YM-240 Thermostart Issues

PDXdrummer

New member
This is my first post after recently acquiring a Yanmar YM-240. Start-up seems difficult despite what appears to be sufficient fuel. Black smoke while cranking. I use the compression release and the weather is quite warm. I followed prescribed startup procedures from manual, full throttle then back off to approx 1500 rpm.

My thermostart was no good so replaced it. It barely drips fuel from the full reservoir and I can hear the plunger opening after heatup makes a gurgle noise and a drop comes out. I checked lines are clear to TS. I squirt fuel on it and ignites fine which brings up some concern on the paper air cleaner element being so close above the flame. Will start if I use a propane torch. Wondering if my compression is too low? How do I check? Maybe could use valve adjustments.

Thanks to one of the members here I obtained a manual but can't find the post now to give him credit. So grateful for that! To sum up my question here is maybe I got a bad replacement thermostart with faulty plunger? Is there a way to check it? My bad for going with the cheapest ebay counterfeit I'm guessing. But like I said, this thing should start without it.
 

California

Super Moderator
Staff member
Site Supporter
Check the Thermostart? Pull the air cleaner and look down the intake - but don't get too close. The element will heat like a car's cigarette lighter, then dribble a little fuel, then ignite at about the 15 second point. There are photos of this on hoyetractor's site. (My photos!). Don't put a torch into the intake. A hair dryer works fine.

If it won't start readily then quality of fuel, or low compression, are the suspects. Possibly valve lash too tight if someone messed with that.

I needed a starter after I bought my YM240 in 2003. There are many starters for Yanmar and Deere that match the physical dimensions. I bought one intended for a 40 hp excavator or something. It cranks the YM240 frantically, I think it would start any small Yanmar no matter how low the compression is. As I recall it is rated 2 amp-hour vs the 1.2 or 1.4 that was OEM. That might be a solution for you if compression is indeed low. Under $100 from Ebay. I assume you have cleaned battery terminals etc.
 

Lee1935

Active member
This is my first post after recently acquiring a Yanmar YM-240. Start-up seems difficult despite what appears to be sufficient fuel. Black smoke while cranking. I use the compression release and the weather is quite warm. I followed prescribed startup procedures from manual, full throttle then back off to approx 1500 rpm.

Have you ever ignored the book and tried start at maybe 1/3 throttle
 

California

Super Moderator
Staff member
Site Supporter
Here's the Ebay listing for the more powerful starter I put on my YM240 in 2011 after its amateur-rebuilt starter faded away. This replacement is 2.0KW and was intended for a larger Yanmar while the OEM starter was 1.2 or 1.4KW, so its 50% stronger. This cranks my YM240 like mad. I expect this would start even a badly worn, low compression engine.

New Starter John Deere Yanmar Excavator 3TN78 3TN78L 41-5218 AT11818 17387 | eBay $76 shipped.

This needs the wire down from the key extended 6 inches longer, otherwise an identical replacement.

If you look at similar starters be sure to match # of teeth and KW rating.
 

PDXdrummer

New member
Check the Thermostart? Pull the air cleaner and look down the intake - but don't get too close. The element will heat like a car's cigarette lighter, then dribble a little fuel, then ignite at about the 15 second point. There are photos of this on hoyetractor's site. (My photos!). Don't put a torch into the intake. A hair dryer works fine.

If it won't start readily then quality of fuel, or low compression, are the suspects. Possibly valve lash too tight if someone messed with that.

I needed a starter after I bought my YM240 in 2003. There are many starters for Yanmar and Deere that match the physical dimensions. I bought one intended for a 40 hp excavator or something. It cranks the YM240 frantically, I think it would start any small Yanmar no matter how low the compression is. As I recall it is rated 2 amp-hour vs the 1.2 or 1.4 that was OEM. That might be a solution for you if compression is indeed low. Under $100 from Ebay. I assume you have cleaned battery terminals etc.


The glow is good, as I mentioned it's brand new. Battery terminals replaced, battery charged but does seem to lack some cranking power. Good tip on the starter. You wouldn't happen to have links to the specs of the started you got in case I need one? I hear the OEM's are ungodly expensive.

The dribble takes place after about 10 seconds but only a drop which tries to light but then dribble stops. I can hear it gurgle, I see no obstructions and took the line off to the reservoir and checked it. Runs out the line just fine disconnected.
 

PDXdrummer

New member
This is my first post after recently acquiring a Yanmar YM-240. Start-up seems difficult despite what appears to be sufficient fuel. Black smoke while cranking. I use the compression release and the weather is quite warm. I followed prescribed startup procedures from manual, full throttle then back off to approx 1500 rpm.

Have you ever ignored the book and tried start at maybe 1/3 throttle

I have actually. That was my initial procedure before seeing the book. I tend to back it off because without ignition it passes too much unburned fuel out the exhaust.
 

PDXdrummer

New member
Here's the Ebay listing for the more powerful starter I put on my YM240 in 2011 after its amateur-rebuilt starter faded away. This replacement is 2.0KW and was intended for a larger Yanmar while the OEM starter was 1.2 or 1.4KW, so its 50% stronger. This cranks my YM240 like mad. I expect this would start even a badly worn, low compression engine.

New Starter John Deere Yanmar Excavator 3TN78 3TN78L 41-5218 AT11818 17387 | eBay $76 shipped.

This needs the wire down from the key extended 6 inches longer, otherwise an identical replacement.

If you look at similar starters be sure to match # of teeth and KW rating.


Oh awesome! Thanks for the info! I should've read all the replies before sending you my last message. I'll have to check my setting and see why I didn't receive notifications of these responses. Thanks to all!
 
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