DN4M pistons

[loosegravel]

Now that’s being resourceful! DM Equipment had the pistons for $102 ea. I could rationalize that expense. With the gaskets, the fuel pipe from GMG and these pistons (and my auction cost with fees) I’ll have about $3500 into this unit. (Plus my time of course) I’m hopeful that it will be a solid watt-maker when I’m done!

Sorry! That was DP Equipment!

 

[jamawieb]

Wanted to share my experience with a similar problem. Been working on this unit. Would start after a few tries. Smoked bad and would clear with a slight haze. Load test to 50% smoked really bad. Couldnt get over 70% and it had bad back pressure in the crankcase. Finally took the exhaust manifold off and could see 1 and 2 smoking all the time. Dead cranked the motor with a paper towel over the exhaust port and noticed 1&2 would suck the towel into the cylinder instead of blowing out. Thought it wast he head gasket. Under further examination the gasket looked good so it had to be rings. Took the pistons out of 1&2 and they are bad. They are 1mm over so .040 oversized. Cant find anywhere, ive reached out to a couple of vendors but no luck so far. What year was your unit reset? Mine is a 2010 and had 500 hours.

 

[loosegravel]

Wanted to share my experience with a similar problem. Been working on this unit. Would start after a few tries. Smoked bad and would clear with a slight haze. Load test to 50% smoked really bad. Couldnt get over 70% and it had bad back pressure in the crankcase. Finally took the exhaust manifold off and could see 1 and 2 smoking all the time. Dead cranked the motor with a paper towel over the exhaust port and noticed 1&2 would suck the towel into the cylinder instead of blowing out. Thought it wast he head gasket. Under further examination the gasket looked good so it had to be rings. Took the pistons out of 1&2 and they are bad. They are 1mm over so .040 oversized. Cant find anywhere, ive reached out to a couple of vendors but no luck so far. What year was your unit reset? Mine is a 2010 and had 500 hours.

Looks very similar to the unit I'm working on. This one had the tier 2 reset in 2008. Has 145 hours on the meter now. From what I've discovered +.25mm is .010" oversized and +.50mm is .020" oversized. This reset engine had the .25mm oversized pistons in it when I tore it down. I received my replacement pistons today from DP equipment. Unfortunately they sent me the .50mm or .020" oversized pistons. I needed the smaller .25mm or .010" oversized. I've also ordered some outside micrometers and inside bore gauges. I'm going to mic the new pistons and the bores. If I get a .005" clearance on all of them, I may be ok. I'll just have to adjust the ring gap.

 

[loosegravel]

Looks very similar to the unit I'm working on. This one had the tier 2 reset in 2008. Has 145 hours on the meter now. From what I've discovered +.25mm is .010" oversized and +.50mm is .020" oversized. This reset engine had the .25mm oversized pistons in it when I tore it down. I received my replacement pistons today from DP equipment. Unfortunately they sent me the .50mm or .020" oversized pistons. I needed the smaller .25mm or .010" oversized. I've also ordered some outside micrometers and inside bore gauges. I'm going to mic the new pistons and the bores. If I get a .005" clearance on all of them, I may be ok. I'll just have to adjust the ring gap.

Again, I'm still not sure what caused these failures. I was hoping to get this one repaired correctly and go from there. Yeah, what would cause pistons to rub off on the cylinder walls other than excessive heat? If it was a gasoline engine I would say severe detonation or preignition. I don't think that we can get that in a diesel engine.

 

[loosegravel]

I thought that I'd post another comment. I'm one of those guys who reads the TM's in my spare time. I know, I know...get a life right? Anyway, the maintenance manual actually has instructions for using a manometer in the dipstick hole to measure the vacuum in the crankcase on a running engine. Apparently a "healthy" engine will pull a few inches of mercury as measured with a manometer. They even say if a manometer isn't available to remove the oil-fill cap and lay a piece of paper over the hole. A healthy engine should hold the paper in place. Kind of interesting, and it could be a good thing to know when assessing a bad engine versus a good one.

 

[Light in the Dark]

I thought that I'd post another comment. I'm one of those guys who reads the TM's in my spare time. I know, I know...get a life right? Anyway, the maintenance manual actually has instructions for using a manometer in the dipstick hole to measure the vacuum in the crankcase on a running engine. Apparently a "healthy" engine will pull a few inches of mercury as measured with a manometer. They even say if a manometer isn't available to remove the oil-fill cap and lay a piece of paper over the hole. A healthy engine should hold the paper in place. Kind of interesting, and it could be a good thing to know when assessing a bad engine versus a good one.

