Clutches, stall speed theory

korndog

korndog

New Member
#1
#1
I have a cheap max torque clutch on my bike and am having some concerns about performance. I think this clutch engages at about 2500 RPM which is causing some serious bog I think. Trying to get the right balance of gearing and stall speed for optimal performance off the line and at higher speeds. Can these clutches be adjusted? i noticed the Draggin Skin model has a variety of springs for various stall speeds. Can someone recommend a clutch, the correct stall speed and gearing for the following setup? i should also say that I am using a band brake.

Raptor 3 ported milled, etc
26mm carb
270 lift cam
heavy duty springs
12/60 gearing

Engine doesn't seem to be running out of RPM but is really sluggish off the line. I haven't been paying much attention to clutch setup; I wonder if i should be.
 
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125ccCrazy

125ccCrazy

Well-Known Member
#2
#2
Is the throttle response quick and crisp? (tuning) Where does the cam start producing power? whats the rpm range? ...You don't want too much stall or it won't make for a very good rider since the clutch will want to disengage at lower rpm's when slowing down and then rev and grab again under more acceleration....If it's going to be mainly a rider a Tav2 may be in order with some sort of drum or band brake on the wheel....
 
korndog

korndog

New Member
#3
#3
125ccCrazy said:
Is the throttle response quick and crisp? (tuning) Where does the cam start producing power? whats the rpm range? ...You don't want too much stall or it won't make for a very good rider since the clutch will want to disengage at lower rpm's when slowing down and then rev and grab again under more acceleration....If it's going to be mainly a rider a Tav2 may be in order with some sort of drum or band brake on the wheel....
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My understanding is that the some have some pre-engagement a few hundred rpm before actual and are smoother than others which are more for dragsters. The cam I have now starts around 3.5k but am going to one that would engage around 4-4.5k. Yes, the motor is tuned and has good throttle response; just boggy. I'm looking at the Premier Titan and Stinger right now, but the stinger won't take my band brake. I have an aversion to Tav's for some reason. Nothing mechanical or practical; just personal taste. 125, what if I didn't set it up to engage at peak, but a little before and idled higher?
 
T

TheRealDeal

New Member
#4
#4
Hey korndog,

My son just ordered the stinger and I was planning on doing a band brake too, can you tell me what the problem is there ?

I really don't know anything about the stall speeds yet and will be watching this thred closely, but I would think that you would want you're stall some where near you're max torque number, hope some the drag bike guys chime in
 
korndog

korndog

New Member
#6
#6
Realdeal - the problem with the stinger is it has a very small drum. I believe 3 3/8. Not sure if 4 or 4 1/2 band will work. Let me know if you find out anything and I will do likewise.
125 -Yes, for the 94ss I was thinking about 3300, and 4k for the 107ss
 
minidragbike

minidragbike

Supporting Speed Nut!
#7
#7
I made the problem of having my clutch setup right at peak TQ for all out power/speed/acceleration like in drag racing. But that's not good for a flat track racing with a racing disc clutch. A soon as I touch the throttle my bike would want to do 25mph no matter what, instantly. But the second event at Elsinore I ran way better with my clutch stall lowered 600 RPM.

You need to make it come in before max TQ and smoother. So a drum clutch is best, now for drag racing you want it right at peak TQ and a disc clutch.

If any body decides to build a modified, or race motor they must think about clutch stall, or even TAV stall. You will not get the most out of your motor having it engage at 1200 RPM when your power starts at 3000+ RPM. The motor may bog, stumble, or just run like a slug until it gets to it's power band.

The power band is normally posted on your cam card. The power band can vary if you have a good, or poor flowing head, good or poor flowing carb, or ratio rockers. A example would be if your motor makes peak TQ @ 3500 and peak HP @ 7000. Your maximum power band for drag racing will be from 3500-7500. While in kart racing, or flat track racing it would be from 3000-7000 RPM.
 
minidragbike

minidragbike

Supporting Speed Nut!
#9
#9
Yeah I just went to there web site. They have updated it so now it doesn't say the power band of the cams any more. Only for the OHV motors now. So you may have to call them. They use to have it posted online, and in there catalogs.
 
