Topic: mystery racing engine

[smacd11]

H750D

[macvit7906]

I'll check the cam for more stamps today.

Sadly I was not able to crack the cases as the countershaft holder under the shift mechanism is completely stuck. JIS impact driver is on the way.

Here is something interesting and another indicator it was raced. The kickstarter shaft was shaved off at the end. Also looks like the splines were ground off and it was lightened?

[Tim2005]

Interesting that the kickstart has had that done to it, as you can also see the electric starter clutch mechanism has been removed from the back of the flywheel too - so it would only have been possible to start the bike by push start or rollers. Makes it rather likely indeed that it was raced.

[slikwilli420]

I'll check the cam for more stamps today.

Sadly I was not able to crack the cases as the countershaft holder under the shift mechanism is completely stuck. JIS impact driver is on the way.

Here is something interesting and another indicator it was raced. The kickstarter shaft was shaved off at the end. Also looks like the splines were ground off and it was lightened?

Did the very same to my race bike. On a race bike, useless weight is just that, useless. I start on rollers, so no need to have that thing sticking out there. Removed the whole ratchet mechanism too.

[macvit7906]

Did the very same to my race bike. On a race bike, useless weight is just that, useless. I start on rollers, so no need to have that thing sticking out there. Removed the whole ratchet mechanism too.

Good to know. Any other changes you would make to your racing engines that I can keep an eye out for here? Essentially I want to figure out what I should change to make this an everyday street bike.

So far I know I want to:
change the pistons, going with a wiseco 836cc kit.
I have to identify this cam to see if it is good for street use - if not. I'll go with a webcam 41. which would then require changing out the rocker arm assemblies.
Change the kickstart shaft back to stock
I think I can keep the lightened alternator rotor.

[PeWe]

RSC (Racing Service Center) was the name of Honda's factory racing parts program.  I am not sure if RSC parts were sold to the general public or not.  If not , you are gonna want to start doing some research on the history of your bike.

Some RSC stuff was available to outside the factory teams, I don't have much detail of it except I know one of my 750s has RSC rods in it that were installed new by a performance shop back in the day. Also there were some RSC parts made for 400Fs, but I don't think there was ever a factory 400F racer.

I wonder what rods this one has?

Interesting. Yeah pistons definitely say RSC. I'll take the washer off the cam and see what we got.

I'm cracking the case today and I'll post some pics. Definitely some nice performance parts in this bike.
Unfortunately, not sure how I could find out anymore history about it. The owner passed away and this was acquired at an estate sale. At first it look like a pile of dust!

Here is the lightened alternator. NICE. Would you guys recommend keeping this for everyday street riding?

Will most likely work fine for street riding and a functional charging system. My K6 has a lightened one that work fine

[PeWe]

Cam card for Norris 750 cams. From a Swedish retailer but the numbers tell their story.
They look a little bit too close. One must have wrong numbers?

[smacd11]

Too bad it doesn't have the H750D specs listed there

[smacd11]

Hey look what I found on another thread!  Not sure why this never came up on all the other searches I did...

[macvit7906]

I removed the washer and bolt from the end of the cam and triple checked for any other markings.

There are no other markings on either end. The only markings around the cam are: D1 and CWC, K134, C1, and A7

Intake lift is coming in at .35" while exhaust is coming in a .345"

I think I might just play it safe and replace the cam with a webcam 41. at that point I should probably replace the rockers and cam cradles as well?

[sixthwisconsin]

I get all you are saying but you might want to consider slowing down and determine what you have first. Is it something worth preserving in current condition and restoring? I don't know but if you just consider financial, it might be worth preserving and either keeping it yourself or selling it for far more than you purchased it for, and buying another bike to do the customization you want.

You're in it for 4 bills so preserving it if it has provenance is the way to go. Sell it off and buy another is what I would do. Just my 2¢.

[macvit7906]

I get all you are saying but you might want to consider slowing down and determine what you have first. Is it something worth preserving in current condition and restoring? I don't know but if you just consider financial, it might be worth preserving and either keeping it yourself or selling it for far more than you purchased it for, and buying another bike to do the customization you want.

You're in it for 4 bills so preserving it if it has provenance is the way to go. Sell it off and buy another is what I would do. Just my 2¢.

Appreciate the feedback, I understand where you're coming from. It's getting restored either way, whether or not to customize becomes a harder decision the more I work on it. Though, the engine has already been so heavily customized, I'm not sure it would be worth preserving, but a perfect customization bike. This is sort of my dream build I've been saving for.

[PeWe]

Hey look what I found on another thread!  Not sure why this never came up on all the other searches I did...

Numbers look very promising on that cam!
Rather high lift and relatively short duration means good response from lower rpm. For street as well as inspired riding

[PeWe]

I get all you are saying but you might want to consider slowing down and determine what you have first. Is it something worth preserving in current condition and restoring? I don't know but if you just consider financial, it might be worth preserving and either keeping it yourself or selling it for far more than you purchased it for, and buying another bike to do the customization you want.

