Topic: What are "must" with big bore kit???

[leogriss]

Hi everyone.

One question!

If I decided to go with a big bore, what must be modified as well? It will be a street only bike.
I heard cam shaft need to be changed as stock cam can't handle it.
What other parts also need to be replaced? valve? valve spring?

Please share your experience!
Ride Safe!!!!

[MCRider]

I've had personal experience with many big bore conversions. Nothing extra is necessary and you can just add it up as far as you want to go.

An 836 by itself runs pretty good. I'd likely add a pipe first, and the rejetting that goes with that. A mild cam might be next, but knowing what i know now, I'd rather put the money into a port and valve job on the head. The head will cost a lot more, but it will work with a stock cam and even better with a hot cam.

Actually, the head by itself is an option. I had a ported head on a 736cc motor and it was really sweet, stock cam, free flowing pipe.

That's my 2¢.

[ekpent]

MC summed it up well. Lot depends on how you are going to be riding it or beating it. An 836 in an otherwise stock motor will function OK as a daily rider.More power and torque.If your going to be riding it super hard or want to max its potential just pour in the $$$$'s.

[sparty]

You are treading on a slippery slope here.    I initially wanted a bigger bore and then I began to consider the "musts".  After all was said and done my engine build took off in a new direction = $$$$$$.

Likely, you will get many different opinions and options from the members here.  If you want to keep it simple, a bigger bore with head work will be plenty, but who can stop just there.  If you go mild cam there is little need to beef up valve springs and retainers.  But with a hotter cam it is highly recommended.

Look into heavy duty cylinder studs, they are worth it.  As is everything that Mike R. helped me do to my engine.

Good luck and let us know what you decided upon.

Sparty

[hesselfuzz]

Although I hesitate, I will respond. Forgive me if you know the following but by your question I think I'll throw it out there. Why have you decided to go to a big bore kit? Have you done what you can to improve the outside of the motor?

An engine is basically an air pump and the more air (mixed with fuel) you can get it to move, the more power it will make. Bigger pistons will move more air IF there is not a single restriction elsewhere in the air "channel". In theory, the air filter, carbs, valves, cams and exhaust are designed for how much air the 750's piston can move. Have you switch to a K&N type air filter? Are your carbs clean, properly jetted and tuned? Do you have a good aftermarket exhaust in place? Is your ignition system in top shape. Have you considered dyno tuning your bike? All these things are much cheaper than bigger pistons and potentially excellent power boosters. What's more all these things need to be in order to really see the maximum benefit from bigger pistons.

I'm new to the 750 engine. These are just general hot rod suggestions. The trick is to find where the biggest restriction in the air path is and open it up. Then find the next one, etc. I agree that head work has a lot of potential. It's labor intensive and manufacturers often skimp here, so that's a good bet.

Anybody know the biggest cork in the stock 750?

[Hinomaru]

The best possible cylinder sealing is always desirable regardless of the bore size. The pistons, rings and valves work together to accomplish this seal. A Serdi precision valve job is a must have and highly recommended on any stock or modified engine.

Good reading about bore sizing and cams from the Satanic Mechanic site:

www.satanicmechanic.org/bigbore.shtml

www.satanicmechanic.org/cams.shtml