Finally starting the 115 /140 crossflow build

[keefallan]

I am finally gettin around to posting the build. I got my block back many weeks ago. This is going to incorporate the piston coating, combustion chamber coating.....all the way thru the exhaust down the tuner.

Today was to take some before and after pics of the motor. It is almost 100 percent ready for cavity coating, but as I was moving it around for the after pics.....I saw some spots I still need to re-blast before I coat it. My son came in with me today and helped me out . Sandblasting just eats up time!!! My account is set up with Techline, and I ordered the cbc-2 and the tfl-1. I dont need the tfl-1 on this build, the piston skirts are already coated.




This is the motor out of the box. It is dirty and needs a cleaning. I took the exhaust fillers out, but not before the lower exhaust bolt snapped off. It was seized . We welded a nut to the pictured stud and removed the broken bolt. The last pic is the cavity, now fixed, ready to be cleaned etc.




This where I have questions. In the left picture, I hope that you can see in the cavity where the pointer is. I want to open up the bubbleback right there.....its blocking the flow of exhaust into the lower portion. The last pic shows what i want to to remove. But I want to know if others have done this before and did it help or hurt? Why was it there from the factory? Was it to stagger the exhaust? But it looks like it crimps down on exhaust flow on the left side flow into adapter. Any advise men? On this build, I am trying to optimize the exhaust.....without going apenuts. Thats why I am asking about more info on that little aluminum tail sticking down into the exhaust area at the bottom.

What I still have to do in the lower area is blend some more before I shoot the exhaust coating. There are areas down there that need smoothing..........just ran out of time today.




This is the adapter after sandblasting in pic 1. My sonis milling .010 off the adapter to remove any pitting that was there. And in pic 3, I temporarily bolted the blasted tuner onto the adapter. i wanted to do some exhaust work at the transition between the 2, but I ran out of time..........I want to open it up a little. I dont have much there to work with, but I want to do a little opening up the hole. And then spray the coating, and bake..........not shake-n-bake but spray-n bake.




In this group, I have a pic of the bback dirty in pics 1 and 2(dont know why the image is upside down). In pic 3 I have it sandblasted and spent some time using a cartridge roll and blending/removing the factory casting lines and some smoothing in general. it is ready for coating. This last pic is my son's first powdercoating. Why not make it chrome?




In these pics, you can see the after pics of the blasting and gentle cleanup in the exhaust areas. I used a burr to remove the little tooth in the exhaust ports and then switched to a cartridge roll. I blended the exhaust areas of the block into the fillers. i have one or two tiny spots that I need to blast again, but I will coat the aluminum of the block(exhaust area) and the filler blocks and the lower area of the bnlock where the bubback brings the exhaust back into the motor on its way out the adapter.

Some of the pics are sideways....sorry about that.......dont know how to fix that.

But thats it for now........hopefully the exhaust coating gets here soon......

[LakeFever]

Looks good. Have you done any of the 9 pages mods to the porting?

[keefallan]

Not on this one LF. I was leaving this one basically stock....... but with focusing on the exhaust side. This one is for my crab/fishing boat. Its got that motor with a cracked ring right now. So, this is the replacement. I am gonna put the halves together and smooth anything that is rough and nasty(on the inside) and do the intake stuffers and reeds etc.

I have 2 other v4's that I plan on doing some extra work on such as lowering the exhaust port and either doing the scalloping or a boost port on the transfer side.

[keefallan]

Can anyone chime in if I can remove that bit of aluminum off of the bubble back? If anyone is having a hard time seeing exactly where from my pics, if you look at the 4th group of pics, look at the second picture. It is that little tab of aluminum that I want to open up. Can someone confirm that its ok to do so? Its clearly in the way as the exhaust turns back into the engine....but is it a deflector?

[LakeFever]

I can’t say for sure but there is definitely a section of block that needs removing when adding the bubble back to the flat back motors. I’ve seen this commented on with pics in a couple of threads here. Search should reveal what I’m talking about

[FMP]

Think you're referring to "port matching" the sections of the system, how far off is it?
Could be deliberate to the short side. To equal tuner effect to both twins.

Came across an OMC paper which had the V4 with two tuners. Each twin had its dedicated tuner under each side. The signal passage between the twins for blowdown stuffing pairing was retained, believe they may have equalled those pairing distances a bit more with the design.

Good pictures BTW

[keefallan]

Fever, the part you are referring to is at the bottom of the block. On the 135, the two sides if the exhaust are divided. OMC milled out that section at the bottom to make a common area as the air goes into the block again and down into the tuner. I believe that is what FMP is stating. the 135 became the 140 with that one piece milled out.

The part I am referring to is that little tab on the actual bubble back that on the left side , it sticks down farther into that little area on the bottom of block. I want to remove that to increase flow, but I dont want to mess up exhaust pulses by doing that. And that is why I am asking.

