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Avon gearing
#21
(07-18-2017, 07:35 AM)David Luciani Wrote: 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
Cool


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.
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#22
Thanks Dave for the input...the MC-75 IS unmodified and I am trying to keep it era correct. I thought the 75 was more in the range of 125cc ? At Sandy Hook I was put in the 8.2 rear class, and got left in the dust on the corners...although I really didn't expect all that much being it was my first time out ever in a kart....I have been Drag Racing and restoring Corvettes most of my life, so I have the mechanics of it all down, I just want to be "somewhat" competitive, at the very least. I'm just trying to learn how all of it ties in. Back to the gearing...I'm thinking that at 6'2" and 250 lbs., it 's gonna take alot more than gearing....the kart runs real good, I ran 9-72 at Sandy Hook, but I understand all track are different as far as straights and corners. I have a few different axle sprockets, so I'll bring a few, ask a few questions, and I guess see what works best for me. But any advice is always helpful !

Thanks.....Doug
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#23
..im not sure about a 75 but my 70 runs in the 8.2 class ..
im still wondering about ur rear tires ..12" are they on 6" rims ..
what blitz chassis you run ..the old long style ..?? or like f1000 style ..
with them big tires you might need a 74 ..
id have to guess you ride with us in historic if your not in 8.2 either way both unscored and great folks in each class ..woops 8.2 scored class this yr ..
you will be surprised how much track time you,ll get ..its all about fun ..
I ride in the rear in sidewinders with john P. we have the best time ..I pass him he pass me we laugh so hard passing each other see who pressure the other guy ..its fun and we are in the back not in any bodys way ..

   
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#24
(07-18-2017, 08:28 PM)steve miller Wrote: ..im not sure about a 75 but my 70 runs in the 8.2 class ..
im still wondering about ur rear tires ..12" are they on 6" rims ..
what blitz chassis you run ..the old long style ..?? or like f1000 style ..
with them big tires you might need a 74 ..
id have to guess you ride with us in historic if your not in 8.2 either way both unscored and great folks in each class ..
you will be surprised how much track time you,ll get ..its all about fun ..
I ride in the rear in sidewinders with john P.  we have the best time ..I pass him he pass me we laugh so hard passing each other see who pressure the other guy ..its fun and we are  in the back not in any bodys way ..

Yes Steve, they are 12" tires on a 6" rim. To tell you the truth I really don't know exactly what chassis it is, it's from about 1964...as far as the long style, I wish..at 6'2" my knees are in my chest. Maybe someone on here who saw it at Sandy Hook might remember. I tried it on the street with a 76 gear, fairly quick off a start, and at about a 275 ft. it was still pulling at top end. When I was in 8.2 at Sandy Hook, if I'm not mistaken, it was scored. This is all very new to me, so I'm learning as I go, and trying to absorb everything.
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#25
..biggest thing you gotta absorb is having fun .. Lol..

in vintage karting there are sooooo many good folks ..and there full of knowledge and willing to share ..
yes ill bet you were in scored 8.2 parta the northeast deal ..few them guys are very fast ..
you come to avon scotts event ...he will find a spot for you to ride if you don't wanna be in 8.2 scored ..

is your kart same style as mine ..if so I cant belive you can ride it ..if it is you need rupp pedals give you about 4 more inches ..

correction to my post 8.2 rear is scored at avon this yr.. as parta the northest shootout ..
woops sorry ..
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#26
ok doug,
i should be sleeping but this is a fun thread.
here's the general mcculloch specs bore and stroke
Model - Bore Stroke Displacement
MC2 - 2.165 x 1.635 = 6.05
MC5 - 2.125 x 1.375 = 4.9
MC6 - 2.125 x 1.500 = 5.3
MC7 - 2.165 x 1.635 = 6.05
MC8 & 9 - 2.165 x 1.635 = 6.05
MC10 - 2.125 x 1.500 = 5.3
MC20 - 2.125 x 1.635 = 5.8
MC30 - 2.165 x 1.635 = 6.05
MC40 & 45 - 2.165 x 1.635 = 6.05
MC70 - 2.217 x 1.835 = 7.08
MC75 - 2.250 x 1.835 = 7.29
MC49 - 2.125 x 1.375 = 4.9
MC90,91,2,3 - 2.165 x 1.635 = 6.05
MC100 - 2.250 x 1.835 = 7.29
MC101 - 2.280 x 1.835 = 7.5 

ok so technically you have a bigger motor than a mc91 if you only take bore and stroke into account.
but there is something else to consider and your motor experience will help.
you have a motor with only six intake ports.
that seems pretty good till you consider all mc91's 92 92 and mc101's have eight ports.
the two extra ports provide a huge advantage in performance.
if you want to be almost competative ask to enter into the mc91 100 cc rear class.
you'll still be a slight fuel flow disadvantage but the longer stroke will even things out a bit.

or you can run in historic un-scored where you'll have a huge advantage with your engine supposedly but your wt. will drag that down a bit.
of course there are some clowns me included that run modified 9 ported motors in that class. totally legal but a bit unfair to the other guys.
my mc10 that i blew up was fast enough to run with the mc91's but it lost alot of historics with carb issues mis-adjusted clutches blown chains bad gearing.
i still had alot of fun running it regardless of results.

point is unless you intend to get into the racing end of things gear tuning is part of the learning process.
so bring what ya got. if you need a different number gear tooth find me in the pits i'll lend ya wghat ever i got in the box.

jeff,
i'm running on less than enough sleep lately and got backwards on the adjustments.
probably why i lose a few races here and there too.
wish i was drinking too much redds then i'd have an excuse.
anyway just trying to see an answer from you and i got it
sort of
i guess.
Big Grin
Dave L.
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#27
Just an FYI......

I noticed that the N.E. Promoters Cup Series was mentioned regarding "scored classes" and "classes in general". 
I would like remind everyone that, anyone with karts that fit into the classes being tracked for the series, can at any of the N.E. Series tracks, opt to run as Tier II (non-scored). 

Also, all classes being scored are scored by the choice of the individual promoters/tracks.
i.e. at Avon there are 6 classes being scored. Only 5 of those 6 are also being tracked for the Series.

Basically, no one has to be scored...... But every one has to have a good time. Or else!
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