Bike seems to die when I open up the throttle?

[Jpich85]

I've recently finished painting my tank and a few other parts on the bike, I assembled it all last wknd but today I started the bike up and it started fine, ticks over nicely but when I try and open up the throttle it seems to die, it doesn't cut out it just doesn't seem to be igniting, it sounds like it's choking or something but then when I back off the throttle it revs fine, I can't get it to rev up without this happening, I hadn't started it for a while while I did the painting but before that it was perfect, could the battery not be the right voltage? Or maybe the breather not working? The only other thing I thought was a carb blockage.

Any help would be great

 

[strima]

Are you getting good fuel flow to the carbs? 

[baldrick]

I would start by checking all your hoses from the tank, including the breathers.

Make sure they are not kinked etc.

Edited September 11, 2016 by baldrick

[Jpich85]

I did check them but I couldn't see any kinked ones, I thought maybe the breather could be faulty but I took it off and still the same, it's like it's getting starved of fuel or I thought maybe electrical but I haven't hardly touched it for a few months, I did change the the petcock seals tho but it's not leaking and if I suck on the vacuum plenty of fuel comes out, should the fuel lines be pretty muck vertical to the carb as it's got the rf900 engine so everything is really tight under there

[Jpich85]

I thought maybe a sticky float but it ticks over and revs gently ok it's just when you give it some stick it chokes out

[strima]

If you suck on the vacuum pipe whilst the engine is running can you get it to run normally?

[Jpich85]

I haven't tried that yet strima, I only did that while the tank was off to see if any fuel came out, could I set it to prime to check it that way? It does have pod filters now but it was running ok with them before I stripped it to paint

[bluedog59]

Have you checked the float heights and air screw settings ?

[Jpich85]

I did set the float heights when I put new seals in the carbs last year but haven't recently, I will check the carbs tho if I can't fix the problem but it didn't enjoy taking them off and on lol, if I can't find the problem that'll be my next thing to look at, could it be the coils?

[teltwosheds]

Put the battery on charge, then while you're waiting block the tank up a bit higher to see if the fuel lines are not running uphill over anything causing an air lock.

[Jpich85]

I'll try that too thanks mate, it's strange because I haven't really done anything expect left it for a month stood and changed the petcock seals.

[Jpich85]

I just remembered that I put a small k and n air filter on the cam cover breather outlet as I didn't know what to do with that as the air box has been taken out, could this be choking it? I can't get to the bike until tomorrow to test this

[Legotoy]

Hi mate, I've just been through a lot of similar pain with my GSXR/RF conversion, so I hope some of my experience is relevant.

In my experience a month is plenty long enough for modern fuels to "go-off" and lose octane rating as well as partially block the jets. Since the pilot jet affects running up to quarter throttle it could be that a partially blocked pilot jet is causing it to run lean overall?

I had mine sat for a month, and then it only ran on 3. A carb clean and fresh fuel sorted it.

I have also just removed the airbox, although it did run the 900 motor on stock airbox and jets for a short period. (112.5 / 115 / 115 / 112.5)

Current settings are as follows:

4x single "V&H" type oval filters

Main Jet: 145 in all four carbs

Pilot Screws: 2.5 turns out

Needle on 4th clip from top, although I may lower it as rich running is causing the idle to hang up a bit.

Float Height: 15mm on all four carbs

Oh and I run my cam breather tube to an old beer can zip tied to the frame rail for now. A new baby means I am poor as you like, so have to save up for a fancy breather bottle ;-)

Finally don't forget to use sufficiently long vent tubes for the diaphragm and float bowl vents. Otherwise cross winds could hurt how your bike runs. There's a good article here on OSS about those two.

[Jpich85]

Thanks legotoy that's great information there and I've got plenty try when I get back on the bike and try and sort this.

Thanks for your information on the carb set up too, I don't know my stuff with that side of things so I'll give that a try, where do you get different size jets from?

Do you  find it hard to squeeze the carbs on and off? because there's hardly any room for it to fit under the frame.Do you think fitting mini airfilters to breather tubes is a good idea? Or just let them breath without?

do you know what the article was called about the vent tubes because id like to read that, i only have two tubes left coming from the carbs, there are two that go into a filter fixed to the cam cover.

Cheers

 

 

 

 

 

 

 

 

 

 

[Legotoy]

Re: jets – I bought a Factory Pro jet set from the USA (e*ay), which also comes with full instructions which is where I got my info from. I can lend you the 147.5 jets to try if you like? I say “lend” because they were expensive and I’d like them back ;-)

 

The kit comes with needles too, but if you have nothing but stock stuff installed now then just the jets would be a good place to start.

 

The carbs are no problem to get on/off. Maybe your carb rubbers have hardened? It is tight to the top frame rail but not really had issues myself.

 

Vent tubes don’t need filters, article link here:

http://oldskoolsuzuki.info/archives/531

 

Search “Journey to the center of Mikuni’s BST38SS carbs” in the OSS Vault

 

[Jpich85]

Thanks legotoy that's great of you, I think like you tho if buy the factory pro kit, I have looked at it but haven't got round to purchasing it yet, it's kind of pricey.

I think they have hardened because they are a pain to get on, is it a bad thing of they've gone hard? Thanks a lot for that I'll have good read if it after tea I think, I thought the bike was nearly done but now all this has come about lol, I'll just have to drive on :-)

 

 

[Legotoy]

Keep at it - the 900 hybrid is a lovely thing to ride once sorted. Smooth and torquey. I have gone for 14/43 gearing too which makes it even more responsive.

If the inlets are hard, try hot air on them and a little silicone grease to ease the carbs on. If they are so hard they have cracked and have air leaks then that's bad of course.

Good luck.

 

[Jpich85]

Thanks mate for all your advice, I've made a list of things to check then if no luck it'll be carbs off but I had real trouble last time wroth petrol coming out the carb breathers and leaking into the cylinders so I'm scared to mess with it again but I might have to.

 

[Joebloggs]

Could also be a split diaphragm, would tick over fine but would struggle to pick up when one of the slides didn't lift. 

As for flooding, check you have fuel in the bowls then turn off the fuel tap (cant flood if there's no fuel) Then start it and see if t picks up cleanly