Author Topic: Cobra motor disassembly and rebuild (Read 107465 times)

Bill/BentON Racing · « **on:** December 16, 2015, 02:38:17 PM »

Yep, as it says. Last week when I tried to crank it, all of a sudden it stopped. Near TDC on 2&3. Now I see why! Guess it wanted to be rebuilt top and bottom! So it will be! Stay tuned. Bill

Bill/BentON Racing · « **Reply #1 on:** December 16, 2015, 02:41:26 PM »

Why you don't force things!! Fixed!

Bill/BentON Racing · « **Reply #2 on:** December 16, 2015, 02:53:04 PM »

More!

70CB750 · « **Reply #3 on:** December 16, 2015, 03:09:37 PM »

Quote from: CycleRanger on December 16, 2015, 03:05:39 PM

The vaseline on the lens makes it kind to hard to see exactly what happened there.

Ain't vaseline, them are tears.

Bill/BentON Racing · « **Reply #4 on:** December 16, 2015, 04:08:38 PM »

LMAO, you close to right.... so what made it stop ? Detectives , c'mon.

Medyo Bastos · « **Reply #5 on:** December 16, 2015, 04:08:55 PM »

phewww, glad you guys are seeing the same thing. i thought it was my tears when i read the first post...

NickO · « **Reply #6 on:** December 16, 2015, 04:36:59 PM »

Quote from: Bill/BentON Racing on December 16, 2015, 04:08:38 PM

LMAO, you close to right.... so what made it stop ? Detectives , c'mon.

Looks like something was jammed in #2 cylinder right at the edge of the piston near the exhaust valve?

There is a witness mark in the chamber on image 174007 which you seem to have polished-out on image 174020, also can see the same mark on the piston crown on image 175206? Seems to me it could have been the spark-plug disintegrating as it is right below the plug-hole?

Bill/BentON Racing · « **Reply #7 on:** December 16, 2015, 04:51:27 PM »

Nick, good observation, yeh #2 had interference! Not a spark plug PC though. Check these pistons out! K.

gschuld · « **Reply #8 on:** December 16, 2015, 04:58:28 PM »

12.5:1 or higher. 12.5:1 should have around a .33" dome. I like the Swiss cheesed skirts. Reminds me of the early RC modified cb350 pistons they were using in the early 836 kits.

More pictures please

.....

George

BPellerine · « **Reply #9 on:** December 16, 2015, 05:07:04 PM »

look like the pistons in your pre cobra article post George.billp

Bill/BentON Racing · « **Reply #10 on:** December 16, 2015, 05:31:31 PM »

It was past time! Cam chain shot! Man, that crank spins so freely! K.

Bill/BentON Racing · « **Reply #11 on:** December 16, 2015, 05:33:21 PM »

RC crank, balanced, lightened and oil holes fluted

scottly · « **Reply #12 on:** December 16, 2015, 05:47:45 PM »

Quote from: Bill/BentON Racing on December 16, 2015, 04:08:38 PM

LMAO, you close to right.... so what made it stop ? Detectives , c'mon.

The holes in the head gasket are too small for the bore, and interfered with the outer edge of the pistons, which protruded above the deck. There appears to be a small chunk of loose metal in the #2 cylinder, but with the crappy pics I can't tell where it came from.

Old Scrambler · « **Reply #13 on:** December 16, 2015, 05:58:39 PM »

I see a mixture of HD and OEM studs

Could be gasket material pinched in the cylinder. I like the flat-faced valves

I've seen dimpled skirts.......but not swiss-cheese

hotdog · « **Reply #14 on:** December 16, 2015, 06:10:31 PM »

Broken peice of guide..? Carb part.?, baby faces favourite chew toy..?, hell I don't know just guessing now.

Sent from my HTC_M9u using Tapatalk

MRieck · « **Reply #15 on:** December 16, 2015, 06:49:11 PM »

Quote from: Old Scrambler on December 16, 2015, 05:58:39 PM

I see a mixture of HD and OEM studs Could be gasket material pinched in the cylinder. I like the flat-faced valves I've seen dimpled skirts.......but not swiss-cheese

Those must be RC studs Dennis. The 2 for the oil feeds were tapered. Not a bad idea but you can't torque them to 22lbs.

Bill/BentON Racing · « **Reply #16 on:** December 16, 2015, 06:56:54 PM »

I never liked that. Going to replace em with better ones, better head nuts also and cylinder stud kit. New cam chain and primary's etc, new mains also. This 1/2 ready for a bath. I cleaned my lens. BF chew toy closest so far!! Closest guess wins a John Stein Drag Racing book!

Jerry Rxman Griffin aka MuthaF'er · « **Reply #17 on:** December 16, 2015, 07:02:05 PM »

Early engine Bill? Bushed and peened RC rods with bigger bolts. Not Goldens.

Post up a couple decent pics of the head and cylinder.

Bill/BentON Racing · « **Reply #18 on:** December 16, 2015, 07:17:29 PM »

After you tell what this is for?

cbr954 · « **Reply #19 on:** December 16, 2015, 07:20:09 PM »

does it have a welded primary?

scottly · « **Reply #20 on:** December 16, 2015, 07:21:56 PM »

Quote from: Bill/BentON Racing on December 16, 2015, 06:56:54 PM

BF chew toy closest so far!! Closest guess wins a John Stein Drag Racing book!

Billy Bling gold tooth cap??

Bill/BentON Racing · « **Reply #21 on:** December 16, 2015, 07:32:08 PM »

Close, but Bill closer! Cases just love luxuriating baths!

Jerry Rxman Griffin aka MuthaF'er · « **Reply #22 on:** December 16, 2015, 07:43:17 PM »

Is the kick starter prawl in the head?

Jerry Rxman Griffin aka MuthaF'er · « **Reply #23 on:** December 16, 2015, 07:43:51 PM »

Quote from: Bill/BentON Racing on December 16, 2015, 07:32:08 PM

Close, but Bill closer! Cases just love luxuriating baths!

Wash that damn dawg after you get done with the cases!

Bill/BentON Racing · « **Reply #24 on:** December 16, 2015, 08:28:04 PM »

LMAO, He got a bath last week. ...me too!! Hehe.

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Author Topic: Cobra motor disassembly and rebuild (Read 107465 times)