jackshaft gearing

Might want to check your final gear ratio or clutch settings. Are you hitting max rpm about half way down the strait. Also what kinda pipe you run sounds like your set up more for top end,if yourgetting pulled out of the corner and catching him at the end of the strait. Is his corner entry and apex also faster than yours or does he just pull ya out of the corner. Most short dirt track racing is won in the corners so work on making your kart faster there with all the things I listed., Gotta have a good low end torque pipe and flex set to get that grunt out of the corner start with setup and pipe.
 
2fast4u said:
Thats what I want to know if it would make more torque to pull off corner
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he could have more torque than you. Have you ever checked your compression pressure? More than likely he has a lower gear ratio than you. Are you both running a clutch? I find that most people slip their clutch too high. You want the clutch stall RPM to be right at peak torque. Now you may not believe or understand that, but until you've tried it, you won't know.

Comments compliments criticisms and questions always welcome.
 
The jackshaft was used on a kart engine to allow you to run on small tracks. Over the years, Buller started running a 4 cycle style clutch on the output side. The 21/57 ratio was implemented because it gave the correct ratio to spin the clutch at the correct rpms so that clutch engagement could be maximized for the springs and weights that provided the best action.

Some people have their options that it should be something different. I have even tried those options. I run the conventional 21/57 primary gearing because it works best with the dry clutches. I have run them since Buller introduced them. I believe Kermit's recommendations are the best. He has tested nearly every conceivable combination. He designed the set-up. If it is good enough for him to recommend it, there is a logical reason. He wants your experience to be the best it can be with his products.
Enough said......
Mike
 
In my area, the tracks tend to have decent bite. Gear ratios are very dependent on that. On my 1/10 mile track nearest to me, I'm in the mid 9s for a ratio. I want to turn my engine about 14,600ish rpms so that I don't disengage the clutch. If the track is really fast (generally a wetter night) we get almost to 9.0s on the overall gear. The bottom line is that it totally depends on your track surface.
Mike
 
I have to agree that Buller knows what he’s doing, but I have a different idea on what his reasoning was for choosing that primary drive ratio.

Knowing how many people would call him for that ratio, and how much time that would take, why not just give out a, “one ratio fits all” number. I’m sure that number works well and it eliminates a lot of discussion time on where to set the clutch and what secondary ratio to run. He knows that any primary ratio, that spins the clutch in a certain range, is okay. The one he gives out is one of those ratios. There’s nothing magic about that ratio. Thing is, he knows a lot of people are going to be calling him on the ratio to use, and having a one-size-fits-all, (not that that’s bad) makes it a lot simpler.

The thing that everybody should consider is that the clutch should be holding the engine at peak torque while slipping on the starts, or coming out of a tight turn.

Another thing to consider is the ratio difference between different gears on this secondary with different primary ratios.
For instance;
Primary secondary difference
21/57…….. 15/60…15/61…. .18
20/50…….. 15/60… 15/61…. .17
in these 2 examples you can see there’s not much difference. The difference does go up the greater the difference in the primary ratio.


Comments compliments criticisms and questions always welcome.
If the data does not support the theory, get a new theory. (Al Nunley)
 
I talked to him about primary ratios back when he developed his dry jackshaft clutch. according to Kermit, the 21-57, 2.71 ratio provides the highest polar moment of inertia. http://simple.wikipedia.org/wiki/Polar_moment_of_inertia
he has also written on the subject, i had it at one time, and probably still do somewhere. not sure if it was from their old web site or one of their catalogs.
 
Just wondering whats everyone thinking on a 1/4 mile track 21 63 or so on secondary or need bigger driver thanks for the info
 
I don't run rear sprockets that big because they can hit the track, so yes, I would run a bigger clutch gear.
Mike
 
MikeGrady said:
I don't run rear sprockets that big because they can hit the track, so yes, I would run a bigger clutch gear.
Mike
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Mike is exactly right , I try to stay 60 tooth and below just for track clearance. What overall ratio are you trying to get, a 1/4 mile track tells absolutely nothing since there are many different types of 1/4 mile tracks.
 
Sorry, smaller clutch gear.....that was a typo. You never want the gear to hit the ground though. I run rocket sprockets for that reason. The frame will hit before the sprocket. I've run some pretty low air pressures over the years. The frame almost always shows rub marks.
Mike
 
I've had a rock hit my sprocket before (65 tooth) and it ruined my day so I always try to base my gearing around a 60t rear sprocket.
 
Idk what ratio I have never ran the track and dont know anyone that have so I was just trying to get a basic idea
 
I run a 20/50 with my Birky mainly because that is what my Birky was, but also because it is very convenient to calculate ratios at 2.50
 
i am liking what im reading. being a newbie myself its good to read this info from older karters.
Id have to say i run a 100cc reedjet ,s4 pipe with my Berky Clutch. I have found that kicking that clutch in nice and low helps me keep it cooler and pull off the coners better... nice and low. never run my motor much passed 15,700. on 110 pump gas. she does great on small tracks and im a rocket off the coners.
 
SmithInVegas said:
i am liking what im reading. being a newbie myself its good to read this info from older karters.
Id have to say i run a 100cc reedjet ,s4 pipe with my Berky Clutch. I have found that kicking that clutch in nice and low helps me keep it cooler and pull off the coners better... nice and low. never run my motor much passed 15,700. on 110 pump gas. she does great on small tracks and im a rocket off the coners.
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It would be interesting to know what octane they run in Europe. I'm pretty sure they have rules on octane and it seems I've heard they don't run 110 race gas. If you could run lower, and get more power, it would save you money.
 
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