Heavy engine mods

[legendary_rider]

Expensive to the tune of 2,000 or 3,000 (for just the engine work)?

Yes. Megacycle X5 cam, lightened 5.5 mm valve kit with guides, Wiseco 67.5mm pistons, boretech guide, heavy cam chain, 200 to bore out jugs, 200 to do the head on top of parts, teflon wrist pin keepers, lots more I've forgotten about. Not cheap. And I'm waiting for a bill from a performance shop to finish putting it together cause after sinking so much money into it I didn't want to screw something up by dialing it in wrong or checking clearances improperly. I'd rather have someone who's insured put it together.
Decided not to race it so I went and modified a 1960's superhawk tank with chrome sides to put on it. Gonna look amazing and perform even better.

I've got a cb750 motor I'm doing all myself mostly stock. So if I screw that up then it's a less expensive experience.

Another thing they don't tell you is to fit that boretech guide in you have to remove a shit load of material from in between cylinders. I actually took and angle grinder to mine!

 

[Sonreir]

I hear that:

$200 for valves
$150 for valve springs and retainers
$100 for bronze valve guides
$400 for custom pistons
$600 in machining work (decked the head, bored the cylinders, pressed and reamed valve guides, cut new valve seats, backcut the valves)
$70 for ignition mods
$80 for copper gaskets (base and head)
$50 for a second set of pistons
$200 for exhaust

And that doesn't even begin to count the time invested. It's a long road, but damn fun. I had the biggest damn grin in my life the first time I put this bike on the road after building the engine.

 

[legendary_rider]

Yeah dude. Some of those #'s look familiar. Can't wait to hit the road with it. Too bad the shop is sooooo busy with VRRA stuff.

 

[MR915]

No porting for either of you men..... Then there is the boring of the seats ...............

 

[legendary_rider]

Boring of the seats? Do you mean a 3 angle valve job on the seats? Yep that was done.

 

[70Cb350]

Money's not the issue, paying for it with scrap, ground change, and savings haha. Point is just to build the motor myself to keep the shop costs down.

 

[crazypj]

I'm looking to really build my CB350 motor, I've been looking into Bore-Tech systems. Looking to see if anyone has any experience with using their products, I need to buy new carbs anyways but am looking to see if anyone has used these products and has an idea of what size carb works best? I talked to the guys at Dime City and they said most people run the new Mikuni 30mm, but I didn't know if w/ using all the mods a 32mm or even a 34mm :-\ . Or if anyone knows of a flat slide carb that would work better? This is the list of what I plan to use

Electronic ignition system
Big bore kit, 67.5mm
Megacycle new billet cam
valve spring kit w/ 5mm conversion kit.

If I remember right, 30mm VM can support around 40bhp per cylinder before it runs out of flow. (been a few years since I posted numbers)
It's real common to be way oversize on carbs then spend a bunch of time and money trying to make them work instead of being more conservative and having something you can ride.
To use 34mm Mikuni's on a CB'350' you need to spend closer to $10,000 on motor and have it spinning around 14K
As forthe point about getting a CB750, 350 will be no more than half the weight and probably less than half of a slightly modified CB750
With some time and lightweight parts the complete 350 won't be a lot heavier than just the CB750 SOHC motor (which weighs 212lbs)

 

[70Cb350]

If I remember right, 30mm VM can support around 40bhp per cylinder before it runs out of flow. (been a few years since I posted numbers)
It's real common to be way oversize on carbs then spend a bunch of time and money trying to make them work instead of being more conservative and having something you can ride.
To use 34mm Mikuni's on a CB'350' you need to spend closer to $10,000 on motor and have it spinning around 14K
As forthe point about getting a CB750, 350 will be no more than half the weight and probably less than half of a slightly modified CB750
With some time and lightweight parts the complete 350 won't be a lot heavier than just the CB750 SOHC motor (which weighs 212lbs)

Thanks, that makes sense, I don't know what they made stock but i heard it was around 29hp stock. If I can get 50hp out of it I'll be happy, I want something that runs top and goes like hell but I don't want to have to keep rebuilding or tinkering with it all the time just to keep it running. Once I build it I have access to a dyno to tune it to my liking. Ultimate goal is to build a show quality rocket haha

 

[crazypj]

40 bhp is more realistic for a street 350 (362cc)
Only the best race motors are making 50bhp and they are pretty high maintainance

 

[mydlyfkryzis]

Stock CB750 is in the high 60's low 70's stock HP....

Takes a LOT of $$ to get that kind of power from a 350/360 Might involve force air intake and some really expensive, extra strong bits.

Legendary is right, if you want to actually go fast, get a bigger bike.

Unless you are racing professionally, I spend my money a reliability rather than HP. High HP is fragile too...