It works too....

 

[loosegravel]

Well, I'm not sure what happened at DP Equipment. I ordered the 750-41610/025 .25 mm oversized pistons. (Onan #186-606 But they sent me the 750-41610/050 .50 mm oversized pistons. I just got off of the phone with the salesperson. He's very apologetic, but they don't have what I need. Furthermore, they appear to be non-existent at this time. Probably just like the 750-41610/100 pistons that Jamawieb is in need of. Supply chain issues? So. I'm going to mic my bores/pistons and go to town with my hones. Going to attempt to get the .005" of piston to cylinder clearance that we need. Just more time up in the shop. Oh darn

 

[Light in the Dark]

I have been corresponding with Lister UK on some parts. I just asked them what availability is on both of these piston numbers for you and Jimmy.

 

[Ray70]

Not sure what you have for a hone, but I have used this successfully.
Lisle 15000 micrometer head cylinder hone.

Lisle 15000 Engine Cylinder Hone, 3" - 4-1/4" Range | ToolDiscounter

15000 Engine Cylinder Hone, 3" - 4-1/4" Range. Shop Engine Cylinder Hone from Lisle at ToolDiscounter

www.tooldiscounter.com

Even with the 80 grit stone it takes hours to get to .020" over, but I have done it successfully.
You will never get there with a ball hone and even a 3 finger will never happen unless you can find some coarse stones and even then it may end up egg shaped.

The Lisle hone puts even pressure that you dial in, not spring loaded.

Once you get close then switch to 240g, and 400g as you go.

 

[Light in the Dark]

So from Lister (or actually their master distributor Sleeman and Hawken... whose owner purchased Lister-Petter)... both of the oversized pistons right now are $301.26/ea without freight, and without tariff. They do include the rings for that price though... so generous! Stock in the UK.

 

[loosegravel]

Wow! Like I previously posted…my good friend Dave who used to drag race could buy HP pistons for a third of that price. I thank you and Ray both for your input. Ray is obviously speaking from experience in honing cylinders and he’s saved me a lot of time. Because I’m not experienced I would have tried. Thanks!

 

[loosegravel]

Not sure what you have for a hone, but I have used this successfully.
Lisle 15000 micrometer head cylinder hone.

Lisle 15000 Engine Cylinder Hone, 3" - 4-1/4" Range | ToolDiscounter

15000 Engine Cylinder Hone, 3" - 4-1/4" Range. Shop Engine Cylinder Hone from Lisle at ToolDiscounter

www.tooldiscounter.com

Even with the 80 grit stone it takes hours to get to .020" over, but I have done it successfully.
You will never get there with a ball hone and even a 3 finger will never happen unless you can find some coarse stones and even then it may end up egg shaped.

The Lisle hone puts even pressure that you dial in, not spring loaded.

Once you get close then switch to 240g, and 400g as you go.

Thank you Ray. You have possibly saved me a lot of time. The cost of that hone can be paid for with the purchase of one piston at the $300 price per piston price.!

 

[Light in the Dark]

OK so I was clearly using my ass to calculate the currency exchange earlier. The price from the dealer is 106.91 GBP, which has a real time exchange over to about $142 right now. Not sure how I got the other figure... but FYI all the same.

All prices shown in GBP

 

[loosegravel]

Wanted to share my experience with a similar problem. Been working on this unit. Would start after a few tries. Smoked bad and would clear with a slight haze. Load test to 50% smoked really bad. Couldnt get over 70% and it had bad back pressure in the crankcase. Finally took the exhaust manifold off and could see 1 and 2 smoking all the time. Dead cranked the motor with a paper towel over the exhaust port and noticed 1&2 would suck the towel into the cylinder instead of blowing out. Thought it wast he head gasket. Under further examination the gasket looked good so it had to be rings. Took the pistons out of 1&2 and they are bad. They are 1mm over so .040 oversized. Cant find anywhere, ive reached out to a couple of vendors but no luck so far. What year was your unit reset? Mine is a 2010 and had 500 hours.

Sir, I was mistaken. This unit that I’m working with was reset in February of 2012. I also have a MEP-804A which I was working with. That one was reset in 2008.

 

[loosegravel]

OK so I was clearly using my ass to calculate the currency exchange earlier. The price from the dealer is 106.91 GBP, which has a real time exchange over to about $142 right now. Not sure how I got the other figure... but FYI all the same.

