Author Topic: Cobra motor disassembly and rebuild (Read 107785 times)

madmtnmotors · « **Reply #625 on:** November 17, 2016, 10:46:33 AM »

I'm curious to see the #3 combustion chamber...

PeWe · « **Reply #626 on:** November 17, 2016, 11:05:55 AM »

WOW! Look like a maniac meat grinder went wild! Not much left to reuse, right? Crank and rods are gone too? Head + cam OK?
Thin piston pin caused it?
I'm curious when I have my engine apart, will grind upper case for bigger bore sleeves, file pistons ring gaps for 71.25mm JE pistons this weekend. German prim chains, std tensioner and Ape ultra crank... If there is anything to be aware of to protect the goodies going in.

No problem with cam chain + tensioner? My metal upper wheel w cogs had marks after cam chain.... 500km max.... std tensioner goes in next time.

No personal damages most important here! NOS old man parts difficult to find.

Bill/BentON Racing · « **Reply #627 on:** November 17, 2016, 11:35:15 AM »

Not sure if I am! Lol

Jerry Rxman Griffin aka MuthaF'er · « **Reply #628 on:** November 17, 2016, 11:43:21 AM »

Did it drain the oil tank too?

dragracer · « **Reply #629 on:** November 17, 2016, 11:43:55 AM »

I hate being right sometimes.

bwaller · « **Reply #630 on:** November 17, 2016, 12:12:45 PM »

Man oh man, a knock is a sign of trouble alright but how long did you run it when it started coming apart? Wow Bill is there anything good left? Any gearbox damage, cam ok?

dragracer · « **Reply #631 on:** November 17, 2016, 12:26:35 PM »

Quote from: bwaller on November 17, 2016, 12:12:45 PM

Man oh man, a knock is a sign of trouble alright but how long did you run it when it started coming apart? Wow Bill is there anything good left? Any gearbox damage, cam ok?

It was knocking when he rode it up to staging to make the eliminations pass. It blew apart about half track. Bill said it was still running and he had to shut it off himself- wow.

754 · « **Reply #632 on:** November 17, 2016, 12:29:52 PM »

It looks like........
...Southern FRIED 754........... Yikes...

BPellerine · « **Reply #633 on:** November 17, 2016, 01:05:41 PM »

has anyone ever seen a primary chain fail!hard to tell what is what!billp

Jerry Rxman Griffin aka MuthaF'er · « **Reply #634 on:** November 17, 2016, 04:29:55 PM »

Just that one

Frank has great ears, Bill's are pretty damn good and I'm just a deaf old SOB cause I didn't hear his engine knocking at all and I was right there too. At least it wasn't as obvious or as loud as mine was in a quiet environment. Guess I still need to learn to hear better.

scottly · « **Reply #635 on:** November 17, 2016, 05:43:59 PM »

I don't think I've ever seen a piston that munched up before!

Did you find the rest of the rod yet? I'm curious about what the cylinder bore looks like; if there is scoring on one side from the pin contacting the wall, a button may have failed first, allowing the pin to move over in the piston.

dragracer · « **Reply #636 on:** November 17, 2016, 06:26:55 PM »

The piston was likely pushed up into the head after the pin broke. The rod kept going up and down banging against the underside of the piston until it destroyed various pieces that then dropped down the cylinder and bounced off the crank throws. Eventually I'd guess a piece hit the primary chain and broke it apart. Just my opinion because the motor kept running even after it lost power. Bill said he shut it off himself.

754 · « **Reply #637 on:** November 17, 2016, 08:49:22 PM »

My buddies Suzuki 1000 ate a piston on I5 ..the piece if crown I saw was less than 1/4 of the crown.. I never got to see the rest of it. He was about 3 lanes from the shoulder when it happened.

PeWe · « **Reply #638 on:** November 18, 2016, 07:11:05 AM »

OK, knocking... If i hear knock on my door someone want to come in... If I hear knock from my engine something want to come out!!

I listen carefully for pinging, high frequence knocking when I do not want to get another set of pistons with hole. Entire engine shredding is worse. Good idea to have spare engines, swap and forget.

