SplitSide Posted May 17, 2016 Report 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
SplitSide Posted May 17, 2016 Author Report 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
trickedcarbine Posted May 17, 2016 Report 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
trickedcarbine Posted May 17, 2016 Report 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
SplitSide Posted May 17, 2016 Author Report 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
locogato11283 Posted May 17, 2016 Report Posted May 17, 2016 JFC. I keep hearing more and more stories like this. I heard two at the BansheeHQ ride. Quote
registered user Posted May 18, 2016 Report 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
Surfrjag Posted May 18, 2016 Report Posted May 18, 2016 Pump gas? 145 may be low. What was it when it was fresh? Quote
locogato11283 Posted May 18, 2016 Report Posted May 18, 2016 Everyone is looking at everything but the real issue here. Quote
sheerider11 Posted May 18, 2016 Report 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
SplitSide Posted May 18, 2016 Author Report 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
theputz Posted May 18, 2016 Report 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
locogato11283 Posted May 18, 2016 Report Posted May 18, 2016 So, why does it only have 145 pounds of compression? Quote
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.