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2nd gear bog when trying to launch.


sycoticbanshee00

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Alright so I have a 4mill stock cylinder putting out about 77hp, 40rwtq, I'm currently running 14/41 gearing and 20x10x10 8 paddle haulers, shearer sb inframes. So I tried launching the damn thing in 2nd this past weekend at dumont and no matter how high I revved it it would simply bog off the line and then a few seconds later hit the powerband. Only 1st seems to work and I'm at the top of 3rd with 4th only holding steady if I shift into it, but I want to be able to launch in 2nd then hit 3rd and 4th. Btw my fatass weighs over 280 so I'm sure that's my problem, but I've seen other big dudes launch hard. Maybe 13/42 gearing? 13/44? Thanks

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Alright so I have a 4mill stock cylinder putting out about 77hp, 40rwtq, I'm currently running 14/41 gearing and 20x10x10 8 paddle haulers, shearer sb inframes. So I tried launching the damn thing in 2nd this past weekend at dumont and no matter how high I revved it it would simply bog off the line and then a few seconds later hit the powerband. Only 1st seems to work and I'm at the top of 3rd with 4th only holding steady if I shift into it, but I want to be able to launch in 2nd then hit 3rd and 4th. Btw my fatass weighs over 280 so I'm sure that's my problem, but I've seen other big dudes launch hard. Maybe 13/42 gearing? 13/44? Thanks

 

Did you rejet for the elevation and temps?

I have a 63 HP bike. 210lb rider with a +6 arm. I run a 14-42 with 22x11x8 12 paddle haulers or 22x11x8 11 paddle and it carries the fronts on the launch.

Sounds like your weight or your jetting is killing you. (Well….the weight is killing you…. but that's another topic.)  :lol:

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I'm thinning you need a bigger tire. You are probably digging in when you fan the clutch with that small tire and your weight.

A small tire that digs a hole will cause the front paddles to have to LIFT the bike, while the rear paddles are driving the tire into the sand. Neither move you forward and both will add force that causes a bog.

There can be more to it, but those are just my general thoughts…...

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^^^^ I disagree completely. I never heard of too small or little of a paddle tire cause a bike to bog. I have have plenty of 260-300lb friends launch in 2nd with more tire than that. Either jetting is too rich or if its spot on then an ignition , port timing or other issue could be the culprit. If you said you had a high output ricky stator I would suspect it possibly.

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Stock flywheel, stock stator, stock swingarm, +6 timing, stock carbs, 400 main, 30 pilot, needle on the 2nd clip from the top, airscrews 2 turns out, my primary drive I assume is stock since I've never touched the tranny itself, 5psi on the tires. I recently just broke in the motor and decided to make some passes to see how it does, my dad who weighs about 180 was having no problem launching in 2nd, so I'm assuming my fatass is holding me back. On my dads stock stroke dune ported setup I was able to launch in second with the same tire setup, but he was running 13/42 gearing. I figured this is making more power so why am I having problems? I was thinking the gearing since I'm at 14/41, but I'm not sure.

Edited by sycoticbanshee00
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I launch my 280# fat ass in 2nd all day with a bolt on stock motor and my gearing is 14/41, but I am on 20x10x10 old school 8 paddle sand skate II's, (v-paddles for all you young stars)...

 

400 mains has to be incorrect.

What's your plug chop look like?

It's gotta be black and about 4mm thick.

I'd guess you need to be in the 330-340 main range.

Not sure why your needle is fattened up too.

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Yeah that's the jetting my builder left it with for the break in. I'm guessing I could start leaning things out? I haven't checked my plugs, I'll do that. If jetting is wrong, why is my dad who weighs 180 launch fine? Also my mix is at 32:1.

Edited by sycoticbanshee00
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Get your engine tuned optimally then worry about gearing and tires.

 

Sent from a van down by the river

 

I assumed since you knew what kind of power it made, that it was tuned.

If he sent it out the door tuned rich….you aren't making the power you thought.

 

NOTE: You don't need to be jetted rich for break-in purposes. That's hella old school.

You should have all your heat cycles and break-in done before it hits the sand anyway.

Edited by WINDYCITYJOHN400
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I assumed since you knew what kind of power it made, that it was tuned.

If he sent it out the door tuned rich….you aren't making the power you thought.

 

NOTE: You don't need to be jetted rich for break-in purposes. That's hella old school.

You should have all your heat cycles and break-in done before it hits the sand anyway.

Yea. That's doesn't make sense.

I'm not saying it's impossible for a stock cylinder and stock carbs to need 400 mains...just saying of all the ones I've seen ( that are tuned in good) are in the 330-350 range.

...that being said, there are some setups out there that are somewhat " unconventional"...so who knows.

I'd recommend that you do a couple full throttle plug chops with the needle in the middle position and see where you are.

 

Sent from a van down by the river

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