Avon gearing

[Doug Jorgensen]

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.