korndog

korndog

New Member
#11
#11
minidragbike said:
Yeah I just went to there web site. They have updated it so now it doesn't say the power band of the cams any more. Only for the OHV motors now. So you may have to call them. They use to have it posted online, and in there catalogs.
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They pulled down all their details a while ago. Maybe people were copying their stuff or something. Think I found a good deal on a Titan. I think it's a throwaway part on the WF engines for some racers.
 
minidragbike

minidragbike

Supporting Speed Nut!
#12
#12
korndog said:
They pulled down all their details a while ago. Maybe people were copying their stuff or something. Think I found a good deal on a Titan. I think it's a throwaway part on the WF engines for some racers.
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Yeah that's a good clutch, but make sure it has the right gear on it. They come with #219 pitch chain, and have to be changed over to #35 chain.

Check out this link to CompCams, look at the power bands of there cams.
http://www.compgoparts.com/Pages/307/ControlledSuperstock.aspx
 
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TheRealDeal

New Member
#13
#13
Hey Korndog,

I just got the clutch today, the drum od is 3-3/4 and will not work with the 4-1/4 band that I have, but i do beleive it will work with a 4" band, so I just ordered one, also the paper work that came with it says the Stinger is good for 10hp and the Titan is good for 15hp
 
korndog

korndog

New Member
#14
#14
TheRealDeal said:
Hey Korndog,

I just got the clutch today, the drum od is 3-3/4 and will not work with the 4-1/4 band that I have, but i do beleive it will work with a 4" band, so I just ordered one, also the paper work that came with it says the Stinger is good for 10hp and the Titan is good for 15hp
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Good info. I thought it was even smaller. I got my Titan today and it's a beefy clutch. Much heavier than what I am used to. Going to have to convert it to inboard later tonight, which requires some effort. Thinking about the stinger for another bike.
 
M

MiniBike Paul

Well-Known Member
#15
#15
Korny, I have said this before, you are too high geared!! You are a big dude, and so at 5 to 1 your bike is a little (a lot?) slow getting going, and probably will go faster than you want to ride it; or worse, the engine just cannot overcome the gearing plus the other forces slowing you down, and so it never really gets into its' power band.
The other day when i rode it i really never went fast, so i don't know - but i would have liked a lower gear taking off!
 
korndog

korndog

New Member
#16
#16
MiniBike Paul said:
Korny, I have said this before, you are too high geared!! You are a big dude, and so at 5 to 1 your bike is a little (a lot?) slow getting going, and probably will go faster than you want to ride it; or worse, the engine just cannot overcome the gearing plus the other forces slowing you down, and so it never really gets into its' power band.
The other day when i rode it i really never went fast, so i don't know - but i would have liked a lower gear taking off!
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Well, I am going to put a 72 tooth rear on it, change the cam, and put the stall clutch on it; the clutch will be first today. Hopefully I will get it moving out the hole. It's plenty fast once you get the rpm up but it doesn't pull low end anywhere near my 6.5 that was on the bike before. that engine only had a header, jet and filter mod.
 
korndog

korndog

New Member
#18
#18
minidragbike said:
Good luck
Let me know how it turns out

Also the clutches maybe have a rating on them, but they can handle way more than advertised.
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Thanks MDB. I only have the 4200 rpm springs and am waiting for others, but I'll see how it goes. I got the billet 107ss in the mail yesterday. I hope I don't have to clearance the lifter bore. Dwight welded it up but I'm not sure if they did any clearance work.
 
korndog

korndog

New Member
#19
#19
I put the clutch on with the 4300 rpm (too high for this cam) springs and i was LMAO thinking someone was going to call the cops for sure. Unfortunately, my brake band is slightly engaged with this clutch so I will have to figure that out. I have to say it was a bit unnerving waiting for that clutch to kick in at those RPM. I'm still laughing thinking about it. That motor sounds so damn good though. Yeah, it definitely takes off better, but still going to do the gearing and cam. Not sure what everyone is using for their hot rod clones, but I saw Turk Brothers has Horstman Rhino clutches with 3600-3800 rpm engagement designed for clone racing on sale for $70.00. Seems like a decent deal.
 
minidragbike

minidragbike

Supporting Speed Nut!
#20
#20
No, you will not like that other clutch.
The motor should have sound much smoother, because it would have been idling with no load, like free revving.
 
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