Turbo plumbing for a simpleton

[MeanBean49]

5 hours ago, El Gringo said:

Unfortunately not much i'm afraid boss.

Clipped another half a coil from the regulator spring to try and drop it down a bit more - haven't had chance to try it again yet.

Have re cleaned the carbs and reset the float heights to 23mm to try and cure the flooding but haven't had chance to fire it up.

The other spring turned up and as Rob said it's completely the wrong size, nevermind eh?

Hopefully i'll get a few evenings on it this week - need to weld up a bracket for the rear light, then i think that's pretty much all the fabrication stuff done.

I've bought a proper remote fuel tank so i can run it up for longer without forgetting to stick fuel down the funnel! I'm going to try and get it revving a bit cleaner before i try the tank again.

One small step at a time

You not got a fuel retun pipe?

[El Gringo]

11 hours ago, MeanBean49 said:

You not got a fuel retun pipe?

I have but only when it's running through the regulator, at the moment i'm just running off a remote bottle to get it running right initially.

Getting the proper tank on and off is a right pain in the arse as theres not much space under it for the hoses and there's not enough space for a shut off tap under the tank.

The tap is down behind the plenum before the pump and won't fit past it so when i disconnect the main flow hose from the tank it's a case of trying to turn the fuel away from the outlet so i don't soak myself in fuel (again......)

It's really not ideal and i need to find a better solution.

The return hose is fine and should be a big enough bore all the way along the system

[Gixer1460]

5 hours ago, El Gringo said:

I have but only when it's running through the regulator, at the moment i'm just running off a remote bottle to get it running right initially.

I know its counter intuitive but if the pump isn't running / having pressurised delivery, then it won't be running right! Otherwise when the pump is switched on, you are back to square one!

[El Gringo]

2 hours ago, Gixer1460 said:

I know its counter intuitive but if the pump isn't running / having pressurised delivery, then it won't be running right! Otherwise when the pump is switched on, you are back to square one!

Aye, it's an all or nothing thing with attaching stuff, trouble is i'm trying not to change to many things at once to narrow down the issues

[El Gringo]

Right, it's all together with the tank on and all of the turbo gubbins attached

Got the base fuel pressure down to 2psi - won't go any lower but should be ok.

With the float heights set to 23mm and the 2psi fuel pressure it's not overcoming the float needles which is a good thing

However, it won't start again - not sure if it's because it was completely dry and needs a bit of help or if it's struggling with the float heights being too low.

It's giving the occasional cough and pop but sounds like it's not getting fuel through.

I've got the mixtures set a little bit leaner than standard from when it was over fueling before - so i will try them out a turn or so. Other option is to up the fuel pressure a bit - does that seem like a logical approach?

[Captain Chaos]

float level should be around 2mm lower than standard, I would guess it's way too low now.

[El Gringo]

3 hours ago, Captain Chaos said:

float level should be around 2mm lower than standard, I would guess it's way too low now.

23mm is about 2.5mm lower than stock so not massively lower

[Captain Chaos]

Ah ok, I have the oilcooled float levels in my head.  

Are the spark plugs new / good?

[MeanBean49]

I would reckon its just a bit too lean on the idle mixture.

[El Gringo]

11 hours ago, Captain Chaos said:

Ah ok, I have the oilcooled float levels in my head.  

Are the spark plugs new / good?

Aye, brand new plugs

1 hour ago, MeanBean49 said:

I would reckon its just a bit too lean on the idle mixture.

That's my thinking, i'll spin them out a turn and see what happens

[El Gringo]

Right, this thing is trying my patience once again,

Tried upping the mixture, 2.5 turns and then 3.5 turns out, still no joy, although it is coughing and burbling it just won't run on and catch on all cylinders.

Tried it with the fuel pump running to raise the fuel level in the float bowl, no difference. Tried upping the fuel pressure a little, no difference.

What effect would the lower float heights have on the idle/starter circuit - i know in theory the lower it is the leaner the mixture.

*Edit - I may try going back up a bit on the float heights as a matter of course - a logical reversal of the process

I could not have picked a worse bike to try turbo-ing!

