Avon gearing

[steve miller]

Al., good to hear from you ..hope to see you folks there ...

[Doug Jorgensen]

Looking forward to seeing everyone at Avon. Sandy Hook was my first ever event and had a great time...met many wonderful and very helpful people..Thank you all ! I had the Blitz kart with the MC-75. I do have a question about gearing. When you mention 9-72 or similar, are you referring to the clutch and drive sprockets ? I also notice driver weight being mentioned..in parallel with ratios. In Sandy Hook my ratio was 8.0 (9-72), good on straight, slow out of turns...I'm also 250 lbs., takes a little more to get going. Just looking for a little help on the gearing, what might be a decent gear for this track ? Thanks for any and all help.

Doug

[jeff brown]

You might want to mention what tire diameter your running.  Is it a dry clutch and a box muffler?

[Doug Jorgensen]

You might want to mention what tire diameter your running.  Is it a dry clutch and a box muffler?

12" tire diameter, Max-Torque 2 shoe dry clutch, box muffler.

[jeff brown]

You might want to mention what tire diameter your running.  Is it a dry clutch and a box muffler?

12" tire diameter, Max-Torque 2 shoe dry clutch, box muffler.

The 12 inch tire is a very large diameter which would require a larger bottom gear.  Also the 2 shoe max torque clutch has a very low engagement which hurts the bottom end power.  Not sure what size tires the others who made recommendations are using, but most likely they are smaller.

[steve miller]

..yes I have to agree with jeff .. that's a pretty big tire ..are they on 6 inch rims ..also with max torque your very limited to any adjustments ..I think stay with the 9-72 you will be very close ...I have 73-74 ill bring but I think you,ll be happy with 9-72..

[David Luciani]

Jeff,

that is solid advise but perhaps you didn't consider the kart he is running.
sometimes going faster by adding the most efficient parts isn't the only consideration.

a blitz kart would've come with a six inch rear rim if it's era correct thus a bigger back tire.
 a dry two shoe is also era correct and appropriate for his kart.
i'm guessing Doug probably wants to keep it era correct so smaller tires doesn't seem like a doable option.
of course to increase tooth count as currently set up he needs to add a huge gear to the rear axle .

i'm thinking with his current set up, as found , adding a ten tooth clutch gear and regearing with that would be a workable compromise.
so where should he be at with his axle sprocket with that set up running a ten tooth drum.

Doug,
driving a vintage kart fast with era correct parts is a skill you learn.
it requires going into corners in such a way as not to lose momentum from tire scrub or over braking.
if done right the only corners presenting a clutch engagement challenge would be hairpins.

since you are running a mc-75 on a blitz i assume it's un modified?
if so you are running roughly 100 cc's but less intake porting than the newer mc91 mccullochs.
that's a power disadvantage you can't make up with gearing.

at your wt. cut engine type and frame style  being a front runner in the typical mc91 powered rear engine class is unlikely.
But you still can find a race within the race dice it out with someone and have alot of fun.

if you want better results so the kart gets more punch in the corner you'll need to go to a 10 tooth on the drum.
then correct the amount of teeth that makes sense for better corner performance.
that'll keep it era correct regear better and not have to run a chain dragger rear sprocket .

my two cents



i run max torque two shoes all the time on all the older engines.
they are not as punchy as an oil clutch or a newer dry but they also don't put alot of strain on my engines.

[David Luciani]

Steve,

you're killing me.
i know his gearing is close but i'm wasn't gonna pass an opportunity to hear an gearing opinion from a guy i'll probably never beat.
jeff is one of the fastest guys responding and i was hoping to hear his opinion on what gear to use with everything else as is.

maybe jeff will answer anyway !!
 

[jeff brown]

I was asking what configuration he had, not asking him to change anything.  I have no clue what gear to use.
You mentioned a 10 tooth for more out of the corners?  He has a 9 / 72 now how can a 10 tooth do that and give him more ground clearance?   He would have to use an 8 tooth and direct drive. Have you been drinking REDDS at GW's?

[Randy Dacus]

Very interesting advice.....but depends on if you are just Vintage karting or serious about racing at a Vintage karting event.

If you are a big guy you probably need two engines to get your kart moving fast enough to have fun .

Smaller drivers need less power to get around the track, but most of the old guys have gained some belly weight and
are having a hard time just getting in and out of their kart, so just gear up so you don't blow up your engine .

Now back to sipping on a cold Redd's....  and reading up on how to get around the track a bit faster ......