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2nd gear bog when trying to launch.


sycoticbanshee00

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It made 77 hp, 40tq on the dyno with that jetting. 400 main, 30 pilot, needle 2nd clip. Now that I went to try it out it bogs in 2nd gear when trying to launch and then it kicks in. Everyone else is taking off well into the powerband just like it's supposed to. My bike was actually better at taking off when it was stock than now that it's putting out double the hp. Fail...

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some sort of setup issue. OR its fine  i'm 280-300lbs and most times need to launch in 1st.    if i put a lightweight on the bike they will launch fine in 2nd.  its just part of being a big dude. do some jetting checks  i dont care what the "dyno" jetting shows.  if i left the same jetting on the dyno runs i have had in the past in the bike when i ran it  it would be dead lean and blow up. hell the 535 i had to shut the power jets off completely before it started making over 900 degree's on egt.

 

cubs with stock carbs are usually in the 410-420 range on mains.   but thats a cub.  

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Def do a leakdown test. 400 mains is huge for that motor. I was spot on with 340 main 27.5 pilot 1.5 air screw mid clip stock needle in warm weather (60+) with stock carbs, since your a bigger dude IMO I would of went with a bigger motor like a 4 mil serval Ect but work with what you have for now. Get the jetting spot on first and then try it out again and report back. If it's still doing that could possibly be a dome issue when jetting is dialed in

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I checked my plugs and they were a brown, caramel color all around the white area, not black or anything like that. CT built my motor and set it up. I'll have to double check on the mains because he might have told me they start with a 400 main and then lean them down accordingly. I know a lot of you are going to pick on me now because I mentioned "CT". Lol

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  • 1 month later...

Old post but, would loose squish or very high port timing cause the same symptoms? 

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  • 2 weeks later...

yes on the high port timing.  maybe not on the loose squish..  much over 200* on the exhaust on a full weight bike and your asking for some bogg issues with "heavyweight jockey's  get in that range on a stock cyl small cc motor and your going to need alky for sure  and a dead on setup.  on my welded sc 350cc, +6 swinger and steel axle with 12 haulers it only likes to take off in 1st with me on it  loose some weight on the jockey and it flys off in 2nd  thats 14/41 gearing  full steel chassis with real shocks.    i left a lot of timing out of it because it also like to kinda stand up a tad on the launch....   but its a quick shift to 2nd and its gone...   

 

the 421 cub on 110 with stock carbs was a blast to ride...   it didnt bog as bad as some other gas ones i have done with larger carbs..  pump gas carb cubs are kinda picky on setup..  i personally just slap in a set of power valves and cure that whole problem......  he hee

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