700cc kit with a Shell #1 cam in a 78XS650E

zrx1100

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Finally got my 700cc top end rebuilt project to a good intermediate pausing point. Earlier this year, I fitted the 700cc (697cc) JE piston kit and a Shell#1 cam from Hoos. The head underwent a cleanup, 'street porting,' and had Kibblewhite valve springs installed by Roger at R&D Motorcycle Service. I also upgraded to Vesrah clutch springs and new EBC friction plates. Special thanks to 5twins and Michael Morse for their help in tuning.

Below is the result with the following configuration: (correction on displacement 698cc)
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The current setup gives just under 50hp, hitting 50hp in one unrecorded pull.
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And here is how this compares to the stock measured on the same bike and same dyno a year and a half ago (Nor Cal Cycles in Millbrae, CA http://www.norcalcycles.com/service.aspx):

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there's a 17% increase in peak torque and hp. Considering that Hoos 700cc race bikes dyno at 55hp and 44 ft-lbs of torque, I am happy with the result. The bike feels completely different, very responsive, and fun to ride. But, there's fine-tuning left: fixing the dip in torque at 4K by leaning it out (will try 5Z1 needles, as suggested by 5twins). I also plan to slightly widen the headers for better top-end performance.


One may ask why I am using stock headers. Initially, I tried 1.75” pipes with torque inserts, but they caused excessive exhaust reversion, making the bike run rich beyond 4.5K rpm. Even adjusting the main sizes and dropping needles didn’t solve it. Only switching back to stock headers with the much lower pipe internal diameter allowed to scavenge the exhaust better, leaning out the A/F mix and bringing out the performance gains.

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Next I will fit 1 3/8" ID torque optimizers from Michael Morse to the 1.75” pipes and may open up the intakes.
 
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Great Info. forgive me if posted before but the stock 650 measurements, did you do anything to the bike when it was stock or was that as you got it?
How was the stock compression at the time you did the dyno?
 
Great Info. forgive me if posted before but the stock 650 measurements, did you do anything to the bike when it was stock or was that as you got it?
How was the stock compression at the time you did the dyno?
The only changes to the engine on the stock config were the addition of Pamco with the stock advance mechanism, K&N stock air filter replacements (with the stock air box) and the iridium plugs. the iridium plugs were installed mistakenly with the original resistor caps. The Exhaust, carb jetting were all stock. the compression was ~125psi. the compression on the fresh build is 160-165 psi
 
What is the explanation for the 5800 rpm dip. It seems to exist in stock motor dinosaur also. Note, I shift before 5800 rpm so I never felt it. Call me old... I am...
Hesitation in this range is usually the needle to main transition. If the main is too rich you feel it quite a bit (see the dyno curve with 142.5 main). In the case of my final configuration, i am thinking that it is actually lean misfire. as the bike is leaned out already and the A/F mixture is overly lean in that range. I am going to try lifting the needle as performance with 135 (stock) main was not as good.
 
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Hesitation in this range is usually the needle to main transition. If the main is too rich you feel it quite a bit (see the dyno curve with 142.5 main). In the case of my final configuration, i am thinking that it is actually lean misfire. as the bike is leaned out already and the A/F mixture is overly lean in that range. I am going to try lifting the needle as performance with 135 (stock) main was not as good.
...except it shows in a stock and highly modified engine with wildly different jetting at the same spot...
Curious is all... Cheers
 
Finally got my 700cc top end rebuilt project to a good intermediate pausing point. Earlier this year, I fitted the 700cc (697cc) JE piston kit and a Shell#1 cam from Hoos. The head underwent a cleanup, 'street porting,' and had Kibblewhite valve springs installed by Roger at R&D Motorcycle Service. I also upgraded to Vesrah clutch springs and new EBC friction plates. Special thanks to 5twins and Michael Morse for their help in tuning.
Very interesting to me to see real-world objective data on this as I have essentially the same engine in a 650 SG that was built by the PO, except that it has Mikuni VM34's and 1.5" headpipes with Cone Engineering mufflers. As you say, quite different in behavior from a stocker. Thanks for posting!
 
Very interesting to me to see real-world objective data on this as I have essentially the same engine in a 650 SG that was built by the PO, except that it has Mikuni VM34's and 1.5" headpipes with Cone Engineering mufflers. As you say, quite different in behavior from a stocker. Thanks for posting!
Being curious is a curse...
 
