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Discussion Starter #1
My dad has an old Yamaha Enticer 340 that's been sitting in a garage for years. I have no idea when it last ran. At first inspection, I found the engine seized. I put oil in the spark plug holes and worked the engine over. I got it to turn but it wasn't freeing up nearly enough. So off come the heads and cylinders. The right side was fine but the left had stuck rings and was dragging on the cylinder wall. I'd like to see if I can get away with just running a hone through the cylinders to give them a fresh surface and replacing the piston/ring assemblies.

Where do I find the following parts at an affordable price?
top end gasket kit
both pistons (standard size)
rings
wrist pins
c-clips
small-end rod bearings

Is that all I should need? Is that more then I should need?

The engine number starts with E338
The tunnel number starts with 8J6
A sticker under the hood says it is a ET340D
There is no electric start but it looks like one could have been added or might have been an option?
The carb is a MIKUNI KOGYO single barrel with a butterfly style throttle plate. (numbers 8J6 00 stamped ion it)
Internet research suggests this is a 1980 model.

I think I found some torque specs on-line. It looked like the head nuts might have had thread locker on the threads. Is that something I should use during reassembly?

This engine has an oil injection pump. How do I determine if it is functioning properly? There is oil in the oil tank. I disconnected the oil supply line (after the in-line filter) and oil ran out so the tank/line/filter seems to be good. It looks like the pump outputs through two smaller lines that end in the throats of the intake manifold. I held the throttle wide open and spun the engine by hand maybe 25 times and I saw no oil appearing in the manifold. Am I testing this wrong? I don't know much about oil injection systems.

Any suggestions/advice/ pointers would be appreciated.











 

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It doesn't say who made the pistons, only that they are OEM style, which means they are cast. Cast pistons will heat and cool at the same rate as the cast cylinders, helping reduce the potential for a cold seize.

Not many places actually make pistons, so quality for the cheap ones is pretty good from all makes. I would not hesitate to use those in a small, low hp application like your Enticer. I would add wrist pin bearings to complete the upper end. Make sure the cylinders are in spec before buying, if they are in need of repair, the stock size may not fit after the cylinder is worked over.

Holding the throttle open won't add anything to getting oil to the intake; there is a pump that operates off of engine RPM. I would disconnect the lines at the intake and see if a bit of oil flows after you pull the rope a few more times. Pull the plugs first to make it easier to turn over.

If the pump is suspect, pre-mix the first tank of gas with oil at a 50:1 ratio to make sure the pump is working. If the pump works properly, the oil in the reservoir will drop as you ride (and you may foul the plugs, as you will be double-oiling.)
 

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Discussion Starter #4
The throttle lever is cabled to both the carb and the oil pump. I imagine this is done so that the pump will alter its output along with throttle position.

The plugs were removed shortly before the heads, cylinders and pistons were. :D I spun the crank by hand but not too quickly. As it sits, the rods are free to flop about and I don't want them doing that. I don't know if the pump is supposed to deliver at all at that low of an rpm.

I do like your suggestion of pre-mixing at first to be on the safe side. A dropping reservoir will tell me if it's injecting but it won't tell me if it's injecting on both sides or only one.
 

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You are right about the oil output. When the engine is idling, the pump may be delivering 100:1; when at full throttle, maybe as much as 40:1. There's less fouling of plugs and better use of oil that way.

It takes a few pretty good tugs on the rope to get oil up into the intake. You won't be able to test until you get the engine back together. Oil everything really well so there will be some lube on the cylinder walls when you do start pulling the rope. You should smoke out the neighborhood when you get it running ;)
 

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Discussion Starter #6
You should smoke out the neighborhood when you get it running ;)
Like a SeaFoam treatment on a car engine... always a spectacle.

I took the time to examine the cylinder walls closely. One has slight axial grooves. You can't feel them with the tip of a finger but you can feel them slightly if you run a fingernail across them. So it looks like I need to go further then just running a hone through them. I took them to an automotive machine shop near me and the guy said his equipment doesn't go that small. He recommended a place in Wisconsin that specializes in this sort of work. He said they'll sell me the piston assemblies too if I want. I'll give them a call tomorrow and see what pricing looks like.
 

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Discussion Starter #7 (Edited)
The place is Millennium Technologies in Plymouth Wisconsin. They estimate about $280 to get me what I need.

$126 to bore and hone the two cylinders.
$106 for two SPI piston assemblies
$27 for two Wiseco top roller bearings
$21 for the Winderosa top end gasket kit

I shipped the cylinders this afternoon. Has anyone used this company? Are they good?
 

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I've used Millennium Technologies four times over the years. The last time, I had a huge chunk broken off the bottom of the cylinder skirt on my 700 when a piston failed. I sent them the cylinder and they sent it back looking like new. I also bought a new OEM piston at the same time and the piston was set up for the cylinder. I've had awesome results from them. Price is about half of what you would pay for a new cylinder (if you can find one.) They do quality work.
 

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Discussion Starter #12
Update: Just waiting for the parts to arrive.

Will I need anything special for reassembly? Torque wrench and specs. Two stroke oil for assembly lube. New plugs. Fresh gas (premixed). Flush carb with carb cleaner.

Nothing needs sealant on it, does it? Cylinder base gaskets go on dry I assume. Same for manifold gaskets I imagine.
 

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Discussion Starter #13
The parts arrived today! Everything looks good. I'm going to see if I can get up to Wisconsin this weekend and reassemble the engine. I found the factory recommended plugs locally. NGK BR9ES for something like $1.44 each.
 

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Congrats! Time to get to wrenching ;)

The BR9ES is a very popular snowmobile engine spark plug, it will work on most of the Polaris Fuji engines as well as most Suzuki Cat engines from the 90's. If I were a parts house, I would stock a bunch of 'em ;)
 

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Discussion Starter #16
It starts and runs but I think the carb needs attention. It won't stay running without the choke pulled. With it pulled one click, it runs high idle and smokes. With it pulled all the way (two clicks), it runs lower rpm and smokes more. Without the choke pulled, it dies. It won't rev in any choke setting. It will begin to rev then bog out and die unless I let off and allow it to return to idle. It seems like it's running off the choke/idle circuit and the main jetting isn't flowing. I don't have a carb kit.
 

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Discussion Starter #17
I pulled the carb and carefully pulled the float bowl. Went through all the passages with spray Brake-Kleen (i don't have any carb cleaner) and a fine copper wire. Reassembled and I have normal carb function! I took it out on the front lawn briefly to test. I had some rubber belt smell at first. The belt is probably old and dried. There is a spare belt in the cubby behind the tail light but that one is probably just as old.

Tomorrow I want to verify the oil injection is functioning.

What do I need to make this vehicle legal to use out here in Wisconsin? Driving in a circle on the front lawn is going to get really old really fast.

I can't find the key so I picked the ignition switch to the ON position. I'll leave that in the ON position and turn the engine on and off with the thumb-kill-switch for now. I'm hoping my Dad has the key stashed in a safe place (and remembers where that place is :cry:).
 

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Discussion Starter #18
Both oil ports (one in each intake manifold runner) are delivering. I snaked a bore scope into the manifold and spun the engine with the pull-start. I'll post pictures when I get home.
 

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Discussion Starter #20
Here's the second intake runner I scoped. I forgot to take pictures of the first one but both were producing about the same.

You see a little oil pooled around the nozzle from when I was turning it over and watching the first runner.



Then I pulled the cord a bunch more times and took this picture. You see more oil pooled and now flowing back towards the cylinder.

 
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