Carb keeps flooding

[cymaz]

I may be barking up the wrong tree but have tried added an extra head shim..just to lower the compression ratio a smidge?

[J D 8 - Moderator]

You can 

4 minutes ago, cymaz said:

I may be barking up the wrong tree but have tried added an extra head shim just to lower the compression ratio a smidge?

 Yes wrong tree, can not be done with a Saito as head and cylinder barrel is one part.

[Paul De Tourtoulon]

1 hour ago, J D 8 - Moderator said:

You can 

 Yes wrong tree, can not be done with a Saito as head and cylinder barrel is one part.

Putting it at the bottom of the barrel works for me.

[Andy Stephenson]

1 minute ago, Paul De Tourtoulon said:

Putting it at the bottom of the barrel works for me.

A club mate did exactly this to reduce the rather savage compression of a Saito 80. You do have to readjust the tappets to account for the extra clearance on the pushrods this produces.

[GrumpyGnome]

3 hours ago, cymaz said:

I may be barking up the wrong tree but have tried added an extra head shim..just to lower the compression ratio a smidge?

Nope. Haven't tried anything yet 🙂 

[Martin Harris - Moderator]

I wind back to compression and then apply the starter. 
 

I did have a pupil with a Magnum 90 (yes, ‘‘twas a BIG trainer) which had a vicious kickback and shed props regularly on trying to start.  
The answer (I’d have shimmed it if it was mine) was to work together to apply the glowstick while the engine was spinning. 

[Jon H]

If the engine has no fuel in it you should get the thing cranking well before it actually fires. Thats why its important not to prime it

[PatMc]

On 08/11/2024 at 09:01, Jon H said:

 

 

This tank is too high by about an inch and should be mounted lower so the top of the tank aligns with the carb. With a tail dragger you might get away with this setup from the point of view of flooding, but its not ideal and will result in tuning compromises to keep it running in the air. Improper tank placement like this is responsible for about 90% of engine issues if you look at root cause. 

 

The tail dragger vs trike discussion is not important when it comes to tank placement as the engine will always pull the fuel through with the tail on the ground and you need the tank set for perfect operation on flight as that is where the engine does its work. 

I was suggesting a "syphon fuel feed" as a possible solution to the OP's question & using a convenient existing drawing to illustrate it. The fuel level shown with respect to the carb is incidental to the advice offered.

However your opinion regarding the tank/carb layout is completely incorrect, as proven by over 30 years of using this set-up in a variety of sport & aerobatic models without any problems.

 

 

[Jon H]

59 minutes ago, PatMc said:

However your opinion regarding the tank/carb layout is completely incorrect

 

No, its not. I worked for an engine manufacturer, i know that i am right and you arent. You clearly do not have sufficient understanding to realise this, but its a fact.  its a fact that is supported by other engine manufacturers too. The image paul posted is lifted from an OS manual, PAW say the same thing in the manuals for their diesels as well. The fuel level in the tank should not be higher than the spray bar and that is all there is to it. 

 

I know you simply disagree with everything i say on principal and will likely try to argue this until the thread is locked, but you are wrong and so is your advice. 

 

[cymaz]

http://www.flyrc.com/images/drupal/f0607how_to_fuel_systems.pdf

[Jon H]

2 hours ago, cymaz said:

http://www.flyrc.com/images/drupal/f0607how_to_fuel_systems.pdf

 

i have seen this before and i am not convinced by the principal. its a solution looking for a problem and the reliability and performance of the system is dictated by the competence of the assembly. There are also so many points of potential failure/leak vs a normal system. He also talks about tuning 200 rpm rich of peak with a standard tank set up. that is a myth and consequently i am dubious about his qualifications. 

 

When at laser the tank height vs carb issue came up often and header tanks were suggested many times as a solution. A customer Steve Dunne worked out a pressure isolated gravity fed system that worked, but i couldnt recommend it as the system was quite complicated to get right. 

 

This caused many a debate, but unfortunately i had to make a recommendation that both an aircraft engineer, and the chap on the phone who was confused by his tank with only 2 pipes on it and couldnt work out where they went. 

 

I will always vote for the simplest system with the least failure points. 

[Paul De Tourtoulon]

I only use header tanks as a means to stop bubbles in the fuel line, like my Raptor 50 and jet/turbine powered Rafale.

[Martin McIntosh]

Not familiar with Saitos, but are the carbs twin needle or air bleed? If the latter, then closing the throttle will not impede the fuel flow so unless you use a clamp on the line or arrange it with a U tube which can be parked on a blanked off tube it will probably syphon.

[Jon H]

1 hour ago, Martin McIntosh said:

Not familiar with Saitos, but are the carbs twin needle or air bleed? If the latter, then closing the throttle will not impede the fuel flow so unless you use a clamp on the line or arrange it with a U tube which can be parked on a blanked off tube it will probably syphon.

 

saito 100's have tn carbs. 

[PatMc]

On 09/11/2024 at 22:27, Jon H said:

 

No, its not. I worked for an engine manufacturer, i know that i am right and you arent. You clearly do not have sufficient understanding to realise this, but its a fact.  its a fact that is supported by other engine manufacturers too. The image paul posted is lifted from an OS manual, PAW say the same thing in the manuals for their diesels as well. The fuel level in the tank should not be higher than the spray bar and that is all there is to it. 

 

I know you simply disagree with everything i say on principal and will likely try to argue this until the thread is locked, but you are wrong and so is your advice. 

 

As I have already said the point of the drawing was to illustrate a syphon arrangement as a possible solution to the OP's problem. The fuel level wrt the cab was merely an incidental part of an existing drawing which was made 19 years ago for the benifit of someone requesting advice on installing the engine in his Silhouette. 

