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Technical Forums => Twin Cam => Topic started by: Badger711 on January 21, 2021, 09:25:29 PM

Title: S&S 640 Compression?
Post by: Badger711 on January 21, 2021, 09:25:29 PM
Currently building a 117" in my 07 dyna, acquired pretty much all the parts and am about ready for the machine shop. Shooting for 140-150hp. I'm currently torn on what to set compression at for this 640 cam. Pretty confident ~11.5-7:1 is where I'm going to go with it but still want to get some more input before finalizing the decision.

Build list is as follows-

Factory 4.375 Crank Trued and Welded
Axtell 4.125 Cylinders bored .010 over
Factory cases, bored
KB Super Duty .010-over dome pistons (9.8cc)
S&S 640 EZ start
SE110 Heads, will be getting MVA intake valve and port work
Wild Things 57mm Throttle Body
Feuling 6.2 Injectors
Big sucker style breather
JBV Guppy exhaust (originally for a softail, retrofitted for dyna) w/ 3" louvered baffle.

Deck height calculator puts the pistons 5 thou in the hole, using a .020 base gasket and .030 head gasket, static comp figures @ 11.58:1 if I cut the heads to 93cc. This is currently the plan, but I'm a little worried about the 640 feeling soft on the bottom but being on a light bike I'm hoping that setting at 11.6:1 it'll help make up for it.

I know heads are realistically going to determine where it tops out, but I'm shooting for as close to 150 as possible while staying on pump gas and without having to pull stupid timing out to keep from pinging. From what I've read i'm toe-ing that line at 11.6 but a lot of guys seem to have ran at 12:1 and had good results.

Input?


Thanks in advance,
  -Dalton
Title: Re: S&S 640 Compression?
Post by: Baddyna on January 21, 2021, 11:42:38 PM
150 hp and + 6000 rom with a factory -07 crank,,,
Title: Re: S&S 640 Compression?
Post by: Hillside Motorcycle on January 22, 2021, 04:14:47 AM
Quote from: Badger711 on January 21, 2021, 09:25:29 PM
Currently building a 117" in my 07 dyna, acquired pretty much all the parts and am about ready for the machine shop. Shooting for 140-150hp. I'm currently torn on what to set compression at for this 640 cam. Pretty confident ~11.5-7:1 is where I'm going to go with it but still want to get some more input before finalizing the decision.

Build list is as follows-

Factory 4.375 Crank Trued and Welded
Axtell 4.125 Cylinders bored .010 over
Factory cases, bored
KB Super Duty .010-over dome pistons (9.8cc)
S&S 640 EZ start
SE110 Heads, will be getting MVA intake valve and port work
Wild Things 57mm Throttle Body
Feuling 6.2 Injectors
Big sucker style breather
JBV Guppy exhaust (originally for a softail, retrofitted for dyna) w/ 3" louvered baffle.

Deck height calculator puts the pistons 5 thou in the hole, using a .020 base gasket and .030 head gasket, static comp figures @ 11.58:1 if I cut the heads to 93cc. This is currently the plan, but I'm a little worried about the 640 feeling soft on the bottom but being on a light bike I'm hoping that setting at 11.6:1 it'll help make up for it.

I know heads are realistically going to determine where it tops out, but I'm shooting for as close to 150 as possible while staying on pump gas and without having to pull stupid timing out to keep from pinging. From what I've read i'm toe-ing that line at 11.6 but a lot of guys seem to have ran at 12:1 and had good results.

Input?


Thanks in advance,
  -Dalton

If 150 hp is your goal, might want to eyeball the .675 also.
Title: Re: S&S 640 Compression?
Post by: Badger711 on January 22, 2021, 05:03:14 AM
Quote from: Baddyna on January 21, 2021, 11:42:38 PM
150 hp and + 6000 rom with a factory -07 crank,,,

Trued and welded...We've had justin's turbo bike at 245hp turning 8k and its held up fine
Title: Re: S&S 640 Compression?
Post by: Badger711 on January 22, 2021, 05:06:08 AM
Quote from: Hillside Motorcycle on January 22, 2021, 04:14:47 AM

If 150 hp is your goal, might want to eyeball the .675 also.