...except it shows in a stock and highly modified engine with wildly different jetting at the same spot...
Curious is all... Cheers
Kevin, one point: the jetting is almost stock. Stock carbs, the main is one size down from stock, the needle is the same and the clip is in stock position. The pilot is one step up from stock. It is curious that the heavily modified engine needs a smaller main. In retrospect, the stock jetting was on a rich side anyway.
 
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Was looking with great interest at your dyno curves. Except for a rephase mine is similar with 707 cc (was 700 with the same pistons you have) and a similar megacycle cam. With the stock air boxes and kn filtets I also find it runs best with 132.5 mains... I think the kn's don't flow the same as stock filters but that is just a theory. What cr are the Pistons? They look like the ones I had. I ended up milling them to lower the cr due to too much pinging on hills riding double.
 
Was looking with great interest at your dyno curves. Except for a rephase mine is similar with 707 cc (was 700 with the same pistons you have) and a similar megacycle cam. With the stock air boxes and kn filtets I also find it runs best with 132.5 mains... I think the kn's don't flow the same as stock filters but that is just a theory. What cr are the Pistons? They look like the ones I had. I ended up milling them to lower the cr due to too much pinging on hills riding double.
The designed cr is 9.5:1. Also a correction on displacement: it is 698cc and not 697. Was rounding down pi().
 
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Very interesting to me to see real-world objective data on this as I have essentially the same engine in a 650 SG that was built by the PO, except that it has Mikuni VM34's and 1.5" headpipes with Cone Engineering mufflers. As you say, quite different in behavior from a stocker. Thanks for posting!
1.5” head pipes maybe just right for these engines to maximize horsepower. I am looking forward to experimenting with TPO inserts from MMM.
 
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There is a very noticeable difference in power between a stock motor and my modified motor according to my seat of the pants dyno. BTW I have a stock special exhaust that I modified by cutting it open and enlarging the internal holes. Seems to work well and it's louder than stock but not too loud.
 
There is a very noticeable difference in power between a stock motor and my modified motor according to my seat of the pants dyno. BTW I have a stock special exhaust that I modified by cutting it open and enlarging the internal holes. Seems to work well and it's louder than stock but not too loud.
The stock headers work very well for most uses on these bikes. You can see that with my setup the 1.75” pipes were pretty much keeping me to stock level performance. Could be that the commando mufflers had something to do with that, but they are considered a ‘ performance’ option.
 
Interesting, verrry interesting. Like seeing the dyno charts!
How was AF measured?
Common wisdom; the XS head, cam are easily over scavenged pulling unburned mix right out into the exhaust port. Muffler design and port to rear "wall" length creating a pressure wave that "stuffs the mix" at the exhaust port, is the design trick I often see mentioned.
Arm chair observation. XS motors that make a lot of horsepower are going to be peaky, power band from +5K to redline. (how high dare you go)
I used a sledge hammer to flatten the power band on a Hotrod XS I have, It was fast AND peaky, :twocents: It's now more enjoyable on the street. I've added 15K miles to it now, it's a bit tired, but no internal parts have found daylight... I may just ride it one more summer before opening for a refresh and measure to see what actually lives inside it.
 
Interesting, verrry interesting. Like seeing the dyno charts!
How was AF measured?
Common wisdom; the XS head, cam are easily over scavenged pulling unburned mix right out into the exhaust port. Muffler design and port to rear "wall" length creating a pressure wave that "stuffs the mix" at the exhaust port, is the design trick I often see mentioned.
Arm chair observation. XS motors that make a lot of horsepower are going to be peaky, power band from +5K to redline. (how high dare you go)
I used a sledge hammer to flatten the power band on a Hotrod XS I have, It was fast AND peaky, :twocents: It's now more enjoyable on the street. I've added 15K miles to it now, it's a bit tired, but no internal parts have found daylight... I may just ride it one more summer before opening for a refresh and measure to see what actually lives inside it.
The A/F mixture was measured by inserting the sensor tube through the hole in the center of the commando silencer baffle. The tube was long enough to reach the middle or so of the head pipe. Gary can you point me to the discussion on exhaust design you are referencing?
 
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