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My RCMK Blew up

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My RCMK Blew up

Old 11-22-2009, 07:37 AM
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Dockman
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Default My RCMK Blew up

Went to the pond yesterday to run the BJ55. Just like last time it was not running very good at all and very hard to start. After last outing of hard starting and poor performance I changed the ring. I don't think it needed it and the piston, cylinder, and ring still looked like new. I made a couple of laps around the pond (Ran like crap) and bought it back in to adjust the pipe (Bruce had suggested 12"). After adjusting pipe was ready to make another couple of laps and it would not start. I tried for about 5 minutes finally I turned the lsn in (1/2) to 1 1/2 out and it fired up, revved up real high, as I bought the rpm's back down it rattled real bad and then locked up. I'm sure it broke a rod or crank, will tear into it next week. I have only run about 2 -3 gallons of gas (8 ozs per gallon 91 octane).
Old 11-22-2009, 09:06 AM
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arrowshark
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Default RE: My RCMK Blew up

i have 2 of these engines they are great both modified they do have a tendency when new to have the the fly wheel come loose due to lack of locktite on the starter pawl talk to bruce at gizmomotors and see what he would recommend
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Old 11-22-2009, 04:32 PM
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Default RE: My RCMK Blew up

How do you have such trouble burning up motors??? What oil ratio are you mixing??? 10 oz per gal of Honda HP2??? Maybe too lean???

I hope it is a starter pawl issue and not a cylinder/piston/ring thing!!!!!!!
Old 11-22-2009, 05:20 PM
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Default RE: My RCMK Blew up

What mounts are you using? sounds like this could be the problem,if you use thin ones the starter catches and this can happen.I know Daniel from the forum posted a thread on the dock about it happening to him twice before he realised what happened.He went through two jugs before he worked out the problem.When i fitted one in a t boat for a friend i realised the problem when i noticed the starter wasnt recoiling freely,we spaced off the starter with washers between it and the mounts.The rcmk mounts are thicker than most zenoah ones so it isnt an issue with them.
Mart
Old 11-22-2009, 07:00 PM
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Default RE: My RCMK Blew up

i just talked to dock on the phone and he says the starter has been mic'd and washers have been previosly placed for spacing before motor was ever ran due to friend having the same problem and knew to check this issue and his motor is still running. he believes this is NOT a starter issue!!! ANY OTHER IDEAS??? He will not tear down until he talks to bruce at gizmo.
Old 11-22-2009, 08:56 PM
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Default RE: My RCMK Blew up


ORIGINAL: arrowshark

i have 2 of these engines they are great both modified they do have a tendency when new to have the the fly wheel come loose due to lack of locktite on the starter pawl talk to bruce at gizmomotors and see what he would recommend
I do intend on talking to Bruce and gettting his in put.
Old 11-22-2009, 08:59 PM
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Dockman
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Default RE: My RCMK Blew up


ORIGINAL: FlogginHarvey

How do you have such trouble burning up motors??? What oil ratio are you mixing??? 10 oz per gal of Honda HP2??? Maybe too lean???

I hope it is a starter pawl issue and not a cylinder/piston/ring thing!!!!!!!
I have done Tony recommendation of Honda HP2 8 oz per gallon every since we meet you at the pond. I just replaced the ring last week and the piston, cylinder, and old ring looked great.
Old 11-22-2009, 09:41 PM
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Dockman
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Default RE: My RCMK Blew up

I do want to say one thing right up front. In no way shape or form do I blame RCMK, Gizmo, or myself at this point. I will contact Bruce and get his input before I do anything. If he does not seem interested in my issue then I will move in my own direction on this. From what I have read on the forums Bruce seems very reasonable. AGAIN I AM NOT LOOKING FOR SOMEONE TO BUY ME A NEW MOTOR. This was not a starter issue. I raced dragboats for years, I done my own setups and maintained my own motors. My team was very good at it (World champ, High points champ in 2 different associations in a class I was not even suppose compete in). I had the best motor guy in the midwest (He done all of Big Foot engines). I told my buddy that has a RCMK motor last night this: You know Brian I need to go back thinking like my drag boat days. If you buy a crate motor (RCMK) you need to take it to your motor guy and have him tear it down, check all clearances and let him put it back together, that way you know it is put together right after that you need to hope the parts are all good parts..
Old 11-22-2009, 09:58 PM
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Default RE: My RCMK Blew up


ORIGINAL: FlogginHarvey

How do you have such trouble burning up motors??? What oil ratio are you mixing??? 10 oz per gal of Honda HP2??? Maybe too lean???

