Author Topic: Another CR750 win... (Read 14582 times)

turboguzzi · « **Reply #25 on:** October 23, 2012, 03:23:22 PM »

just a sec guys.... bike won its up to 1969 class, but look at the lap times..... a best of 2:01 against many guys in 1:56-1:57 from the up to 1980 class. Hats off to them but dot think a sohc750 can win a current Biker's Classic race or an Imola 200 against the Zeds, GS or GSX or big Guzzis for that matter

guess they run a really solid race, no mishaps or breakdowns and then at best, you can be close to a podium just not quite on it. In classic racing riders counts more than the bike, sure, but overall a great sohc is still going to be quite a few seconds slower than a top DOHC / 16 valver, ex GP rider or not.

Alex, I am still waiting to hear about those top fairings

Darvill Racing · « **Reply #26 on:** October 23, 2012, 04:14:10 PM »

Evening....
I haven't forgotton about the fairing, I have one in the workshop now (been as there since the Manx GP to be honest just been Sooo busy I handling gotten round to taking a phot for you), I will take a photo tomorrow and post it on here for you ;o)

Regards,
A

Retro Rocket · « **Reply #27 on:** October 23, 2012, 05:37:12 PM »

Quote from: turboguzzi on October 23, 2012, 03:23:22 PM

just a sec guys.... bike won its up to 1969 class, but look at the lap times..... a best of 2:01 against many guys in 1:56-1:57 from the up to 1980 class. Hats off to them but dot think a sohc750 can win a current Biker's Classic race or an Imola 200 against the Zeds, GS or GSX or big Guzzis for that matter

guess they run a really solid race, no mishaps or breakdowns and then at best, you can be close to a podium just not quite on it. In classic racing riders counts more than the bike, sure, but overall a great sohc is still going to be quite a few seconds slower than a top DOHC / 16 valver, ex GP rider or not.

Alex, I am still waiting to hear about those top fairings

TG, have a look at the link that i posted in Alex's post, that 750 {915cc}is setting lap records against much bigger 1000cc + superbikes from the late 70's early 80's and some much more modern bikes as well....

It is one very quick Honda SOHC, Mike Rieck can fill in more detail than I...

Darvill Racing · « **Reply #28 on:** October 23, 2012, 11:49:23 PM »

As promised....
Pic 1 front shot

Darvill Racing · « **Reply #29 on:** October 23, 2012, 11:51:20 PM »

And a side shot.......

Regards,
A

voxonda · « **Reply #30 on:** October 24, 2012, 01:44:16 AM »

Quote from: turboguzzi on October 23, 2012, 03:23:22 PM

just a sec guys.... bike won its up to 1969 class, but look at the lap times..... a best of 2:01 against many guys in 1:56-1:57 from the up to 1980 class. Hats off to them but dot think a sohc750 can win a current Biker's Classic race or an Imola 200 against the Zeds, GS or GSX or big Guzzis for that matter

guess they run a really solid race, no mishaps or breakdowns and then at best, you can be close to a podium just not quite on it. In classic racing riders counts more than the bike, sure, but overall a great sohc is still going to be quite a few seconds slower than a top DOHC / 16 valver, ex GP rider or not.

Alex, I am still waiting to hear about those top fairings

A bit apples and oranges. Just look at the engine sizes of those DOHC/16 etc. Take it down to the same size and see what happens. Agree that within current rules it is hard to really compete them. But maybe if the races would be longer..................

turboguzzi · « **Reply #31 on:** October 24, 2012, 11:23:43 AM »

Quote from: Darvill Racing on October 23, 2012, 11:51:20 PM

And a side shot.......

Regards,
A

pm sent alex...

voxonda · « **Reply #32 on:** October 24, 2012, 12:47:44 PM »

Quote from: voxonda on October 24, 2012, 01:44:16 AM

Quote from: turboguzzi on October 23, 2012, 03:23:22 PM
just a sec guys.... bike won its up to 1969 class, but look at the lap times..... a best of 2:01 against many guys in 1:56-1:57 from the up to 1980 class. Hats off to them but dot think a sohc750 can win a current Biker's Classic race or an Imola 200 against the Zeds, GS or GSX or big Guzzis for that matter

guess they run a really solid race, no mishaps or breakdowns and then at best, you can be close to a podium just not quite on it. In classic racing riders counts more than the bike, sure, but overall a great sohc is still going to be quite a few seconds slower than a top DOHC / 16 valver, ex GP rider or not.

Alex, I am still waiting to hear about those top fairings

A bit apples and oranges. Just look at the engine sizes of those DOHC/16 etc. Take it down to the same size and see what happens. Agree that within current rules it is hard to really compete them. But maybe if the races would be longer..................

Can always build something like this:

At least they made an effort and put Honda on the way to RCB's. Piper with DOHC head and 16 valves in Piper frame.

Darvill Racing · « **Reply #33 on:** October 24, 2012, 01:17:50 PM »

Yossef - PM Sent

Rob,
Like the idea but what would be the effort involved to graft a DOHC onto the SOHC..?
Is it worth it?

