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Inverted 2-stroke with Perry Pump problems
I mounted an OS .91 2-stroke on a Fliton Inspire 60 (great plane btw). The fuel take is over the CG so I decided to use the Perry VP-20 ossicilating pump to help with draw. The tank is low in the fuse. Once I get the engine running and heated up it runs great - but starting it at the beginning of the day is a real chore.
I start out by removing the glow plug (oil settles on the heat because I store the plane on its landing gear -engine inverted) and blowing out/off the oil. Then I put the starter on the plane and give it about a 5sec turnover to clean out any fuel/oil in the cyclinder. Then I replace the plug and fuel it up. I give the prop a couple of hand flips with the throttle open to prime it, attach the igniter and start turning it over with the starter. It doesn't want to fire after several 10 sec tries. I usually have to remove the plug and dry it out and re-install. Once I get it to fire (if I can get it to fire), it won't throttle up without dying (like it is too lean). However, it will start much easier from this point on. Once I can get it to full throttle for a few seconds it will run perfectly in the air and on the ground. If I let the plane set and completely cool off then I run into the same headache as before. I'm not sure if this is typical for inverted engines or is the VP20 adding to the complications. Either way, I'm thinking about buying a Cline reg and taping the crank case. Can someone please advise on my situation? Thanks. BTW: the Perry VP-20 is mounted on the bottom of the crank case bolts. So the pump is 2 - 3 inches above the carb (this was the only way it would fit). |
RE: Inverted 2-stroke with Perry Pump problems
I have several inverted 2 strokes, and go through (pretty much ) the same plug drying ritual with the 1st start of the day.
I don't think the V-20 is complicating your starting difficulties? The V-20 operates only when there is sufficient vibration to shake it so...(?) Although it might be acting as a small reservoir and causing part of your plug wetting problem, but if you can't find room for it any where else, whadareyagonnado? If it runs fine once you get it going, I wouldn't mess with it...I think I would just chalk it up to one of those idiosyncrasies (sp?) of that particular plane, and put up with it...(if it does run well at all other times ) |
RE: Inverted 2-stroke with Perry Pump problems
That business of removing and cleaning the glowplug is one of thos things with inverted engines. Oil runs into the bottom of the cylinder if the model is stored upright, as you noted. Nothing to do with the pump, IMHO.
Perhaps you need to put you hand over the muffler when you flip it through to prime it. You CAN force fuel the VP-20 if you try hard enough. In a nutshell, I suspect that you are just not getting it primed right to start it after you blow out the plug. Also I have a feeling that you might need a bit more pump volume so that your engine's needles can be in control. Keep in mind that you want the pump volume adjusted so that the needles can make the engine run over-rich. You may have it a bit lean overall. CR |
RE: Inverted 2-stroke with Perry Pump problems
CR - How do you determine if the pump is not pumping enough? I don't notice it leaning out in low/mid/or high rpm. I can hover just past half throttle and it runs great.
You are probably right - I don't prime enough (I'm afraid of flooding the plug again). I'll try it again with more priming and see how it goes. |
RE: Inverted 2-stroke with Perry Pump problems
ORIGINAL: Jeff_edge540 CR - How do you determine if the pump is not pumping enough? I don't notice it leaning out in low/mid/or high rpm. I can hover just past half throttle and it runs great. You are probably right - I don't prime enough (I'm afraid of flooding the plug again). I'll try it again with more priming and see how it goes. CR |
RE: Inverted 2-stroke with Perry Pump problems
The REAL problem is the inverted two-stroke engine.
