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  1. #1
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    Default Forum for air cooled diesel engines and clones

    I have 2 genuine air cooled Yanmar diesels and a Chinese quiet generator set with an L100 clone.
    The Yanmar air cooled diesels are excellent engines very well designed, durable and easy to work on.
    My Chinese quiet diesel generator rated at 6500 watts has however proven otherwise, this generator failed at 41 hours due to a failure of the small bearing end of the camshaft. The cam bearing surface was not hardened and wore causing the engine to shut down due to low oil pressure from metal contamination of the filter.
    It has taken me 2 years to find (Chinese) replacement parts. The engine is back together and currently running fine however I have little faith in it.
    Finding information or user experience on the Yanmar and Chinese clones is difficult and finding Chinese parts is worse.
    I have learned quite a lot about these engines and would share it with others however there is no forum that focuses on the L series Yanmar or clones.
    Would it be possible to create a forum dedicated to the air cooled Yanmar and Chinese clones??

    Thanks Tim
    Last edited by 90cummins; 05-08-2011 at 09:29 PM. Reason: spelling

  2. #2
    Super Member California's Avatar
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    Yanmar YM240, YM186D, and another YM186D

    Default Re: Forum for air cooled diesel engines and clones

    Were those Yanmar air cooled engines derived from boat engines? What is the operating rpm?

    I would like to read about them. They seem to be everywhere. But I don't know anything I could contribute.

    I thought the China replicas were unsupported throwaways. How did you repair the cam bearing surface?

  3. #3
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    Default Re: Forum for air cooled diesel engines and clones

    I thought the China replicas were unsupported throwaways. (QUOTE)
    I don't know history of Yanmar engines but the operating rpm is the same as gasoline engines up to 3600.
    I could not find parts until 3 months ago when an e-bayer started listing parts such as injection pump & injector, crankshafts, pistons, bearings, camshaft, and seals & gaskets at very low prices.
    My experience is the price directly reflects quality.
    Yanmar dealers cannot/will not cross reference parts for these.
    Also some china parts listed as fitting the Yanmar L100 will not fit.
    The engine failure I mentioned was being used in a winter emergency situation.
    Do not use these in critical applications!!!
    Putting a genuine yanmar part next to a china replica they look identical and may be interchangeable but there are obvious differences in detail and more importantly quality.
    How did you repair the cam bearing surface?[/QUOTE]
    The repair required a new Chinese camshaft and needle bearing.
    Tim

  4. #4
    Elite Member houstonscott's Avatar
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    Default Re: Forum for air cooled diesel engines and clones

    I have been interested in an new Yanmar portable 3700 diesel aircooled generator. Anyone have an opinion there. I want to go to diesel because it stores better then gas with ethanol and fits my long term off the grid plan better. What brands are Chinese clones to avoid?

    HS

  5. #5
    Gold Member Boeing's Avatar
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    Default Re: Forum for air cooled diesel engines and clones

    I'm looking for the same thing as HS. and for the same reason.....unit sitting for months. Home Depot lists a diesel generator but says "sold out", don't know if that means discontinued or back ordered.....don't know where it was made......
    Any suggestions here would be appreciated.

  6. #6
    Elite Member houstonscott's Avatar
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    Default Re: Forum for air cooled diesel engines and clones

    This is what I am looking at...

    YDG3700 - Yanmar YDG3700 3.7kW Diesel Generator

    This is a real Yanmar, right?

    HS

  7. #7
    Super Member California's Avatar
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    Yanmar YM240, YM186D, and another YM186D

    Default Re: Forum for air cooled diesel engines and clones

    Quote Originally Posted by houstonscott View Post
    This is a real Yanmar, right?
    The link on their web page goes to YanmarAmerica so I would say yes. But look under the hood of the unit you are considering and verify the engine says Yanmar.