Regards,
A

voxonda · « **Reply #34 on:** October 24, 2012, 02:06:28 PM »

Effort would be enormous and imho not worth doing since there are so many bikes to choose from nowadays, but back then................ We all know the cylinderhead is the limiting factor for the 750.
But then again, why not stay with the old girl as she is and give her a good makeover? She always got the job done and may not be a winner but to look how far she could come is a challenge. I for one have seen enough Kawi, Suzi's and even Guzzi. Just take a good look at this beasty:

Laverda 1000 from Gijs van Dijk. No winner anymore but it is a stunner.

Darvill Racing · « **Reply #35 on:** October 24, 2012, 02:19:43 PM »

Agree Rob,
Something different and unique is the way forward.....

NickO · « **Reply #36 on:** October 24, 2012, 02:29:22 PM »

Quote from: voxonda on October 23, 2012, 02:17:53 PM

The guys on the MotoBel Guzzi know how to corner...... And sure would like to know what engine they use???
Carry a lot of speed out of corners onto the straights too.
Thinking of maybe 100 rwhp, depending on engine size. Does not seem too much but need to keep it in one piece. Good streamline would help too. Look at this bike as example:

Cheers, Rob

Bloody hell thats the road where I live on the side of that van!

simon#42 · « **Reply #37 on:** October 24, 2012, 04:22:24 PM »

i live in the road just behind the old shop , it was the old garage that is now does gearbox repairs just past jehrico lane nick. pity bill smith was never quite as streamline as that bike .

Tintop · « **Reply #38 on:** October 24, 2012, 05:24:28 PM »

Quote from: Darvill Racing on October 24, 2012, 01:17:50 PM

Yossef - PM Sent

Rob,
Like the idea but what would be the effort involved to graft a DOHC onto the SOHC..?
Is it worth it?

Regards,
A

The Piper head was made for the SOHC, and not a plug and play. Denis Curtis did one for a customer to go into one of his mono shock frames back in the 70's. Story is near the bottom of the page - http://curtisracingframes.com/articles.html

754 · « **Reply #39 on:** October 24, 2012, 07:36:05 PM »

I ran into the guy that had the Piper,it was a sandcast. He passed on a few years back..Jim Brokenshay, think was the name..

johno · « **Reply #40 on:** October 24, 2012, 08:45:12 PM »

Boys !
racing Honda SOHC was so competitive in the 70's that what ever a human mind could dream up was tried. In addition to that there were ideas generated from folks while dropping tabs and smoking joints that far exceeded the average race engineers capabilities. Makes it difficult to come up with some new angle on how to pass those Z's .

Remember the SOHC was designed as a touring bike, when the other marques seen how Honda sales were going they had the luxury of a bench mark set by Honda to to provide superior engineered engines... and in turn Honda to them a bit later and so on.

Mind you that is the challenge I dream about, revenge on the Z,s

I also appreciates Robs angle on endurance racing, be there at the end and opportunities happen. A personal example of that was in the early 70's I raced in the Australian TT ( we had no GP then) and out of a field of approx 50 bikes my CB750 K2 was the only production bike in the race. There were two heats and the first 12 from each heat went into the TT for a field of 24 starters.
In the heat I just road around casually thinking it was fun, , lots of blokes crashed and lots blew up, walla I finished in 12th and went to the final. On the start grid I ended up on the second row directly behind Murray Sayles works Kawasaki 750 and Greg Hansford on a smaller works 250 and a works Suzuki 500 ridden by an American bloke and vividly recall the starter Glen Dix walking up to and say " are you meant to be out here?" we both laughed ! as a result of the ol hare and tortise philosophy I rode around, more crashes and blow ups saw me finish 12 th in the OZ TT on a production road that I used to ride to work.

So endurance racing lends itself to reliability and conservatism , regarding the power required on the solidworks program I have the hi port flowing around 90 CFM at 10 inchs, using max valve lift at .500 .
If any of you machining gurus can stop the valve interference encountered trying to achieve that lift you would be in a good position to have a competative SOHC engine for the endurance scene.
The only two options I am thinking of is different cam lobed inlet to exh, and slightly offsetting the exhaust valve. Hell Rob your a machining guru, get your teeth into that. If you want to talk horsepower with 90 cfm avaiable I'll do a computer engine up with what ever bore and stroke you nominate and post the graphs.

cheers Johno

voxonda · « **Reply #41 on:** October 25, 2012, 03:45:57 AM »

Thanks Johno,

IMO you're right about the story of the SOHC concerning being a tourer and not designed as a racebike. To give sales a boost they entered Daytona with the known outcome! But even the factory bikes could not match the competition aftere that. But in Endurance it was a different story, Too high powered engines did not go the distance. Engine wise, like you said, all has been done and tried. Sometimes one has to live with what one got. The design of the cylinderhead will be the limiting factor. Would be a great to do something like that but for what? Speaking for myself, riding in (demo) classic endurance do not have the need for BIG power numbers driveability is much more important. Having visited a lot of classic(?) endurance races and see the effort put in it to win it would be like dragging a dead horse............1062cc 16V DOHC with 160 RWHP! No way we can ever match that with our beloved lady.