There simply is no way to start these engines without running into problems, especially if you want the engine start as easily as it does when side mounted or upright. Four-stroke engines have the valves in the head to alleviate the problem of too much fuel in the combustion chamber. "Just say no" to inverted two-stroke engines and your problems will disappear. No pump or regulator that is made today will prevent fuel from pooling in the head of a two-stroke glow engine. Sorry. Ed Cregger |
RE: Inverted 2-stroke with Perry Pump problems
Say Jeffedge540 - The topic of your forum caught my attention as I use the Perry Pump on my two-strokes but it is a different model than what you are using. I'm sitting looking at the directions that came with the pump that I'm installing in my new CMP Yak 54-140 with an OS 160 and it's a different model than you are using. Mine (and the other two that I have installed on a 61 and 76 GMS 2-stroke) is a diffenent model number. Mine are all VP-30 models (blue for glow 2-stroke) and they are not ossicilating pumps, but diaphragm pumps that operate from crankcase pressure. I thought the ossicilating pumps were for 4 stroke engines??? I may be wrong, but that is also what I have read and been told by my local hobby shop. All of mine are VP-30 models and are blue and work very, very well.
Also, I flew C/L for a while several years back with engines (although they did not have a throttle) that were inverted without a problem, and most recently a Seagull PC-9 with an Irvine 51 (no pump) that was inverted. I had a problem initially until I figured out (with the help of a friend) that the tank was mounted about half-an-inch too high. I lowered the tank, leaned the low-speed needle, and the engine ran like a dream. The engine was always started in the inverted position, and never loaded up after I re-positioned the tank. I'm of the opinion that you have the wrong pump for a two-stroke engine, but I've been wrong before!!! LOL! But by all means remember, "Experience is a hard teacher. She always gives the test first and the lesson sometime later!" Phillip |
RE: Inverted 2-stroke with Perry Pump problems
That is a good saying at the end of your post.
Engines do not "know" what kind of pumps are being used. There is really no reason for calling the oscillating pump a four-stroke pump, other than the fact that four-stroke crankcase pressure, pressure that is needed to drive the VP-30, is not normally considered to exist with the four-stroke engine. Paul McIntosh proved the latter theory wrong as he pointed out a few years ago in the rec.models.rc.air newsgroup. Paul used a Y-connection to obtain pulse pressure for his four-stroke engine's Perry VP-30 pump. Yes, you can start an inverted two-stroke if you are willing to learn the drill. My Top Flite Nobler (RIP) and its inverted two-stroke engine took me a while to learn so that it started quickly. That was long, long ago. Most folks just aren't that patient these days. I know the learning curve was steep for me (1966). This was before electric starters and such were popular. Ed Cregger |
RE: Inverted 2-stroke with Perry Pump problems
ORIGINAL: Jeff_edge540 I mounted an OS .91 2-stroke on a Fliton Inspire 60 (great plane btw). The fuel take is over the CG so I decided to use the Perry VP-20 ossicilating pump to help with draw. The tank is low in the fuse. Once I get the engine running and heated up it runs great - but starting it at the beginning of the day is a real chore. I start out by removing the glow plug (oil settles on the heat because I store the plane on its landing gear -engine inverted) and blowing out/off the oil. Then I put the starter on the plane and give it about a 5sec turnover to clean out any fuel/oil in the cyclinder. Then I replace the plug and fuel it up. I give the prop a couple of hand flips with the throttle open to prime it, attach the igniter and start turning it over with the starter. It doesn't want to fire after several 10 sec tries. I usually have to remove the plug and dry it out and re-install. Once I get it to fire (if I can get it to fire), it won't throttle up without dying (like it is too lean). However, it will start much easier from this point on. Once I can get it to full throttle for a few seconds it will run perfectly in the air and on the ground. If I let the plane set and completely cool off then I run into the same headache as before. I'm not sure if this is typical for inverted engines or is the VP20 adding to the complications. Either way, I'm thinking about buying a Cline reg and taping the crank case. Can someone please advise on my situation? Thanks. BTW: the Perry VP-20 is mounted on the bottom of the crank case bolts. So the pump is 2 - 3 inches above the carb (this was the only way it would fit). |
RE: Inverted 2-stroke with Perry Pump problems
The problem with perry pumps is that fuel is delivered to the carb whenever they see pumping pulses or vibration. The engine to be strated is not running yet, and will flood very easily. Prime the engine with plug out! and spin shortly. Pinch the fuel line to the carb to prevent more fuel from entering the engine, put the plug back in and start. Remove the line pinch as soon as engine fires up.
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