Lock Out/Lock-Up Tuning

[J-Madd]

 

Note to self about primary gear ratio affecting clutch set-up.

We really got caught off guard with the primary gear ratio affecting our clutch set-up. I knew it would change our set-up, but I didn't figure this much. Anyway, our new primary ratio is a 2.54. We chose this for 1/4 mile primarily. We have ran 2.68s when we 1st started in 2005 & then switched to 2.86s around 07.

 

It's hard to find information on primary ratio changes affecting clutch basket speed. Most that I have talked with says going from a 2.86 to 2.68 to 2.54 etc. speeds the basket speed up. I agree with that, but a few say it slows it down. Also, in my studies I found that there's less torque being seen by the clutch, because of the change. That worries me & I found some of these results in our 1st track outing.

 

The 1st thing we noticed was the motor wanting to bog at the drop of the clutch lever. No big deal, I'll just take some base pressure out. Well, I kept taking & still haven't found the sweet spot yet. We were at a point of 40+ lbs. less base pressure than we ran on our Cub.

 

2nd thing we noticed was the motor rpms being pulled down 20'-30' out. The arm weights were coming in to fast.

 

While we made changes in the right direction on both areas, it was not enough.

 

The last part of the evaluation was inspecting the clutch pack after getting home. It can tell you your clutch tune-up; kind of like reading your spark plugs. There was not enough heat in the steels for it to even show. The type of hot lapping we were doing should have shown a slight brown discoloration, but nothing.

 

For me, this last information along with the above info. Gave me a pretty good insight to what the clutch was doing & really what it wasn't doing.

 

Note for myself: clutch changes made & reading the clutch pack.

FWIW we went from 2.52 ratio due to broken teeth to 2.36 (I was against changing the ratio, but it was recommended to my brother who also tunes the bikes). I was afraid it would completely jack up our clutch speed (and it may have) but it didn't hurt a thing. We also went from 90" RO STUs to some flat paddle rippers though. I will say that you can't pull the clutch in after a dyno pull due to weight, though that may have been the case before as well. I do little to no clutch tuning. The track changes too much and I'm lazy. I get it close, then use tire pressure and gearing. Clutch tuning will obviously yield the best results if you have the patience and a case of clutch fibers and steels, lol.

[SlowerThanYou]

Not to derail your thought process, but im in for some of your thoughts on "reading the clutch pack". I looked at one of our clutch packs friday and noticed a significant amount of heat concentrated in the steels in the center of the clutch pack. Also the heat was concentrated along the outer ring/edges of each steel that showed heat. Upon further inspection, the steels affected that way were warped,,actually they were cupped if that makes any sense.

   Thoughts on that?

 

You basically answered your own question. Plates need to be checked even when new & with periodic inspections thereafter.

[SlowerThanYou]

FWIW we went from 2.52 ratio due to broken teeth to 2.36 (I was against changing the ratio, but it was recommended to my brother who also tunes the bikes). I was afraid it would completely jack up our clutch speed (and it may have) but it didn't hurt a thing. We also went from 90" RO STUs to some flat paddle rippers though. I will say that you can't pull the clutch in after a dyno pull due to weight, though that may have been the case before as well. I do little to no clutch tuning. The track changes too much and I'm lazy. I get it close, then use tire pressure and gearing. Clutch tuning will obviously yield the best results if you have the patience and a case of clutch fibers and steels, lol.

 

Again thanks for sharing the information. As for chasing the clutch at the track we normally don't do that. Unless it's totally wrong like our 1st time out with the DMX.

 

When we have a good baseline clutch set-up. We change the easy things like tire pressure, gearing, wheelie bar & launch rpm to name a few. 

[sprinklerman]

You basically answered your own question. Plates need to be checked even when new & with periodic inspections thereafter.

You bet . Clutch maintenance should include regular inspections...I guess what im asking is this:

1. What are your thoughts on the particular heat marks i found? ( Center of the pack only & outer edges of steels affected only)

[locogato11283]

The center of the clutch pack is going to get hotter than the rest. It should also be harder to dissipate heat from the center of the pack than the ones towards the outside.

[SlowerThanYou]

I looked at one of our clutch packs friday and noticed a significant amount of heat concentrated in the steels in the center of the clutch pack. Also the heat was concentrated along the outer ring/edges of each steel that showed heat. Upon further inspection, the steels affected that way were warped,,actually they were cupped if that makes any sense.

   Thoughts on that?

1. What are your thoughts on the particular heat marks i found? ( Center of the pack only & outer edges of steels affected only)

 

1st, I want to say. I don't not have this clutch pack reading totally figured out. Still learning as with the rest of the clutch tuning.

 

IMO, the answer is staring you in the face. The warp/cupped plates is causing the abnormal heat marks. If the plates would have been flat. You probably would have no heat showing like the rest of the pack.

 

Now, when did the warped/cupped problem start & how do you fix it? Would be the 1st questions I would ask.

 

The center of the clutch pack is going to get hotter than the rest. It should also be harder to dissipate heat from the center of the pack than the ones towards the outside.

 

I agree with your principle of the center of the clutch pack. However, we have found some different things that actually take place. I think Calvin from CP or maybe Tim from Titan Racing talked about it on PS. The actual lock-up tuning can move the heat around.

