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Old 10-25-2019, 04:44 PM
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If you want a really acurate tach, look at FromeCo, with their TNC Tach (it is expensive, but if you want to wait, you can find someone selling one for about 50% the cost of new). I have one, and I love it. Best thing about it is, you dont have to be right behind the prop to get a measurement. It increases the safety margin for tach'ing.

By listening to the engine, does the engine sound like it is laboring (struggling) to achieve the RPM you indicate? Does it sound crisp and clear at wide open throttle?

Your thread makes me want to get my Dalton 300 out, readjust my throttle linkage, and fly it! I have too many airplanes and not enough time to dedicate to them and my family.
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Old 11-01-2019, 04:45 PM
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I got ADHD

Quote:
Originally Posted by Bunky F. Knuckle View Post
If you want a really acurate tach, look at FromeCo, with their TNC Tach (it is expensive, but if you want to wait, you can find someone selling one for about 50% the cost of new). I have one, and I love it. Best thing about it is, you dont have to be right behind the prop to get a measurement. It increases the safety margin for tach'ing.

By listening to the engine, does the engine sound like it is laboring (struggling) to achieve the RPM you indicate? Does it sound crisp and clear at wide open throttle?

Your thread makes me want to get my Dalton 300 out, readjust my throttle linkage, and fly it! I have too many airplanes and not enough time to dedicate to them and my family.
No, there is no laboring of any kind. The engine if not at the correct timing may backfire while decelerating, and i am not happy with the idle at advanced timing. When properly tuned, the engine runs great except for the missing rpm.
The test frame weighs 65 lbs and when at 54-5600 rpm it wants to pull it out of the ground.

I just got the leak tester from highpoint and detected no leaks in the crank case. I like this test set. I also purchased a flexible carburetor needle stick to enable carburetor adjustment while running. It is an excellent product. On the 150 it works well with the manifold and cans, but not as well with the stock mufflers because of the spacial limitations. I also received from them, plates, gaskets and air hook-up manifolds for the other size engines I have. I will post a video this weekend of the leak test.

So, this leaves only two things: Bad spark, poor RPM meter, or carburetor adjustment in that I don't know what the hell I am doing. There was another post on a DA100 not running right, and there were some advise in that thread I may use. I am also seeing a temp difference between the two cylinders. Swapping the spark plug leads may tell me if I have spark problems.

I will also assemble the other engine this weekend as that one has a new crank. I can then run the engines side by side with the same carburetor and compare.

Last, banging my head on the wall with this project, I started building a Gerstner type machinist chest. You all have no idea how hard it is to find 1/2" thick mahogany and how much it costs.
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Old 11-03-2019, 08:16 AM
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If you have another ignition unit, you can try swapping it and testing.
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Old 11-04-2019, 09:49 AM
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Video Leak Down Test

Attached is a video of the Leak Down Test utilizing kit purchased from High Point. Unfortunately, I did not use the pump with the kit because I damaged the hose and had a small leak. The gauge is much better on the High Point unit because it is more accurate than the pop-off pressure pump used. Both would work.

20191103 2332181 (2 min 35 sec)



The kit purchased from High point worked well. Please use a little oil or petroleum jelly on the rubber seal on the intake and exhaust port to make a good seal.

I used OATEY leak detector fluid to test seams. This fluid is used on gas line leak detection and bubbles at very low flow. I think it costs around three dollars.

I have a new ignition that I will try.
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Old 11-06-2019, 01:55 PM
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Have you checked the squish yet??
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Old 11-06-2019, 02:38 PM
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Quote:
Originally Posted by RTK View Post
Have you checked the squish yet??
What do you mean by squish?

BTW...To paraphrase our President during his recent problems, the assembly of this engine is "perfect", although something is not right.

I am frustrated in that carburetor ignition work is my weak point in that i don't know how to measure the problem. For all I know, I may not have any problems, and i am chasing a ghost because of poor rpm readings. I did take brother Hoffman's advise and pointed the rpm meter at the fluorescent bulb and indeed i got 3600 rpm.

One more item, I ordered a new sensor and head aluminum bolts to finish the assembly of the other engine.
I will compare the two engines side by side.
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Old 11-06-2019, 08:34 PM
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Squish is the clearance/distance between the piston and the squish band inside the cylinder. If too large you will lose power if to small it can cause other bad problems. It can be easily measured with soft solder.
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Old 11-06-2019, 09:12 PM
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Squish

Thanks, RTK.