We already had the 640EZ's on hand and this is a somewhat budget build so i'm sticking with them but I had the same thought. I feel like it would definitely feel soft on the bottom with the 675's though as well.
Title: Re: S&S 640 Compression?
Post by: SB107 on January 22, 2021, 05:37:30 AM
I run the TW-68 at 12:1 which closes a tad earlier (2°) and have no issues whatsoever. I believe you're safe at that compression in terms of PMS. The guppy is a LOT of pipe for a 117, you're probably going to be soft on the bottom whether you use the 640 or 675. My dyna is soft on the bottom but its so light it doesn't really matter, mine also has a 30t comp sprocket which helps. The Boarzilla will hold back HP but the tq curve will hit earlier.

Side Note: My custom pipe is 1-7/8 off the head and stepped 4 times with the collector right after the transmission. I will be doing a baffle to mainly quiet it down and I think the low end will benefit as a result. My dyno sheet is in the dyno section. It may or may not be a Guppy baffle....
Title: Re: S&S 640 Compression?
Post by: Badger711 on January 22, 2021, 06:07:36 AM
Quote from: SB107 on January 22, 2021, 05:37:30 AM
I run the TW-68 at 12:1 which closes a tad earlier (2°) and have no issues whatsoever. I believe you're safe at that compression in terms of PMS. The guppy is a LOT of pipe for a 117, you're probably going to be soft on the bottom whether you use the 640 or 675. My dyna is soft on the bottom but its so light it doesn't really matter, mine also has a 30t comp sprocket which helps. The Boarzilla will hold back HP but the tq curve will hit earlier.

Side Note: My custom pipe is 1-7/8 off the head and stepped 4 times with the collector right after the transmission. I will be doing a baffle to mainly quiet it down and I think the low end will benefit as a result. My dyno sheet is in the dyno section. It may or may not be a Guppy baffle....


Good to know, appreciate the info. And yeah, it's got some large primaries but being a little soft in the bottom may be beneficial as far as launch goes. We cut down a 3" baffle we had laying around and it definitely helped the curve. Ignore the clutch slip line on the sheet, that was previous pipes and didn't have the pro clutch in at the time.

This has been a pretty budget build, a lot of the parts are stuff we had laying around the shop (guppy included). And i think it's fun to do one-off type stuff and see the results so we'll see how the sheet turns out.
Title: Re: S&S 640 Compression?
Post by: Badger711 on January 22, 2021, 06:16:18 AM
It's also worth noting I'm getting caught up in the dyno sheet and not how it's actually going to feel on the road. If there's not a real noticeable difference between 11.5:1 and 12:1 on the @ss dyno then I don't feel like it'll be worth the extra potential aggravation
Title: Re: S&S 640 Compression?
Post by: turboprop on January 22, 2021, 06:31:07 AM
Quote from: Badger711 on January 21, 2021, 09:25:29 PM
Currently building a 117" in my 07 dyna, acquired pretty much all the parts and am about ready for the machine shop. Shooting for 140-150hp. I'm currently torn on what to set compression at for this 640 cam. Pretty confident ~11.5-7:1 is where I'm going to go with it but still want to get some more input before finalizing the decision.

Build list is as follows-

Factory 4.375 Crank Trued and Welded
Axtell 4.125 Cylinders bored .010 over
Factory cases, bored
KB Super Duty .010-over dome pistons (9.8cc)
S&S 640 EZ start
SE110 Heads, will be getting MVA intake valve and port work
Wild Things 57mm Throttle Body
Feuling 6.2 Injectors
Big sucker style breather
JBV Guppy exhaust (originally for a softail, retrofitted for dyna) w/ 3" louvered baffle.

Deck height calculator puts the pistons 5 thou in the hole, using a .020 base gasket and .030 head gasket, static comp figures @ 11.58:1 if I cut the heads to 93cc. This is currently the plan, but I'm a little worried about the 640 feeling soft on the bottom but being on a light bike I'm hoping that setting at 11.6:1 it'll help make up for it.