 

Here's what I do know from our experience. We have completely fried clutch packs. We have moved the heat from the inside to the middle & to the outside of the clutch pack. I also remember having heat on the inside & outside of the pack with none in the middle.

 

While we still generate a lot of heat/slippage. Our clutch pack vary rarely shows it anymore with the procedures & modifications we do 

[sprinklerman]

1st, I want to say. I don't not have this clutch pack reading totally figured out. Still learning as with the rest of the clutch tuning.

 

IMO, the answer is staring you in the face. The warp/cupped plates is causing the abnormal heat marks. If the plates would have been flat. You probably would have no heat showing like the rest of the pack.

 

Now, when did the warped/cupped problem start & how do you fix it? Would be the 1st questions I would ask.

 

 

I agree with your principle of the center of the clutch pack. However, we have found some different things that actually take place. I think Calvin from CP or maybe Tim from Titan Racing talked about it on PS. The actual lock-up tuning can move the heat around.

 

Here's what I do know from our experience. We have completely fried clutch packs. We have moved the heat from the inside to the middle & to the outside of the clutch pack. I also remember having heat on the inside & outside of the pack with none in the middle.

 

While we still generate a lot of heat/slippage. Our clutch pack vary rarely shows it anymore with the procedures & modifications we do

1. I fixed the steels by replacing them. haha

I'm assuming (after reading Loco's input) that the pack just got overheated and since they were in the hottest part of the pack,they warped quickest. I must have caught it early enough to "save" the rest of the steels before they got overheated.

 

2. As to what CAUSED the overheating in the 1st place,,that i don't know. Im starting to think it has to do with waiting for the "flagger" at the dunes...they are just keeping us staged waaaayyy too long and my dad tends to really rev the crap out of his bike while he's waiting for the arm drop. I think he's slightly riding the clutch at the line. That coupled with his trans being a "pro-mod" style where he still has to lightly clutch at full throttle to upshift, may be where the extra abuse is coming in.

      Those are just my ideas,but im no pro at clutch pack "reading".

                    Thanks for the input so far.

[locogato11283]

1. I fixed the steels by replacing them. haha

I'm assuming (after reading Loco's input) that the pack just got overheated and since they were in the hottest part of the pack,they warped quickest. I must have caught it early enough to "save" the rest of the steels before they got overheated.

 

2. As to what CAUSED the overheating in the 1st place,,that i don't know. Im starting to think it has to do with waiting for the "flagger" at the dunes...they are just keeping us staged waaaayyy too long and my dad tends to really rev the crap out of his bike while he's waiting for the arm drop. I think he's slightly riding the clutch at the line. That coupled with his trans being a "pro-mod" style where he still has to lightly clutch at full throttle to upshift, may be where the extra abuse is coming in.

      Those are just my ideas,but im no pro at clutch pack "reading".

                    Thanks for the input so far.

 

You're exactly right. As you sit there with the clutch in, waiting for the flagger, you're just making those plates hotter and hotter. The fibers will swell and the plates will "burn up."

[Surfrjag]

this may be a stupid question but I am wondering how much different oils could play a roll in how we tune these clutches. right now im using atf type f and im wondering if some thicker type of oil would give me a little more slip.

[SlowerThanYou]

this may be a stupid question but I am wondering how much different oils could play a roll in how we tune these clutches. right now im using atf type f and im wondering if some thicker type of oil would give me a little more slip.

 

Not a stupid question & we had worries when we started testing different oils in the gear box. We tested different oils & trans fluids. Then settled on synthetics & will not switch back to the Dinosaur oils.  

 

We never noticed much of a clutch tuning difference using the different fluids. The Synthetics are supposed to cause slip, but we haven't noticed it much at all.

[badassbanshee479]

What synthetic oil are you using if ya don't mind me asking? Also, what causes broken fibers? I managed to break the first three fibers in the pack the last outing... No wonder the clutch acted so funny

[SlowerThanYou]

What synthetic oil are you using if ya don't mind me asking? Also, what causes broken fibers? I managed to break the first three fibers in the pack the last outing... No wonder the clutch acted so funny

 

We was using Royal Purple Synchromax. It's the best we have tested so far, but at $17-18 a quart. That was the only down side. We are testing a cheaper fluid right now & it seems to be doing very well. It's a lot cheaper, but so far it shows good results.

 

Breaking fibers is usually caused by clutch chatter. I would need to know more about the clutch pack/set-up before giving a better diagnosis.

[J-Madd]

The cushions being worn out behind the clutch basket will break the fibers.

[SlowerThanYou]

Here's some clutch tuning updates I got from a member today. He's pretty happy with how his tuning is going he may or may not chime in. The results are from a smaller motor.

 

He started with low 1.40 60's, with some basic clutch tuning he getting into the low to mid 1.30 60's on the last tuning session.

 

There was other gains made also, but that's up to the member to decide if he wants to share. 

[phunt]

the change that was made was all base pressure, week one testing was 3.84-3.86 1.37 60ft 79.1mph. Week 2 was 3.75-3.77 1.33 60ft 80.2mph. The bike is a 4mill cub, I'll keep my times updated as I test more