Topic: Change of plans

[nitrofish1]

OK so I was planning on boring out my honda to an 849, getting porting done, the works, but my wallet has decided otherwise. Is the git kit from Cycle X with the new valve springs and cam going to still give me good power? Or is the full kit with the valve guides and super flow valves a better choice? Still planning on running 4-1 exhaust on it. Just decided not to spend quite so much on the engine, as the cost approaches a whole other faster motorcycle....

Or even just rebuilding the engine with new gaskets and 4-1 exhaust still good enough? I was told that the valve springs are weak on these motors and that I should replace them, as they can free up alot of power.

[turboguzzi]

define good

[nitrofish1]

define good

I guess 'good' to me would mean at least 70hp or so, or at least a somewhat noticeable amount above stock.

Also other question, is the "adjustable cam sprocket" really "free horsepower" as its labeled?

[Jerry Rxman Griffin aka MuthaF'er]

The valve springs are adequate UNTIL you miss that one power shift from 1 to 2 and it floats a valve into a piston around 11,000 rpms but that is only on the pre K8 and the F2/F3's which have somewhat stronger springs. If you don't ride this way then leave it alone.

If you cam, do the springs. It will make a difference as long as you make a good cam choice. I wouldn't worry about valves until you go bigger. Save that cash for later.

I wouldn't rebuild the engine unless it needs it and then I'd go big. There are SO many things you can spend your $$ on, just plan ahead for the next time you crack the cases open.   

[nitrofish1]

The valve springs are adequate UNTIL you miss that one power shift from 1 to 2 and it floats a valve into a piston around 11,000 rpms but that is only on the pre K8 and the F2/F3's which have somewhat stronger springs. If you don't ride this way then leave it alone.

If you cam, do the springs. It will make a difference as long as you make a good cam choice. I wouldn't worry about valves until you go bigger. Save that cash for later.

I wouldn't rebuild the engine unless it needs it and then I'd go big. There are SO many things you can spend your $$ on, just plan ahead for the next time you crack the cases open.

The engine sat in a barn for a very long time, the cases are open already.... I wanted to inspect the lower end as it was parked so long ago due to being previously broken but time had taken its course as to what that condition was, so I was going to inspect it all and rebuild the engine. So far I've only planned on doing the cam and springs, as the budget I set for the engine started to get a bit out of hand after a while. Instead of spending 1600 on just the motor I realized I could have the entire bike finished for around the same price. Or rather even a whole other bike....

[nitrofish1]

bad to split the cases to inspect for possible previous damage? id hate to get it all back together to find out that the previous owner chipped off a gear tooth or an oil galley is plugged

[nitrofish1]

also wanted to split the cases so its easier to polish all of the aluminum. that lower end can be a bear if youre holding it up to the buffer wheel all day 

[Doctor_D]

define good

I guess 'good' to me would mean at least 70hp or so, or at least a somewhat noticeable amount above stock.

Also other question, is the "adjustable cam sprocket" really "free horsepower" as its labeled?

A mildly ported 836 with a mild cam, nice exhaust and CR29's made 68 hp on our dyno.  So, no, you won't make anywhere near 70hp.

[NitroHunter]

With the adjustable cam sprocket you can move the opening / closing number of the valves. Closing the intake earlier (rather than later) gives more cylinder pressure = more torque. While not a great amount, doing it right can make a difference you will feel in almost any vehicle.
I had an 836 with mild RC 240 cam that was a very fun ride, and my .02 is that pulling midrange wheelies with a thoughtfully built combination is more fun far more often than having to wind the piss out of a hotrod motor due to too much cam. And yeah I had some of those too. 

[nitrofish1]

Stock is 67hp, why would it be a stretch to expect 70hp out of a cammed 750?

[bwaller]

That 67hp is a number Honda advertised. Regardless if that figure is right or wrong the power was measured at the crankshaft. Most often these days people use rear wheel dynos. There are losses through primary drive, gearbox, and final drives so rarely does a really good stock CB750 make much more than 50 odd RWHP.

So 70 rear wheel HP is around a 25-30% improvement over stock...very significant.

[Bill/BentON Racing]

That's right.Calendar Girl made 65 rwhp,old engine,built by a buddy,836 RC kit,Yosh Daytona cam,Yosh rods,29mm smoothbores,Yosh pipe.Seeing 87.07 on an automatic,Samauto made me feel good!!10-12 lost thru torque converter.Bill

[nitrofish1]

gotcha. well shell at least see a good improvement over stock without breaking into the bank for extra project funding

[nitrofish1]

What would be the best next step for power on top of a cam and springs?

[Jerry Rxman Griffin aka MuthaF'er]

head work

[NitroHunter]

Compression

[MRieck]

Larger bore.

[nitrofish1]

these ideas are all things id like to do, but none of them are free 

[Jerry Rxman Griffin aka MuthaF'er]

OK then, gas and oil 

[nitrofish1]

OK then, gas and oil 

I'll just buy a barrel of VP 100 octane then? lol