Topic: would you put in a big bore kit and a hot cam if you had the chance?

[b5rider]

I need to replace the pistons on my bike. Should I go for the 600cc big bore kit on eBay?
I also need a new cam. Should I get the one from a 650?

To get 4 new Wiseco pistons would cost $450. The big bore kit is $260. Boring runs around 200, so it's a wash.
A 650 camshaft is running close to $200 (I guess there's a huge market for these!) and a stock is about $60.
I tried to research the forum, but could not find anyone who had both mods installed.

My bike has Uni-pods and a 4-into-1 exhaust.

I usually have a lot of weight attached to the bike, so I could use the extra power.

Any issues expected with reliability ?
Any issues with tuning?

thanks, any info would be helpful

[calj737]

Tews just finished this very similar build. His 605 is running a 650 cam, MotoGP 4:1 and he seems pretty happy with it.

[Don R]

do it,

[mrfish2]

do it,

+1

Then get the head ported by MRieck

[b5rider]

What does porting involve? voodoo? rocket science?

[Davez134]

What does porting involve? voodoo? rocket science?

In my opinion, experience.

[HondaMan]

What does porting involve? voodoo? rocket science?

You could send the head to MRieck..or me..

[SOHC4 Cafe Racer Fan]

Both great resources.  Porting involves the removal of casting imperfections and additional material to increase flow of gases into and out of the head.  It results in the best power gains you can achieve.  A big bore kit and cam will produce the best performance gains in connection with porting the head.

[Old Moe Toe]

What does porting involve? voodoo? rocket science?

You could send the head to MRieck..or me..

I have only heard good about MRieck's head work. However I have also got your book HondaMan and read about how to grind/port the head to get a better flow. Just found the pics in your book a bit ambiguous. No offence intended at all, it's just that it can be sometimes hard to tell from 2 dimensional pictures what is actually going on in 3 dimensions.
When I get round to stripping down my mystery clapped out motor that is in my K2(numbers are way out and match up with no other bike I've seen) I would really  like to have a crack at porting the heads that are in there myself. The description you give in your book when you compare it to glassblown objects  is pretty cool.
I'm an engineering patternmaker by trade so have half a clue about castings. However am also aware you can over cook a goose.
Guess what I'd like to know is what not to do to "overcook" the job?

[Scott S]

 I'm doing a .50 over rebuild with Yoshimura high compression pistons, CB650 cam and home ported/polished head.
 The head work is the big power maker.

[b5rider]

Thanks for the information. I would need more power at the bottom end. I'm not concerned with doing 100 because I will have a sidecar attached

[ekpent]

 A hotter cam may move the power up the rpm band. A big bore kit with a stock cam would give you some needed grunt down low.

[SOHC4 Cafe Racer Fan]

Porting work is not for amateurs. That's why most pro wrenchers take it to people with expertise. I guess you can find out the hard way!

[b5rider]

A hotter cam may move the power up the rpm band. A big bore kit with a stock cam would give you some needed grunt down low.

OK, thanks! Good to know- I can leave the cam stock and go with the big bore kit.

[b5rider]

What does porting involve? voodoo? rocket science?

You could send the head to MRieck..or me..

Would the porting achieve power gains across the entire power band? Can you tailor the porting for lower end grunt?
thanks

[Tews19]

Cal is correct about the 605 kit. I bought the cruzinimage kit for 155 shipped. Had Mrieck do the port and polish. He did bigger valves. I believe in all he did the stage 2. I have the 650 cam. Upon first build I put the gears in wrong but rebuilt the engine again. I've done around 60 miles or so this week and it's a blast. I need to sync the Carb but it was well worth the expense. I have more low end grunt and have yet to really open it up.

If you want to go the easy route get a 650 engine and put it in. 20 percent more HP than a stock 550. Direct bolt in and only weighs 2 lbs more.

[b5rider]

Cal is correct about the 605 kit. I bought the cruzinimage kit for 155 shipped. Had Mrieck do the port and polish. He did bigger valves. I believe in all he did the stage 2. I have the 650 cam. Upon first build I put the gears in wrong but rebuilt the engine again. I've done around 60 miles or so this week and it's a blast. I need to sync the Carb but it was well worth the expense. I have more low end grunt and have yet to really open it up.

If you want to go the easy route get a 650 engine and put it in. 20 percent more HP than a stock 550. Direct bolt in and only weighs 2 lbs more.

Thanks,
I would get a new engine, but there are some other issues out of my control that prevent me from doing too much to this engine. If I blow this engine at some point down the road, I will definitely get a 650 engine!

[FunJimmy]

I would get a new engine, but there are some other issues out of my control that prevent me from doing too much to this engine. If I blow this engine at some point down the road, I will definitely get a 650 engine!

Check around. A used 650 engine could quite possibly cost less than the proposed rebuild. Especially if you're considering port work.

[754]

If you built a manifold to run a single Weber 40DCOE, you would have the low and midrange grunt you need for the sidehack..

[Retro Rocket]

A hotter cam may move the power up the rpm band. A big bore kit with a stock cam would give you some needed grunt down low.

OK, thanks! Good to know- I can leave the cam stock and go with the big bore kit.

Not necessarily, if you are going with bigger pistons you will automatically get more torque, to get the most out of the over bore, use a hotter cam { not necessarily a hot one, if you understand}, remember, most of the cams and carbs on these old bikes were NOT performance parts, they were there for a balance of ridability, price and emissions control. You can still have a reasonable cam and bore and have plenty of usable power. I wouldn't go bigger pistons with a stock cam, it kind of defeats the purpose. Bigger pistons, clean up the inlet ports a reasonable spec cam and jet the carbs and you'll have a nice rideable bike with better power all throughout the rev range.....

[tlbranth]

No

[Don R]

Mine was a 750 but I had the chance and did it. The 650 swap idea sounds good too, the best part is it's proven and reliable.

[b5rider]

A hotter cam may move the power up the rpm band. A big bore kit with a stock cam would give you some needed grunt down low.

OK, thanks! Good to know- I can leave the cam stock and go with the big bore kit.

Not necessarily, if you are going with bigger pistons you will automatically get more torque, to get the most out of the over bore, use a hotter cam { not necessarily a hot one, if you understand}, remember, most of the cams and carbs on these old bikes were NOT performance parts, they were there for a balance of ridability, price and emissions control. You can still have a reasonable cam and bore and have plenty of usable power. I wouldn't go bigger pistons with a stock cam, it kind of defeats the purpose. Bigger pistons, clean up the inlet ports a reasonable spec cam and jet the carbs and you'll have a nice rideable bike with better power all throughout the rev range.....

ok 650 cam back in the running

[MoMo]

No

agree,  with the amount to money one would have to put into the bike I'd just buy a bigger bike...My .02...Larry

[Retro Rocket]

No

agree,  with the amount to money one would have to put into the bike I'd just buy a bigger bike...My .02...Larry

Horses for courses Larry, No one makes old school looking bikes with more power than the old girls stock, besides, anyone can buy a new bike, actually, a lot of our members have both..