That little tab that sticks down FMP is grouping 4, 2nd pic. Its the little black area on the dirty bback pic on the smaller opening side. Thats where the exhaust is hitting it on the way out the motor. But as you can see from a side profile in another picture, its an angled piece, like its directing flow into the motor?

[FMP]

No, I'm referring to the part you questioned. The division wall difference between the 140 is another difference which changes distance timing port to port to benefit the bubble use.

[FMP]

To compare, but not the same animal.

[FMP]

...

[keefallan]

I was all excited to get alot of stuff done today........so I could build the motor out. But things came to a crashing halt very fast

here's why...................

1) When I left things last weekend, I knew I had things to do before I coated everything today, but I didnt realize how MUCH I had to do

2) I did spray the adapter and filler blocks today, but thats all. I cooked them for an hour @ 450 to cook any contaminates out before I sprayed. That took too much time away from me, because I had to let the adapter cool before spraying the ceramic. So, bake them on Monday morning and take some photos for you.

3) I was gonna do the tuner today. But, I remembered that i had to close up the idle reliefs. But WAIT!! i just used up the argon at the beginning of the week and forgot to get a new refill..........so no tuner work.

4)I realized that i only have one head available to coat. SO, no combustion chambers done either.

5) I was gonna do my block. But I remembered that I needed to clean it a little more before I prebaked it. Then upon closer inspection, I realized that I wanted to smooth the exhaust tract where the bubbleback sends the exhaust back into the block at the bottom and down into the adapter. It had alot of sharp edges. So, no coating on that either


So, from here, I will post pics of what I did do..............





This was what i worked on while the adapter and fillers were cooking out. The first is the "before" picture. Pic #2 was the sandblasted/sanded mid...........and the last one is the final pic of it in primer. I wanted to use white epoxy primer, but temps were not conducive for epoxy. So, I was forced to used etching primer. At this point, I will shoot a couple coats of regular primer and block it down, and then shoot Southern Polyurethane's white and their clear cloat............amazing company BTW.





So, since I couldnt coat this until I smoothed it out, I was able to use a burr, cartridge roll and then some hand sanding to smooth and polish the lower area. I felt that there were too many shart edges down around the divider. Its now ready to prebake, then spray.....then finally bake for good.








And the last thing that I did for today, was to remove any sharp edges in the intake tract. I know the pics are not the best on these, but my lighting was less than desirable. I also double checked to see how the halves lined up and they were pretty good already. I did do some light sanding on a couple of edges to the lower half. But, its nothing compared to the v6 halves. In my experience, they need some serious blending at the section halves.......v4's? much better

Thats all for now...............

[Chaz]

Keef ,
You never want any passageway to run into a step. If anything you want a mating surface that the next part in line to be slightly bigger. Too much bigger and the air will tumble out of the hole. But anything is better than hitting a ledge.

Keep in mind those are far from being a race motor. Anything you do to improve the "line of sight" will help. And with what they did with the in / out conduit .. you'd have to go way out of your way to hurt anything ..

Until you change the timed events at the sleeve , your not going to see any more RPM , just a little more where it's powerband is currently at.

[Chaz]

Here is a tuner I just did for a 15" Yamaha 90 horse I'm doin ..

It started life as a long / straight bazooka tube like you have ..

[keefallan]

Keef ,
You never want any passageway to run into a step. If anything you want a mating surface that the next part in line to be slightly bigger. Too much bigger and the air will tumble out of the hole. But anything is better than hitting a ledge.

Keep in mind those are far from being a race motor. Anything you do to improve the "line of sight" will help. And with what they did with the in / out conduit .. you'd have to go way out of your way to hurt anything ..

Until you change the timed events at the sleeve , your not going to see any more RPM , just a little more where it's powerband is currently at.

".......better than hitting a ledge" and thats exactly what the stock B-back is doing right now in stock form. If you were to measure volume area between the port and starboard side, the port side is 30% smaller opening?....with a tab sticking down in the exhaust path on that side. If this were a street motor(not 2 stroke), I would have removed it without ever thinking about it. But since I dont fully understand all the dynamics involved in 2 strokes.......I hesitated.

"........not a race motor" I completely understand that I was just looking for a freer flowing exhaust system to just free up some power. Thats the purpose of the build.....to clean up all the castings on the inside on the intake side, coat the entire exhaust and free up the air on the outgoing side to make a little more power. I like the power band where its at on this particular motor's use. That's why i opted Not to do any porting either. That's for the next one

[keefallan]

Here is a tuner I just did for a 15" Yamaha 90 horse I'm doin ..

It started life as a long / straight bazooka tube like you have ..

Your pic reminds me to get argon at the welding store tomorrow

Very interesting pic there.....very nice welds......things that make ya go hmmmmm