I know heads are realistically going to determine where it tops out, but I'm shooting for as close to 150 as possible while staying on pump gas and without having to pull stupid timing out to keep from pinging. From what I've read i'm toe-ing that line at 11.6 but a lot of guys seem to have ran at 12:1 and had good results.

Input?


Thanks in advance,
  -Dalton


I have a TC124 with S&S 640 cams at 11.9 that makes 158h SAE through a modified G carb, AC and JBV Guppy exhaust. The dyno sheet from the break in tune at Zippers is in the dyno section.
Title: Re: S&S 640 Compression?
Post by: SB107 on January 22, 2021, 06:36:55 AM
Quote from: Badger711 on January 22, 2021, 06:07:36 AM


Good to know, appreciate the info. And yeah, it's got some large primaries but being a little soft in the bottom may be beneficial as far as launch goes. We cut down a 3" baffle we had laying around and it definitely helped the curve. Ignore the clutch slip line on the sheet, that was previous pipes and didn't have the pro clutch in at the time.

This has been a pretty budget build, a lot of the parts are stuff we had laying around the shop (guppy included). And i think it's fun to do one-off type stuff and see the results so we'll see how the sheet turns out.

Track oriented, the guppy wins hands down. I don't blame you for using the guppy, as that would be my choice 10/10 times with this type of setup. Brian has a new 4" baffle that I will be using on mine since it is a completely open meg.

I 100% agree with you about the launch. you have such a small time window where the low end actually matters. Even during the point it matters you're trying to avoid lighting up the tire or doing a wheelie. After that you want more tq between shift points. Win/win.
Title: Re: S&S 640 Compression?
Post by: rigidthumper on January 22, 2021, 06:59:14 AM
The 640 with 90cc chambers/9.8 domes/.030HG/zero deck on top notch heads should get you close (gonna depend on the heads/intake combo). Static CR just a tic over 12:1, corrected compression just under 9.9 should be manageable.
Title: Re: S&S 640 Compression?
Post by: Badger711 on January 22, 2021, 07:05:45 AM
Appreciate the input all!
Title: Re: S&S 640 Compression?
Post by: Don D on January 22, 2021, 07:06:35 AM
It is a 117" so realistic expectations would be ~150/140 at 12:1+ if the heads are working right. Want 150/150 from the 117? That is a lot bigger task NA. This will not be a big torque producer until 3K is passed. I have done the same with a build posted in the dyno section here a few years ago, it was a dyna on Wes's dyno.
Title: Re: S&S 640 Compression?
Post by: Badger711 on January 22, 2021, 07:14:08 AM
Quote from: HD Street Performance on January 22, 2021, 07:06:35 AM
It is a 117" so realistic expectations would be ~150/140 at 12:1+ if the heads are working right. Want 150/150 from the 117? That is a lot bigger task NA. This will not be a big torque producer until 3K is passed. I have done the same with a build posted in the dyno section here a few years ago, it was a dyna on Wes's dyno.

Being in a dyna I'm after horsepower numbers, I'm alright with not making 150 square. Cubic inches limits that for sure.
Title: Re: S&S 640 Compression?
Post by: kd on January 22, 2021, 07:44:29 AM
Back to the basics, I would consider cutting the barrels for zero deck.  Then the .030 gasket is being used properly to control the detonation. (presently .038 total quench with deck at .008 in the hole) There are plenty of folks running 12:1 with a good tuner device like TTS and someone that knows how to tune for performance.

