Author Topic: Cobra motor disassembly and rebuild (Read 109918 times)

Bill/BentON Racing · « **Reply #450 on:** July 08, 2016, 02:55:37 PM »

We'll see. I bet you that Pace bike had wheelie bars and dual Webers! And a distributor or magneto! And quite possibly a stroker. Don't matter, we'll see what we can do soon enough. Putting this on also. So close, stay tuned.

gschuld · « **Reply #451 on:** July 08, 2016, 03:44:34 PM »

Well, the record states the displacement at 1162 for the Pace 11/74 A/A record, so yes, sounds like a stroker motor to me unless it had some huge sleeves and pistons shoved in there somehow.

George

Bill/BentON Racing · « **Reply #452 on:** July 08, 2016, 04:41:52 PM »

Yo, last time I did the math, it took a 73.75mm piston to hit 1080. Someone please do the math for 73, 73.25, 73.50 and 73.75mm's, thanks. I think when I said it was 1062 at 73mm, Medyo said that was 1054. Thanks, Bill
I'm driving, lol.

Jerry Rxman Griffin aka MuthaF'er · « **Reply #453 on:** July 08, 2016, 06:36:24 PM »

Billy, I like that starter clutch holder!

MCRider · « **Reply #454 on:** July 09, 2016, 06:20:43 AM »

Quote from: Bill/BentON Racing on July 08, 2016, 04:41:52 PM

Yo, last time I did the math, it took a 73.75mm piston to hit 1080. Someone please do the math for 73, 73.25, 73.50 and 73.75mm's, thanks. I think when I said it was 1062 at 73mm, Medyo said that was 1054. Thanks, Bill
I'm driving, lol.

http://www.nightrider.com/biketech/calc_displacement.htm

Medyo Bastos · « **Reply #455 on:** July 09, 2016, 06:39:00 AM »

70mm + 69mm stroke

gschuld · « **Reply #456 on:** July 09, 2016, 07:19:55 AM »

Technically, a 73mm bore would need a 69.3mm stroked crank to make 1162cc. Basic RC welded stroker crank/73mm combination. This is reportedly the same bore/stroke as used on the 1975 Byron Hines built Pro Stock Honda.

For reference:

Standard 63mm stroke.

70mm. 970cc
71mm. 998cc
71.25mm 1005cc
72mm. 1026cc
73mm. 1055cc
73.73mm 1076cc

George

Bill/BentON Racing · « **Reply #457 on:** July 09, 2016, 12:35:40 PM »

Cool, so Cobra Girl is 1055, Frank's is 1026cc, pretty close, Just got through taking a little over 2lbs off the bike and especially the crank! K, Thanks George Schuld and Mike Rieck and Master Zin the balancer! K, Bill

MRieck · « **Reply #458 on:** July 09, 2016, 01:16:08 PM »

Can't get that piece much lighter than that Bill. Frank has one too.

dragracer · « **Reply #459 on:** July 09, 2016, 03:53:33 PM »

Quote from: MRieck on July 09, 2016, 01:16:08 PM

Can't get that piece much lighter than that Bill. Frank has one too.

Quote from: MRieck on July 09, 2016, 01:16:08 PM

Can't get that piece much lighter than that Bill. Frank has one too.

Yes, I've got one thanks to George. Not quite as light as Bills but its a bare bone piece. Plan to use it on the motor for the project bike. I may need some head work soon Mike. Trying to salvage an old K model head.

gschuld · « **Reply #460 on:** July 09, 2016, 04:37:21 PM »

Actually Frank, yours is JUST like Bills. Perhaps yours didn't arrive yet...

George

dragracer · « **Reply #461 on:** July 10, 2016, 12:10:42 AM »

Quote from: gschuld on July 09, 2016, 04:37:21 PM

Actually Frank, yours is JUST like Bills. Perhaps yours didn't arrive yet...

George

Didn't realize the one you sent me months back had lightening holes. I had a birthday since then so excuse my feeble mind - play tricks on an old man sometimes.

gschuld · « **Reply #462 on:** July 10, 2016, 03:06:31 AM »

Frankie,

The first one was CLEARLY just a modest first effort

. No holes in that one. I got a little out of hand with the pair of "holey" ones.

George

MRieck · « **Reply #463 on:** July 10, 2016, 06:10:24 AM »

Bill's went Priority...Frank went out a slower rate as it was just a small box. Bill's had some other parts in it too.

Bill/BentON Racing · « **Reply #464 on:** July 10, 2016, 06:35:07 AM »

Some other parts......

, LMAO! Yes , it did! Hehe, Bill

gschuld · « **Reply #465 on:** July 10, 2016, 07:14:46 AM »

Quote from: MRieck on July 10, 2016, 06:10:24 AM

Bill's went Priority...Frank went out a slower rate as it was just a small box. Bill's had some other parts in it too.

Ok, cool thanks again Mike

George

Jerry Rxman Griffin aka MuthaF'er · « **Reply #466 on:** July 10, 2016, 07:51:20 AM »

Are you guys cutting down rotors or are you turning these from lightweight aluminum?