I will call DA and find out what the number should be. I have soft lead wire I use to measure bearing clearances, I can use it to compress and measure this number at top dead center, I got to look at the process to make sure I do not damage the skirt on the piston, I think if I stick the lead rod parallel to the piston shaft I should be ok. The lead is so soft that it bends with little force.

From my measurement, one piston is .005 different to the spark plug seat then the other. I did not think .005 is significant. If I have to compensate, I can put a thinner gasket between the head and the crank case as recommended by MadScientist a few posts back.

I will have to change the assembly procedure to add these QC measurements.
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Old 11-07-2019, 02:08 PM
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Squish Test

All, I am going to perform this test to determine the gap between piston and head ring. After looking into this, I would not recommend using solder or even other softer metal like lead.

I found a product at the local auto store called Plastigage. This small plastic rod can be safely compressed without damaging the head or piston. It comes in different thicknesses.

I will look at this method. If this is not satisfactory, I will take the heads off and utilize putty to measure this gap. I should do this measurement before final assembly when putting an engine together. It is a little late now that the aluminum bolts have been torqued. I will add this to the procedure!!!

Please be advised that this is going a bit out of the scope of this thread and I am uncomfortable making any recommendation to the readers. As always, I would recommend that you let DA do the work on your engines. As you all can see, I have spent a lot of time and money on what DA would have done at a fraction of the cost. To me, this is a science project to learn about what makes an engine tick.

After consulting DA, I was given a minimum distance between ring and piston at 0.4 mm, which is equivalent to 0.0157 inches. I am sure I will find a larger gap in my measurement. From some of the research I am doing the gap can be between .030 to .050" for this type of engine. If I were to guess I will find the hotter piston will have a smaller gap, ie more compression. Will measure tonight.
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Old 11-07-2019, 02:29 PM
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After consulting DA, I was given a minimum distance between ring and piston at 0.4 mm, which is equivalent to 0.0157 inches. I am sure I will find a larger gap in my measurement. From some of the research I am doing the gap can be between .030 to .050" for this type of engine. If I were to guess I will find the hotter piston will have a smaller gap, ie more compression. Will measure tonight.
The gap between the ring and the piston is very different (not the same thing) than the squish clearance between the top of the piston and the outer most portion of the cylinder head called the squish band. I'm not sure where the .0157 measurement would apply to anything on a ring / piston relationship. Plastigauge is good stuff but very difficult to find for the wide squish clearances. In fact, I don't even know they make it for those kinds of clearances. Yes the squish clearances are quite wide in our engines. I've always just used rosin core solder to check these as its always in my drawer, its the right size and it smashes easily to measure the clearance. The main thing on a twin is checking that one cylinder measures close or the same as the other one. If it was off by much, I'd then degree the port timing on each cylinder to help determine what was causing the difference. Most likely just clearance stack up differences between one side and the other that could be taken care of with a different cylinder base gasket. Even though they look the same, many times cylinder base gaskets are of different thicknesses.
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Old 11-07-2019, 03:20 PM
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The gap between the ring and the piston is very different (not the same thing) than the squish clearance between the top of the piston and the outer most portion of the cylinder head called the squish band. I'm not sure where the .0157 measurement would apply to anything on a ring / piston relationship.
Truck racer, thank you for the correction. I used incorrect nomenclature.

You are correct about the plastigage. The .022 thickness is as wide as they do. I will need at least .050" thickness.
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Old 11-07-2019, 06:17 PM
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You can put a long piece of solder though the spark plug hole to the side to check squish, that way you don’t have to take the jugs off.
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Old 11-07-2019, 06:26 PM
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Best to use two pieces of soft solder. one bent to each side or the piston can rock to one side messing up the measurement...
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Old 11-07-2019, 07:26 PM
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Quote:
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You can put a long piece of solder though the spark plug hole to the side to check squish, that way you donít have to take the jugs off.
ok! Just did the test with soft solder and I get .041 on the hot cylinder and 043 on the colder one. If the minimum is .016 and a new jug gasket I have measures .028, then the total gap should be .044" theoretical gap. I don't know if .002 should make that much difference.

I have to buy new solder in the AM and repeat the test. I had 020 solder. I took three pieces and spun them together and pressed the three pieces. I may be getting variation from this as I try to measure the tip of the solder.
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Old 11-07-2019, 08:39 PM
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Considering the compressible nature of base gaskets, machining tolerances, etc, I would consider a .002" difference between cylinders to be quite good. Certainly nothing that would account for performance loss.
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