Author Topic: A Bike Is Born....750/1000cc (Read 40657 times)

jweeks · « **Reply #25 on:** February 11, 2013, 08:15:29 PM »

Frank and Bill,

Here's the two topics that pretty well cover the 900F stroker cranks.

http://forums.sohc4.net/index.php?topic=82262.0
http://forums.sohc4.net/index.php?topic=54803.0

Frank,
I'd recommend that you get a used 900F crank. They're out there for a hundred or less. Ebay, Craigslist, etc. Have your crank and Bill's crank modified by the same machinist to turn off the snout end (It's relatively soft metal). Giving the machinist a stock 750 crank for dimensions to turn that cut end to match the 750 points housing end. The crank parting line is the same for both cranks (750 and 900). It's a simple lathe job. Doing a second one is very easy as the learning is done on the first one. It would be the cheapest way to get a "drop in" stroker crank. You can store it until you get the other parts/money/time to put it into your motor. If you've got a spare case, you can trial fit the stroker crank to find out where you slightly releave the web below the bearing mounts for counterweight clearance. Yes the crank is a few pounds heavier than the 750 one. If you're on a budget, you clearance for the stock counterweights. As you get more serious, send out the stroker crank for lightening. This will take care of the clearance problems. I use a stock 900F crank in my stroker Hondamatic. I rev it up to 10,500 rpm without problems using stock length CB750 steel rods. There's a lot more little details (including pictures) that the two topics cover well. Bear is also a good source of information on this stuff. I'll be around as always to help.

Jon Weeks

Bill/BentON Racing · « **Reply #26 on:** February 11, 2013, 08:26:18 PM »

Jon,thanks,will be in touch.Bill

dragracer · « **Reply #27 on:** February 11, 2013, 08:32:39 PM »

Thanks again for the crank info Jon. I guess it makes sense for Bill and I to go about this in tandem. I'll be searching a few sites to see if i can pick up a used 900 DOHC crank. I've got a few cases i can play around with and a machinist who likes a challenge.

Bill/BentON Racing · « **Reply #28 on:** February 12, 2013, 05:20:43 PM »

OK,Frank....pay attention!!!!

,It's the start,will post as we go!!!

Pretty simple put the thing on the rt into the thing on the left,just need my BIG hammers!!!

Cost so far $100.00 with shipping for crank.Ebay Frank!!

Bill

dragracer · « **Reply #29 on:** February 12, 2013, 06:18:05 PM »

Quote from: Bill/BentON Racing on February 12, 2013, 05:20:43 PM

OK,Frank....pay attention!!!! ,It's the start,will post as we go!!! Pretty simple put the thing on the rt into the thing on the left,just need my BIG hammers!!! Cost so far $100.00 with shipping for crank.Ebay Frank!! Bill
http://s992.beta.photobucket.com/user/bentonracing/media/TheStart002_zpse3efd169.jpg.html

Bill,

Right after looking at the posts Jon made i was all over Ebay. Found quite a few of the 900F cranks with rods still hangin for under $100. I just won a bid on some 73mm high compression pistons with sleeves. While i didn't intend to do anymore SOHC builds, a potential marriage of the pistons and that 900F crank seems like its going to push me forward kicking and screaming. Kinda wish i had paid closer attention to Kenny's head when i had my hands on it- i doubt i could have it duplicated exactly but straightening out the intake ports like they done is a doable thing for me locally. I suppose i'll just follow along with you in getting the bottom end done with the 900 crank and see where I go from there.

Too many projects but not enough time, money or motivation.

Bill/BentON Racing · « **Reply #30 on:** February 12, 2013, 06:52:18 PM »

K, going to be fun and challenging!

Bill

jweeks · « **Reply #31 on:** February 12, 2013, 07:06:19 PM »

Next step is getting a 900F Hy-Vo chain. I believe that you both will use the same one.

Frank,
You'll start looking for early Goldwing tranny parts to mate that chain with your clutch. The topics previously mentioned covers the modifications needed to mate the parts.

