Velocity stack

Discussion in 'Performance Mods' started by mrbg, Oct 13, 2015.

  1. mrbg

    mrbg Member

    Recently installed velocity stack, on 66cc with NT carb 64#jet,needle clip on mid notch, no airfilter, about 100'ASL. I'm getting a little bog after it warms up. Any suggestions?
     

  2. jaguar

    jaguar Well-Known Member

    hate to say this but these engines aren't drag racers, just poopy put-puts.
    frame your velocity stack and put an ESSENTIAL air filter on that thing!
     
  3. butre

    butre Well-Known Member

    does it bog at part throttle or full throttle?

    These engines are plenty capable of making power, just because they don't from the factory doesn't mean they aren't built to handle it. the only issue they regularly have when a lot of power is being put through them is breaking top end bearing cages, which can be mitigated by installing a higher quality bearing
     
  4. mrbg

    mrbg Member

    On the way home I picked up a molded sink strainer that fits over the stack, I'll give it a try tomorrow if it doesn't work I'll put the stock one back on.
     
  5. mrbg

    mrbg Member

    If it seizes up I've got another topend from a motor with seized bearings on the clutch shaft. I'm retired it gives me something to do
     
  6. mrbg

    mrbg Member

    It bogs at full throttle. If I gradually accelerate it's ok. I'll look at the plug tomorrow I was thinking about raising the clip to the topnotch.guy down the street got a motor stuffed in a mtn bike no filter, carbs out of plumb so the throttle cable clears top bar. No problem oh well
     
  7. butre

    butre Well-Known Member

    with no other problems, bogs if you go straight to full throttle but not when you gradually increase throttle until you get to full is dirty jet, too lean, or float out of adjustment
     
  8. mrbg

    mrbg Member

    It ran good before stack. I hadn't cleaned the carb in a while, stock filter had some oil in it. It could have some dirt in the bowl. I haven't had alot problems with this motor.I changed out clutch pads, chain wheel, cleaned the chain It got some miles on it though.
     
  9. butre

    butre Well-Known Member

    adding the stack is changing the engine. it's most likely a jet size or two too lean now.
     
  10. mrbg

    mrbg Member

    Stack

    That makes sense it's getting more air, I'll try raising the needle. If that doesn't help I'll try a 66#.thanks
     
  11. HeadSmess

    HeadSmess Well-Known Member

    *smacks head*

    raising the needle isnt going to help...

    just the jet. go bigger.

    try to enclose it in a box with a lid of some kind and use one of them square airfilters from a mower or something. you need a pretty large box and nothing near the intake of the stack if you want it to do anything. hi flow filter with no restriction... mesh over the face of it defeats the purpose of the thing. destroys any of the smooth flow the stack is meant to produce...


    or shrug and say what you said... its just for giggles... they last a surprisingly long time with no air cleaner ;)

    grit just loosens it up and makes it run faster! :rofl:
     
  12. butre

    butre Well-Known Member

    I don't have the clearance for an air filter, I just got a bit of screen door material keeping the big chunks out of it
     
  13. mrbg

    mrbg Member

    What's most common stock nt jet? Also I just put a new motor on another bike, 64#jet clip is on mid notch. I have around 5 miles on it, I don't remember them being this tight it runs but won't idle, midrange is good no top end yet. I bought the motor off of eBay it's warrantied I've never used him before and the bolts are flathead it's probably ok just needs some time on it and I've been checking headbolts
     
    Last edited: Oct 22, 2015
  14. mrbg

    mrbg Member

    I went back to the old Post's on break in, sure are alot of theories out there! I'm still on 1st tank of gas 40:1 short rides its fine just tight! It'll be after a couple more tanks
     
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