Topic: CB550 Vintage Racer

[phillip56]

I'm building a 550 vintage racer for next year (was suppose to be this year - working for a living sucks) and I have a couple of questions regarding engine mods.

I think I'm going to put the 555cc big bore kit that's on ebay in it.  Will a CB500 cylinder block fit in a CB550 engine?  I've got a CB500 engine that's seized and I'd like to use some of the parts from it on another engine that I've got.

Is a CB650 cam going to give me much of an increase in power? Can I use the stock CB550 valve spring with it or should I find improved springs?

The track where I race is more rewarding of better handling so I'm going to replace the swing arm bushings like I've seem in the forum. I've decided the engine should be built for reliability not huge horsepower.

I've looked at past posting and I seem to get lost with all the info.

[Tim.]

I'd try to find another 550 cylinder block - should be easy and cheap.

The 555cc kit on eBay (I've used 2 of them) works out to ~0.5mm over on a 550 engine vs. 3mm over on the 500.  This means you're removing much much less material from the cylinder sleeve, which should be better for you in the long run, especially I would think on a racer.

[bill440cars]

                      Good luck on your build, there's alot of info here from several guys, who could really give
         you a heads-up, and tintin is one of them. I feel like there'll be more responses coming
         when your post has been here just a little longer. I don/t know the regs governing the class that 
         you will be running in, so I won't be of much help. As suggested, you do need to check out
         getting another 550 cylinder block for your build though. Keep us posted, okay?

                                                       Later on, Bill 
   

[hymodyne]

I'm watching this thread as well as I gather parts for a cb500 to 555 upgrade using the overbore kit on ebay. i'm using a 550 top end.
aren't there issues with the lower end of the sleeves in a 550 set of jugs fitting properly into a 500 lower end? I recall reading somewhere that the sleeves are larger than the openings that would usually receive the 500 jugs.

hym

[phillip56]

I've got a another cylinder block for a CB550 so I'll use that.  All I have to do now is to get the time to do all these plans

[crazypj]

Personally I wouldnt waste either time or money on a 0.5mm overbore for 550. get a set of CB750 pistons and bore a 550 block to take them. It works fine, I did at least 70,000 miles on mine although it was getting very tired at the end. (see avatar ) Get a decent cam and electronic ignition which will allow it to rev out.
 Modify CB 750 pistons to close to same weight as 550 ones. I now have a set of 0.50 OS CB750 pistons o fit into the 550 when I get time
PJ

[phillip56]

Any idea of the displacement that a set of CB750 pistons would give?  I'm trying to keep within the limits of the class that I'm going to be racing in.

[isred]

good for you I have been gathering peices for the same thing. are you going to use the 550 swing arm or a erly 750 swing arm? I also have been wondering about a 750 rear hub laced to a gl 1000 rim, but could not find any thing on it. any way are you going with vama? becase you could use the 836 750 kit in the mid waight superbike class. good luck, keep use posted

[Peter]

wouldn't the displacement for the 750 slugs be 605?  isn't that what is given to you in the 605cc overbore kit?

[phillip56]

The class limit is 550 and with a 5% overbore allowance the 555 would still be legal.  I race here in Nova Scotia and we use the VRRA rules for our vintage classes.  I would like to stay within those limits.  I'm actually using a CB500 frame and swing arm. The frame and engine parts were froma scrapped bike my dad had.  I race as well so I decided try something else.  If I had it to do over again I would have bought a race ready bike.  The time required to build a bike was more than I anticipated. 
I've got enough stuff to build dual brakes and I bought a complete dyna ignition system.  I run the stock points in the CB350 and I seem to be setting points all the time so went the electronic igntion.  I've progressive shocks in the back and progressive fork spring in the front.  I can't wait until next year the run the crap out of it.

[crazypj]

Stock CB750 (61mm) gives 591.5 something cc. which keeps you inside the 600cc limit (3.14159 x 30.5 x 30.5 x 50.6 x 4 / 1000 = 591.50673334)
The max oversize CB750 pistons (62mm) give the 605
5% of the 544cc gives 571.2cc, you want CB650 pistons or somehing else at 60mm

PJ

[phillip56]

Will the stock CB650 pistons work in the CB550 cylinder if it is bore?  I guess the question would the height of the pistons be same?

[ryder60]

Good for you.  I can't claim to be an expert on this but I understand the 650 pistons are a different shape than 550s.  They may be dished or something.  I don't know if you can use a 650 cam either.  If you are sticking to the recommended red-line, stock springs will do.

I also think that you are right when you go for reliability over big horsepower.  After all, I think most of us race for the fun.  My 550 has a stock frame with brass swing arm bushings and stock front end springs.  I use Bridgestone BT47 Battleaxes.

When you build something like this I'd recommend that you don't have to go for all the goodies the first year.  It takes more time and money.  My single brake stops me pretty well and I set points.  They are a project for the next off-season.  This off season I have had a set of 550 cylinders machined to take an Action Four's kit made to take a 500 out to 570.  It was weeping oil so I had to take it apart anyway.  I won't put it together until I've worked on the head also.

I had to get Raask rearsets from Omar's.  If you can fabricate something up you'll probably save money.  I've also put in new forks from Frank.

It's a great thing when you've built your own bike, you will feel real good about it.  I've raced a super-motard and a FZR4000 but this thing is a barrel of fun.  Good luck.

[phillip56]

Thanks  Ryder60.  I've been racing for 5 years now.  All on my CB350 that I bought race ready.  I've been using stuff to build the 550 from spares I've collected and stuff that I've gotten from ebay.  Vintage racing is the best.  Everyone seems to understand that Monday morning means that you have to go to work to pay for the habit.  It seems the younger folks that race the modern stuff may forget that at times.  I guess you could call the vintage racing the gentlemans racing.  Can't freaking wait until next race season.