The later close of the 640 will probably never be noticed on a Dyna and in fact be a benefit on the street. My experience in the 145 - 150 square realm is it can be dangerous on some road surfaces or when wet.  As said previously any launches at the track (or street  :wink:) will not be happening below that 2500 - 3000 rpm level anyway.  If it is a little soft, you can use that to your advantage in a parking lot or sneaking through the neighborhood at night or early morning.   :smiled: 

That's my impression of what I would consider to get the most out of the free stuff. Gearing considerations will have a huge effect and must not be forgotten. The head work, intake choices and tuning will set the stage for the performance.
Title: Re: S&S 640 Compression?
Post by: 1workinman on January 22, 2021, 07:58:35 AM
Quote from: kd on January 22, 2021, 07:44:29 AM
Back to the basics, I would consider cutting the barrels for zero deck.  Then the .030 gasket is being used properly to control the detonation. (presently .038 total quench with deck at .008 in the hole) There are plenty of folks running 12:1 with a good tuner device like TTS and someone that knows how to tune for performance.

The later close of the 640 will probably never be noticed on a Dyna and in fact be a benefit on the street. My experience in the 145 - 150 square realm is it can be dangerous on some road surfaces or when wet.  As said previously any launches at the track (or street  :wink:) will not be happening below that 2500 - 3000 rpm level anyway.  If it is a little soft, you can use that to your advantage in a parking lot or sneaking through the neighborhood at night or early morning.   :smiled: 

That's my impression of what I would consider to get the most out of the free stuff. Gearing considerations will have a huge effect and must not be forgotten. The head work, intake choices and tuning will set the stage for the performance.
Good advice . I driven the 640 with both compression ratios and the higher ratio seems a lot more responsive . I have not experienced any more problem with the higher cr than the other one
Title: Re: S&S 640 Compression?
Post by: Don D on January 22, 2021, 08:00:27 AM
The head work, intake choices and tuning will set the stage for the performance.

Yep and especially the pipe.
Title: Re: S&S 640 Compression?
Post by: Badger711 on January 22, 2021, 08:11:08 AM
Thanks for all the input guys.

Headwork is going to be done by Jim Robinson at Head Hoggers, he's a great guy to deal with and I trust his work.

Intake is up in the air currently, and I'm confident in our tuning. Looks like i'm leaning towards getting deck to 0 and running with 12:1.
Title: Re: S&S 640 Compression?
Post by: SB107 on January 22, 2021, 08:11:31 AM
I wont speculate what power numbers you will make because dynos and how the bike is dynoed vary. However, if you're not  240lb like myself, you should be able to get into the 10s with practice with this recipe.
Title: Re: S&S 640 Compression?
Post by: Badger711 on January 22, 2021, 08:16:35 AM
Quote from: SB107 on January 22, 2021, 08:11:31 AM
I wont speculate what power numbers you will make because dynos and how the bike is dynoed vary. However, if you're not  240lb like myself, you should be able to get into the 10s with practice with this recipe.

10's are the goal, I'm sure I won't be able to ride it into the 10's right off the bat but hopefully with practice I will be. And it will be a street and strip bike so i'm leaning towards being soft down low to be a benefit not a curse now.
Title: Re: S&S 640 Compression?
Post by: SB107 on January 22, 2021, 08:25:54 AM
Quote from: Badger711 on January 22, 2021, 08:16:35 AM
10's are the goal, I'm sure I won't be able to ride it into the 10's right off the bat but hopefully with practice I will be. And it will be a street and strip bike so i'm leaning towards being soft down low to be a benefit not a curse now.

My tq curve is ugly, but the bike is stupid fast. I havent even intentionally gone to/past peak tq. Only time I did was when I did a pull in 4th, hit a bump, and lit the back tire up at 65mph (cold tire didnt help).
Title: Re: S&S 640 Compression?
Post by: CVOKing on January 22, 2021, 09:27:03 AM
I ran a 124 crate at 11.8 on a heavy bagger. On a hot rod dyna. Id want to get it to 12to1 on a 640. This cam isn't that soft on bottom when set up proper. The biggest thing with big cr is you really need a skilled dyne tech 
Title: Re: S&S 640 Compression?
Post by: Badger711 on January 22, 2021, 09:32:34 AM
Quote from: CVOKing on January 22, 2021, 09:27:03 AM
I ran a 124 crate at 11.8 on a heavy bagger. On a hot rod dyna. Id want to get it to 12to1 on a 640. This cam isn't that soft on bottom when set up proper. The biggest thing with big cr is you really need a skilled dyne tech


