Author Topic: a very small 4 stroke engine : 1.35cm3  (Read 10568 times)

Offline Zephyrin

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Re: a very small 4 stroke engine : 1.35cm3
« Reply #30 on: December 30, 2020, 04:25:58 PM »
Thanks for the answer Roger, it makes sens...





Offline Zephyrin

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Re: a very small 4 stroke engine : 1.35cm3
« Reply #31 on: March 03, 2021, 08:39:28 AM »
hi

The time has come to install the engine in the shunter frame now finished, but alas,  it doesn't want to run as I would like to :  just like he did during the test, ie as in the video above post #22 !
the engine now runs slowly, without power, has difficulty to turn alone, stalls immediately at the least mishap, impossible of course to ask him the slightest effort...
yet I feel good compression, the valves are tight, and I'm very happy with my electronic ignition, I don't understand what's going on with my engine!
where does this loss of power come from, too much wear of the tiny parts during the power tests?
do i need to rebuild an engine?

Offline Admiral_dk

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Re: a very small 4 stroke engine : 1.35cm3
« Reply #32 on: March 03, 2021, 11:28:50 AM »
If it can be avoided - do not take it apart ...!
As with any engine - every time you take it apart it usually deteriorates a bit (or more).

There was a Joke in my moped youth - Why don't you take i apart to see why it runs so well ??..!! - The reason was that everybody knew that it wouldn't run as well afterwards -> only the stupid did so.

I can relate to your frustration, but with good compression it ought to be mechanically sound - except perhaps for timing of valves or ignition ....  :thinking:

The last bit would be the carburetor (mixture) / Inlet passage or the Exhaust side blocked ...?

Best wishes and good luck

Per

Offline Roger B

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Re: a very small 4 stroke engine : 1.35cm3
« Reply #33 on: March 03, 2021, 01:10:22 PM »
Some thoughts:

You say that the compression is similar to before. Is there more friction from anything?

Is the valve timing and valve lift similar to before?

Is this the same ignition system you used in the earlier tests? Has it been disconnected and reconnected?

Is the ignition timing the same as before?

Could there be an air leak in the inlet pipe?
Best regards

Roger

Offline gbritnell

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Re: a very small 4 stroke engine : 1.35cm3
« Reply #34 on: March 03, 2021, 01:54:16 PM »
You can check all the things that Roger suggested It's easiest to eliminate the things that usually don't change, the ignition and carburetor and the valve seal. That generally leaves the timing and compression. I have found that a lot of my engines are affected by heat after running for awhile. The heat soaks into the manifold or carburetor and creates a vapor lock to some degree or another. My tiny engines all have home-made spark plugs and they either work or they don't so I wouldn't suspect that would be the case with your engine.
gbritnell
Talent unshared is talent wasted.

Offline Zephyrin

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Re: a very small 4 stroke engine : 1.35cm3
« Reply #35 on: March 03, 2021, 06:59:15 PM »
thanks for the input...
I did this afternoon a test without the rocker on the intake valve, ie, like an auto or atmospheric valve (but with a somewhat stiffer spring), with a clear improvement in running, suggesting that the cam or the rocker or both doesn't function properly.
it seems to me that my engine is not able to take a big breath of air and gasoline, and to run with the air wide open as before.

Offline Zephyrin

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Re: a very small 4 stroke engine : 1.35cm3
« Reply #36 on: March 08, 2021, 09:32:08 AM »
look at how my engine runs now, this jerky running is more or less strong but constantly present, I'm confused, I've checked that the sparks don't go out with the speed, and the jet inlet seems clean, I know it's not a real carburettor but it's the same as before !
spring valve too weaks, too stiff ?

https://photos.app.goo.gl/1kEwxgt5gMFVqXaL7

I am well beyond my skill level...

the complete album is here
https://photos.app.goo.gl/aDQ5aQCqALkuMuGs9

« Last Edit: March 08, 2021, 09:42:12 AM by Zephyrin »

Offline michaelr

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Re: a very small 4 stroke engine : 1.35cm3
« Reply #37 on: March 08, 2021, 11:18:12 AM »
It sounds to me that the engine is Hunting, a check on the fuel supply may help.

Mike.

Offline Admiral_dk

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Re: a very small 4 stroke engine : 1.35cm3
« Reply #38 on: March 08, 2021, 11:33:35 AM »
My first thought was the same as Mikes .... and followed by - it might also be missing sparks .... I do not think that the cause is a mechanical, like a spring etc.

Can you see any air bubbles in the fuel to the carb ?

Best wishes

Per

Offline Roger B

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Re: a very small 4 stroke engine : 1.35cm3
« Reply #39 on: March 08, 2021, 04:54:14 PM »
Unfortunately I can't see your video but another question; Have you changed the height or position of the fuel tank from your first runs?
Best regards

Roger

Offline Zephyrin

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Re: a very small 4 stroke engine : 1.35cm3
« Reply #40 on: March 08, 2021, 06:05:11 PM »
Hi,
nice to have advices...thanks !
it seems to me that the intake phase is shortened owing to worn cam and rocker, hence the engine can't cope with an increase in speed, the engine is simply starved, as suggested.
the cure therefore is simply to make new cam and rocker...I hope.

I'm not against the making of a brand new engine, but it is frustrating to do not understand the causes of failure before !

Roger :
yes the fuel tank is higher, with a clear improvement...everythings that make easier the intake of fuel seems beneficial !

I don't know how comes you can't see the video on my google album
 you may test this site for the video

Offline Zephyrin

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Re: a very small 4 stroke engine : 1.35cm3
« Reply #41 on: March 15, 2021, 09:11:07 AM »
Hi
Despite all the problems with the engine I tried a real test of the loco...just to see!
The engine is still far from giving all its power as it did before, due to an intake problem if I believe the noise in puffs...
it's the major problem, I'm working on it!
Nevertheless, she ran and I was very useful to see the many things to change :
- Transmissions with chains, there is too much slippage with the actual belts.
- The clutch switching wheel is a real pain, much too slow, and should be replaced by a lever.
- The clutch plate and the roller are quickly slipping at the slightest drop of oil, keeping this devices oil free will not be a simple affair.
I plan to make a real carburettor, with a decent idle.

<a href="https://www.youtube.com/watch?v=KCC9kLKGQrs" target="_blank">http://www.youtube.com/watch?v=KCC9kLKGQrs</a>

The positive point is that my miniaturized ignition on board works well, it is reliable, if I had the courage to change something in it, it would be to put a Hall effect switch.

Offline MJM460

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Re: a very small 4 stroke engine : 1.35cm3
« Reply #42 on: March 15, 2021, 10:02:16 AM »
Hi Zephyrin, despite the problems still to be solved, that does look like a very encouraging run.

Having it run reliably like that is very encouraging for the fine tuning which remains.

Well done.

MJM460

The more I learn, the more I find that I still have to learn!

Offline Zephyrin

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Re: a very small 4 stroke engine : 1.35cm3
« Reply #43 on: March 15, 2021, 05:01:20 PM »
thanks MJM,
yes I found it very encouraging, as the little shunter can cope with the tight curves of the plastic track, and the sloping surface...

many things to amend, but which are minor as soon as I recovered full power of the engine.

Offline Roger B

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Re: a very small 4 stroke engine : 1.35cm3
« Reply #44 on: March 15, 2021, 05:50:50 PM »
Wonderful  :praise2: you must be proud of that  :wine1:

That sounds to be a too rich mixture problem ( I can see this video  :) ) Getting a good carburettor at that size will be an interesting problem.
Best regards

Roger

 

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