700cc, what do you get?

[racerdave]

Thinking of making my tracker's big hunk of aluminum into a 700 with a Shell #1 cam with appropriate valve springs, stock head with valve job, stock cv carbs jetted with Uni filters, Omars half mile pipes with exhaust optimizer kit. Is this a good setup for a midrange gain in torque and hp? What on average would this gain over stock? Not looking for a high rpm screamer, just good acceleration to 65-70. Gearing is stock frt sproket and 36 tooth rear. This has to run on pump fuel ethanol 91 octane at most around here.

For the money spent, would the mikes xs 750 big fin kit running stock cam and all the others above the same, give the same performance.

 

[Tomterrific]

The 750cc big bore kit is a sure bet. The only way the 700cc build will beat it is price and higher compression and you don't want high compression due to the available octane. As far as a cam, I like stock cams for my old bikes. These used to be new bikes to me and that is when I wanted the fastest bike on the street so in went the hot cam in my Norton. To be more powerful than a stock cam, aftermarket cams must be harder on the valve train.

To answer your question about performance: I suspect the cammed and high compression 700cc engine would be more powerful if run hard.

Tom Graham

 

[blackbetty]

I'm building this engine with the exact same specs you listed.

You can run 9.5:1 running a base gasket and still get good streetability.

I'm waiting for my parts to come back from Roger at Hoos, all in all with RD springs, 700 kit, bore job, bead blasting, cam and cylinder head exchange I'll be in for around $850.

I'll have another 2-300 in basic rebuild stuff as well, cam chain, guides, gaskets, etc.

 

[jay760]

There's a kit on ebay at the moment including the barrels http://www.ebay.co.uk/itm/270860729...AX:IT&_trksid=p3984.m1423.l2649#ht_500wt_1413

 

[dwyatt]

I have the 700cc JE pistons from Hoos and they worked great. I added a slightly thinner copper head gasket to bump the CR to about 11:1, ported head, hot cam and can still run pump gas with no knocking. Mine is a track only bike, but very streetable power curve.

 

[C-Los SD]

I have two XS's one with a 750 big bore kit on my 79 w/stock cam and the other has
700cc JE Pistons with Hugh's rephased crank and cam on my 77. Hands down, the rephased motor smokes my XS with the big bore kit. It gets up to speed faster, more RPM, and higher top speed...both have the same gearing. I'm still breaking in the motor on the rephase, but it goes 90mph easy with plenty more on tap. Rephase is the way to go!

 

[racerdave]

C los in your opinion how would they compare if the 700 wasn't rephased? That's not in my budget!

 

[jay760]

I run a 707cc engine, recently I had an 840 engine, I swapped the cam and carbs over from the 707 to the 840 thinking there would be a massive difference, there was none, if anything the 840 was slower, can't even put it down to the chassis as they were both in the same chassis

 

[racerdave]

700 is sounding better again. What, if either, is the Shell #1 cam biased towards, midrange torque or upper end hp?

I haven't done a pricing yet, but in a quick look, it seems it's pretty close for a shell cammed 700 with hd springs vs a stock cammed big fin 750, if the 750 comes with fitted pistons that won't need to have the final bore size bored?

Either way I'd get a valve job, and have to buy gaskets etc.

 

[jim540]

I have done a little checking on big bore kits and cams for this engine. What I have been told is if you don't port the head you are wasting your time. Basically an engine is an air pump, you can't get it in if you can't get it out. You would probably see more performance porting the head and maybe raising the compression some. Good carburetors and exhaust would complement it. Just some ideas to mull over. Lots of ways to go.

 

[Jack]

I run a 707cc engine, recently I had an 840 engine, I swapped the cam and carbs over from the 707 to the 840 thinking there would be a massive difference, there was none, if anything the 840 was slower, can't even put it down to the chassis as they were both in the same chassis

most likely the performance limiting factor of the 840 being slower was due to the smaller cam choking the engines breathing abilities as was the smaller carbs limiting the fuel demand. You increased the engines displacement a fair amount which will require higher demands of fuel due to the increase in air volume. That 840 with a Megacycle cam#-30 and 36 or 38mm flaslides would of been a beast to tame,let alone a blast to ride

 

[jay760]

most likely the performance limiting factor of the 840 being slower was due to the smaller cam choking the engines breathing abilities as was the smaller carbs limiting the fuel demand. You increased the engines displacement a fair amount which will require higher demands of fuel due to the increase in air volume. That 840 with a Megacycle cam#-30 and 36 or 38mm flaslides would of been a beast to tame,let alone a blast to ride

I was running webcam 59a and 36mm dellorto's

 

[Cafe Murdock]

700 is sounding better again. What, if either, is the Shell #1 cam biased towards, midrange torque or upper end hp?

I haven't done a pricing yet, but in a quick look, it seems it's pretty close for a shell cammed 700 with hd springs vs a stock cammed big fin 750, if the 750 comes with fitted pistons that won't need to have the final bore size bored?

Either way I'd get a valve job, and have to buy gaskets etc.

If ir haveing doughts n want a honest answer ask daddy g cycles he'll give u the facts n not sugar coat it . And hes a xs guru from way bak if i have a problem or just a question hes the first man i call