Sounds good. I'm confident in our tuning so we should be alright there.
Title: Re: S&S 640 Compression?
Post by: kd on January 22, 2021, 11:41:37 AM
Like Don said, the pipe goes without saying and you have that.  The clutch and basket will be weak links at that power if you plan on punishing it. It may be a good time to consider the EVO Industries basket and a 49 tooth sprocket to get your gearing down.
Title: Re: S&S 640 Compression?
Post by: Badger711 on January 22, 2021, 12:21:57 PM
Quote from: kd on January 22, 2021, 11:41:37 AM
Like Don said, the pipe goes without saying and you have that.  The clutch and basket will be weak links at that power if you plan on punishing it. It may be a good time to consider the EVO Industries basket and a 49 tooth sprocket to get your gearing down.

Running a Rivera pro-clutch so basket should be alright, I'm thinking. Gearing may be in order though.
Title: Re: S&S 640 Compression?
Post by: No Cents on January 24, 2021, 04:41:13 AM
    my bike blew through the Rivera Pro clutch making 150hp.
You might want to re-think that clutch holding 150hp.
Title: Re: S&S 640 Compression?
Post by: Badger711 on January 24, 2021, 05:56:07 PM
Quote from: No Cents on January 24, 2021, 04:41:13 AM
    my bike blew through the Rivera Pro clutch making 150hp.
You might want to re-think that clutch holding 150hp.


Guess we're gonna see how it does in that case. Worst case i'll double up on the springs but it'll feel like "Potty mouth" if i do
Title: Re: S&S 640 Compression?
Post by: kd on January 25, 2021, 07:06:27 AM
Have no fear.  There are options.  :wink:
Title: Re: S&S 640 Compression?
Post by: Badger711 on January 25, 2021, 08:12:00 AM
Quote from: kd on January 25, 2021, 07:06:27 AM
Have no fear.  There are options.  :wink:

Indeed, But they all cost more money lol :wink:
Title: Re: S&S 640 Compression?
Post by: 1workinman on January 25, 2021, 08:50:32 AM
Quote from: No Cents on January 24, 2021, 04:41:13 AM
    my bike blew through the Rivera Pro clutch making 150hp.
You might want to re-think that clutch holding 150hp.
Yea I think I have one of those clutches in a box used very little , would have to check for sure as the Bandit is back in the bike .
Title: Re: S&S 640 Compression?
Post by: sfmichael on January 26, 2021, 12:08:55 AM
more cam, more compression
maybe put some rockers on the 640
Title: Re: S&S 640 Compression?
Post by: 1workinman on February 01, 2021, 08:59:31 AM
Quote from: sfmichael on January 26, 2021, 12:08:55 AM
more cam, more compression
maybe put some rockers on the 640
If I get up your way this summer I can drop by with both of my money pit bikes . I think the 143 set at 12.2 and the 640 will be a pleasant surprise how well it runs against the 124 set at 11.4 I think now and 640 .  In my limited experience the 640 responds to compression
Title: Re: S&S 640 Compression?
Post by: C-Cat on February 01, 2021, 11:29:16 AM
 Why more compression on the 143ci?
Title: Re: S&S 640 Compression?
Post by: Badger711 on February 01, 2021, 04:22:07 PM
Decided on 12:1, Parts are in Jim's hands now so now it's the waiting game, and crossing my fingers the pro clutch holds. If not I'm shelling out another bit of cash for a scorpion.
Title: Re: S&S 640 Compression?
Post by: No Cents on February 04, 2021, 04:28:30 AM
 ...think Bandit  :wink:
If you need to buy another clutch that will hold the power and you want to only buy one more and being done with it...it's Bandit all day long.
Title: Re: S&S 640 Compression?
Post by: Barrett on February 04, 2021, 10:00:17 AM
Stock, Barnett & Bandit.
Title: Re: S&S 640 Compression?
Post by: No Cents on February 05, 2021, 08:22:48 AM
Quote from: Barrett on February 04, 2021, 10:00:17 AM
Stock, Barnett & Bandit.

  perfect example!  :up:
Title: Re: S&S 640 Compression?
Post by: Ohio HD on February 05, 2021, 09:15:09 AM
And to be fair, the above Barnett is not the Scorpion. Below is the Barnett Scorpion and a a stock disc.