The cam chain is wider than the CB750 ones, so you'll need a way to guide and tension it. You can mix stock 750 parts and 900f guides, make up your own racing one, or contact others who run the Bol D'or cranks to buy/copy what they use.

If I only had the money, I'd be interested in a high straight port head for my efforts. Bill should be also interested as the stock ported heads will limit airflow more than the stuff you have handled. Don't go too crazy as I don't think that you're trying for the 8's... and Bill shouldn't be shooting for 9's....

Just my opinions, welcome others...

Jon Weeks

Bill/BentON Racing · « **Reply #32 on:** February 12, 2013, 07:30:28 PM »

Looked tonight,only used Hy vo primarys on ebay,Going to see if still available from Honda? Bill

jweeks · « **Reply #33 on:** February 12, 2013, 08:16:21 PM »

On Bike Bandit, 1982 900F primary chain is their part number 576276. $129.08 but they won't ship it? I suspect that they can be found. Glad I bought mine several years ago when it was about half the current price....

Jon Weeks

Jerry Rxman Griffin aka MuthaF'er · « **Reply #34 on:** February 12, 2013, 09:08:54 PM »

01 CHAIN, PRIMARY
13610-438-004 DISCONTINUED

Jerry Rxman Griffin aka MuthaF'er · « **Reply #35 on:** February 12, 2013, 09:11:45 PM »

partsnmore

http://www.partsnmore.com/parts/honda/cb900c/?filters%5Bfitting%5D=custom

754 · « **Reply #36 on:** February 12, 2013, 09:17:46 PM »

Is rod journal same size as cb 750?.. And how much stroke ?.. Cuz i got stroker rods here..

Bill/BentON Racing · « **Reply #37 on:** February 12, 2013, 09:22:02 PM »

Yes,6mm!!

Bill

dragracer · « **Reply #38 on:** February 12, 2013, 10:28:54 PM »

Jon, you're right. Not shooting for the 8's. My pockets are not the size of Kenny's nor are my goals as lofty. Just want to see if i can go a bit quicker without spending a ton of money and without nitrous. Its more of the challenge of getting that crank to work as others have. Fortunately with people like yourself who have gone down the path before us, all we need to do is follow, listen carefully and prep correctly. I think you said you picked up 4 tenths??? Now that is a lot. My only issue is your set up seems to require are outboard starter and i would prefer either an onboard or kick starter. Has the onboard/kick starter been addressed with the 900 crank or did i miss this part???

Retro Rocket · « **Reply #39 on:** February 12, 2013, 11:05:17 PM »

If you guys want to know about very quick cb's with 900 cranks then this is the guy..

Rex Wolfenden
T-Rex Racing Developments
3/45 Kolora rd,
West Heidelberg,
Victoria, Melbourne,
Australia 3081.
(03) 94575411

Here's a story on Rex, pretty impressive...

http://www.mctrader.com.au/news-and-reviews/article/articleid/72640.aspx

jweeks · « **Reply #40 on:** February 13, 2013, 04:08:55 AM »

Rex is exactly the kind of guy to talk to about the cam chain tensioning. He'd probably have the cam gear situation also resolved. It's just a question of cost of buying vs making it yourself.

Yes, I dropped from 11.3's to high 10.8's when I stroked my 1080 combination to about a 1180 cc.

The self start or kick start will be some more of a challenge, but it has been done. That end of the 900F crank is splined with a bolt hole in the center. I took the easy way out and went with a welded nut on the mating spline piece with a bolt holding it together. I ran an external starter. I've seen a picture on a topic on here of someone who made a spacer to run the one way starter gear from a stock CB750. It had to be spaced out some to properly align. He used some aluminum stock as a spacer. I'll start looking for it. If anyone else knows of the topic, it would help. As I remember it was used for kick starting the bike. Heck, maybe Rex has already solved that also?