All prices shown in GBP
View attachment 862315

Thanks! I can deal with that. Interesting…I received an email quote from “ Sean” at Sleeman & Hawken last week. His was higher than DP Equipment, so I chose to go with DP Equipment. I sent Sean an email request again a little while ago asking him if he could still honor his 106 pound price. I know they’re closed now. I’ll give him a call in the morning. Thank you again for your help and support! Jeff

 

[jamawieb]

I was dealing with Sleeman_Hawken from an ebay post. I got so frustated because I bought the .040 rings from them and asked about pistons. They said they had them and instead of sending me an invoice, they listed them on Ebay UK. they keep telling me it was an item on ebay so they didnt know why I couldnt see it. Finally figured out they posted it on EbayUK. In the 2 days corresponding with them I found Kraft Power. They are a distributor for Sleeman & Hawken (Lister Petter) and they got the pistons ordered for me. $195 each but they say 5 weeks to ship. So its going to be a while before I get it back together.
On my unit, I assume that the compression rings froze but the oil ring did not. The oil ring broke and separated, this is what caused the piston to move and jam the oil ring against the cylinder wall, which caused the damage to the piston.

 

[loosegravel]

I was dealing with Sleeman_Hawken from an ebay post. I got so frustated because I bought the .040 rings from them and asked about pistons. They said they had them and instead of sending me an invoice, they listed them on Ebay UK. they keep telling me it was an item on ebay so they didnt know why I couldnt see it. Finally figured out they posted it on EbayUK. In the 2 days corresponding with them I found Kraft Power. They are a distributor for Sleeman & Hawken (Lister Petter) and they got the pistons ordered for me. $195 each but they say 5 weeks to ship. So its going to be a while before I get it back together.
On my unit, I assume that the compression rings froze but the oil ring did not. The oil ring broke and separated, this is what caused the piston to move and jam the oil ring against the cylinder wall, which caused the damage to the piston.

It's been a little frustrating for me this past week too. But, like they say "patience is a virtue." Still, what would cause compression ring seizure? I did see in your previous photos that the top compression ring gap was closed indicating seizure.

 

[loosegravel]

I wanted to post an update on the piston situation for this MEP-803A that I'm working on. Good news today! Sleeman & Hawken in the UK have already shipped my .25 mm OS pistons. The price (including shipping) ended up at $178 ea. And...check this out! The ETA on the UPS tracking number they provided for me is Friday 03/25/22! I'm very grateful for the input that I've received here. I heard a good quote once. "We must learn from the mistakes of others, because we'll never have time to make them ourselves." The only thing worse than getting bad information is getting good information and not heeding it! I always get a lot of good information here, so I try to learn from you all! And I've seen other posts related to a "reasonable" amount of time and resources it takes to get or keep these wonderful machines running. I suppose this could be a debatable topic and I won't get into it here. I do know that I'm much happier spending the money on the pistons that I need rather than spending the "hours and hours" honing these cylinders to fit the wrong ones that I received from DP Equipment. Thanks Ray! And BTW, DP Equipment is providing me a refund. I put the parcel back in the mail this morning. The only thing that I don't know is if they'll refund my shipping charges also. $40 for the original shipment and $25 for the return. I can only hope. I'll post some more when I get this thing running.

 

[jamawieb]

I wanted to post an update on the piston situation for this MEP-803A that I'm working on. Good news today! Sleeman & Hawken in the UK have already shipped my .25 mm OS pistons. The price (including shipping) ended up at $178 ea. And...check this out! The ETA on the UPS tracking number they provided for me is Friday 03/25/22! I'm very grateful for the input that I've received here. I heard a good quote once. "We must learn from the mistakes of others, because we'll never have time to make them ourselves." The only thing worse than getting bad information is getting good information and not heeding it! I always get a lot of good information here, so I try to learn from you all! And I've seen other posts related to a "reasonable" amount of time and resources it takes to get or keep these wonderful machines running. I suppose this could be a debatable topic and I won't get into it here. I do know that I'm much happier spending the money on the pistons that I need rather than spending the "hours and hours" honing these cylinders to fit the wrong ones that I received from DP Equipment. Thanks Ray! And BTW, DP Equipment is providing me a refund. I put the parcel back in the mail this morning. The only thing that I don't know is if they'll refund my shipping charges also. $40 for the original shipment and $25 for the return. I can only hope. I'll post some more when I get this thing running.

Loosegravel. Keep us updated on the shipping. Did they ship it from a US distributor or are they shipping from the UK?

 

[loosegravel]

Loosegravel. Keep us updated on the shipping. Did they ship it from a US distributor or are they shipping from the UK?

The tracking number says that it was shipped from Castle Donington, United Kingdom on March 23rd. It's showing in Philadelphia, PA now.