Cheers mate,

Rob

Bill/BentON Racing · « **Reply #42 on:** October 25, 2012, 09:22:28 AM »

That's why I parked the Yoshi kitted CB500/550 in '87 and bought a 600 Hurricane! Can't beat 'em,join them!

Bill

voxonda · « **Reply #43 on:** October 25, 2012, 11:00:49 AM »

Will not do that Bill. Try my best to beat them but know it's a lost cause. But will definitely not let her go, so will probably struggle on forever.....................................

Cheers, Rob

jweeks · « **Reply #44 on:** October 25, 2012, 12:49:17 PM »

The 900F DOHC crank, cylinder block, and head can be used with SOHC cases. Some of the challenges include reworking the cases for the DOHC cylinder stud pattern. The bore centers are identical. Since I wouldn't trust welding on the cases to hold new location cylinder studs, I'd think about a spacer/adapter on top of the case half. Other topics in this forum have covered big cc CB750 motors. Since you can stroke a 900F crank another 3 mm in some cases, you'd have a 4.5 mm spacer to fit everything in. Could that spacer be the adapter plate for the revised cylinder stud pattern? There would still be the need for some welding and grinding to handle the wider opening for the 900F cam chain. If you went for more stroke, a custom length cam chain would be required. The Hi-Vo primary chain would require some Goldwing clutch parts. It can be done. The 900F crank would need a diet. It's a heavy crank. The DOHC cylinder head wasn't that great as DOHC heads go. You can't rev them that much higher since they run out of air much sooner than more modern heads. It's still on my bucket list to do ...

Jon Weeks

Retro Rocket · « **Reply #45 on:** October 25, 2012, 02:24:20 PM »

Quote

The 900F DOHC crank, cylinder block, and head can be used with SOHC cases.

Rex Wolfenden {TRex racing} has been racing SOHC's with 900f cranks for years now very effectively, he has some very fast championship winning Sohc's....

simon#42 · « **Reply #46 on:** October 25, 2012, 02:34:02 PM »

Quote from: JWEEKS on October 25, 2012, 12:49:17 PM

The 900F DOHC crank, cylinder block, and head can be used with SOHC cases. Some of the challenges include reworking the cases for the DOHC cylinder stud pattern. The bore centers are identical. Since I wouldn't trust welding on the cases to hold new location cylinder studs, I'd think about a spacer/adapter on top of the case half. Other topics in this forum have covered big cc CB750 motors. Since you can stroke a 900F crank another 3 mm in some cases, you'd have a 4.5 mm spacer to fit everything in. Could that spacer be the adapter plate for the revised cylinder stud pattern? There would still be the need for some welding and grinding to handle the wider opening for the 900F cam chain. If you went for more stroke, a custom length cam chain would be required. The Hi-Vo primary chain would require some Goldwing clutch parts. It can be done. The 900F crank would need a diet. It's a heavy crank. The DOHC cylinder head wasn't that great as DOHC heads go. You can't rev them that much higher since they run out of air much sooner than more modern heads. It's still on my bucket list to do ...

Jon Weeks

jon i hope you live a very long time ! that little lot would seem a long and pointless exercise .

lordmoonpie · « **Reply #47 on:** October 29, 2012, 06:00:02 PM »

Quote from: JWEEKS on October 25, 2012, 12:49:17 PM

The 900F DOHC crank, cylinder block, and head can be used with SOHC cases. Some of the challenges include reworking the cases for the DOHC cylinder stud pattern. The bore centers are identical. Since I wouldn't trust welding on the cases to hold new location cylinder studs, I'd think about a spacer/adapter on top of the case half. Other topics in this forum have covered big cc CB750 motors. Since you can stroke a 900F crank another 3 mm in some cases, you'd have a 4.5 mm spacer to fit everything in. Could that spacer be the adapter plate for the revised cylinder stud pattern? There would still be the need for some welding and grinding to handle the wider opening for the 900F cam chain. If you went for more stroke, a custom length cam chain would be required. The Hi-Vo primary chain would require some Goldwing clutch parts. It can be done. The 900F crank would need a diet. It's a heavy crank. The DOHC cylinder head wasn't that great as DOHC heads go. You can't rev them that much higher since they run out of air much sooner than more modern heads. It's still on my bucket list to do ...

Jon Weeks

Well I didn't use a 900 Dohc head but did all the rest in my cr750 build with the Foch crank so it's all very possible. It had a lightened balanced crank, custom rods, custom cam and primary hyvo chains, custom tensioner a for both, reworked cam gain tunnel and custom cam sprocket alongside the gl1000 mods to the primary drive gear. All works a treat so with the 900 dohc head and reworked stud holes I reckon a grafted 900 dohc head is not too much of a stretch.....

fang · « **Reply #48 on:** December 07, 2012, 11:26:02 AM »

Quote from: cb1100rb on October 23, 2012, 02:04:38 AM

This is a very lovely machine, cb1100rb. Is it yours?

-fang

turboguzzi · « **Reply #49 on:** December 08, 2012, 02:03:04 AM »

Good morning fang

that's guy bertin's bike, see first post in the thread

News:

Author Topic: Another CR750 win... (Read 14582 times)