Your post ignored the OP's request for advice & simply gave a gratuitous unrelated opinion regarding the tank level.

Sorry if it offends your ego to be wrong but as I have already said the layout actually has stood the test of time giving me no problems for literally decades. This is hardly  surprising as the models the tanks are in don't spend much of there active life allowing the fuel level to be held at a fixed position wrt the carb.

It also strikes me that since dropping the tank by an inch would have it protruding below the fuselage floor. The engine & tank sizes shown would have been fairly standard for most Silhouettes so I probably had a fairly common tank installation in this model.

 

Don't flatter yourself that I rebuffed your critisism because I disagree with you as a matter of principal or that I take you so seriously as to want to continue a prolonged argument over the validity or otherwise of your critisism.

To say that I disagree with everything you say is ludicrous verging on paranoia. I rarely read anything you post, not due to any antagonism but simply because I don't have much interest in ic or the type of models you prefer & I dare say you have little interest in my choice of models or electric power. To date I think I've only posted in the same thread as you 2 or 3 times at most & made any reference to your post(s) twice. If you had not initiated this disagreement I probaly wouldn't have responded to anything you have said in this thread. 

[Jon H]

give it a rest pat, your whole reasoning is wrong and your 'i have done xyz for 30 years' argument isnt convincing. To see what i mean, just go for a drive if you like. Plenty of people who have been at it for 30 years are still hopeless at it. Doing the same thing wrong for 30 years dosent make it any less wrong. 

 

My tank level comments were totally relevant, as a tank setup like yours is likely why the engine was flooding. We really are approaching broken record status here but water (or fuel in this case) will flow down hill. If the tank is higher than the carb, it will flow down into it. I am fairly sure an 8 year old would understand this simple concept, but its apparently lost on you. 

 

As for the rest, for years you have disagreed with me on principal. If i told you the sky was blue you would argue about it. I have no idea why you do this, but its a trend which has persisted for the decade or so i have been on here. Fortunately for me, having left my former position i dont have to be as diplomatic these days. 

[PatMc]

1 hour ago, Jon H said:

give it a rest pat, your whole reasoning is wrong and your 'i have done xyz for 30 years' argument isnt convincing. To see what i mean, just go for a drive if you like. Plenty of people who have been at it for 30 years are still hopeless at it. Doing the same thing wrong for 30 years dosent make it any less wrong. 

 

My tank level comments were totally relevant, as a tank setup like yours is likely why the engine was flooding. We really are approaching broken record status here but water (or fuel in this case) will flow down hill. If the tank is higher than the carb, it will flow down into it. I am fairly sure an 8 year old would understand this simple concept, but its apparently lost on you. 

 

As for the rest, for years you have disagreed with me on principal. If i told you the sky was blue you would argue about it. I have no idea why you do this, but its a trend which has persisted for the decade or so i have been on here. Fortunately for me, having left my former position i dont have to be as diplomatic these days. 

I'm afraid you're someone who won't look past your own preconceptions.

 

Your tank comments were irrelevant to the inverted 2 stroke shown in the drawiing, at that point we didn't know the OP had a 4s. It would seem you were doing exactly what you accuse me of - disagreeing with me on principal.

 

Edited November 12, 2024 by Martin Harris - Moderator
Removed personal comments

[Martin Harris - Moderator]

Let’s not get too carried away.  I think we should respect that everyone has a right to an opinion and to respond robustly but I’ve had to edit the previous post as it was just too personal. 

[Jon H]

11 hours ago, PatMc said:

Your tank comments were irrelevant to the inverted 2 stroke shown in the drawiing, at that point we didn't know the OP had a 4s

 

2 stroke, 4 stroke, glow, diesel, inverted, upright, sidewinder, twin needle, air bleed... Its all the same and makes no difference at all. The fuel level should not be higher than the carburettor for any of them and the fact that you try to make this distinction between engines is clear example of you not knowing what it is you are talking about. 

 

 

11 hours ago, PatMc said:

It would seem you were doing exactly what you accuse me of - disagreeing with me on principal.

 

No, i am disagreeing because you are wrong and your advice is also wrong. If you posted something that was factually correct, i would agree with it. 

 

 

[PatMc]

3 hours ago, Jon H said:

 

2 stroke, 4 stroke, glow, diesel, inverted, upright, sidewinder, twin needle, air bleed... Its all the same and makes no difference at all. The fuel level should not be higher than the carburettor for any of them and the fact that you try to make this distinction between engines is clear example of you not knowing what it is you are talking about. 

 

The point I was making regarding relevance of not knowing whether the OP's engine was 2s or 4s had nothing to do with the fuel level. It referred to the 0P's flooding problem & reinforced my opinion that your post regarding the tank level shown in the drawing was gratuitous to the advice offered by myself.

 

I think the Mod's editing of the post may have distorted this .

[Jon H]

Yea i dont really care at this point. The OP had a flooding problem and high tank/fuel level is the most common cause of this issue so i offered advice accordingly. 

 

AS you post about tank height was wrong and would make the problem worse i had to correct it so our poor OP wasnt mislead....and here we are

Edited November 13, 2024 by Jon H

[PatMc]

2 minutes ago, Jon H said:

Yea i dont really care at this point. The OP had a flooding problem and high tank/fuel level is the most common cause of this issue so i offered advice accordingly. 

 

AS you post about tank height was wrong and would make the problem worse i had to correct it so our poor OP wasnt mislead....and here we are

For goodness sake just give up this irrelevant mantra.

[john stones 1 - Moderator]

You've both given your advice, the O.P and everyone else is free to choose which to take. So give it a rest please, or open a thread of your own to continue.