Carburator Screw
 

Seems I fix one thing then another thing breaks...it's really getting on my nerves, but still this hobby sticks to me:D

The engine is a .61 ASP 2 stroke.

I took off my caburator yesterday to put the throttle linkage on...Sorry to those guys who suggested the EZ connector in the "Throttle pushrod" thread. I checked out a couple of other guys setups and 6 out of the 10 guys used a Z bend. So I'm going to try that since it's going to be the easiest now.

Now, I took off the caburator because I couldn't get a proper Z bend onto the carbs side. The carburator has two screws (see picture below where you can see the top one) which tightens it - one at the top and one at the bottom. I took the screws/bolts (I sometimes don't know when to call it which lol - stupid me) out - they were tightened down well. Took the carb off and put on the Z bend. Then came the headache...the bottom screw now tightens a bit, but not that it feels safe - I can ALMOST unscrew it with my fingers, the top however I CAN unscrew with my fingers. I struggled with this for about one hour and gave up. I don't know if the thread was stripped sometime close to the bottom or whether the screws are long enough - since the thread seems to be on the carbs holes, but the screws first have to go through the "carbs mount?" It's not very long screws but they did work up until now.

Is there a trick to this or when the engine start up will the carb get "sucked" tight (putting my hopes on something not realistic here I guess)? I know the 75 I have has one screws which serves as in sort of a clamp to tighten the carb down. My 46 has this same setup as the 61, but they seem tight.

If this is faulty and that the thread has stipped - is there a way to fix this without getting a new carb?

*forgot to add pic*
*and then I add the wrong one to - lol - its too early - now it should be right*

RE: Carburator Screw
 

im not familiar with ASP engines, but the screw you are pointing at looks like the muffler bolt

RE: Carburator Screw
 

Sorry MetallicaJunkie. After I posted I saw when I edited the pic to put the arrow in I accidently was looking at the wrong one. Corrected it and posted again. Thx

RE: Carburator Screw
 

In your picture what you are pointing to with the arrow is indeed what holds the carb in position. It is a tapered jam bolt inserted from the opposite side and it jams aginst a flat on the carb boss.

To resecure it you must loosen the jam bolt by tapping it back after loosening the lock nut several turns and when the carb can be rotated free it is positioned correctly then holding it hard into the engine so the o ring is compressed while that nut is tightened If that jam bolt threads are stripped it will need to be replaced.

Expecting it to 'suck' in is just wishful thinking.

If you are using a 72 Mhz radio system and using a z bend in a metal throttle arm then that is is an exceedingly bad idea and just like lighting a very long fuse on a stick of dynamite under your airplane. I don,t care how many voted to use a z bend, Bad ideas don,t listen to voters anymore than politions do.

If you are using a 2.4 system then its still a bad idea since you are now the chief flight test engineer on vibration induced RF interferance with 2.4 systems.

John

RE: Carburator Screw
 

I apologise for my incompetence, but when you are refering to,

"To resecure it you must loosen the jam bolt by tapping it back after loosening the lock nut several turns and when the carb can be rotated free it is positioned correctly then holding it hard into the engine so the o ring is compressed while that nut is tightened If that jam bolt threads are stripped it will need to be replaced."

There is no nut. The carburator slides into it's socket and then has two bolts which from each direction bolts down the carb. Maybe I'm just misunderstanding you. This link is an exploded view of the 61 OS, but the ASPs carb which I'm talking about now, works on the same principle http://downloads.hobbico.com/evpl/osm/ev17750aa.pdf (have a look at the right of the page). I know my 75 has one bolt which gets tighten into a nut where you have to press the carb tightly and start tightening the nut that it can compress the o ring. I don't know - I'm missing something.

Oh and I'm on 2.4 thats why I feel FAIRLY safe to use a Z bend. But I know in the end I'm going to go with EZ connections anyway - give me two days :eek:.

