Holey Piston!!

[Ken Retallick]

Finally got some decent speed out of my rigger. Old 1 Cube CMB, own pipe and prop.

Have a look in my photo album and tell me why piston is now dished..... :blink: Almost but not quite a hole burned through.

Glow plug was blue outside, so it was hot, inside the element was AWOL. No signs of recent detonation.

Is this a compression, Engine temp or Pipe Stinger prob? or other? If lean i would have thought Detonation would be seen on rest of piston and headbutton.

Ken

 

[Terry Keeley]

Looks like it's been getting hot, it's black all over, next comes detonation and a hole. Plus the plug being blue. Are you getting airflow over the motor, ie. through the cowl? What's your stinger diameter? Sure you're not running lean?

Here's a direct link:

https://www.intlwaters.com/gallery/displayimage...10188&pos=-5155

 

[Jerry Wyss]

Hi Ken, I haven't seen your Gallery but sumthin' happened to put the "fire" in your engine instead of

your pipe. Could be a "header" leak right at the block or she's gettin' air some place besides the carb.

You said that you made your own pipe, is this the first time you have ran it with this pipe?

How is the air density the day you ran it? was it exceptionally dry?

Like the old sayin' goes "It Ran Real Good Right Before It Blew Up"

A component of "detonation" is also high compression,,your situation leans to too lean,,no pun intended.

 

[Jim Allen]

Ken,

If you look in my photo album under "the high price of engine building" you will see a twin brother to your heat dished piston. The problem was eliminated by re-cutting the angle on the main transfer window next to the exhaust. I continued to use the same pipe, fuel, compression ratio, & plug, without any problems.

Jim

 

[ozzy2]

Ken

I would be looking at the stinger or the muffler back pressure if the back pressure is to high it will cause excessive heat with in the combustion chamber this is evident through your description plug body turned blue.

What stinger diamiter ? what muffler exit diamiter? how mush baffling?

 

[Ken Retallick]

Thanks everyone for your replys

Engine timings are stock. just cleaned up ports.

Custom 14.5mm carb.

1 cc head volume, maybe a bit small with standard timings. I did this to make torque not revs. Not much airflow at all would be available to the engine.

Pipe has 12mm ID stinger, 50mm length. outlet of muffler section is 12mm, about 3 mm length. no baffles, straight through. i think i will watercool the header.

I spent the day trying to get it to go more than a lap before quitting, running gurgling rich. Leaning it down before each run. Last run was rich on launch, after a couple of laps i leaned it down until it just cleared. a few laps running well then a lap sounding rich, then just stopped.

Will get some pics of the boat and pipe to post.

 

[ozzy2]

Ken

Pipe has 12mm ID stinger, 50mm length. outlet of muffler section is 12mm, about 3 mm length. no baffles, straight through. i think i will watercool the header.
The stinger should be OK could be a little bigger but with the outlet of the muffler the same size as the stinger you are going to increase the back pressure quite a bit, would suggest you enlarge the muffler outlet to 1.5 X the stinger diameter

I have been doing this with all my add on mufflers with very good resaults.

 

[RIGGERMORTISE]

Told ya Kenny !

Cant beat a MP92 for the Cubes SPP CF pipes impact resistant to stray trees h34r: LOL

PS MP92 Pipes in stock B)

Dave

Just cant help myself!

 

[Tofastformellow]

what does the tree got to with it ???? LOL's

Jason

 

[Ken Retallick]

Told ya Kenny !

Cant beat a MP92 for the Cubes SPP CF pipes impact resistant to stray trees h34r: LOL

PS MP92 Pipes in stock B)

Dave

Just cant help myself!

Ok, you were right Dave, lucky guess hey lol.

I was leaning towards to much back pressure, must be all that air getting in that carb haha.

Pics of hydro now in album. No white ants in this one.

Ken

 

[Brettos]

Told ya Kenny !

Cant beat a MP92 for the Cubes SPP CF pipes impact resistant to stray trees h34r: LOL

PS MP92 Pipes in stock B)

Dave

Just cant help myself!

Ok, you were right Dave, lucky guess hey lol.

I was leaning towards to much back pressure, must be all that air getting in that carb haha.

Pics of hydro now in album. No white ants in this one.

Ken

You might like to check that your glo plug is not to hot also, if it is to hot ignition of the fuel might be to soon.

Regards Brettos.

 

[Don Ferrette]

You're over carbed in my opinion. By the time you get it needled down low enough to keep it running she's smokin' a$$ lean up on top end. Bigger carbs do not always mean bigger speeds. I had a full mod CMB90EvoII that I fitted an OS 9B onto that was very fast. B)

 

[Ken Retallick]

Don, i see where your coming from, but the carb has low speed mixture adjustment. Fuel flow is controlled through full range from idle to wide open screaming.

Ken

 

[Don Ferrette]

Don, i see where your coming from, but the carb has low speed mixture adjustment. Fuel flow is controlled through full range from idle to wide open screaming.

Ken

Do you have a smaller carb you can try on it? You might be surprised...........

 

[Jerry Wyss]

Hey I was wonderin' Don, If you take a big motor like that with a big carb , home made pipe and try to

"wing" it up, with a "too small of a prop",,you can maker perdy hot cain'cha? h34r:

 

[Mark Stein]

One thing you may have overlooked as I did for a year. Make sure you are running the biggest fuel line you can get and oversize fuel pickup tube in the tank(Im thinking garden hose). . Those motors love fuel FLOW. It doesnt matter if it is gurgling rich on the bench, when the motors under load and it wants more fuel it has to be able to get there. I ran my rigger like that for 4 races and never finished a heat until I found that out. Check the fuel fittings and nipple on the carb also. Prather large fuel line - keep that for your .45 motors. If I remember correctly I used Aeromarine Large tubing - if ithe fuel line is falling off the nipple its probably the right size. A friend of mine pointed this fuel starvation problem out to me. The most laps it ever ran was 3 and most of the time dying just before the start of the race. Those were the only changes I made to mine and it always came back to the dock after that.

Just a thought

Mark

 

[Ken Retallick]

Mark, got the big fuel line everywhere.

Even on the water it can be gurgling rich. I have the last run on video.... but where to put it?

Prop is 64mm dia with 4.8 inch pitch. Thats to how i measure them.

Next time out i will have larger muffler outlet, an maybe try increase water cooling.

 

[Don Ferrette]

Mark, got the big fuel line everywhere.

Even on the water it can be gurgling rich. I have the last run on video.... but where to put it?

Prop is 64mm dia with 4.8 inch pitch. Thats to how i measure them.

Next time out i will have larger muffler outlet, an maybe try increase water cooling.

Take a smaller carb with you as well ................ just for grins.

 

[Ken Retallick]

Take a smaller carb with you as well ................ just for grins.

Been there tried that Don No difference. Was a while ago, had forgotten till you mentioned it.

Thanks for jiggling the grey matter

Same pipe was used so has to be pipe.

 

[EatMyShortsRacing]

I would be trying a deeper head bowl with more squish band width....... and as tight a deck clearance as you can get....

Think of what provides your piston cooling!!!!