1.01 cmb burning holes in pistons

[stan simpson iv]

Just figured I would pass on some testing results.

Have bin running my 1.01 with a .87 cc chamber at 9.7cr with 187 ex timing with a .010 clearance with 60% 20% nitro oil mix.

33 on the BM flow meter.

The button is my own design brass.

No holes !!!

A few blown plugs finding the sweet spot.

Also no groves or holes in the sleeve under the ex port.

Big carb and .125 spray bar with the transfer angle change.

What pipe and length...just curious.

 

[dwilfong]

AB billet 90-1.01 11 1/2. pulling a ABC 2818

going to test the MAC 13cc .470 stinger also it is almost the same pipe.

Going to bump the CR to 10 and see what happens next.

 

[Tom Foley]

Sounds like you have it running well !! Now build a clone to put in the killer twin !

 

[dwilfong]

Not yet

Sounds like you have it running well !! Now build a clone to put in the killer twin !

Not yet still testing.

The VAC 1.05 is a bust. The bearings will not hold up to the beating and too much flex in the small crank.

But I did learn how to get the 1.01 to breath with this exercise.

OPS 1.26 next up. Big crank and big bearings.

Will be some time before I go to a twin.

Have to get a single to run right first.

 

[charles siler]

Not yet

Sounds like you have it running well !! Now build a clone to put in the killer twin !

Not yet still testing.The VAC 1.05 is a bust. The bearings will not hold up to the beating and too much flex in the small crank. But I did learn how to get the 1.01 to breath with this exercise.OPS 1.26 next up. Big crank and big bearings.Will be some time before I go to a twin. Have to get a single to run right first.

David how's the project going.

 

[charles siler]

Guy's is there a difference between the new EVO 101S having the same problems???

 

[Joe Warren]

Guy's is there a difference between the new EVO 101S having the same problems???

I own several EVO101s None have piston problems. This engine does requires a head bowl volume change to run 60% fuel

 

[charles siler]

Guy's is there a difference between the new EVO 101S having the same problems???

I own several EVO101s None have piston problems. This engine does requires a head bowl volume change to run 60% fuel

So 20% bowl reduction and no changes in the carb?

 

[BigChuck]

Both Rs and EVO will benefit for the volume increase....

 

[charles siler]

Both Rs and EVO will benefit for the volume increase....

I'm pretty sure you are to lower the bowl volume as you up raise the nitro%???

 

[dr gary turner]

Both Rs and EVO will benefit for the volume increase....

I'm pretty sure you are to lower the bowl volume as you up raise the nitro%???

We increase the head volume for higher nitro for the 101 and change the shape

 

[dr gary turner]

45's and 21's reduced the volume

 

[charles siler]

I see the difference in the old and the new motors from the factory bowl volumes. What about carbs the old motors it was a must to in larger the carbs are you guy's doing the same with the 101 EVOs.

 

[bermudadude]

Both Rs and EVO will benefit for the volume increase....

I'm pretty sure you are to lower the bowl volume as you up raise the nitro%???

 

[Tom Foley]

I see the difference in the old and the new motors from the factory bowl volumes. What about carbs the old motors it was a must to in larger the carbs are you guy's doing the same with the 101 EVOs.

Carbs were never a problem . I ran the same 101 in my X Mono for 3 years then out of nowhere burned a piston . Not sure why . The repair method I developed does work and I have not have one come back but it is clear that some of the CMB pistons that were dished had about a .040"

dome thickness which is totally stupid IMHO . A new piston by Scott Bouchie is way better than the OEM piston .

 

[Chris Wood]

I know mark Bullard was drilling holes below the exhaust port to help with cooling in the piston if I am not mistaken. Could be wrong though

Personally. The 101 is a bomb. Good torque motor but not a durable motor. But what do I know

Sent from my iPhone using Tapatalk

 

[happybradboating]

I know this is not about the CMB 101. However, a few years ago I burned a hole through a Picco 90 motor. It was the first time I had seen the boat going that fast, until the piston burned up. Most likely was running lean as well. At the time I was running 55% nitro running 20% oil.

I went back to 40% and never had another problem. Brad

 

[Joe Warren]

Both Rs and EVO will benefit for the volume increase....

I'm pretty sure you are to lower the bowl volume as you up raise the nitro%???

nope. EVO101 & RS101s require you to increase the bowl volume.

 

[JRXHydros]

Both Rs and EVO will benefit for the volume increase....

I'm pretty sure you are to lower the bowl volume as you up raise the nitro%???

nope. EVO101 & RS101s require you to increase the bowl volume.

Joe Warren is right about the increase of bowl volume...

 

[Jeff Lutz]

I see this is a old thread picked back up, but will comment on the biggest issue about the .101's. The biggest problem with the rs 101's is the transfer ports were too small. Around .585" wide. The old 1 inch had around .635". I've ran much larger than both with success, but you have to tune it different. It was a lot of work to hog out the crankcases though. The new evo 101 rs now has a transfer area around .660" and even with the divider that it has, it should work much better in stock form for most people. Jeff Lutz