Topic: CB500 Four - Engine rebuild ideas, please!

[EDU]

I finally took my bike to mechanic today and he said that the engine will need at least some 'refreshment'. I was sort of expecting that (if not worse) from the way it sounds and the smokes it blows... But instead of focusing on the negative, I'll try and remain cool and focus on the positive side of all this: Great opportunity to give the engine a bit more poke!

I was having a look at ebay for some big bore kits but I have no idea of what is good and what isn't... or even what size pistons to order. I met this guy who also rides a CB500 when I refueling the truck (had the bike on the back) and he said his bike has a 605cc big bore kit. It sounded a bit too much but if they're not too expensive then why not...

I was also reading here on the forum about using the 650 cam and I think I'm sold on that! Except I don't know exactly what year model I should look for.

The main idea is to rebuild the engine a bit stronger but I really want reliability!

So if anyone here could help me, my questions are:

-605cc big bore kit, good or bad idea?
-If the above kit is either not recommended or can't be found anymore, what size pistons should I get?
-Are those ebay piston kits any good? They only offer them up to 1mm bigger from I what I saw but if I can't find a big bore kit I might just go for that then and save the money. Not sure if 1mm would even provide any performance advantage though:

http://www.ebay.com.au/itm/HONDA-CB500K-CB500F-1-0mm-57mm-OVERSIZE-PISTON-SET-Four-Pistons-included-/130596527087?pt=Motorcycles_Parts_Accessories&hash=item1e6828dbef


-Last but no least, when shopping for a 650 cam what years should I be looking for?

Thanks for any advices/help and I promise I'll post a lot of pics of whatever I decide to get!

[Retro Rocket]

Once again EDU, talk to Dave500, the 500's can develop some gearbox problems so big kits may be a no no. Don't take that as gospel mate but once again, Dave's your man....

[dave500]

i think your expecting too much too soon,,once the engine is apart and you know what bore its on id just oversize it one step,aswell as have the head gone over,the stock heads can be cleaned up as far as factory casting dags and faults for an improvement,have you ridden this bike much yet,,like for an hour or two,,hows the gear selection?an old smokey engine also reeks of a well used gearbox,,yours might be ok,,it might end up a gear jumper though, if you plan to enhance its power id look at the transmission closely,,this involves a total strip down,,youve already mentioned you dont have much experience or tools,ive taken this into consideration in this reply,,plan A soon becomes plan B and a lot more money if your paying someone else to do the work for you,im thinking just a rebore and head will bring it back to life,,you can use a 650 cam easy enough,not easily found here in australia though.

[EDU]

Cool, thank you both for the input! 

My plan A was to work on the bike 100% myself but since I don't have the space/tools/knowledge to do the engine and do reasonable job, I contacted the guy that works on my race bike and he'll take it from here. He'll only do the engine/gearbox side of things. I'll still have to do the rest (even remove the engine and drop it off to him).

My idea (and please feel free to tell me it is a bad one!!) is to take advantage of having the engine open and then get him to do as much as possible in one go. As I said before, I'm in no rush to have this bike going, so my plan is to start accumulating parts for it and then take it all to the mechanic when I'm ready. If the gearbox turn out to be a problem, I will do my best to get it fixed too!

At the moment, my plan is to start stripping the bike and buy some engine parts for it (hence the questions on the first post). I've planned my budget in a way that I know how much I can spend on each bike every month (race bike/CB500), this way I'm not missing out on track time and the CB project is going ahead as well.

I'm happy with rebore and headwork as dave500 suggested, it'd be cool if it had a bit more poke but what I REALLY want it reliability and ease of maintenance!

List of parts I'm considering to get first:

-New set of pistons/rings/etc (will have to wait till the engine is opened though)
-New set of gaskets
-Dyna Ignition System**
-650cam/tacho gear (not sure what year model to get one from though)




**From what I read I'm not keen on the whole points thing but at the same time I don't know much the Dyna products either. Prices and models seem to vary wildly.

[turboguzzi]

well, you posted in hipo, so  here's some insight from someone who raced a 500

to Retro... K0,K1,K2 might develop wear in one of the shift forks and its unrelated to how much power you put down, just a design flaw. check your shifts forks when the motor is open. if there's a problem, then bad luck because that shift fork is not available anymore and youll have to reweld it. while you are at it, undercut the offending gear. cant remember what gear it is right now, 3rd or 4th

K3's and 550's have improved box

605 is a great idea, will bump up the compression too. doubt if youll feel any difference with a 1mm+ 57 kit other than the fact that its going to be a fresh motor. check dynoman's site, hes got some big bore kits now

other than the solvable gearbox issue, the 500's are quite overengineered, you can almost double the power without much issues.

i do agree with dave that if you are not really handy/experienced, then leave things to someone who is

[MRieck]

well, you posted in hipo, so  here's some insight from someone who raced a 500

to Retro... K0,K1,K2 might develop wear in one of the shift forks and its unrelated to how much power you put down, just a design flaw. check your shifts forks when the motor is open. if there's a problem, then bad luck because that shift fork is not available anymore and youll have to reweld it. while you are at it, undercut the offending gear. cant remember what gear it is right now, 3rd or 4th

K3's and 550's have improved box

605 is a great idea, will bump up the compression too. doubt if youll feel any difference with a 1mm+ 57 kit other than the fact that its going to be a fresh motor. check dynoman's site, hes got some big bore kits now

other than the solvable gearbox issue, the 500's are quite overengineered, you can almost double the power without much issues.

i do agree with dave that if you are not really handy/experienced, then leave things to someone who is

I agree. I'm in the process of building a late model/low mileage one with a 592 JE kit. That thing is stout.