(https://i.imgur.com/B76hRIU.jpg)
Title: Re: S&S 640 Compression?
Post by: kd on February 05, 2021, 10:06:37 AM
Thanks for that pic.  I often wondered how they compared physically to the stock and Bandit plates.  Both the Bandit and Scorpion will require the smaller diameter hubs.  Now I am wondering if they will work with each others (hub that is).
Title: Re: S&S 640 Compression?
Post by: Ohio HD on February 05, 2021, 10:14:52 AM
That I don't know. I don't have a Scorpion out at this time. But have a Bandit clutch on the shelf.
Title: Re: S&S 640 Compression?
Post by: cheech on February 05, 2021, 10:16:17 AM
And furthermore with the pic of the 3 plates being misleading.
Isn't the stock one shown in that pic, the narrow one that is 1st in along with the damper spring and seat?
Title: Re: S&S 640 Compression?
Post by: Ohio HD on February 05, 2021, 10:25:32 AM
I think you're right.
Title: Re: S&S 640 Compression?
Post by: 1workinman on February 05, 2021, 04:36:13 PM
Quote from: No Cents on January 24, 2021, 04:41:13 AM
    my bike blew through the Rivera Pro clutch making 150hp.
You might want to re-think that clutch holding 150hp.
A  I have a Rivera Pro that I don't think would hold 145 hp or so . The bandit that in there now works good . In my Road Glide it has a lock up clutch in it . The clutch that was in there when I got the bike would not hold after the motor was not stock ,  For me at the 150 hp or so a Bandit clutch and I want a better basket . I have just did not want to have a basket come apart at any speed
Title: Re: S&S 640 Compression?
Post by: Nick L on February 05, 2021, 05:53:03 PM
Bandit AND DONE .
Title: Re: S&S 640 Compression?
Post by: Badger711 on February 07, 2021, 12:44:17 PM
To each their own, but I've ridden a few bandit bikes and they have never felt the greatest to me. The scorpion on the other hand holds power fine and feels very good IMO. If I blow through the rivera it'll be a scorpion lockup that goes in. That being said if you like the feel of the bandit then have at it I'm just personally not a fan compared to the barnett.
Title: Re: S&S 640 Compression?
Post by: Hossamania on February 07, 2021, 12:45:26 PM
What didn't you like about the Bandit?
Title: Re: S&S 640 Compression?
Post by: C-Cat on February 07, 2021, 01:09:09 PM
They're plenty out there, I'm happy with both my EVO Industries and Rekluse clutches on my bikes. I haven't ran either the Bandit or Scorpion so I haven't an opinion on either. If I'm in need for another clutch, it will be the Rekluse. Below pic of EVO Industries plates, they're Beefy, lots of surface.
Title: Re: S&S 640 Compression?
Post by: Ohio HD on February 07, 2021, 01:31:50 PM
Quote from: C-Cat on February 07, 2021, 01:09:09 PM
They're plenty out there, I'm happy with both my EVO Industries and Rekluse clutches on my bikes. I haven't ran either the Bandit or Scorpion so I haven't an opinion on either. If I'm in need for another clutch, it will be the Rekluse. I'll post pics of the EVO clutch plates soon.

I agree with you. What ever works for you is all that matters.

Too many people have opinions on things they personally haven't tried. I bought a Bandit to put behind my 124. Bought it while I was building the motor. Started the 124 and had it dyno tuned with the Scorpion still in there. Zero issues. Holds it fine. Bandit is still on the shelf for when I may need or want to use it. The Scorpion now has about 30k miles on it. Back road, hot rodding being 50% of the time.