RE: Carburator Screw
 

My explination is based on the photo you posted with the red arrow drawn in and that engine clearly shows the single nutted jam or wedge bolt set up a common method with a lot of engines.

RE: Carburator Screw
 

The newer ASPs and Magnums have 2 screws one one each side of the carb, not the draw bar and nut. I have had a couple Magnums strip out and had to retap the carb to the next size bigger screw.

RE: Carburator Screw
 

So one can just put a bigger bolt in?

RE: Carburator Screw
 

You should try locktite on the screw before you try anything that will damage the screws. The carb should have two holes that correspond to the positions of the two screws you're pointing to. If those holes aren't lined up, the screws won't go in the full distance, and you might have stripped the threads trying to force the screws in. If thats the case, you'll probably need to tap the threads one size over and use new screws.

For future reference, most carbs have a throttle stop screw. Normally its located on the top of the carb on the same side as the throttle arm. Loosening that screw allows you to take out the entire barrel assemble, and is a much easier way to attach a z-bend. Then just reinsert the barrel and retighten the stop screw.

Brad

RE: Carburator Screw
 

Okay I'm going to try locktite first. If that doesn't work then I will tap the threads.

Throttle Stop screw? Thanks I will definitely keep that in mind. I did try to loosten the throttle arm (did this with the 75), but it wouldn't budge and I didn't want to force it. So thats why I removed the carb. But thank you for the advice

RE: Carburator Screw
 

Korps,

Could you find a thicker O-ring of the same dimensions?
That would help keep the bolts secured by friction, besides the Lock-thread.

Isn't the arm where the Z-bend connects to plastic?

I feel sorry for all your troubles.
We can help from here, but finding local experienced help would be less frustrating for you, as well as safer for your model.

RE: Carburator Screw
 

I was thinking about that last night and seems like an option. But to be quite honest with you I don't even know where to start looking for it.


No it's metal - this is the throttle arm. The servo side is plastic of course, but on that side I have a connector to make it a bit easier for adjustment.

Yeah I know, it's always difficult to assist someone when you are not there with the problem infront of you. I know someone who has the tools to tap the thread properly - he is an engineer so he will know what he is doing. I tried to get a hold of him now, but no answer. Will try later. But I think tapping new thread and putting in bigger bolts is the safest way out of this one I think. Just bad that it happened now just before the long weekend for flying. I'm really considering putting the new 75 on the Edge for the weekend. But a 75 2 stroke on a 46 plane I think is pushing it a bit.

RE: Carburator Screw
 

In that case, and if the connector is plastic, could you flip the linkage in a way that the connector goes to the carb's arm and the z-bend to the servo arm?
In that way the radio interference would be solved.
I have that layout in my models, working fine for years.

If you find a mechanical way of keeping those bolts from coming out the crankcase-carb body, you could fly this weekend.
That is the only function of the thread, which should be sealed somehow, in order to avoid air leaks.
The function of the bolts is to keep the carb body pressing down on the o-ring.

Something provisional, like wrapping vinyl tape around the heads of the bolts and holding the wrapping with two plastic tie-wraps, would work for a weekend.
No pretty but practical.

RE: Carburator Screw
 

The connector is an EZ connector as the pic below. But yeah I could change it around, but isn't it also metal against metal then?

Haha the wrapping will work if it comes down to that. It will be hidden under the cowl so no one will see :)

*forgot the pic...again*

RE: Carburator Screw
 

No, that will not work; you will be back to the original situation!!

I was referring to this:

http://www3.towerhobbies.com/cgi-bin...&I=LXK069&P=RF

Or this:

http://www3.towerhobbies.com/cgi-bin...?&I=LXK090&P=7

RE: Carburator Screw
 

Sorry LNEWQBAN. The connector in my previous post was the type which was on the throttle arm aswell originally on the engine. So I don't have any plastic parts like that, since I have never used them on any engine. I will have to get some of those then. All the clevises etc on my Edge are all metal.