[Bill/BentON Racing]

TG,I believe it was 3rd!Experience!! Bill

[EDU]

well, you posted in hipo, so  here's some insight from someone who raced a 500

to Retro... K0,K1,K2 might develop wear in one of the shift forks and its unrelated to how much power you put down, just a design flaw. check your shifts forks when the motor is open. if there's a problem, then bad luck because that shift fork is not available anymore and youll have to reweld it. while you are at it, undercut the offending gear. cant remember what gear it is right now, 3rd or 4th

K3's and 550's have improved box

605 is a great idea, will bump up the compression too. doubt if youll feel any difference with a 1mm+ 57 kit other than the fact that its going to be a fresh motor. check dynoman's site, hes got some big bore kits now

other than the solvable gearbox issue, the 500's are quite overengineered, you can almost double the power without much issues.

i do agree with dave that if you are not really handy/experienced, then leave things to someone who is

Thank you! I posted on the hipo 'cause if I can get some more hp I'll go for it but like I said, I'll still favor reliability first.

Great info re the gearbox, it seems to be the bike's Achilles heel from what I'm reading. Since the 550 has an improved gearbox, is it possible to use that one instead in case my is toasted?

I just checked dynoman's kit but from what I saw he only has them for the 550's, can they be used on a 500?

Cheers!

[dave500]

as for ignition id have a look at the boyer micro power from gremlin,,it was about 280 delivered,it comes with a pair of high output coils/leads etc,,ive used a few boyer units over the years and i like them,the advance is all in the circuit.,the coils are compact like this,i had to make those little stand off tubes for the mounting bolts,one end is beveled to a 45 degree at the frame end.

the points advance unit is removed.

i silicon the control unit on top of the air plenum,its that blue square just visible behind the carb.

[EDU]

That looks like a really nice setup, thanks for the pictures! I also really liked the paint job on the engine! I'll definitely have a look at the boyer!! What does it compare to in the Dyna line up, just so I can have an idea?

I've been playing some figures and I'll try to keep my engine budget south of 1.5K. If I can do that, I'm happy. I haven't priced everything (even the 'everything' is not clear to me yet) and a lot of what I factored in was based on my experience with modern sportbikes so I'm pretty sure I'm off the mark, just don't know by how much.

I found a piston kit (rings/pins/clips + complete set of gaskets) with 2mm oversize pistons for 360AUD delivered and a big bore kit for over $600... I'm leaning towards the first one atm so I stay within the budget. Also trying to tell myself there's no need for more power since I won't be racing the bike or anything but that's even harder to do!! hahaha

[turboguzzi]

well, you posted in hipo, so  here's some insight from someone who raced a 500

to Retro... K0,K1,K2 might develop wear in one of the shift forks and its unrelated to how much power you put down, just a design flaw. check your shifts forks when the motor is open. if there's a problem, then bad luck because that shift fork is not available anymore and youll have to reweld it. while you are at it, undercut the offending gear. cant remember what gear it is right now, 3rd or 4th

K3's and 550's have improved box

605 is a great idea, will bump up the compression too. doubt if youll feel any difference with a 1mm+ 57 kit other than the fact that its going to be a fresh motor. check dynoman's site, hes got some big bore kits now

other than the solvable gearbox issue, the 500's are quite overengineered, you can almost double the power without much issues.

i do agree with dave that if you are not really handy/experienced, then leave things to someone who is

Thank you! I posted on the hipo 'cause if I can get some more hp I'll go for it but like I said, I'll still favor reliability first.

Great info re the gearbox, it seems to be the bike's Achilles heel from what I'm reading. Since the 550 has an improved gearbox, is it possible to use that one instead in case my is toasted?

I just checked dynoman's kit but from what I saw he only has them for the 550's, can they be used on a 500?

Cheers!

it would work on a 500 too but at +4mm you'd need to resleeve, getting a used 550 cyl block and boring it would be cheaper IMHO

the cases in the 550 are different, the gear cluster will not fit in 500 cases,

 

[dave500]

i have a good 550 barrel bored to 61mm i wont be using,i have it advertised in just bikes for $100,yours for $50.

that makes them about 590cc

[EDU]

Interested!  Let me just see if I can find pistons and etc to go with it!

[dave500]

these are bk performance pistons CB/XL125 to 150cc big bore and use a one piece oil ring,he still has piston sets and the head gasket for these,61mm 750 pistons can be used aswell,i think the crown has to be machined down a little

[Kemp]

You can't put a 550 cylinder block on a 500 unless you widen the top cases to accept the larger sleeve. That is a machine shop job and you'd need to split the cases. Otherwise look for an old Powroll big bore pkg for the CB500 as they came with larger sleeves that had the OD of sleeve turned down to fit the 500 cases, or you could just pull the sleeves from a 550 and mill down each cyl sleeve to fit the 500 cases and then just pop em back in the cyl block