6V if that's what your bike runs on) into it. I can't find listings of your bike on ronayers.com or similar to see what if any fuel pump setup you have.

As an aside with regard to hose clamps get the ones with the hex heads on the screw and use a little 6mm (or sometimes smaller) socket with a 1/4" drive screwdriver handle or other attachment. Easier and less likely to strip/slide off. Be careful though because if you hang a ratchet or t-bar off the end you'll be able to get way more force behind it than a screwdriver handle and it's bad to overtighten things.

That's interesting, i havent seen anything that resembles a fuel pump on this bike, but then again, i havent actively been searching or looking for one.. I'll check it out this weekend!

Thanks for the tip on the clamps too

[Rusty]

Sweet, well overhaul number three, here i come...

i should mention something strange that happened, but thought nothing of it (oh boy, i bet this is going to indicate the problem straight away) .

When we chucked the carbs back on the last time, when we poured some fuel down the fuel lines, a bit of fuel came out of the jets(?) that you can see through the top of the carbs, once a bit had bubbled out, it stopped, so we thought nothing of it... Reckon this could be a problem?

Nah, that's pretty normal after a clean out. It's just the needle seating properly. That carby's at least getting fuel. What about the others? There's a drain on the bowls that you can use to check. If nothing comes out, the needle/seat has a small screen that can get clogged. Of course, it may just mean that you haven't cleaned the bowls out (in which case you probably haven't cleaned the rest out properly!)

Basically, follow the fuel flow through the carbs. It comes in the needle and seat, into the bowl and through the jets.

It'll probably be blocked emulsion tubes or something silly like that. Make sure the emulsion tubes are CLEAN. Looking into the holes on the side you should be able to see out the holes on the other side. Otherwise they won't work. If you can't get 'em clean, soak 'em for a few minutes in carb cleaner then grab a bit of fishing line to poke through.

When you're trying to start it, are you trying with or without choke? If with, try it with half choke - the mixture's actually slightly richer in the middle on mine due to wear. Maybe yours is the same. If without, then try a bit! Even if it doesn't idle, as long as it fires you know you're on the right track.

I don't recall 'em having a pump - mine's gravity fed, anyway.

[sicarius]

Sweet, well overhaul number three, here i come...

i should mention something strange that happened, but thought nothing of it (oh boy, i bet this is going to indicate the problem straight away) .

When we chucked the carbs back on the last time, when we poured some fuel down the fuel lines, a bit of fuel came out of the jets(?) that you can see through the top of the carbs, once a bit had bubbled out, it stopped, so we thought nothing of it... Reckon this could be a problem?

Nah, that's pretty normal after a clean out. It's just the needle seating properly. That carby's at least getting fuel. What about the others? There's a drain on the bowls that you can use to check. If nothing comes out, the needle/seat has a small screen that can get clogged. Of course, it may just mean that you haven't cleaned the bowls out (in which case you probably haven't cleaned the rest out properly!)

Basically, follow the fuel flow through the carbs. It comes in the needle and seat, into the bowl and through the jets.

It'll probably be blocked emulsion tubes or something silly like that. Make sure the emulsion tubes are CLEAN. Looking into the holes on the side you should be able to see out the holes on the other side. Otherwise they won't work. If you can't get 'em clean, soak 'em for a few minutes in carb cleaner then grab a bit of fishing line to poke through.

When you're trying to start it, are you trying with or without choke? If with, try it with half choke - the mixture's actually slightly richer in the middle on mine due to wear. Maybe yours is the same. If without, then try a bit! Even if it doesn't idle, as long as it fires you know you're on the right track.

I don't recall 'em having a pump - mine's gravity fed, anyway.

I think you're right Rusty...I dont recall mine have a pump either...But acting on advice from other KSRC members, I fitted an inline filter which seemed to iron out the flat spot around 6-7,000 rpms, but when it died, it died and all the Kings Men at Pro Honda have not yet been able to accertain the problem. Yes.I have practically replaced everything I could think of and still no joy. The last report was that they thought number one cylinder could be slightly low on compression but were waiting on the equipment to test it. Frustrating? KEN'OATH...

[dave#3]

Hey Dave#3, did i meet you at Pie in the Sky a few weeks ago? I was the one that used to work with Cath at WM?

Yeah mate, that was me. How's the bike going?

[gazza2008au]

i just brought the bike ill keeps ya's up to date on what was actually wrong with it the bike wreckers only wants $140 for a set of 4 carby's so i might toss them on sometime early next week or just take the bike strait to the shop fingers crossed it doesnt need a top end rebuild from the engine running on the carby cleaner as i think carby cleaner doesnt contain a lube? i could be wrong... stay tuned

[gazza2008au]

bike is fixed all four carby pilot jets were blocked and i was told everything inside of the carby's were loose bike only cost $430 with a new battery to fix