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  #21  
Old 11-09-2019, 01:59 PM
Smerft85 Smerft85 is offline
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Quote:
Originally Posted by Wilson_Engine_Shop View Post
I cant find any sprockets bigger than 66t which would make my ratio 6.6:1 but i'm looking for a 72t live axle sprocket or split sprocket for #40/420 chain. I'm still looking though. What classifies a chain as worn out? Thats something I need to know about. My current #40 chain was locked up when i got it but i soaked it in evaporust for 2 days then soaked it in good oil for half a day. I spray it with chain lube after riding it everytime and its a night and day difference in the way the chain works now

A new chain will be "silky" in motion from end to end. I have a few sitting in auto transmission oil with no determined removal date, I consider them to be my rainy day chains. If they've been rusted or developed any stiff links there will always be some degree of wear. That could mean anything from stretching, scoring and grinding between links and can be potential weak points. A new chain has no weak points up until installed and used, friction from movement starts work on the chain the first use and continues with use, other factors can speed up the process.

If you have a jackshaft you should have at least three sprockets, possibly four. Any sprocket that can be removed and replaced with more or less teeth can be swapped to play with ratio, I'm no guru of ratio, so I recommend googling a calculator that works with a jackshaft at least, I believe both of my t/c units have a 9t, then they can run to an axle or jackshaft containing sprockets. Tire size, engine rpm and sprocket sizes can all affect ratio and the speed of the kart.

Disclaimer: this is just my non-professional opinion, but I'd gear it calling the sprocket on the t/c as your engine sprocket, to a larger count (say 14t) sprocket on the engine side of jackshaft, then on axle side of jackshaft use a smaller count (say 10t) and run the chain to the axle sprocket from there, say your axle has 54t, if the calculator gives you anything higher than a 6.7:1, play with sprocket counts again.
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  #22  
Old 11-09-2019, 05:10 PM
Wilson_Engine_Shop Wilson_Engine_Shop is offline
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I finally got to ride the Murray since the belt change tonight. It has better torque off the line but even going downhill it refuses to go faster than 25mph
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  #23  
Old 11-09-2019, 10:48 PM
Wilson_Engine_Shop Wilson_Engine_Shop is offline
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I honestly think that the governor is keeping me from getting the speed i want to achieve. I'll be getting the 212 soon
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  #24  
Old 11-10-2019, 07:53 AM
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Quote:
Originally Posted by karl View Post
This is very true, but ground clearance is also a factor, smack something while drifting ect , and the sprocket is tacoed and a total loss , So wear would be irrelevant.
that'S why I said:

Quote:
Originally Posted by itsid View Post
So as long as you have the clearance for a larger axle sprocket that's what I'd suggest.

Azusaparts sells split sprockets up to 85 teeth in 420 size
but I'm sure there are other sources as well.

if you want to compound gear (install another jackshaft to reduce sprocket sizes)
it's easy to get a matching set..

say you want 7.5:1 gear ratio

you only need to find factors to get to 7.5
say 5:1 and 1.5:1 (10->15-10->50) [tc->jsin-jsout->axle]
since 5*1.5 = 7.5

or 2.5:1 and 3:1 (10->25-10->30) [tc->jsin-jsout->axle]
since gain 2.5*3 = 7.5

etc.pp

Since the smallest sprocket is always the 10T it doesn't really matter
in terms of wear;
what makes a slight difference however is drag.
the added chain and bearings add frictional losses
not much really and only really relevant in competetive racing I'd say..

so as long as you have the space and the ability to line them up perfectly straight you'd be good with another jackshaft.

sprocket ODs for half inch pitched chain:
60T : ~10"
75T : ~12.2"
85T : ~14"

leaves you with 4", ~3" or 2" of ground clearance on 18" wheels roughly.

'sid
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  #25  
Old 11-10-2019, 01:09 PM
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I'm not that interested in a compound gear setup. I dont think I have the space for it either. I will measure my ground clearance for a different live axle sprocket if i need one. I think I found the limiting factor on my 6hp Tec anyway lol. The governor is kicking in and keeping me under 30mph. I think i'll leave it in and swap a mild build predator on it
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  #26  
Old 11-10-2019, 05:56 PM
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The non hemi head on the hemi block would be why Id do if I had both laying around. I run clone heads on my hemi block.
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  #27  
Old 11-10-2019, 08:22 PM
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talking of different size sprockets made me think of a different size pulley instead ...

So a series 30 with a 7" driven pulley will give you some benefit in terms of gear ratio..

so 6:1 is actually feasible with 18" wheels and 6.5 or more hp with 566lbs or less of total weight.

now all you need is 5500 rpms (removed governor and improved air throughput essentially)

and you crack the 40mph
KartInfo by kartcalc.net:
Code:

KART
RW diameter: 18 in | 45.72 cm Total weight: 566.59 lbs | 257 kg
ENGINE
Original HP: 6.5 Asummed HP: ~7.25 Torque: 9.48 ft lbf | 12.86 Nm RPM: 5500
TRANSMISSION
Final ratio: 6:1 TC type: series 30 7" driven Lowest ratio: 18.78:1 Highest ratio: 6.72:1
PERFORMANCE
Max Wheel Torque: 178.13 ft lbf | 241.51 Nm Min Wheel Torque: 63.74 ft lbf | 86.42 Nm Acceleration: 7.55 ft/s | 2.3 m/s Top Speed: 43.83 mph | 70.53 km/h
not too difficult, and no sprocket to be changed either,
just the driven pulley
https://www.mfgsupply.com/gomini/gom...q30driven.html
(well... a longer belt of course)

and very mild mods (not even really what one would consider "stage 1" )

not bad IYAM especially since the driven pulley isn't even more expensive than the large sprocket @ azusaparts ...

