Clutch/tires/gearing to pair with build

#1
Hey guys,

Below is a bit about my build.

My current build
predator 212cc
rtc-6 cylinder head with 27mm intake 25mm exhaust valves
stock automotive style retainers
26lb valve springs with .060 shims on intake and exhaust sides
stock rods
stock rockers
billet rod +.020"
hemi flat top piston
.010" head gasket
ngk spark plug
billet flywheel 32 degree timing
black mamba senior camshaft
Mikuni 22mm with 115 main jet 15 pilot jet
header

On a doodlebug 30 older body style (DB30)

As you can see I am running the black mamba senior camshaft, and with this build it really starts ripping at around 3600rpm+. My current clutch is unknown, with an unknown engagement, but swear its engaging around 1600rpm. It was a cheap ebay buy $18, and I think its engaging prematurely might be messed up. It was causing the engine to cut off at idle, and engaging making start up/idle a nightmare. The chain is not tight, and was not causing engagement. The chain has about 1/2" of play on the top of the sprocket. I finally took the POS clutch off, and the engine idled great at around 2500-2800rpm.

I want my engine to idle high 2500-2800rpm, and want a clutch that engages around 3000rpm stock without messing with springs or anything. Would appreciate any suggestions as this is one of the last items needed to complete my mini bike besides tires.

Main jet is dialed in, and I have seen 55mph on my mini bike with this build. Engine kept winding up, but I was starting to question the frame at that point was a bit shakey lol.... :scooter:

Current gearing
12t clutch 59t rear with 15" tires (4.9 ratio), but going to swap 15" tires for 13" tires. So final gearing will be 12t clutch, 59t rear with 13" tires giving me a bit more acceleration.

Tire options
1) Basic slicks front, and back from off-brand MaxAuto Slicks (2) ?
2) Or should I go for a Carlisle Slick rear, and Carlisle ribbed front ? Carlisle smooth rear Here would be the front tire Carlisle ribbed front tire

Second question is whether I should have front & back slicks or ribbed front tire, and rear slick...

Appreciate any guidance/suggestions/criticisms.
 

Cuda54

Active Member
#2
Call MAX TORQUE they can set you up a clutch for your need. Or start cutting coils of your clutch spring till you get what you want.
 
#4
anyone have any experience with NORAM STINGER clutches? Seem like a good clutch with adjustable RPM engagements via springs, and can also run bully drivers?

Hilliard flames are also really popular, but I want something bulletproof, and stupid proof:)
 
#11
I think I am going with the hilliard fury with the black springs. Seems like a very popular clutch, and don't want that hard hitting acceleration that disc clutches give. My build is already a little too much for me fractured my rib about a month ago from mountain riding lol went from 45mph to zero, and the handlebar went straight to the ribs! Appreciate the help all.
 

Davis

Active Member
#12
Whats your engine build look like, camshaft etc? Whats your engagement look like? Black springs or mix with black/white? Using any weights?
My engine is a hemi predator block crank and piston with a arc side case 17cc head with 28.5-25 valves #26 springs .010 head gasket ported. Built by Ole4. Gx200 pushrods arc flywheel. Dynocams cl275 cam. Mikuni 22mm carb 110 main 12.5 pilot. Hilliard flame clutch with all four black springs. It runs very well. Ole helped me with the entire build.
 

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#14
I think I am going with the hilliard fury with the black springs. Seems like a very popular clutch, and don't want that hard hitting acceleration that disc clutches give. My build is already a little too much for me fractured my rib about a month ago from mountain riding lol went from 45mph to zero, and the handlebar went straight to the ribs! Appreciate the help all.
The SMC clutch uses roller levers which make the engagement very smooth.
 
#15
I believe 4 black springs in the Hilliard inferno flame is roughly 3400-3800 depending on what weights are installed on the shoes. This would be a perfect engagement range for the black mamba since it’s powerband is from 4000-8000 rpms. Would hit right at it’s sweet spot ;).


The SMC clutch uses roller levers which make the engagement very smooth.
Massacre what camshaft are you running, and what do you have your engagement set at?

Appreciate both your responses!
 
#16
Well that clutch I ran on my Blockzilla engine. I forget the specs on the cam but it’s def built for high revs. I turned that thing to 9350 rpm a couple times lol power comes in around 5000rpm
Engagement I believe was set at 36-3800 rpm but I think it can be set higher i’ll Have to check

But now am using polar clutch and only turning 7800rpm
 
#20
Yeah I got a Hilliard flame clutch with all black springs. I’m really liking it so far, and I also changed the gearing 13:59 with 13” tires on front, and back(the smooth max auto ones I posted)
This thing hit 60 mph last night, and that was at around 7100 rpm... still had plenty more to give, but cut the run short because it was cold lol. I don't know why those pictures are showing upside down on the forums when they are right side up on my files.
 

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