JAE Help- .12 engine tune

[chris armstrong]

Hi all

so i finally got the jae hitting the plane.. the problem is it does not stay there for too long

Here is what i am running

An older buggy engine, 30% nitro and a 35mm berilium prop

I will buy a better prop once i get the boat reliable.. I am really struggling to get the fuel mixture rite.

If i run it rich it is slow and boggs down hard in the corners.. To a point (boat is going extreamly slow) where if i dont back off from the corner and straighten the rudder the engine dies.

If i run as lean as i think it runs well in the straight but same thing happens in the corners... it just dies and sounds like it is too rich

If i go leaner again, the boat is hard to launch and does the general "Quick die" as a lean engine does

I just cant keep the engine running on revs for more than one lap.

If someone could chime in and perhaps flick a few ideas at me it would be much appreciated.. the strut is set up (a z12) exactly where the plans say.. on the bottom of the ski...

Today i richened it rite up and slowly started leaning.. Extreamly rich i would get 3 laps ultra slow... any leaner and it would loose revs in the corners, fall off the pipe and die. i have tried an ultralong pipe and slowly shortened it..i just cant seem ro find a happy medium/.

Im thinking it could either be fuel mixture or the engine..

 

[TomMoorehouse]

sounds like a fuel delivery problem to me. have you removed your needle and cleaned it out?

 

[chris armstrong]

Thx Tom, ill give it a go now

I pulled out the engine and tank tonight and discovered if i turned the tank 0 degrees so the stopper faces the floor, there was a small leak.. a new screw in the tank stopper ensured it sealed properly this time.. i was thinking now that you mention delivery is the slight leak under pressure could have an impact on delivering fuel under load..

I am now sure this is the contributing factor in the engine stalling regardless of mixture setting... Does this sound correct to any one?

I have also tightened every screw/ blind nut bolt ect.. Re-clamped the pipe all of the precautionary measures

Lets hope the trip to the pond tomorrow brings a reliable boat.. Then its all about tuning from there...

What do you think.... Is this where the problem is?? Personally it makes sence to me however i could be wrong?

Thanks again for a great forum

 

[gooycheese]

I will say its always good to actually find some sorta problem when something goes wrong. In my case if my .12 boat dont wanna run, most of the time i will attribute that to bad bearings.... like ya said this is an older engine, not sure how good the bearings are.... but a bad bearing will make tuning a 12 really tough.

Paul

 

[moparbarn]

bad bearings will make tuning any engine tough. the fuel tank leak & resulting low pressure in the tank prolly has a lot to do with your running issues, chris. if it's no better now, either the engine is tired, or just not well suited to boats. some killer car & buggy engines just aren't suited to boat use. the power requirements can be too different .

 

[chris armstrong]

The bearings are ok. i will try running today and if no good, change to an os buggy engine i have sitting here. I just dont want to go through cutting off the pull start again in order to make it fit when there is something wrong with the set up..

I have been thinking of the TOP .12 and and pipe next.. For just over 200 bucks i think this represents good value.

When i can get fuel to the current engine it goes really well which makes me want to get it going with the current engine and build another light weight for the TOP engine..

This way i will have a rigger that my lil daughters can drive and if it breaks, so be it.

I will get some vid if the problem persists today.. Another thing i have considered is compression however it feel ok..

 

[chris armstrong]

Ok so i ran it.. got about two laps and the same thing... Is this compression?

I have an older os cv15 but not sure if it will be up to it.

The current engine turns a 35mm prop and hitts the pipe sometimes.. any leaner and it will stall after about 1 lap.

Think i might build another and do it properly.. or, any one got a jae 12 or 21 with engine, pipe, prop and hardware they want to sell?

 

[Jay Skutle]

Ok so i ran it.. got about two laps and the same thing... Is this compression?

I have an older os cv15 but not sure if it will be up to it.

The current engine turns a 35mm prop and hitts the pipe sometimes.. any leaner and it will stall after about 1 lap.

Think i might build another and do it properly.. or, any one got a jae 12 or 21 with engine, pipe, prop and hardware they want to sell?

Chris,

if you decide to change engines, I have a lightly used Nova Rossi 12 race engine for sale...check out the FOR SALE forum or send me a message...this is the engine you want for a JAE!

Jay

 

[chris armstrong]

How much.. can u pm me?

Do u have a vid of it running?? Do you have or know the correct pipe?

Im in Aus (melbourne) so would need postage to there

 

[TomMoorehouse]

id try the other engine. if it does the same thing... then it's not the engine.

 

[chris armstrong]

i was thinking the same TOM

How is the tank set up ment to be?? I have used a sullivan 6oz tank.. Is the clunk set up the same as an aircraft?

