Barn find

[340sracer]

The seller said these pistons would fit 340S, but when I received them, they are different.
Anyone know what they will fit? On the box it says JD 340 CCW.

The latest problem is , the carbs are not usable ; water sat in them to long.
So I am in desperate need for carbs for a 340 S .
Thanks, Glen

[400brian]

HoosierDeereman ( Troy ) knows more about the Wiesco pistons regarding the 340/S than anyone else I know.

There are some BSE pistons that can be made to work. I'll give him a call.

[HoosierDeereMan]

Glen,

When I built my 340/S a few year back I went through this same thing. Here is what I can tell you from the picture you posted of the piston boxes and numbers. The 2012PS is a std 60mm bore piston. The 2012P1 is a .010" oversized of the 60mm bore. So you have two different size pistons which you already knew. The ring number is the bore size in Wiseco. Both of these pistons use the CD ring arrangement which is a issue for me in the RS/2 engine. Because the bottom ring of these pistons are much lower than the original RS/2 design, the bottom ring will drop below the tear drop in the intake port which will cause the ring to snag and break right out of the gate. I guess you could run these with only the top ring. These pistons are really made for the CCW KEC-340 engines used in the 400 & JDX4 sleds. Wiseco makes these pistons with two different ring arrangements. The CD and the LC. The LC is what you are looking for as the ring placement is more in line with the RS/2 design.

Here is picture of a KEC 340 piston(left) compared to a 340-RS/2(right). Notice the difference in height of the ring placement and thickness of the lower ring. Photo courtesy of 400Brian.

[HoosierDeereMan]

Here is a picture of the intake port showing a original RS/2 piston. It's not the best but it shows how low the bottom ring falls and how the tear drop holds the end gap of the ring in place at BDC.

[HoosierDeereMan]

Here is a picture of the 2012LC ring design you are looking for.

[HoosierDeereMan]

Don't rush out and buy a set of these and expect to drop them right in. These pistons will require modification to work. You will have to measure the skirt length. The 2012PS has a .040" longer skirt than the RS/2. The one 2012P1 box mentions 2260BSE. That piston may be the right length. The timing ports (side cut outs) on the RS/2 piston are .025" deeper than the 2012PS. The 2012P1/2260BSE may be the same as the RS/2. Lastly is the clearance at the corners on the timing port window. The port skirt of the 2012PS will bottom out on the throw of the crank and lock up. It needs clearanced. Again the 2012P1/2260BSE may already have this. You will have to compare it with a original 340-RS/2 piston.

This photo shows a modified 2012PS piston on a 340/S crank. Notice the clearance of the skirt and corners of the timing port windows against the crank throws.

[HoosierDeereMan]

I would be curious how the piston you have labeled 2012P1/2260BSE compares with a original 340-RS/2 piston. Here is a photo I have. The front piston is a 2260BSE. The rear is a 340-RS/2 piston. There is more clearance for the crank throw but the skirt and timing port appear to be the same height. I know there were alot of similarities between the CCW KEC Kioritz 340 and the BSE (Bouchard Special Engine) 340.

Troy

[JDT]

Very good explanation and detail in your post Troy.

Thanks for sharing your experience and knowledge.

[AirborneX4Special]

Very interesting......

[340sracer]

Thanks for the info on the Pistons.Will have to go with the originals for now and will sort out that later.
I want to thank Allen Tucker(One of my mechanics When we ran the I-500 and the I -250 with the 340 S)
for lending me his carburetors off 340 liquefier 1976.My question is will they work OK on the 340 S with changing some of the internal parts? what is the purpose of the baffle plate number m 65348 in the Liquifire?
Also what is the purpose in the 340 S carb of the plate M65348 and also extra bowl gasket?

[400brian]

The baffle plate stabilizes the surface of the fuel in the bowl ( controls sloshing I suppose ) And they put a bowl gasket on each side to seal it all up.

I guess I would transfer all the internal components over to the 76 carbs.

[340sracer]

Found brand-new carburetors in Saskatoon at rec creation supply after just the week before I understood him to say that there was no such thing. The only thing we had to change was the pilot jet and the main jet otherwise everything else was the same as the curbs that we had in the 340 S.got the engine running today and the kill switch and the tether switch both shut off the engine the only problem we have is the tack does not work and there is no lights so we must have something hooked up wrong. The wiring diagram does not do justice asit is suggesting that there is colored wires that are not in the new wiring harness.
Any suggestions would be greatly appreciated.

[400brian]

Unplug the connector at the engine. The top two wires should be yellow, these are the leads from the alt. You should have AC current at each with engine running. No juice from alt means no tach, as the tach is counting the AC cycles to read RPM.

[340sracer]

All the electrical is new except the timing ring will I burn out anything if I take it for a test run
I'm assuming we have the wires mixed up from the plug going to the wiring harness because there's two blacks ????and two whites how are you supposed to tell the difference which goes where??????

[JDT]

Either the black or the white will also go to ground on the engine.

An ohm meter will tell you which one.