Jon Weeks

bear · « **Reply #41 on:** February 13, 2013, 04:18:12 AM »

Quote from: dragracer on February 12, 2013, 10:28:54 PM

Jon, you're right. Not shooting for the 8's. My pockets are not the size of Kenny's nor are my goals as lofty. Just want to see if i can go a bit quicker without spending a ton of money and without nitrous. Its more of the challenge of getting that crank to work as others have. Fortunately with people like yourself who have gone down the path before us, all we need to do is follow, listen carefully and prep correctly. I think you said you picked up 4 tenths??? Now that is a lot. My only issue is your set up seems to require are outboard starter and i would prefer either an onboard or kick starter. Has the onboard/kick starter been addressed with the 900 crank or did i miss this part???

You can still run the kick starter Frank.
If you are both doing this on a budget I'm your man.

We use a modified 900 cam sprocket and a cam tensioner from a YZF quad bike I think.
Our A motor is on the bench at the moment pics to come.
We are probably going to use a manual tensioner this time around.
Rexy's a lovely fella but you will struggle to get much detail from him.

Cheers,
Brian

dragracer · « **Reply #42 on:** February 13, 2013, 05:14:14 AM »

Quote from: bear on February 13, 2013, 04:18:12 AM

Quote from: dragracer on February 12, 2013, 10:28:54 PM
Jon, you're right. Not shooting for the 8's. My pockets are not the size of Kenny's nor are my goals as lofty. Just want to see if i can go a bit quicker without spending a ton of money and without nitrous. Its more of the challenge of getting that crank to work as others have. Fortunately with people like yourself who have gone down the path before us, all we need to do is follow, listen carefully and prep correctly. I think you said you picked up 4 tenths??? Now that is a lot. My only issue is your set up seems to require are outboard starter and i would prefer either an onboard or kick starter. Has the onboard/kick starter been addressed with the 900 crank or did i miss this part???

You can still run the kick starter Frank.
If you are both doing this on a budget I'm your man.
We use a modified 900 cam sprocket and a cam tensioner from a YZF quad bike I think.
Our A motor is on the bench at the moment pics to come.
We are probably going to use a manual tensioner this time around.
Rexy's a lovely fella but you will struggle to get much detail from him.

Cheers,
Brian

Cheers,
Brian

Bear, i forgot you also had done this conversion. We'll be picking your brain too.

Crap, now what have i gotten myself into-lol.

dragracer · « **Reply #43 on:** February 13, 2013, 05:16:04 AM »

Bear, how is your rig started?? Kick, onboard or outboard???

jweeks · « **Reply #44 on:** February 13, 2013, 05:16:23 AM »

Bear,
I'm not a clutch guy. The automatics use the 900F Hi-Vo chain with that crank. As I read about the previous clutch efforts, the clutch versions use a different length primary chain. What are you using on your motors? I want Frank to get the correct parts! Availability?

Jon Weeks

Bill/BentON Racing · « **Reply #45 on:** February 13, 2013, 05:19:03 AM »

Bear,will be in touch! Bill

Thanks!

bear · « **Reply #46 on:** February 13, 2013, 05:24:08 AM »

Quote from: dragracer on February 13, 2013, 05:16:04 AM

Bear, how is your rig started?? Kick, onboard or outboard???

We use an on board kick starter Frank.

bear · « **Reply #47 on:** February 13, 2013, 05:42:05 AM »

Quote from: jweeks on February 13, 2013, 05:16:23 AM

Bear,
I'm not a clutch guy. The automatics use the 900F Hi-Vo chain with that crank. As I read about the previous clutch efforts, the clutch versions use a different length primary chain. What are you using on your motors? I want Frank to get the correct parts! Availability?

Jon Weeks

I will chase it up tomorrow Jon.
Off the top of my head our two motors run different chains for some reason.

Cheers,
Brian

Syscrush · « **Reply #48 on:** February 13, 2013, 06:36:27 AM »

Subscribed - I don't have a CB anymore, but I love seeing the stuff you experts do with these motors.

bear · « **Reply #49 on:** February 13, 2013, 04:42:56 PM »

Quote from: Syscrush on February 13, 2013, 06:36:27 AM

Subscribed - I don't have a CB anymore, but I love seeing the stuff you experts do with these motors.

Yep that's me I used to be a drip under pressure.
Come to think of it I probably still am.

Cheers,
Brian

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Author Topic: A Bike Is Born....750/1000cc (Read 40657 times)