707cc kit

scotts · Posted: July 11, 2009, 2:03 pm Post subject: 707cc kit

I've tried searching a few forums and can't find what I'm looking for.
By the time I add up all the stuff that's needed for, say, a 2nd overbore, I'm only a few more dollars away from this 707cc kit:
cgi.ebay.com/ebaymotor...MEWAX%3AIT

Not gonna do the 750 right now. I don't want to sepnd the bucks for Mikes kit and I don't want to sleeve what I have.
That leaves a 2nd, 3rd, or whatever overbore OR the above kit.
I'm looking for real world experience with the 707cc. How thin are the walls? Any overheating problems? Anything else to add?
I'm thinking cleanup the exhaust ports myself, run a 1.5" exhaust, good ignition, rejet stock carbs. I have everything to do this except the overbore stuff...which I will eventually need for my Brat bike. Why shouldn't I spend the extra few bucks and go 707cc?

nj1639 · Posted: July 11, 2009, 3:42 pm Post subject: Re: 707cc kit

I did a 2 over bore and then the 8-1 compression change. Wonder what that would add up to (cc wise, that is.)?

Jack · Full Member Joined: Mar 15, 2005 Posts: 411

a 707 big big bore kit is really kissing the limits of adequate liner thickness to promote good ring sealing and if overheating should ever occur you could end up cracking a liner during cool down cycles, I'm building a 707 myself just depends if you like to gamble,s*** does and will happen when you least expect it. For a cheap BB kit you might wanna consider the 680 route,now these piston are not light weights at all,so you might wanna consider cutting and installing Suzuki GSXR 1100 light weight piston pins to bring the reciprocating weight back near stock pistons.

When you start to roll up your sleeves to port the exhaust and if you're a perfectionist,you'll want to pay particular attention how the roof aligns with the floor,how the longside inside wall and outside wall align with each other as they make the turn and how the shortside radius from the floor turns. The turns are 50% of what makes or is the downfall of maintaining decent velocity throughout the flow curve. Good luck to you and post some pictures while your in the process Scott.

650skull · Support Staff Joined: Jul 19, 2007 Posts: 1186

nj1639, If mikes 6th over size = 680cc then a 2nd oversize will be about 660cc.

scotts a 707 is the largest to go before new sleeves. It is your money, but the question i would be asking myself, do i have room to move if do some damage to the bore. My self i would go to mikes 6th over size then to 702/7 on the next. That way at least i have a back up to go to before a re sleev. At the end of the day Mikes big bore is the cheapest way to go, then you still have a set of barrels to keep or sell, and it will run be cooler with the bigger fins.

yamaman · Posted: July 11, 2009, 7:08 pm Post subject: Re: 707cc kit

Std engine 75 x 74 = 654cc
75.25 bore = 658cc
75.5 = 663cc
75.75 = 667cc
76 = 671cc
76.25 = 676cc
76.5 = 680cc
78 = 707cc

Wonder if any of them are worth it? Aside from boring to meet cylinder needs, I wouldn't bore anymore than I had to! Whats an extra 30/40/50cc going to give you? 1 maybe 2 horsepower?????

scotts · Posted: July 11, 2009, 8:30 pm Post subject: Re: 707cc kit

yamaman wrote:

Wonder if any of them are worth it? Aside from boring to meet cylinder needs, I wouldn't bore anymore than I had to! Whats an extra 30/40/50cc going to give you? 1 maybe 2 horsepower?????

That's pretty much my question. If Mikes 4th overbore is XXX cc's and I can get the 707 for a few bucks more, why not?

I'm hearing some compelling reasons why NOT to do it. But just how big should I go? I mean, if the 1st overbore is the same price as the 6th, what's the best CC for the buck?

650skull · Support Staff Joined: Jul 19, 2007 Posts: 1186

Some things you have to work out for yourself. Wink

Or if you prefer give me your money and i will try a few things out and let you know Smile

Jack · Full Member Joined: Mar 15, 2005 Posts: 411

scotts wrote:

yamaman wrote:

Wonder if any of them are worth it? Aside from boring to meet cylinder needs, I wouldn't bore anymore than I had to! Whats an extra 30/40/50cc going to give you? 1 maybe 2 horsepower?????

That's pretty much my question. If Mikes 4th overbore is XXX cc's and I can get the 707 for a few bucks more, why not?

I'm hearing some compelling reasons why NOT to do it. But just how big should I go? I mean, if the 1st overbore is the same price as the 6th, what's the best CC for the buck?

Don't go under 650CCs and don't go over 750CCs,that pretty much covers it all for street reliability. A 650 set up with a mild cam,free flowing exhaust that pulls rather than making a bunch of noise,good carbs,filters and ported head, can net you near 58 rear HP and a 750 your probably looking at 62 to 65HP,again these HP figures are based on razor sharp tuning. Your the one who's gonna have to make the final decision on bore size and what not. If you're looking for more power get a modern sport bike.

weekendrider · Posted: July 12, 2009, 7:45 am Post subject: Re: 707cc kit

I haven't seen Mikes current price, but isn't his 750 Kit the best bang for the buck?

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