Another TD 20 idling question

[Fastwin18]

I removed the low speed needle, still could not prime the motor.

Then I took a low speed needle from my donor motor to compare, see below. If it isn’t obvious enough, the left one is from my good motor, the right from the donor. Guess what’s causing the obstruction? That’s going to be a pain to get out.

[Tom]

It may not be that hard to get out… the threaded part is intact.  Some solvent, maybe a little heat, it should come out with a tap on a wood table.

T

[Fastwin18]

Actually a bit of compressed air aimed at the front hole blew it straight out.

Screwed in the donor needle and it started almost instantly, much easier then previously. Then I started tinkering with the needles and it died again, and now it starts difficult, if at all.
all in all I think I (or rather you) have found the culprit. I will try again this evening (really have some work to do now) and let you know how it worked out.

• This reply was modified 3 years ago by Fastwin18.

[aquasonic]

aquasonic wrote:

Try removing the low speed needle, and push the primer with the low speed needle removed. Sometimes this will clear an obstruction.

Try this again with the replacement needle removed.

Improvise-Adapt-Overcome

[Fastwin18]

aquasonic wrote:

aquasonic wrote:

Try removing the low speed needle, and push the primer with the low speed needle removed. Sometimes this will clear an obstruction.

Try this again with the replacement needle removed.

The obstruction was the broken needle point. With the new needle the motor actually responds when I’m turning the low speed needle, whereas previously it wouldn’t. I couldn’t resist giving it another go (work can always wait, right) and now it runs much, much better. Still not as slow as I know they can, but I think I’ll get there with a little bit more time.

Thank you so much all!

[lloyd]

74.5  and 77.6  psi are good numbers. Sounds like your new rings have seated properly and you are good to go with a little tweaking.

[Fastwin18]

lloyd wrote:

74.5  and 77.6  psi are good numbers. Sounds like your new rings have seated properly and you are good to go with a little tweaking.

Well, actually…..
I’m almost too embarrassed to admit, but I was in a hurry when testing compression the last time. So, I just used the first drill at hand to crank the motor. And obviously, the faster you crank it, the higher the numbers are 😳. Rookie mistake.
Even though I was surprised by the sudden increase in numbers I gave it no more thought. The motor runs very nice now at moderate and high speed, but still won’t idle. So, another compression test (proper this time) gave me the same numbers as before. So too low.

I’ve tore my seized donor motor apart and was able to get the pistons out. Nothing appears to be damaged, cylinders look in perfect shape, so I’m cleaning it and will put it back together for a compression test. If the numbers are good enough I’m considering restoring it and swapping the power heads to see if that improves thing. Worst case scenario is that I have 2 low compression but running power heads

[lloyd]

Sounds like a reasonable plan.

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Fastwin18

[joecb]

The smaller motors that lack crankshaft seals are susceptible to poor crankcase compression, and that surely affects the ability to idle down.  You might try a richer oil mix, like 12:1 and use old fashioned 30 W or 40 W nondetergent oil, just as a test to see if the idle improves.

Joe B

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Fastwin18

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