SplitSide Posted May 17, 2016 Report Share Posted May 17, 2016 Have 421 cub have trouble launching falls on it face when you drop the clutch out of the hole. Has 145 compression timing +6 drag port gearing is 15/42 41mm flat side mikuni carbs shearer oof pipes 65 pilot jets 260 main 6fj41 needle 2600 elevation in Canada Quote Link to comment Share on other sites More sharing options...
SplitSide Posted May 17, 2016 Author Report Share Posted May 17, 2016 It's a buddies quad Matt shearer was the last one to work on it. We did a leak down test last night was good. Ya that's what we thought the pilot jet was pretty high has a build sheet on it I'll see if I can find the fourm page and post it thanks for your help Quote Link to comment Share on other sites More sharing options...
trickedcarbine Posted May 17, 2016 Report Share Posted May 17, 2016 (edited) Drop the front tooth back to a 14 tooth. Get some proper jets in those carbs. No way Shearer set those carbs up like that. You'll be around a 32.5 pilot max. What fuel? Edited May 17, 2016 by trickedcarbine Quote Link to comment Share on other sites More sharing options...
trickedcarbine Posted May 17, 2016 Report Share Posted May 17, 2016 Ya, I didn't notice they were K&T PJ carbs till I saw the other jetting thread. That explains the small main. Quote Link to comment Share on other sites More sharing options...
SplitSide Posted May 17, 2016 Author Report Share Posted May 17, 2016 Yeah Matt said to run 14/43 and running 110 fuel. What do you think with the needle it's the leanest one 6fj41 Quote Link to comment Share on other sites More sharing options...
locogato11283 Posted May 17, 2016 Report Share Posted May 17, 2016 JFC. I keep hearing more and more stories like this. I heard two at the BansheeHQ ride. Quote Link to comment Share on other sites More sharing options...
theputz Posted May 17, 2016 Report Share Posted May 17, 2016 Stories like what? 1 Quote Link to comment Share on other sites More sharing options...
registered user Posted May 18, 2016 Report Share Posted May 18, 2016 sounds like it wont pull the gearing you have. maybe you have to much tire or its a heavy bike. cheapest thing to change is front sprocket and see what happens. then again you might have a mechanical problem Quote Link to comment Share on other sites More sharing options...
Surfrjag Posted May 18, 2016 Report Share Posted May 18, 2016 Pump gas? 145 may be low. What was it when it was fresh? Quote Link to comment Share on other sites More sharing options...
locogato11283 Posted May 18, 2016 Report Share Posted May 18, 2016 Everyone is looking at everything but the real issue here. Quote Link to comment Share on other sites More sharing options...
sheerider11 Posted May 18, 2016 Report Share Posted May 18, 2016 Everyone is looking at everything but the real issue here.That shearer suggested X setup by OP chose to run Y setup Quote Link to comment Share on other sites More sharing options...
SplitSide Posted May 18, 2016 Author Report Share Posted May 18, 2016 It's runs on vp 110 and Matt said he didn't touch the carbs k&t set them up and talked to them and he said that's the way he sets those carbs up at 5000ft in Utah Quote Link to comment Share on other sites More sharing options...
SplitSide Posted May 18, 2016 Author Report Share Posted May 18, 2016 Running 12 paddles extremes Quote Link to comment Share on other sites More sharing options...
theputz Posted May 18, 2016 Report Share Posted May 18, 2016 (edited) Here is the original post by Matt after the build/dyno (graph is on last page). He ran the carbs as set up by k&t and noted it was rich then at their elevation (we are higher yet). http://www.atvdragracers.com/forum/dyno-results-33%3B/5913-gas-4mm-cub-set-up.html#/forumsite/21322/topics/5913?page=1 Edited May 18, 2016 by theputz Quote Link to comment Share on other sites More sharing options...
locogato11283 Posted May 18, 2016 Report Share Posted May 18, 2016 So, why does it only have 145 pounds of compression? Quote Link to comment Share on other sites More sharing options...
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