If the tank was bouncing around a little, could this perhaps be the issue?

I( have just slotted the tank up the front and it fits perfectly however there is about 5mm either side that could possibly vibrate. I packed in the gap with a wedge yesterday to see if it made a difference however still no luck.

I appreciate your help too Tom

 

[chris armstrong]

Could it be the tank set up?

I am using a sullivan 6oz tank which fit perfectly with about 5mm gap either side.

How is the clunk set up?? Same as setting up an aeroplane?? I have set up tanks on Mono's and tunnells however this is my first rigger

 

[chris armstrong]

Could it be the tank set up?

I am using a sullivan 6oz tank which fit perfectly with about 5mm gap either side.

How is the clunk set up?? Same as setting up an aeroplane?? I have set up tanks on Mono's and tunnells however this is my first rigger

 

[camaroboy383]

we as in most of us,,,, dont use clunks... bend the brass tubing so it sits in the rear left corner,,,, but leave space between the edge of the tank and the end of the tube or you will have issues...

alden

 

[chris armstrong]

ok so i had the tank set up like an aircraft with the clunk facing the engine.. Is this correct?

I will make the adjustment.. I have already started milling away a bit of the engine mount to get the os in with the pull start attached.

The last engine i cut the pull start off. seemed to not make any difference but this could also be why the boat is running like crap..

 

[moparbarn]

what temps are you getting after a run? maybe not getting up to temp.....

 

[camaroboy383]

ok so i had the tank set up like an aircraft with the clunk facing the engine.. Is this correct?

I will make the adjustment.. I have already started milling away a bit of the engine mount to get the os in with the pull start attached.

The last engine i cut the pull start off. seemed to not make any difference but this could also be why the boat is running like crap..

no,,,,,,, dont use a clunk... better off not using one at all.... you say the pullstart was cut off.....what do you mean by this??????? if the case of the engine is not sealed then thats your issue,,,and it will never run right till its sealed... when you remove a pullstart the backplate should be switched to a non pullstart one... that will take all the guess work out of it...

again,,,,,,,,,,,,,,,,,,,,,,,,,,,,DONT USE A CLUNK..................................................

 

[Ted buckley]

ok so i had the tank set up like an aircraft with the clunk facing the engine.. Is this correct?

I will make the adjustment.. I have already started milling away a bit of the engine mount to get the os in with the pull start attached.

The last engine i cut the pull start off. seemed to not make any difference but this could also be why the boat is running like crap..

no,,,,,,, dont use a clunk... better off not using one at all.... you say the pullstart was cut off.....what do you mean by this??????? if the case of the engine is not sealed then thats your issue,,,and it will never run right till its sealed... when you remove a pullstart the backplate should be switched to a non pullstart one... that will take all the guess work out of it...

again,,,,,,,,,,,,,,,,,,,,,,,,,,,,DONT USE A CLUNK..................................................

Yes, don't use a clunk. Assuming that you don't have an engine leak from the Starter removal, let's walk it backwards. Fuel lines good/remote needle clean/fuel filter clean/pressure good from pipe?? If all these are good - then it's possible that you are not getting to temp. Unless it's 90+degrees in Melbourne, then don't use any water - period.. I don't use any water in mine and I have a top.12. The problem with my Top - was the Carb was never Modded and it did the same exact thing.

It would run around the pond - real slow, then about lap 2 - it would take off.. It got to temp.. but the real reason why it did that in the first place was because the engine was being starved of fuel from the un-modded carb..

P.s. Don't forget to check your drive line. It should spin freely with NO noticeable resistance.

 

[moparbarn]

ted - he's using an air cooled buggy engine. if low temps are the issue, try taping off the cooling fins.

alden - when he talked about removing the pull start, i don't remember cutting being part of it.....figured it was just unbolting the starter - that shouldn't affect sealing. he did say that the pull start end of the crank was on a bushing, not a bearing. i doubt if any pull start is a "sealed unit", but haven't seen all of them out there, for sure.

 

[Ted buckley]

ted - he's using an air cooled buggy engine. if low temps are the issue, try taping off the cooling fins.

alden - when he talked about removing the pull start, i don't remember cutting being part of it.....figured it was just unbolting the starter - that shouldn't affect sealing. he did say that the pull start end of the crank was on a bushing, not a bearing. i doubt if any pull start is a "sealed unit", but haven't seen all of them out there, for sure.

I guess the next question would be: what is the pipe length & prop size? Until I remedied the Carb. issue I went out with the Pipe and dropped-down the prop size.. The pipe length(too short) could be the result of his varying needle. Do you agree?