295/s top end fix.

[Kurts]

So with the lack of pistons and rings for 295/s's a solution is needed, heres what I got.

1. Yamaha ET300 piston. It's the right bore, but has a 16mm pin, also the 2nd ring may have to be left out. I did some checking and, I'm not sure. I need to source a 16x22 bearing and see how it is. Pros: cheap and easy to find, lighter than 295/s piston. Cons: Kinda jerry rigged, possibly can't use bottom ring.

2. Cylinders/pistons from a 340/5. I picked up a nice 340/5 tonight, and compared cylinders to my 295/s stuff. The intake and transfer ports are basically identical to the 295/s cylinders. The exhaust port roof is about 3mm lower than a 295/s. What this means you can raise the port to 295/s specs, then modify the 340/s y pipe to work with the 295/s expansion chamber, and add just a little length to it to make the pipe work at the right RPM for the 340 stuff. Doing this should cause the engine to develop peak power at about a 10% lower RPM than the 295/s, but because your gaining 40cc, it should still make about the same power. Pros: Easy to do, save your rare 295/s stuff for later, not hacked. Cons: Not really a KEC295RS/2 anymore, not 300cc anymore, pistons are kinda scarce.

3. You could do just like above, but with 440/5 cylinders, but the HP peak would be at an even lower RPM.

Also: If you were extremely crafty, you could have a base gasket spacer made to effectively raise the roof of all the ports. Then you'd have to have the top machined off the right amount to get your squish clearance back, and lower the bottom of the ports to meet the piston crown. Done right you could get the RPM peak back up, and maybe make 50hp out of it.

Finally, does anyone out there know what a 295/s actually did on a dyno? Where was the peak at? Knowing where its was would help in finding out how much longer to make the y-pipe. Does anyone know of a place that will dyno snowmobile engines reasonably? If I could afford it I'd take it there to get it setup, and then we'd know what to do with it, not just "calculating" it.

[lwb140]

there is a land and sea dyno for sale on vintage sleds 4500 , i have a few of these pistons for sale ,i have them in +10+20+30and +40 , i do have a few sets of extra rings too thanks wade

[Kurts]

Got the degree wheel out, here is the results

295/s:
Exhaust open 83*ATDC close 83* BTDC
Transfers open 62* BBDC, close 62* ATDC
Intake open 76* BTDC Close 76* ATDC

340/5
Exhaust open 89* ATDC close 89* BTDC
Transfer 62* BBDC close 62* ATDC
Intake open 76* BTDC close 76* ATDC

So you can see the porting is very similar between the two, except for the exhaust port. It's possible a bit more intake and exhuast duration could give quite the power increase.
I'm going to try and do a complete time area study on the 295 and see what I get.

[Kurts]

Tuned length of the pipe is about 40", which puts its operating RPM at 8250RPM. BUT because its enclosed, and a twin the pipe probably runs hotter, and therefore the wave speed is higher, meaning the pipe actually works at a higher RPM.

If you just put it on a 340/5 with no other work, it would be set to run at 7800 RPM.

[Cabindweller]

There Is a JLO 16x22 wrist pin bearing that will make up the differnce with those Yamaha pistons.

Hey I Jerry rig things all the time.

Jerry

[Kurts]

295/s port areas:
Transfer 7.32 cm^2
Exhaust 9.175cm^2

Mean angle areas
Transfer 4.32 deg-cm^2/cm^3
Exhaust 8.45 deg-cm^2/cm^3

340/5 port areas
Transfer 7.32cm^2
Exhaust 9 cm^2

Mean angle areas
Transfer 3.73 deg cm^2/cm^3
Exhaust 6.74 deg cm^2/cm^3

As you can see the 295/s is set to maximize peak power, and the 340/5 is for a broader power range. Getting the exhaust angle area up to about 8, would definatly get it to have a 295/s power curve, only shifted to about 5-700rpm to the left.

[80spitfire]

Wow you really now your motors don't you!

-Brian

[lwb140]

wow thats great info , need to take time and absoarb it all have you compared these to the 440 /5 ? thanks wade

[jd_decalguy]

As Jerry said there is a Jlo bearing that will work as it is the size you need.. If I was home I could give you the correct number..

Kenny on Chris's computer

[Kurts]

I got this turd together and running. It seems like its going to work out very well. Its dark, blowing, and super drifty so I couldn't run it out and see how it goes, but so far it feels like it pulls really good. I think I almost flipped it over backwards on a holeshot, lol. Its revving out to about 7700, which it right where the numbers say the pipe should be working. So a quick summary of what I ended up doing.

