Black Mamba Jr. vs Sr.

#1
Has anyone done a comparison between the two? will I notice much difference?

I have a mild Hemi build, and went with the Jr, but thinking the Sr might have a little more up top, and a little less torque to make riding more manageable.

Stock rockers on the hemi, and don't have the P to V for more lift.

What springs should be used with Sr? I have 26lb now.

Thanks!
 
#2
Sr works better with better head. Jr requires more spring than sr for same rpm. P to v is critical during overlap period. Lift is of much less importance than duration and lsa/icl. For your mild motor hands down the jr IMHO.
 
#4
Thanks for the feedback. I was thinking with the TAV, i could sacrifice some torque. I still have some tuning to do before throwing more parts at it.

The head is “ported”, but stock size SS valves. For sure I would clay it before just stabbing the cam in as my clearance was close with my domed piston.
 
#6
ITs funny im having a real hard time deciding which to use i have both atm ive tried both and im not sure what to go with im using a 19 inch tire tav set up and with a 8 to 60 tav to sprocket the thing does wheelies and has good speed to about 25 but it just wont go faster then 40 atm with the black mamba sr cam in it gets to approx 4300 rpms then kinda just stays there goes up very slowly this is with the sr, i thinking maybe with a tav set up it just wont ever be able to spin enough for the cam to really make good power. IT kinda driving me nuts lol i guess ill try the jr again with the new gear ratio set up i also have a ported and polished head and up compression going on it soon.
 
#7
What is you overall gearing? On my Drag bike I am running 8:1 with a TC with a 1 to 1 high gear and BM sr. I have another also equipped with a SR and it pulls to 7K and probably more but I run out of street. A lot of guys with the TAV don't give it enough gear and the load is too much for the motor. The tav itself has some drag and that is the tradeoff of TAV vs Clutch. Tav gives tons of torque on takeoff but sucks some power at higher rpm while the clutch needs to slip and has a lot less torque on takeoff but less drag at high rpm where they shine. Because the TAV can cause wheelies starting out people will lower gear to control it but then as they shift they cant pull the load. I extend the wheelbase to control the wheelies. I think in your case the JR is the best option.

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#8
My Jr pulls hard to 6000-6500 depending on gearing and tops out around 7650 on the flats. I dont run a TAV though. I dont think you can go wrong with the JR.
 
#9
i went from a 10 tooth to a 8 tooth on the tav and the rear sproket is a 60 tooth atm i have the 6 inch driven so my final ratio is like 6.75 to 1. the mini bike itself is a trailmaster 200. my other option would be to go the 72 tooth on the rear but lol it already does wheelies with ease idk if a 72 might be just too much lol. would give me a 8 to 1 ratio. on overdrive. i can def feel it just kinda slow down once it hits 32 and struggle to go any faster really with the sr and how its set up atm. when i had the jr in it was a lower ratio then the current with the 10 tooth but i also had a stiffer driven spring and it pulled much harder to approx 38 or so and toped out around 46. Im thinking that the jr extra torque and the stiffer spring may be what im looking for. Im looking to hit really no faster then 50 mph i just want it to get there at a good clip. the sr just never seems to really get into its powerband but if your suggesting that its better then the jr and worth it then ill have to look into lowering the gear ratio more somehow i guess.
 
#12
Ow ok kool makes sense i misread cause you were talking about srs in your post. and for the previous post it has the lightweight alumin weight with a blue spring approx 3400-3700 engage if i remember correctly.
 
#14
I have a head coming from a site you posted on another forum ole4 18cc head ported and polish 27 25 ss valves etc and he says it flows about 70cfm gonna try that with the jr cam i guess and see if i like the improvement vrs the stock head and sr i had before.
 
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#15
with the 6" secondary, mine struggled to pull past 4500rpm, with the 7" secondary and 8/54 gearing with a 15" tire, things are better, still need to sort out the shifting, it launches hard then shifts too quickly. I made some changes but haven't gotten out to the track since.
 
#16
i couldnt get my 7inch to work properly the belt was too big with the set up i had and it wouldnt disengage for some reason. i figured a 6 inch sset up with 8 tooth is the same ratios as the 7 with a 10 so went that route see if it works out once im done swithcing heads tommorow.
 
#17
just and update put in my new head higher compression bigger valves etc with the black mamba jr cam and shes a toruqe monster pops wheelies real easy and doesnt seem to platue like it was before just keep pulling didnt check rpms or speed but seems way way better,
 
#19
If you dont mind me asking who did your cylinder head for you. I am in the market as well and hoping to find a guy who knows what he is doing. Not much info out there on the web for guys who port heads.

Thanks RCB
 
#20
I may be able to help. What are you looking for? I have some of the symmetrical honda style 18cc heads one with 28.5/25 and one with 32/25, and 5 14cc heads on the bench now with 32/25 valves. I found 14cc heads from Everest supply for 16 bucks and bought a bunch of them which I am working on now. They have been porting up real nice. I need to know your application and if engine is stock size or bigger what cam and rockers you are thinking of running and if it is for just driving around all around use or a drag application. DSC01293.JPG DSC01294.JPG DSC01295.JPG
 
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