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Old 04-01-2007, 03:16 PM   #1
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Default Mega ZX12 Rod.

I've just got one of these little engines (second hand) Looks in great condition, but thought i'd take a look inside and whip it apart.

All's fine inside apart from the rod, apparently its had a new rod in 20mins racing ago(new style rod) However on inspection seems to be a little longer, i'm not sure?!

Its seems the brass bushing is a little loose inside the big end of the rod, meaning there is a little slop at top dead center as it slips over...is this normal with Mega engines or other engines brands, i'm relativly new to the sport so not 100% on these things.

When re-assembled the engine seems fine, can't really notice the crank slop as it goes over tdc, just a bit concerned as whether to replace the rod or not.

I fired it up and it runs great on the bench, just not sure the longevity of it if i put it in my car and race it, what dangers are there if i dont put a new rod in?
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Old 04-01-2007, 05:32 PM   #2
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what dangers are there if i dont put a new rod in?[/QUOTE]
BOOM!
CHANGE THE ROD,MEGAS ARE VERY FAST,BUT YOU NEED TO KEEP AN EYE ON THAT ROD.IF IT POPS YOU WILL DAMAGE THE PISTON/SLEEVE.
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Old 04-01-2007, 07:45 PM   #3
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It is normal to feel a little slop in the big end bushing, like a little "clunk" as you turn the motor over, especially if the motor is dry, no lube. It would however be cheap insurance to replace the rod, you could compare it to the old, and save the old one if it feels like it has the same play.....
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Old 04-01-2007, 08:19 PM   #4
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With the new MEGA T3 Rod which is stronger, it will last a while.
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Old 04-02-2007, 01:44 PM   #5
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Thanks for all the quick replies everyone, i think i'm going to do like Ffejdat said, get a new one for insurance and keep the old one as a spare.

Just taken it to my lhs also, and he said its not that bad, but replace it just to be safe (and he doesn't stock these engines so got nothing to gain) He said i should also be worried about the bushing turning in the big end, its got a little play in it and and move front to back a bit...so just gonna get a new one.

Look at the pic, that aint good surely, the brass bushing being able to be moved front to back out of the rod?!!
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Old 04-02-2007, 02:11 PM   #6
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looks like you need a rod,piston,&sleeve. they are none for rod breaking.
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Old 04-02-2007, 02:31 PM   #7
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Quote:
Originally Posted by rocca30
looks like you need a rod,piston,&sleeve. they are none for rod breaking.

Whats wrong with the piston and sleeve. the black stuff is normal, more than I would like, but its OK.

Rocca30 Call me. or PM me, to see if I can get the trays for the Region 4 race.

Thanks,

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Old 04-02-2007, 03:31 PM   #8
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Yeah it looks like its been run kinda on the hot side, not really that much carbon, more heat discolouration, don't worry i've cleaned and polished the crank and sleave in the last hour, so both look brand new, and i've polished the top of the piston a bit to remove the carbon, wasn't really that bad at all, perfectly smooth & no pitting, there is plenty of compression left in it, still fairly tight, but i'll get a new sleeve and piston later on, just want to run it properly first.

With regards to that, i see mega do an outlaw 5 port cyl and piston set, am i able to put that in my crankcase or do i need another case?
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Old 04-03-2007, 04:06 PM   #9
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Do any Mega owners, or other....know if i can put the outlaw 5 port cyl and piston set into my crankcase are they interchangable or do i need to stick with the 3 port that it comes with?
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Old 04-03-2007, 05:28 PM   #10
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Quote:
Originally Posted by supermoto552
Do any Mega owners, or other....know if i can put the outlaw 5 port cyl and piston set into my crankcase are they interchangable or do i need to stick with the 3 port that it comes with?
Yes you can, but I feel the 3 port is a stronger motor.
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Old 04-04-2007, 05:12 PM   #11
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Never had a crank out of an engine before but am i right in thinking there should be an o-ring on the shaft in the grove on the threaded end?? or is it a lube groove, just the crank comes out nice an easy, engine i've had apart in the past the cranks seem hard to push out, this is easy?!
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Old 04-04-2007, 07:01 PM   #12
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The black stuff on the piston is great sign i would not polish anything because that creates a coating that helps the life of the piston, i dont understand why people do not like the black stuff on the piston but i love it and i run Mega ZX engines and i have noticed that when they get like that is when they are at its best,just my $0.02..........
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Old 04-04-2007, 07:51 PM   #13
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Default piston Varnish

slight varnish build is not a bad thing as Roniel said. However Sligh not excessive, however removing the varnish can open up the cylinder to blow by. I would be careful with cleaning, esp if you think its just a cosmetic issue. Now I would clean the top of the piston and the cylinder head/combustion chamber as you want combustion at it's best. Varnish buildup can never be prevent in combustion as long as oil is present in the process. Now keep in mind that a clean surface disipates heat better than a varnished surface, which can possibly rob the engine of power.

My 2 cents.
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Old 04-04-2007, 07:57 PM   #14
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oh...your fuel mixture has alot to do with the amount of varish accumulated.
More castor more varnish.
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Old 04-05-2007, 12:16 AM   #15
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Never had a crank out of an engine before but am i right in thinking there should be an o-ring on the shaft in the grove on the threaded end?? or is it a lube groove, just the crank comes out nice an easy, engine i've had apart in the past the cranks seem hard to push out, this is easy?!

Whoops, just read my post...forgot to attach the picture about the groove in the crank.

The engine's all back together now with new rod, and piston top's been polished, did the crank as best i could, didn't wanna go mad as to remove tolerences, and just a gerneral clean up....hope she works well now, just a bit concerened about how easy the crank came out, i took pictures of all components before re-assembly as i'm gonna make a 3d model of it for my portfolio, and saw the grove at the end of the crank shaft??
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