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Author Topic: chinese hit and miss again  (Read 298 times)

phil

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chinese hit and miss again
« on: July 26, 2019, 05:27:11 am »
Hello as a new member , a friend  has bought one of these engines , he said it started once but wont go again . There doesn't seem to  be any compression on it , can anyone with one tell us if there should be compression ? This just spins over , valves seem to be shutting Ok and a good spark , I don't want to dismantle it to look at the piston , if I dont need to , PS trying it on colmans fuel
regards Phil

Stoker

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Re: chinese hit and miss again
« Reply #1 on: July 26, 2019, 11:03:19 am »
Howdy Phil .... and welcome from the Eastern Sierra!

Yes, they should have compression on every other revolution so it is likely that your O-ring has failed. It is quite easy to check this by simply removing the head (6 bolts) and splitting the crank bearings on the big end of the piston rod (2 bolts). Then you just push the piston up out the top of the cylinder far enough to check your O-rings and replace them if they are not right. I've heard that anything from 20 x 1 to 22 x 1 mm O-rings work fine, and you will want to get ones that are resistant to hydrocarbon compounds like gas and oil.

It is also possible that one of your valves is stuck slightly open, which would also kill compression, but which can also be checked for once the head is off.

I've found Coleman fuel to work fine, though there are other fuels these low compression engines work well on also.

There are a number of threads about these engines, with a vast amount of good information, so I'd suggest you tour around the Forum and check several of these out for more detailed information!


Try checking these threads:

https://www.officeofsteamforum.com/general-discussion-scale-model-gas-engines-hit-miss-throttle-governed-non-compression-etc/eachine-et-1-adjustment-and-fixing-(fiddling)/

https://www.officeofsteamforum.com/general-discussion-scale-model-gas-engines-hit-miss-throttle-governed-non-compression-etc/microcosm-m90-hit-miss-engine-arrived/

https://www.officeofsteamforum.com/general-discussion-scale-model-gas-engines-hit-miss-throttle-governed-non-compression-etc/yet-another-m90-hit-n-miss-thread/

 .... and there are others as well.

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classixs

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Re: chinese hit and miss again
« Reply #2 on: July 26, 2019, 12:21:44 pm »
Welcome aboard from Scandinavia !!!

Had the exact same problem with mine shortly after it arrived here, and it turned out to be the exhaust valve, that was kept slightly open by a tiny piece of whatever.

No appearent indication of it visually, but still more than enough to loose compression and kill any vacuum sucking in fuel.

I simply exercised the exhaust valve with a finger, while spraying the valvestem generously with WD40. In my case this "washed" the contamination away from the valve seat, and compression was regained.
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Jim

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Re: chinese hit and miss again
« Reply #3 on: July 26, 2019, 06:23:14 pm »
Hi Phil and welcome to the forum, glad you started up an account to ask your question here and don't take any notice of that person
saying that these engines are crap on the model engineering site where you originally asked this question and got then linked to this
forum to come over for help. Lots of members here have these engines and are enjoying them and have a lot of hours up on them.
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Dr.Rev.DelmarMacReady

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Re: chinese hit and miss again
« Reply #4 on: July 26, 2019, 07:13:27 pm »
Hiya from Alabama. These are fine little engines. Mine also has had a similar issue, turned out to be the intake valve stuck to its seat. Easy fix. Let us know if you get it running or not, and we can help figure it out
Bennydaheeb

Steamandoil (Tim)

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Re: chinese hit and miss again
« Reply #5 on: July 27, 2019, 12:57:26 pm »
Hi Phil, like others say these little runners have a lot of hours on them. Im sure your problem is minor. Either a stuck valve or o rings on the piston have failed. Web site orings and more has orings to fit I think they are 20mm x 1mm.
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Stroke973

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Re: chinese hit and miss again
« Reply #6 on: July 27, 2019, 03:55:44 pm »
It may sound dumb but make sure the latch out is not engaged. I had it happen.

St Paul Steam

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Re: chinese hit and miss again
« Reply #7 on: August 11, 2019, 05:39:06 am »
Hi Phil, welcome & warm greetings for Indiana, lots of good information here,(I learned a lot) I have one & have not had any issues ,but a spare O-ring might be handy to have extra in the future I see.
Bruce
St. Paul Indiana , USA


 

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