I've never had to adjust it unless I was taking the clutch apart, or replacing the cable. I also don't run a VP pressure plate. The spring pressure and clutch surface is enough. 

Title: Re: S&S 640 Compression?
Post by: Badger711 on February 07, 2021, 08:45:21 PM
Quote from: Ohio HD on February 07, 2021, 01:31:50 PM
I agree with you. What ever works for you is all that matters.

Too many people have opinions on things they personally haven't tried. I bought a Bandit to put behind my 124. Bought it while I was building the motor. Started the 124 and had it dyno tuned with the Scorpion still in there. Zero issues. Holds it fine. Bandit is still on the shelf for when I may need or want to use it. The Scorpion now has about 30k miles on it. Back road, hot rodding being 50% of the time.

I've never had to adjust it unless I was taking the clutch apart, or replacing the cable. I also don't run a VP pressure plate. The spring pressure and clutch surface is enough.

Agreed. Also, you don't run the lockup on yours? We've got the lockup version on the turbo bike because it seemed necessary at 250hp, i haven't felt one without the lockup.


And I personally didn't like the bandit especially in the friction zone, not a good breakaway feel on the springs, and tough level pull compared to the scorpion.

Plenty of people love them though.
Title: Re: S&S 640 Compression?
Post by: Ohio HD on February 08, 2021, 03:16:48 AM
Quote from: Badger711 on February 07, 2021, 08:45:21 PM
Quote from: Ohio HD on February 07, 2021, 01:31:50 PM
I agree with you. What ever works for you is all that matters.

Too many people have opinions on things they personally haven't tried. I bought a Bandit to put behind my 124. Bought it while I was building the motor. Started the 124 and had it dyno tuned with the Scorpion still in there. Zero issues. Holds it fine. Bandit is still on the shelf for when I may need or want to use it. The Scorpion now has about 30k miles on it. Back road, hot rodding being 50% of the time.

I've never had to adjust it unless I was taking the clutch apart, or replacing the cable. I also don't run a VP pressure plate. The spring pressure and clutch surface is enough.

Agreed. Also, you don't run the lockup on yours? We've got the lockup version on the turbo bike because it seemed necessary at 250hp, i haven't felt one without the lockup.


And I personally didn't like the bandit especially in the friction zone, not a good breakaway feel on the springs, and tough level pull compared to the scorpion.

Plenty of people love them though.

No, I'm running all green springs and that holds fine. I used all short gold springs with the 117", but the 124" needed more spring pressure.

Turbo, no doubt need some additional pressure to hold.
Title: Re: S&S 640 Compression?
Post by: Hillside Motorcycle on February 08, 2021, 04:09:44 AM
Quote from: SB107 on January 22, 2021, 08:11:31 AM
I wont speculate what power numbers you will make because dynos and how the bike is dynoed vary. However, if you're not  240lb like myself, you should be able to get into the 10s with practice with this recipe.

We've set up a client years ago with even 113" engine that went into the 10's with ease.
He broke into the 9's after some seat time.
124" Softail went 10.5's first time out about 1 1/2 ago.
10's should be in easy reach.
Title: Re: S&S 640 Compression?
Post by: Badger711 on February 08, 2021, 04:58:05 AM
Thanks for the info. Tempting to ditch the lockup as I've heard the added pressure on the mainshaft makes trans bearings unhappy.
Title: Re: S&S 640 Compression?
Post by: Badger711 on February 08, 2021, 05:00:13 AM
Quote from: Hillside Motorcycle on February 08, 2021, 04:09:44 AM
Quote from: SB107 on January 22, 2021, 08:11:31 AM
I wont speculate what power numbers you will make because dynos and how the bike is dynoed vary. However, if you're not  240lb like myself, you should be able to get into the 10s with practice with this recipe.

We've set up a client years ago with even 113" engine that went into the 10's with ease.
He broke into the 9's after some seat time.
124" Softail went 10.5's first time out about 1 1/2 ago.
10's should be in easy reach.

That's good news.