POPS 911 · « **Reply #467 on:** July 10, 2016, 08:43:20 AM »

Frank got two batteries I think, and Bill with a big cut on his head and special pistons he might need two and your right leg will take a beating self starting a ST/ET SOHC 750. Looks to me like the Blinkster [ BLINKSTAR ] will be the new number for SEL ................. 10 flat.

gschuld · « **Reply #468 on:** July 10, 2016, 10:06:50 AM »

Quote from: Jerry Rxman Griffin aka MuthaF'er on July 10, 2016, 07:51:20 AM

Are you guys cutting down rotors or are you turning these from lightweight aluminum?

Started out as factory late model rotors.

George

cbr954 · « **Reply #469 on:** July 10, 2016, 10:41:10 AM »

I did something similar but didn't go as extreme. I have since made a lighter one but dont have a photo. Been using it for a while now, nice to have a quick reving motor but still have a push button to start. 13:1 kills my leg to try and kick it, especially when hot.

Bill/BentON Racing · « **Reply #470 on:** July 10, 2016, 01:58:03 PM »

+1, LMAO, my days of kicking....will prolly be slim, Purple Rain is still kick only, Just fired the "Beast" up with lighter rotor, haha, soon as it cranked you could tell it revved quicker! K,.

dragracer · « **Reply #471 on:** July 11, 2016, 07:55:02 AM »

Quote from: POPS 911 on July 10, 2016, 08:43:20 AM

Frank got two batteries I think, and Bill with a big cut on his head and special pistons he might need two and your right leg will take a beating self starting a ST/ET SOHC 750. Looks to me like the Blinkster [ BLINKSTAR ] will be the new number for SEL ................. 10 flat.

Pops, my F model is kick start only. You might be thinking about my Crazy 8’s KZ. It’s a 1325, 13.5:1 engine so I had to have 24 volts to crank it up.

In respect to my F model, it’s somewhat crossbred in the fact that the pistons are for a K model but the head is an F2 head with the larger combustion chamber. In essence, the pistons do not fill the chamber like Bill’s 1080 since he has a matched K head and piston set. Think of it as putting a J model head on top of a set of KZ pistons. The J model head has a large combustion chamber, but even high compression KZ pistons won’t fill the chamber enough to get the compression up. Even by milling the head to get to closer to the KZ pistons, it won’t help to optimize the better flowing head until you get the right pistons to match the chamber. That’s the scenario I’m working from on my current package. Bottom line, Bill’s matched parts should net much more compression and a lot more horsepower and torque than my engine. As a result, his engine should be capable of 10.0’s. The dilemma is, the total package including bike has to be set up correctly to put that power down on the drag strip. In addition, the rider has to be able to fully utilize the overall package to produce a low ten second time slip. I don’t feel this engine will get into the 9’s without being placed into a properly set up wheelie bar bike chassis- unless you put a 120lb experienced rider in the seat.

POPS 911 · « **Reply #472 on:** July 11, 2016, 10:21:00 AM »

Tuning lesson this past weekend : Racer has a 1150 base Suzuki motor, lockup and a air trans brake = run 9.40...... I st. pass he went nowhere and pulled thru the lights on the 2 step and I asked did you touch anything since last race

Yes in his hopes to go faster he add a spring to the clutch and with a 7000 chip in the two step it pulled thru the line lock. My fix to him why 7000 chip for two step = seems high, put in a 5500 chip two step and a 10,000 rpm auto shift up from 9500 and he ran 9.16 and the best 1.2 60ft time he ever had in 1320 and this guy is a wrench spinner. Lesson learned in drag racing motorcycles is balance....... he complained about MPH NOT AS HIGH and I ask him do the pay for MPH or WIN TICKETS !!!!!

dragracer · « **Reply #473 on:** July 11, 2016, 12:55:45 PM »

Quote from: POPS 911 on July 11, 2016, 10:21:00 AM

Tuning lesson this past weekend : Racer has a 1150 base Suzuki motor, lockup and a air trans brake = run 9.40...... I st. pass he went nowhere and pulled thru the lights on the 2 step and I asked did you touch anything since last race Yes in his hopes to go faster he add a spring to the clutch and with a 7000 chip in the two step it pulled thru the line lock. My fix to him why 7000 chip for two step = seems high, put in a 5500 chip two step and a 10,000 rpm auto shift up from 9500 and he ran 9.16 and the best 1.2 60ft time he ever had in 1320 and this guy is a wrench spinner. Lesson learned in drag racing motorcycles is balance....... he complained about MPH NOT AS HIGH and I ask him do the pay for MPH or WIN TICKETS !!!!!

No doubt that proper tuning is important on a bar bike. Leaving harder doesn't always net the best results as I learned a long time ago.

So true about the MPH. I see so many people get caught up in that number its crazy. When I see high mph, it usually indicates a crappy short time. That's why when my mph increased this season I paid close attention to my time slips and sure enough, my 60' and 660' times dropped off.

POPS 911 · « **Reply #474 on:** July 13, 2016, 04:07:27 PM »

Bill: How did the dyno pulls go this past Friday with [ PACE or RC COBRA head ] ? Their is a guy who has a HARLEY shop near my home with a DYNO he has not used in the past so I will stop by his shop and ask if he wants to pass it on for a fair price [ I mean a low price ] could be a tool for you to learn to run and tune your many race bikes. In the PRO-STAR days MSP brought their own dyno in the big double stack trailer and made cash dollars night and day. I would like to see your Yellow turbo Hondamatic SOHC750 make passes in 2016.......

News:

Author Topic: Cobra motor disassembly and rebuild (Read 109918 times)