1QwkSport2.5r

I quit following this thread for quite some time, but recently thought of something. I have a question for the guys that have a relatively current model Fox .40 small case engine with iron piston and steel liner. I'd like to know if anyone has measurements or could get measurements of the OD of the liner, the ID of the liner/bore, and the stroke. (Insert dead horse beat-down comment here...)

I've had an idea and I want to confirm or bust... Thanks.

Sport_Pilot

Is it blowing plugs when it quits? Fox has a new colder plug the #8. Have you tried that>

mytemotors

My Feedback: (1)

Hi Roy,
Jack Lipka here, I read of your problem with the engine dying. I had a similar problem with an O.S. .91 FX last summer. Takeoff, make one or two circuits and it would quit. I tried everything everyone has suggested. Tried the engine on a different airplane and got the same result. I bought a new engine and have not had any problems.
I did fix the problem wit the .91. It seems the front crankshaft bearing seal was bad. Installed a new bearing and problem solved. Just a thought, as I am not currently a FOX user, so I am not fimilar with their setup.

aspeed

Usually a piped motor has to be quite rich on the top end.  It is a bit more trouble than a muffler.  It sounds like there isn't enough compression to keep it lit. Maybe take out a shim and see if that helps.  If you blow plugs then you went too far.  You could try more shims but I don't think that is the direction.  Just another variable to try, oh and keep it close over the field in case of flameouts ;-)

roy3785

Thanks all, it does not blow the plug all i need to do to restart is put glow clip on and flick prop do not need a starter.only cuts within first few seconds after take off if it continues it will run the tank dry. this is the same with pipe or muffler fuel pressure system or not.I am thinking air leak from crank as mytemotors mentioned.I have not tried the new fox plug i need to put in something i do not mind breaking as its normaly not above 10 feet high.This engine has about 3 hours run time from new.

hsukaria

There was a discussion in this thread some time ago about air leaks around the front bearing. The Fox engines don't use sealed front bearings but have a method to let the oil reach the front bearing. Seeing that you have an older Fox engine, those were typically non-sealed front bearings in those days. But the oil channel in the crankcase to the front bearing might be letting too much air to leak in. That is all I know about that, others here have a good knowledge about it. You might also want to look back a year or two in this thread to find that discussion. Sorry that might be a lot of reading, but it is all informative.

earlwb

I cannot really think of anything that could explain this problem where the engine cuts out a few seconds after take off, or if it gets through that then it runs fine for the rest of the flight.  If it was a leak through the front bearing, it would manifest itself and stay that way for the whole time them after the engine warmed up. It does it with and without a tuned pipe or using a muffler. It doesn't blow glow plugs either. So that makes it a interesting mystery.

The only thought I have at the moment is that the engine produces a momentary slug of fuel that quenches the glow plug just as the engine is unwinding on take off. A idle bar glow plug might cure the problem. It could still be a mixture issue too. But hard to say if one isn't there to see it, etc. One other thought is many years ago, I used to use a type of on-board glow ignitor system. This unit would be left on for the entire flight, as it could sense the current flow through the glow plug and adjust itself so the plug wouldn't burn out. I haven't seen that exact type of on board glow ignitor since the early 1990's though. I don't know if other ones work like that either.  Anyway it was handy at the time for a few troublesome engines that I had been using then. But in this case it would keep the glow plug from being quenched out by a slug of fuel hitting in at that critical RPM change point on takeoffs.

We used to see this quenching effect with Fox 1.20 twin engines many years ago with the left cylinder turning off as you throttled the engine don or up. Also if someone setup a .60 engine with a left facing exhaust and sometimes with .60 engines setup for rear exhaust too. For the Fox 1.20 twin some folks flipped the cylinder base gasket over so it blocked the transfer port leaving only the two bypass ports open, and that solved the problem on the twin engines. It did reduce the power a little, but at the time the Fox 1.20 was about the biggest glow engine one could get then, so the power loss was neglible.

roy3785

I think your idea of onboard glow is a good one and is worth trying,i will check them out. Although it would only be a bandage covering the problem at least i will be moving in the right direction. If this works i will ring fox about one of there new carbs(.sounds like a good excuse to get one of there new carbs.)

earlwb

I myself have bought like 5 or 6 of the new carbs to use on my engines. I really like them a lot.

fujiman

My Feedback: (133)

1 more thing to think about with this problem and it's not to say this is actually the answer, because you installed another eng. w/ good results. But here goes, is the pick clunk too far at the back of the fuel tank and when you firewall the eng. for take off the fuel surge to the back of the tank ''forces'' or pressurizes the fuel line to the carb. and is pressurizing the fuel delivery to the eng. Then if you make it thru take off and burn off some fuel the problem seems to go away also the eng. you put in the plan was less sensitive to this problem. 1 more thing, check the position of the spray bar, it mite have turned at bit and fuel draw could be effected under hi demand. how is the transition from idle the top end full throttle? just some of my thots.

roy3785

Glow driver. This sounds like what you are talking about.

AGS-1 and AGS-2

If you want total reliability from your glow engine, then you need an AGS on-board glow driver.

The AGS Glowswitch is still the only glow driver that monitors the glow temperature and heats the glow-plug only when necessary so only a small (light weight) support battery is needed and there is no risk of damage to the plug. Unlike other glow drivers, the AGS supports the glow even at high throttle settings so, for example, an aborted approach need present no problems; you just open up the throttle and the engine responds as desired.