Edited June 15, 2017 by El Gringo

[MeanBean49]

9 hours ago, El Gringo said:

Right, this thing is trying my patience once again,

Tried upping the mixture, 2.5 turns and then 3.5 turns out, still no joy, although it is coughing and burbling it just won't run on and catch on all cylinders.

Tried it with the fuel pump running to raise the fuel level in the float bowl, no difference. Tried upping the fuel pressure a little, no difference.

What effect would the lower float heights have on the idle/starter circuit - i know in theory the lower it is the leaner the mixture.

*Edit - I may try going back up a bit on the float heights as a matter of course - a logical reversal of the process

I could not have picked a worse bike to try turbo-ing!

Might want new plugs. They are absolute bastards for killing plugs after just the slightest hint of flooding/running too rich. They look like they are sparking nice and strong but bike wont start. Had it a gew times.

Not using iridium plugs are you? They are even worse than standard

[badger]

Most of the time mine wouldn't start it was plugs. If you have a heat gun, warm them up a bit and stick them back in. Worked well each time it wasn't doing anything. Like meanbean said, it'll look fine but it's doing shit under pressure if they're vaguely wet

[El Gringo]

I'll pick up another set this weekend. The ones i've got in it now are effectively new but it's worth a go

[MeanBean49]

3 hours ago, El Gringo said:

I'll pick up another set this weekend. The ones i've got in it now are effectively new but it's worth a go

Done it a few times, brand new plugs, not even manged to get bike running before its killed them

[El Gringo]

2 minutes ago, MeanBean49 said:

Done it a few times, brand new plugs, not even manged to get bike running before its killed them

Its good to know it's not just me!

 

[slingy1157]

With the float height 2 things to remember.

1. You lower the float height because the fuel pressure has increased from virtually only 0.25 psi of gravity pressure from the tank to 2psi of regulated pump pressure.

So now more force is required on the float valve to hold back the fuel. This extra force can only be generated by the float displacing more fuel to create more buoyancy . So imagine, for a given set float height, as the fuel pressure goes up, the fuel height in the bowl will rise as the buoyancy of the float needs to match the force required to hold the float valve shut. So by lowering the float height ( as viewed durring normal opperation or an increase in the float height as measured with the carb upside down and bowl off) at increased fuel pressure we are only really returning the fuel height in the bowl closer to factory levels and definitely should not be lowering the fuel level.

2. Every type of carb will vary wildly with how they handle the fuel pressure. One of the best ways i think is to put a bit of clear pipe on the bowl drain

And open the drain with the pipe run up the side of the bowl. With everything factory, mark the fuel height on the outside of the bowl. Then with reg and pump running, use the clear pipe and adjust the float to try and match the original mark or just slightly higher. Should be alot quicker as saving any guess work. You will see what is happening and it will be set correct for any given pump, reg gauge, combo .

 

 

Edited June 18, 2017 by slingy1157

[slingy1157]

Are running the GK76a carbs?

If so the standard float height is 20mm. Looking at the float design and measuring point, at 23mm there is a real chance the float is jammed between the float bowl and the valve and there is no movement left to let fuel in. 

[El Gringo]

9 hours ago, slingy1157 said:

Are running the GK76a carbs?

If so the standard float height is 20mm. Looking at the float design and measuring point, at 23mm there is a real chance the float is jammed between the float bowl and the valve and there is no movement left to let fuel in. 

Thanks for the info Slingy,

They are GK76a carbs so that could well be the issue, i think i'm going to go back to 20-21 and try the clear pipe idea and see what it's doing on the pump/regulator.

I had it running again over the weekend, seems like it had eaten a couple of the plugs.

At one point it sounded like it was trying to chime in on all 4 cylinders - which was odd as i thought it already was running on all 4?!

Carbs are now fully apart again to be cleaned and float heights re set. Will also get another fresh set of plugs

I shall not be beaten!

[slingy1157]

3 hours ago, El Gringo said:

Thanks for the info Slingy,

They are GK76a carbs so that could well be the issue, i think i'm going to go back to 20-21 and try the clear pipe idea and see what it's doing on the pump/regulator.

I had it running again over the weekend, seems like it had eaten a couple of the plugs.

At one point it sounded like it was trying to chime in on all 4 cylinders - which was odd as i thought it already was running on all 4?!

