500cc CB77 Conversion - starting and reference points?

LOUD MOUSE · Post by **LOUD MOUSE** » Mon Jan 05, 2009 6:48 am

You are correct about the works inside the engines. Lots of cutting, welding and machining with every part.
I have pics which show machine rework which is a work of art.
J. ask I not share them because there is many hours of design time and work that makes the engine what it is and can do.
Talked to J. Saturday and he and Mandy will start the new season in a couple of weeks.
I'm sure they will do well again. ..............................lm

305racer wrote:I kinda figured thats what you were shootin for when I noticed the AUS in your screen name. LoL Since the cutoff date is '62 you could get away with using a modified 450 head that would mimic the CR72/77 ,no?
I have seen pictures of Mandy Beales('08 Jnr.champ) racing the 350 & 500cc and have often wondered what the inside of the 500cc engine must look like. That has got to be one helluva labor intensive set of pieces. Also curious about the frame as it looks like a CR wonder if it is real or a repro?

L.M. you got anymore insight/info into this?

Ausracer · Post by **Ausracer** » Mon Jan 05, 2009 5:06 pm

Indeed, I have no doubt that the internals no longer look anything like a cb77/72.

I will try to catch Jerry when I see him throughout this season, but surely there are others out there who have done this conversion and may be willing to share/provide some guidance? A few points of reference would be very useful and ultimately more productive I think. If there are a number of 500s existing today, there would have been dozens back then............... worth searching for the original info!

Cheers - the search continues.

LOUD MOUSE · Post by **LOUD MOUSE** » Tue Jan 06, 2009 8:53 pm

Tis a little back in the discussion as to engine mods and frame work however here ya can see a small view of how Jerry K. in AUSTRALIA starts a real and competitive GP racer.
I'm told to look for a couple of articles about this and more of this sort of engineering with the his bikes with pics.
Thanks for sharing J. .....................lm

Ausracer wrote:Hi All,

Thanks for the replys so far. There are a number of examples of people converting the 305 into a 500cc, through various means including modifications to stroke length and bore size. All are radical changes involving the manufacture of special parts. Very exciting stuff. There is one for sale on this site that looks the goods.... hoping to hear from the seller??

As the idea is to use it for vintage racing, the bike components must stay within period - this does not include the internals though!

Cheers.

LOUD MOUSE · Post by **LOUD MOUSE** » Tue Jan 06, 2009 10:51 pm

This is a rare pic of a 6 speed trans installed (with many mods to all case demotions) of the HONDA early 250/305 HONDA engine cases which as ya can see isn't a "Just put it in There" application. Thanks again J. ................emo

LOUD MOUSE wrote:Tis a little back in the discussion as to engine mods and frame work however here ya can see a small view of how Jerry K. in AUSTRALIA starts a real and competitive GP racer.
I'm told to look for a couple of articles about this and more of this sort of engineering with the his bikes with pics.
Thanks for sharing J. .....................lm

Ausracer wrote:Hi All,

Thanks for the replys so far. There are a number of examples of people converting the 305 into a 500cc, through various means including modifications to stroke length and bore size. All are radical changes involving the manufacture of special parts. Very exciting stuff. There is one for sale on this site that looks the goods.... hoping to hear from the seller??

As the idea is to use it for vintage racing, the bike components must stay within period - this does not include the internals though!

Cheers.

305racer · Post by **305racer** » Wed Jan 07, 2009 12:23 am

Let me take in these 2 picts for a few days and I'll get back to ya. LoL

bfd402 · Post by **bfd402** » Wed Jan 07, 2009 8:34 am

Wow LM, those are some hot photos
looks like maybe a little material taken off the crank?
These kind of topics really excite me. I just got my race bike completed last August (my first CB77) and got a couple of races in before the end of the season (one was Barber). My motor is bone stock and seems to run well, but it smokes a little. I'm slowly trying to gather enough good parts to build another motor.
I'll keep checking on this section for more info and inspiration!
I appreciate all the time and effort folks put into building these gorgeous restorations but it's the race bikes that truly excite me.
bfd

Ausracer · Post by **Ausracer** » Wed Jan 07, 2009 5:30 pm

Yes, thanks for the enthusiasm everyone and LM for the pics.

I agree with the last post, it is the making a bike go as fast a possible through whatever means required that interests me. I have just completed a 350K4 racer (if they are ever really completed!) - the one thing I have learned is you may as well just buy a set of engine cases with a gearbox (to get you started!) for a race project - every other engine component will be removed/replaced/modified/destroyed in some way - the purists would be horrified, but the "gods of speed" love it.

But hey, thats what its all about!

The gearbox looks very close to the K4 five speed, including the clutch. But then again, most period Honda boxes look the very similar.

Great to see this thread really moving now. I am really interested to determine what bore and stroke has been used successfully in this conversion.......... I figure just about everything else can be figured out on the fly during development - but the basics must be right! will keep looking and post anything I find out of course!