I hope it is a starter pawl issue and not a cylinder/piston/ring thing!!!!!!!
This motor is not burnt up it is blown up.
Old 11-22-2009, 11:38 PM
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Ron Olson
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Default RE: My RCMK Blew up

I set my carb to recommended settings, 2 on low and 1 on high and ended up with this. I feel that he carb needs to be richer than what they said.
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Old 11-22-2009, 11:41 PM
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Jon DesJardins
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Default RE: My RCMK Blew up

Did the bearings fail?
Old 11-22-2009, 11:45 PM
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Ron Olson
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Default RE: My RCMK Blew up

I kind of got an idea he's going to find what I did or close to it. I feel lucky as it only took out the piston and ring, the sleeve is fine, not a scratch.
Old 11-23-2009, 01:18 AM
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Default RE: My RCMK Blew up

Nice sun roof you got in that piston there Ron.....

Were you running it when that hapened or at idle on shore...???[X(]
Old 11-23-2009, 01:29 AM
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Default RE: My RCMK Blew up

It was in the water. I just happened to be shooting a video of it when she went south, my kid was driving it around for me getting some run time on it. I shut off the camera just before the "Aw Shucks" or something like that were said. Bruce sent me a new piston as it was one of those know to have problems but the problem is more obvious looking at the piston. I still need a new ring so I may just use a Zen ring as they are softer and require less break-in.
[youtube]http://www.youtube.com/watch?v=5VJsknn4kL4[/youtube]
Old 11-23-2009, 01:30 AM
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Scott Schneider
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Default RE: My RCMK Blew up

My guess a piston stop was used crushing and cracking the pistons dome, then running finished the job

Yes DO USE a 260 Zen ring ... much better
Old 11-23-2009, 01:35 AM
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Default RE: My RCMK Blew up

Ouch...heard it go, but your focal camera work needs work....

Is that the engine you won at Hobart...????
Old 11-23-2009, 01:49 AM
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Default RE: My RCMK Blew up

Yes, I know, lousy camera but got a new one now.
No, that engine is now sitting in that boat but hasn't been fired up yet but you can bet that it'll be running rich! I should have known that something was amiss when we brought it in to check the fuel bag and the tuned pipe was sizzling. It wasn't quite getting any speed although it didn't sound lean.
Old 11-23-2009, 02:13 AM
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Default RE: My RCMK Blew up

Welcome to gas boats or as we Aussies call them Petrol boats....[8D]

Bit different to those Nitro engines hey Ron.......

What boat are you putting the new engine into again, It was a green hull from memory...???
Old 11-23-2009, 07:44 AM
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Default RE: My RCMK Blew up

The Falcon 41. The green one already has an RCMK in it. The Lazer 45 will get that one above when I get the new ring.
Old 11-23-2009, 12:12 PM
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Dockman
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Default RE: My RCMK Blew up

Here is what I found any suggestion as to why the piston would come apart? At least it's not the lower end I guess a new cylinder and piston are in the works. Who sells the cylinder/piston already modded?
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Old 11-23-2009, 12:14 PM
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Default RE: My RCMK Blew up

ouch!! we've seen plenty of them in our day, huh dock???
Old 11-23-2009, 01:07 PM
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Default RE: My RCMK Blew up

suck. there are a lot of guys modding...Scott S, Steve at SS, CC RAcing?, GizmoMotors...I thought it would be fun to try out the CNC piston on an EVO cylie or a modded cylie...
Old 11-23-2009, 02:51 PM
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Default RE: My RCMK Blew up

Is the top of the piston turned down? Did it catch a port edge?
Old 11-23-2009, 03:11 PM
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Default RE: My RCMK Blew up

Do you have wear marks on the piston carb side? Hard to see in photo. If so it looks like the piston heated up before the cylinder did. Piston touched the wall then got caught on the port. Nasty.....
Old 11-23-2009, 05:23 PM
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Dockman
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Default RE: My RCMK Blew up


ORIGINAL: PEERPSI

Is the top of the piston turned down? Did it catch a port edge?
It is a stock piston

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