1. Acquire a solid 340/5 engine.
2. Dissasemble engine, clean parts.
3. Gasket matched cylinders to 295/s intakes, and y pipe.
4. Radiused transfer port inlets at the bottom of the cylinder.
5. Machined 0.015" off the edge of the piston at an 11* angle. This is to bring the compression height of the 340/5 piston to be the same as a 295/s piston
6. Balanced the piston assemblies to within 0.05 gram
7. Re assemble engine using 295/s intakes, y pipe, shroud, and fan tower, and heads. I'd also reuse the OEM steelish head gaskets.
8. set timing to 340/5 specs.
9. I'm running 185 mains, 40 pilots, and raised the clip one slot. I have the air box on too.
10. Clutch it to about 77-7800RPM.

Also, if you don't have good CDI stuff, I have been having good luck running the points ignition off the 340/5 engine. I can't justify spending the money on a new cdi box, and possibly coils and stator too, for a sled that only gets a few miles a year. I'm fine with filing the points on occasion.

Keep in mind this is completely reverseable if 295/s pistons ever become availible. So now NOONE has any reason to not have a running 295/s.

[Matt]

Nice work. I'm curious if you will have any issues fouling plugs with the points and a setup like that.

[Kurts]

dead thread revival. I've been running it like this way for a while. Not a ton of time, but decent amount. Have not fouled a plug yet - running a points ignition.

Anyway it hasn't been running very well. Acts like it has a 7500RPM rev limiter on it. I suspect its the points bouncing, or something else bad in the ignition, coils perhaps. As it gets hot the condition gets worse, eventually it won't hardly run over 6000. Some day I'll spend more time on it and get it better.

[Kurts]

I had a little time to tinker with it the other day, before I started it seemed run about 7500, and act like it was on a revlimiter. It wouldn't start to shift out at all, and it would sit at like 30mph or so.

I ended up cleaning the points, and closed the point gap down to about .009", Improved it quite a bit. Found a junk fan belt about to fail, so that was good i took it apart. Looks like a 1975 E100 with a 351 airpump belt fits it, and napa had one in stock. I also thought it was a little lean on the mag side, so i pulled the jets. I had a 145mag, and 150 pto. I went to 150/150. I took the secondary down 1 notch from the stock 295/s setting after running it on the stand a while.

I took it out today and it feels much better pulls clean to about 8000, and starts shifting out, but seems to flatline at like 8000 and 45mph. Played with the timing a bit, and it didn't seem to have a huge effect. I'm thinking that I probably need to loosen up the secondary just a bit to try and pull the rpm down just a bit. Looks like I could go up one more size on PTO now that it runs clean at WOT.

I wish I could afford some dyno time to play with it, It seems like the power must fall off really fast at 7500/8000. On the stand I couldn't hardly get it to go over 8000. We are kind of up against a wall on this. It looks like even the production 340/5 has more exhaust duration than it needs. I'm not sure if the pipe is too long or what is going on, maybe it just wants bigger carbs and to get rid of the stock airbox?


It leaves really hard, picks the skis up about 3', but then starts setting them down. I can't tell if the motor lays over, or it looses traction. I know it drags the tunnel in the rear lol. I have it set up for max ski lift, and even a little stiff on the springs in the front, and soft in the rear. I need to back that of a bit some.

Anyone else tinkering with one?

[Kurts]

Been working on this again.

Picked up a new hewtech and a set of coils. Runs clean to 8200 or so, but still seems to stall out at about 35-40mph. So tonight I gave up an cleaned up the worn 295 jugs/pistons and put them back on. They are worn, but in my experience not enough that it shouldn't run good for a while. They really killed the bottom end, but maybe picked up a little on the top. Still stuck at 35-40mph and 8200rpm or so. Maybe the spedometer is wacked, and it's going a lot faster. On the stand it will shift all the way out and rev 8500 or so now, and the speedometer says about 55.

Anyone else playing with these? I'd figure with pistons available now there would be more people playing with them instead of looking at them.

[400brian]

On hard pack, I would think this sled should be topping out better. Certainly 60. I am no expert here, but being as you are seeing 8 grand, I am thinking it is not shifting up. Have you marked the sheave faces with magic marker to see the range of belt movement?