Carbs are now fully apart again to be cleaned and float heights re set. Will also get another fresh set of plugs

I shall not be beaten!

I found new old stock plugs on Eblag from the us and ended up buying a dozen at a time as ngk's seem to die for a pass time as has already been mentioned. I could even park mine up running good and come back to it a few weeks later and struggle to get it running due to dead plugs. 

On a side note, i had an old dirt bike with a self tuned 2 stroke. It ran great on an old Champion plug i plagged from an ancient boat engine. Twice i thought, i really should give it the propper plug, and twice they died within literally seconds of running. I ended up just running the old Champion plug which it just bloody loved for some reason.

 

Keep at it. If it was easy, everyone would do it lol

[El Gringo]

Right, it's been a weekend of carbs on ,carbs off, carbs on, carbs off repeat ad infinitum

Slight progress and a problem,

Having stripped and thoroughly cleaned the carbs for the umpteenth time i reset everything to factory settings and did as slingy suggested - fuel gravity fed on stock 20mm float heights and marked the 2 outside float bowls. Then repeat on the tank/pump/regulator combo with the pressure turned as low down as it will go.

I did have a slight issue that #1 float fuel level seemed drastically lower to begin with but when re tested was about the same as the other side.

Here's the problem - bottom line is the gravity fed level, upper line is the fuel level when on the pump. Difference between the 2 is approx 15mm. #4 float bowl

Other side (No1 float bowl)

I tried adjusting the fuel level down - tried 21.5mm, re tested, and fuel level was roughly 1.5mm lower - surely i can't adjust the floats down as far as i need to get the lines to match?

I can't go any lower on the fuel pressure as it's backed all the way off - would increasing the return line size help? its 8mm bore all the way back to the tank.

On the plus side, i reset everything back to factory again after fiddling with it and fired it up on the remote bottle, and not only did it started pretty much instantly, it idled nicely too aside from cylinder #4 which was popping and coughing - quick swap for an old old plug and it chimed in nicely and gave the best idle i've had since getting it running.

It almost accepted a bit of throttle though i think without the airbox/plenum it's always going to struggle.

Just proves what i thought was running on all 4 previously wasn't

So, once i've sorted the fuel pressure level i can start looking at the next step.

Many thanks to @slingy1157 for your help, i'd have had no hope getting it to work from where i was without it!

[slingy1157]

Good work mate. Cant beat actually seeing what is going on. I would be questioning those gravity fed levels. I would of thought, looking at the carb design that the gravity level would be about halfway between the two marks you have. So they seem rather low. The 2.5psi marks are about what i would have expected. On my carby build using a modified webber fpr i think, i drilled out the fpr return right from the seat through, as i had an 8mm return line but couldnt get the pressure below about 2.5 either as the actual seat hole was about 4mm and was having flooding issues. I also ended up leaving the spring out. 

And i used 2 relays to run the pump, so it only ran while the engine was cranking or running. Much safer as if you drop the bike the pump will stop and not pump fuel everywhere as well as not subjecting the carbs to pump pressure for any longer than necessary and I'm not a fan of listening to winey pumps without the engine running lol

[El Gringo]

Cheers Slingy, i thought they looked a bit low, i'll retest them tonight now it been run for a while - might also stick a drop more fuel in the remote bottle as it was quite low so wouldn't have had much weight of fuel on them.

I did wonder about the return outlet - it's about 4-5mm IIRC, might be worth opening it up a bit and also checking the inside diameter.

The spring is redundant now as it doesn't touch both seats at the same time when off the bike so i've got the adjuster wound in so its just touching both ends and not increasing the pressure at all.

[El Gringo]

I also think it might be worth replacing the float needles, they don't look to have any wear on the tips but the sides are a little shiny

[slingy1157]

13 hours ago, El Gringo said:

I also think it might be worth replacing the float needles, they don't look to have any wear on the tips but the sides are a little shiny

Yeah mine looked fine but didnt stop flooding untill i replaced all 4. An expensive exercise on the old bst36 carbs as you had to buy the whole plastic float and frame assembly to get them .

Carbs really do need to be in 100% as new condition, not just clean. ANY wear seems to be greatly exaggerated by the fuel pressure and boost.