'sid
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  #28  
Old 11-11-2019, 09:28 AM
Wilson_Engine_Shop Wilson_Engine_Shop is offline
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Luckily i have a 7" driven pulley on the Murray already. I think I might be lacking in the horsepower department. The old Tec probably has 6hp at the most since the motor has never been modded but if i stay in the gas long enough going downhill, it finally starts to get through the mid range and I can hear the revs clearly increase and it gets up to around 29mph. But i had a 1/8-1/4 mile stretch of safe road to try

---------- Post added at 09:28 AM ---------- Previous post was at 09:27 AM ----------

Also, i'm 21 and I only weigh about 120lbs soaking wet lol. Im sure that helps
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  #29  
Old 11-11-2019, 09:53 AM
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maybe the old tec had it's barn open and lost a horse or two by now

checking the compression is likely amongst the first things to do,
decarbonizing the exhaust and getting a good fresh and clean airfilter
is also a good idea to regain some lost ponies.
then cleaning up the carb (as long as it's working it's good to maintain it properly)
once once those two important factors (compression and fuel mix) are back to specs again..
maybe it's doing as it should (pushing you to 28+mph with little effort)
since yes.. governed @3600rpm on 6:1 ratio with 18" wheels and your series30 7D
28.68mph is the nominal top speed

And apart from maybe a set of oversized piston rings,
there's no need to spend much money just yet.
It might be even worth removing the governor
(no billet parts, no cam, no heavy valve springs.. just a removed governor and maybe a larger main jet and highflow airfilter)
to see what rpms come out of the tec then (I assume 5k to be well doable)

you can then take your time with the 212 build having a good quality decently running engine installed, there's no need to rush.
You can look around what cam is actually the best for you
if you want more lift or rather longer duration,
if a cam that only improves performance above 6k or if a 4k idealised cam is more to your liking.

'sid
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Old 11-11-2019, 11:57 AM
Wilson_Engine_Shop Wilson_Engine_Shop is offline
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Quote:
Originally Posted by itsid View Post
maybe the old tec had it's barn open and lost a horse or two by now

checking the compression is likely amongst the first things to do,
decarbonizing the exhaust and getting a good fresh and clean airfilter
is also a good idea to regain some lost ponies.
then cleaning up the carb (as long as it's working it's good to maintain it properly)
once once those two important factors (compression and fuel mix) are back to specs again..
maybe it's doing as it should (pushing you to 28+mph with little effort)
since yes.. governed @3600rpm on 6:1 ratio with 18" wheels and your series30 7D
28.68mph is the nominal top speed

And apart from maybe a set of oversized piston rings,
there's no need to spend much money just yet.
It might be even worth removing the governor
(no billet parts, no cam, no heavy valve springs.. just a removed governor and maybe a larger main jet and highflow airfilter)
to see what rpms come out of the tec then (I assume 5k to be well doable)

you can then take your time with the 212 build having a good quality decently running engine installed, there's no need to rush.
You can look around what cam is actually the best for you
if you want more lift or rather longer duration,
if a cam that only improves performance above 6k or if a 4k idealised cam is more to your liking.

'sid
The kart has a new carb on it already from the previous owner. They didnt adjust the idle or anything, they slapped it on and sold it pretty much. I bought a new filter for it not too long ago since the old one reeked of gas from the needle not being adjusted correctly(it ran great without a filter for an hour or two after my dad fixed the flooding issue, then i bought a new filter). I havent had an idling problem since then.

I havent checked compression yet though. What are the specs for compression? I'll do that soon. The crank has quite a bit of endplay in it if that means anything. Im pretty happy with the performance so far with just the carb adjustment, new belt and hotter plug. Its very enjoyable offroading even though its not fast.

The old Tec has grown on me now lol so i'd kinda like to keep it stock and save it as a spare after i build the 212. It doesn't smoke or leak anything right now which is nice. I'm still going to take my time building the predator of course so i'll just run the Tec until the new motor is done

---------- Post added at 11:57 AM ---------- Previous post was at 11:46 AM ----------

The description of the 265 cam from GPS that I was looking at says and I quote "this cam has tons of power from the bottom end of the rpm range all the way to the top. Perfect for minibikes and yard karts for road racing and off-road riding because of its versatility and wide range of power." This will be perfect for my build along with 22lb springs, billet lifters, HP lash caps, Chromoly pushrods, lightweight retainers and keepers. Ive done a lot of research on what parts I need for my specific build
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