The Advanced Glowswitch (AGS) has all the features of the well known original Intelligent on-board Glowswitch (IG), but in addition it:

Ø Automatically adjusts to any support battery voltage from 1.2V to 4.2V.

Ø Works with a receiver voltage of up to 7.2V.

Ø Is suitable for all battery types including LiPo, LiFe, Lead-acid and NiMH.

Ø Needs no Y-lead connection.

Ø Optionally fully automatic or transmitter controlled.

Ø Has remote ultra-bright, daylight viewing, indicator LEDs connected with mini screw terminals.

Ø Has a remote adjustment panel also connected with mini-screw terminals.

Ø Automatically compensates for battery voltage fall-off in use.

Ø Has simple two-terminal plug connections (three terminals for the twin version).

Ø Still has the Start-Up Boost feature.

The LED(s) tell you when the AGS is testing the glow and when it is boosting it. They will also give you information about your glow and receiver batteries – indicating the type of battery it has detected and whether or not the battery is getting low.

The AGS turns off when the Rx is switched off, so you can leave everything permanently connected, ready for starting and the next flight.

Installation is easy. Just connect the support battery and the glow plug to the AGS and plug the AGS into the Rx. Full instructions are provided with each unit and in the Advanced Handbook.

fujiman

My Feedback: (133)

sound like a have to have item. mite pick me up one, do you have their web link????

roy3785

site for onboard glow,Not sure if i am allowed to put this on ,if not i will take it off.www.southhertsmodels.co.uk/IGs.htm

123Cat

Yes I have had the same thing with various motors , its just loss the crankcase compression due to loosing pressure between the shaft and case , happens a lot,

last motor I machined up a plug for the case then loctited it in and machined the case to shaft fit with a 1 thou clearance

, tuned perfect after that , before it was just quitting here and there and not responding to the needle well ,

The message is check your crankcase to shaft clearance ,

Its a fine line between blowing a little fuel up to the front bearing and loosing crankase pressure- and also your tune,

the clearance has to be just right

earlwb

That AGS glow plug driver is it for sure. They used to sell one like that here many years ago. I am glad to see someone still does.

Cougar429

My Feedback: (3)

Before installing the onboard glow, give a 4-stroke plug a try. They remain much hotter and are the only ones I use when running 2-strokes inverted. In that position the plug is a lot more likely to be quenched with fuel/oil and the 4-stroke plugs resist this much better.

koastrc

Got a FOX question. Has any of you heard or seen a FOX Rocket? A friend has one and I do not recall ever seeing one,
Thanks.

earlwb

In 1959 Fox introduced a low cost range of model engines called the "Rocket". The engines were a .35 displacement size. Fox continued to make the engines up until 1962 when the crankcase design was changed. The engines had a little smaller intake venturi than the combat engines and the venturi wasn't removable either. It basically looked like a first or second model combat .35 engine. The Series three Combat .35 engine also had the rocket on the side too. Depending on which class of combat competition you were in, the venturi insert was used or removed. If you removed the insert, then you had to provide pressure to force fuel into the engine.

Now then they also called the Fox .09 a "Rocket .09" engine too. It had a rear intake and something of a more radical design shape to it. But it was a nice running beginner type of engine.

carlgrover

In regards to the engine flame-out problem at takeoff; have you tried running the engine extremely rich (just enough power to get it off the ground) to see if it will still quit on takeoff? I'm wondering if it is leaning out just enough with a load on the engine to kill it every now and then.

hsukaria

Did Fox Manuf. give you a bulk discount for buying so many at one time? These are $40-50 each.

earlwb

No discounts or anything. I bought the carbs over a long period of time. One or two at a time. Usually when I ordered some other stuff.
Sorry no factory sponsorships for me. I wish.

Of course the new Fox carb works good on other brands of engines too.

hsukaria

I like those carbs a lot too. I am no engine expert, but tuning that carb is a breeze. Plus the throttle transition is tremendous, even a non-issue regardless of tuning condition.

Yeah, I was wondering if you had either a sponsorship or a Texas Oil Well in your backyard.

Changing subjects a bit, the ASP 91 that I have hasn't had any trouble with the carb. What displacement is your ASP? Have you had sub-par carb performance with it?

earlwb

It is on a .61 engine. The original OEM carb worked OK but it was too rich for my liking through the mid-range. So the Fox carb was a nice improvement for it.

hsukaria

Hmmm!!! I will keep an eye on my 91. I just installed a Jett Stream tuned muffler on it, but have not run it yet. The 91 ASP was on super-duper sale and I needed an exact copy of the old OS 91FX to fit a pre-cared engine cowl. The ASP91 is the biggest ABC-type engine I have operated so far. I am more used to ring-type for this size range. It's an all-new learning curve for me.

I considered a Fox 74 for this application, but it needed a heavy engine to balance CG. The Fox 74 is much lighter than the ASP 91.

Have you played with the ASP 3-piece muffler? The muffler center piece is removable to make it smaller. Also, the muffler has a baffle disk inside that is also removable. So, there are possibilities to modify behavior/performance by re-configuring the stock muffler.

earlwb

You need the expansion volume with the muffler. Making the muffler smaller reduces the performance. The hot exhaust gasses cool down a little inside of the large muffler and slow down and become more dense. It is why the exhaust outlet can be smaller. The exhaust gas speed through the muffler stays about the same, even though the outlet is more small than the inlet.  Removing the baffle may improve performance but the noise level goes up. But it depends on the engine and prop, etc as to whether the performance loss is noticeable or not.