  8. #8
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    Default Re: Forum for air cooled diesel engines and clones

    Since rebuilding my 186 china diesel clone for my generator (which is a copy of a Yanmar L100) and running it for several hours with a test load of 3 to 6kw it appears to be working fine.
    New parts installed were, piston, camshaft & needle bearing, main bearing (looks like cam bearing in auto engine) and connecting rod bearing & gaskets.
    Attached photos show the worn cam journal and the gouge I found when I pressed the cam gear off the camshaft. This damage happened during the original assembly and is a good indication of how soft the cam material was and Chinese workmanship.
    I also installed a new main bearing because a lot of junk ran thru it.
    I replaced the piston because it was only $14.00.
    I measured the pistons to compare dimensions and I found the new piston was 0.0020 larger than the original which put it closer to the desired piston to cylinder clearance.
    I used a heater with (3) 3kw heating elements for a load.
    I have some interesting notes I would like to share.
    The engine is pressure lubricated with no regulation and when started cold the oil pressure will run as high as 250psi and will drop to 30psi after a long run at full load with Rotella T5 10w30 diesel oil. A search verified that this is normal.
    During the run in I checked the oil filter which is a removable screen several times to catch any premature signs of failure.
    It can be removed without draining the oil and no mess by tipping the generator up on it's side, it then can be easily removed and inspected for particles.
    On the first inspection of the filter there were some particles on it which concerned me but I cleaned it and reinstalled it and continued the run.
    On the second and third inspections the filter became cleaner and cleaner.
    Bottom line; no matter how careful you are during a rebuild something always manages to get inside.
    After approx 5 hours I removed the engine and tore it down to inspect the cam and crank bearings.
    The new cam journal which runs in a needle bearing looked to be excessively polished I could not see any of the original machining/grinding marks, this suggests that this cam may be also be on the soft side with a failure in the future.
    The connecting rod upper bearing shell had irregular wear which suggests poor quality control during the manufacturing of the bearing or an irregular bore in the connecting rod big end. The bearing was otherwise (happy) but I installed a new rod bearing set because I had an extra.
    During the test I used a multimeter to monitor the HZ (engine speed) and I varied the injection timing to obtain the best performance.
    I found the govenor to be quite precise in speed control.
    Also removing the air cleaner cover but leaving the air filter in place picked up 60+ rpm.
    Next I measured the exhaust/hot air outlet which was 260deg, it dropped to 250deg when I opened the service door.
    Conclusion is that the air filter housing and cooling air inlets are a bit restrictive.
    I also installed a 300psi guage in the housing so I can monitor the oil pressure.

    Now the electrical end of the machine.
    I found that regardless of the load or overload the breaker would not trip so I started to check out the wiring.
    There is a switch to select either 120v or 240v you cannot have both at the same time.
    I found that the neutral and hot terminals on the 120v 20 amp and 120v 30amp outlets were switched.
    The 240v outlet was OK.
    The 2 pole breaker had 1 hot line and 1 neutral line going through it.
    I attempted to rewire so both hot lines went thru the breaker but it got the best of me so I put it back as I found it.
    Fortunately before attempting to rewire I took several pictures incase I got into trouble.
    I did manage to properly rewire the 120v outlets and also have 120v power when in 240v.
    These are my current observations.
    I bought 3 of these new at an auction and sold 2 of them during a winter emergency the 2 which were sold are fine but this one failed at 41 hours.
    Bottom line do not rely on a Chinese generator for emergency power.
    I will try to post some pictures of the failed cam and a new connecting rod bearing that was run for 5 hours.

    Tim
    Attached Thumbnails Attached Thumbnails -dscn3509-jpg   -dscn3510-jpg   -dscn3512-jpg   -dscn3526-jpg  

  9. #9
    Super Member California's Avatar
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    Default Re: Forum for air cooled diesel engines and clones

    Attached photos show the worn cam journal...failed at 41 hours.

    ...I found that the neutral and hot terminals on the 120v 20 amp and 120v 30amp outlets were switched. ...
    The 2 pole breaker had 1 hot line and 1 neutral line going through it.

    Maybe we can call this version a pretend Yanmar.

    Some of the first imported Chinese tractors had similar problems. Apparently in some firms over there, design for export consists of copying the appearance without matching the materials quality.

  10. #10
    Elite Member Skyco's Avatar
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    Default Re: Forum for air cooled diesel engines and clones

    Great info 90cummins!
    I have two of the generic chinese gensets with those engines, One at my camp has hundreds of hours on it...no troubles. The other one at home for backup only has a few. I probably need to take the low hour one to my camp and put some hours on it to check for early failure.
    The camp one is heavily used to run AC in the summer since I have no commercial power available there.
    One thing I saw in an online "service manual" I found was head bolts need to retorqued after run in but they listed no spec! Do you have one?

    PS- I was astounded at the amount of metal debris in the screen filters after initial break in of a few hours. Greatly declined since but still find some, running Rotella 5w-40 in both.

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