Bill/BentON Racing · « **Reply #639 on:** November 18, 2016, 04:42:10 PM »

All good, except don't FORGET!

PeWe · « **Reply #640 on:** November 20, 2016, 02:05:50 AM »

...learn and forget the bad thing.... When my pistons melted + bluish rods in need of replacement + valves + guides etc.etc. I had too see it that a higher force want to stop me riding the bike that year to avoid something worse. That made me Ok with the situation and fact that I was unharmed... I felt a mix of happiness and sorrow. Happy that the engine did not got kaputt in Germany, Austria or Jugoslavia the month before. I missed the hail storm of huge ice balls falling down in Germany with 24 hours
I had spent a lot of money in the engine and bike the previous winter and had still bills for it

Bill/BentON Racing · « **Reply #641 on:** November 20, 2016, 09:20:08 AM »

Well, how about a pic of #3 intake and carb! Little pieces are ring material! Took the left side cover off....found this! Damn, I'm a lucky man!

BPellerine · « **Reply #642 on:** November 20, 2016, 10:57:15 AM »

unreal bill,you sure know how to make big things small!again glad you ok!bill

PeWe · « **Reply #643 on:** November 20, 2016, 01:30:34 PM »

Bike will get another engine? Pics in your thread show other race parts on your shelves.
Bike will become a "Bird Phoenix" rising like in the old mythology? Paint job with flames too?

Bill/BentON Racing · « **Reply #644 on:** November 20, 2016, 01:54:18 PM »

New engine being built ,K8 cases, 72mm hi compression 12.5 to 1 JE some guys fancy billet cylinder with Nikasil, rebuilt primary by someone who built some old rear wheel for someone recently, a gold one ,can't remember their names.....
We're shooting for the 9's like someone else is, no wait ,they just want to be consistent, no way they'd get caught up in trying to lower their ET! Lol, Bill

kmb69 · « **Reply #645 on:** November 20, 2016, 02:55:32 PM »

Quote from: Bill/BentON Racing on November 20, 2016, 01:54:18 PM

New engine being built ,K8 cases, 72mm hi compression 12.5 to 1 JE some guys fancy billet cylinder with Nikasil, rebuilt primary by someone who built some old rear wheel for someone recently, a gold one ,can't remember their names.....
We're shooting for the 9's like someone else is, no wait ,they just want to be consistent, no way they'd get caught up in trying to lower their ET! Lol, Bill

Yah, right! I'm betting that someone would like their SOHC to be consistent alright...................in the 9's!

BPellerine · « **Reply #646 on:** November 20, 2016, 03:15:03 PM »

you goin all modern on us bill,haha.billp

dragracer · « **Reply #647 on:** November 20, 2016, 03:17:45 PM »

Lol, next season fellas, next season. Still shooting for consistent ETs on my current bike- it'll never see a 9. But i do want to win a race with it and finish in the top 5 in the field. I fell short of that goal this year but I'm not giving up. I'll freshen it up over the winter with a new crank.

The nines are reserved for the project bike. Lots of work ahead so its going to be a long winter in the shop working with my junk parts. Stay tuned, I got high hopes. Hahaha. Remember now, the Honda is the slowest bike I own. Most are in the 8's and one is capable of running mid sevens on spray. Nothing to prove here.

Bill/BentON Racing · « **Reply #648 on:** November 20, 2016, 03:42:48 PM »

I got a slightly used crank for you.....lol, Frank you definitely got nothing to prove....but you're a racer and one hell of a competitor. We'll have big fun next year! Got my permission you hear engine noise shut me off! See you in the lanes....rt next to me! Lol, Bill

dragracer · « **Reply #649 on:** November 20, 2016, 04:08:28 PM »

Quote from: Bill/BentON Racing on November 20, 2016, 03:42:48 PM

I got a slightly used crank for you.....lol, Frank ! Got my permission you hear engine noise shut me off!

Just don't forget your statement Bill. It's here until the forum shuts down and the whole world can look back on your request. Lol. I got your back my friend and expect you to do the same thing for me. You could save my life.

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Author Topic: Cobra motor disassembly and rebuild (Read 107785 times)