You're in it for 4 bills so preserving it if it has provenance is the way to go. Sell it off and buy another is what I would do. Just my 2¢.

Appreciate the feedback, I understand where you're coming from. It's getting restored either way, whether or not to customize becomes a harder decision the more I work on it. Though, the engine has already been so heavily customized, I'm not sure it would be worth preserving, but a perfect customization bike. This is sort of my dream build I've been saving for.

Good idea to check the engine and sell it as is as an old racer engine. I'm sure people  will be interested.
Or trade it in for a good restored close to stock engine with similar number range if you do not look for more power than stock.

[macvit7906]

I get all you are saying but you might want to consider slowing down and determine what you have first. Is it something worth preserving in current condition and restoring? I don't know but if you just consider financial, it might be worth preserving and either keeping it yourself or selling it for far more than you purchased it for, and buying another bike to do the customization you want.

You're in it for 4 bills so preserving it if it has provenance is the way to go. Sell it off and buy another is what I would do. Just my 2¢.

Appreciate the feedback, I understand where you're coming from. It's getting restored either way, whether or not to customize becomes a harder decision the more I work on it. Though, the engine has already been so heavily customized, I'm not sure it would be worth preserving, but a perfect customization bike. This is sort of my dream build I've been saving for.

Good idea to check the engine and sell it as is as an old racer engine. I'm sure people  will be interested.
Or trade it in for a good restored close to stock engine with similar number range if you do not look for more power than stock.

Definitely. If I crack the case and see that every component has been modified for racing I'll just be preserving it and selling it.
But if it looks like someone just threw some fancy parts on for the hell of it, I'll probably rebuild the way I want it.

[macvit7906]

case is apart! I few things I notice is the kickstart and start motor assembly/gears are completely missing.

The crank looks stock or maybe lightened? but doe not look pork chopped.

All gears are in great shape. looks like maybe an aftermarket shift arm and holders.

Rods look aftermarket. Stamps say "S27f" and "47    /"

[KuangGradeMark11]

RSC (Racing Service Center) was the name of Honda's factory racing parts program.  I am not sure if RSC parts were sold to the general public or not.  If not , you are gonna want to start doing some research on the history of your bike.

Some RSC stuff was available to outside the factory teams, I don't have much detail of it except I know one of my 750s has RSC rods in it that were installed new by a performance shop back in the day. Also there were some RSC parts made for 400Fs, but I don't think there was ever a factory 400F racer.

I wonder what rods this one has?

my understanding is that RSC was the forerunner of HRC and like HRC they had stuff anyone could buy (or at least order then maybe buy) and stuff that they kept for themselves particularly if they were racing that bike themselves:  I read a really interesting article about RC30 engines in World Superbikes in the early days.  It appears not to be on google but it was one of the british gurus (Tony Scott) talking about the various bits they had, could get, and wanted to get.  Fascinating.

[macvit7906]

UPDATE

Hey All. Need some more of your expert opinion.

I noticed a few differences in the crankshaft of the "race" bike compared to a stock crankshaft.

The biggest difference is that the oil collector "balls" seem to have been removed. I've included a picture of the "ball" on the stock crank and the removed ball on this crank. whats your recommendation here? I've heard of a method to tap with crews. Get the crank balanced and lightened? 

Second is there seem to be little grooves cut into some of the counterweights that the stock crank does not have.

The only stamps on the whole crank is one "px"

UPDATE:

Figured it out. after cleaning, oil collectors are already tapped with removable screws!

Alternator rotor came of nice and easy, has RC ENG stamp on it.

[macvit7906]

keep everything in one place!

The mainshaft has 24 teeth and the rest of the gear ratios do not match a super sport at all.
every model here has 18 teeth on mainshaft: http://www.hondachopper.com/engine/fiche_pages/fiche_pages.html


Final drive is 48/56 - super sport is supposed to be 43/50.

If anyone has an info on what mainshaft this is, it would be much appreciated.

[Tim2005]

Can you work out the ratios and see how they compare? If they are closer together than stock it would suggest it may be an aftermarket gearbox, such as a Quaife or Nova, and worth good money to the right people

[macvit7906]

Can you work out the ratios and see how they compare? If they are closer together than stock it would suggest it may be an aftermarket gearbox, such as a Quaife or Nova, and worth good money to the right people

I'll start counting teeth!

At least checking the Nova website, all the 1st gears are 18 teeth on the mainshaft.
http://www.novaracing.co.uk/ProductK0-K8F1-F3HondaCB7505SpeedCloseRatioGearbox.html

[macvit7906]

UPDATE:

With the help of an awesome SOHC forum member, the transmission is a confirmed RSC close ratio racing transmission.

ratios:

24/41
27/38
30/36
30/32
34/31

Definitely happy with the barn find now - anyone interested in these let me know!

[MRieck]

Those rod bolts are not OEM. Have the rod beams been polished. Crank oiling holes have been worked....I'd think it has been balanced after the work performed to it.