stroking Posted June 12, 2010 Report Share Posted June 12, 2010 (edited) I just put some 34MMpj on a 421 setup and it runs good up top but boggs really bad on take off. pilots 58 main .108 needle on first clip...... dump tube .122 i had the main at .120 and the bog was worst....also where should the choke knobs be set at because it seem to rev better when i turn them out. sealevel vito's HIGHFLOW powerjets......and they dump alot of fuel!!! 180psi +10 timing CPI's O/F Will the pilotjet cause a bad bog if its to big? its not a lean bog because its hard to clear it out....OR is it that PJ's are just bad carbs to run on Alky? Edited June 12, 2010 by stroking Quote Link to comment Share on other sites More sharing options...
shanYE west Posted June 12, 2010 Report Share Posted June 12, 2010 A lil more info on your setup would help give us a better idea on whats going on.. Is this a stock cylinder 421? 58 pilot sounds pretty fat.. It could be loading up wich could be why your had to lean back the mains to get it to clean out.. I'd drop the pilots back to a 50 or 48 and start there. Quote Link to comment Share on other sites More sharing options...
stroking Posted June 12, 2010 Author Report Share Posted June 12, 2010 A lil more info on your setup would help give us a better idea on whats going on.. Is this a stock cylinder 421? 58 pilot sounds pretty fat.. It could be loading up wich could be why your had to lean back the mains to get it to clean out.. I'd drop the pilots back to a 50 or 48 and start there. vito 4mil cylinders Quote Link to comment Share on other sites More sharing options...
shanYE west Posted June 12, 2010 Report Share Posted June 12, 2010 yah.. ur definately rich.. I'd start by leaning back the pilot. you'll probably end up going to a leaner needle.. then fating back up on the main... But.. start with the pilot. Quote Link to comment Share on other sites More sharing options...
RadarRacing Posted June 12, 2010 Report Share Posted June 12, 2010 I hope you get the bogg cured and it may be jetting but if you cant get it cured. There was a similar post about a bogging problems on atvdragracers about Vitos BB cyls when degreed out with a 4 mil crank the exhaust duration was stupid high like 205 or 208 degrees which can kill TQ. Vitos told him those numbers were fine but thats wrong IMO. If it were me I'd use either no base gasket or a real thin one like .005 and try it. Just make sure your squish clearance is .040 or so with tightening it up. Quote Link to comment Share on other sites More sharing options...
shanYE west Posted June 13, 2010 Report Share Posted June 13, 2010 I hope you get the bogg cured and it may be jetting but if you cant get it cured. There was a similar post about a bogging problems on atvdragracers about Vitos BB cyls when degreed out with a 4 mil crank the exhaust duration was stupid high like 205 or 208 degrees which can kill TQ. Vitos told him those numbers were fine but thats wrong IMO. If it were me I'd use either no base gasket or a real thin one like .005 and try it. Just make sure your squish clearance is .040 or so with tightening it up. Good info Todd. Quote Link to comment Share on other sites More sharing options...
stroking Posted June 13, 2010 Author Report Share Posted June 13, 2010 I hope you get the bogg cured and it may be jetting but if you cant get it cured. There was a similar post about a bogging problems on atvdragracers about Vitos BB cyls when degreed out with a 4 mil crank the exhaust duration was stupid high like 205 or 208 degrees which can kill TQ. Vitos told him those numbers were fine but thats wrong IMO. If it were me I'd use either no base gasket or a real thin one like .005 and try it. Just make sure your squish clearance is .040 or so with tightening it up. they sent a base gasket of .060 which is needed to get the piston to not come out of the cylinder. i change the pilot jets to 48 and it got better but it still bogs......also it seems like it's taking off in 2 gear and bogs when shifting though the gears......1-5 override...you can hear the rpms drop when you shift. im starting to think it has some thing to do with the cylinder setup though Quote Link to comment Share on other sites More sharing options...
RadarRacing Posted June 13, 2010 Report Share Posted June 13, 2010 If it uses a .060 base gasket forget what I said about using no gasket or a .005. I like Vitos as company for cables,sprockets etc but as an engine builder or designer I do not like em. If you can get more info like your squish clearance, compression ratio or at least dome size, or even measure the top of the exhaust port up to the top of the cyl. We can maybe help you with some calculations. Might start a new post if you do.I'd keep it in the drag section there's a lotta good help here. Quote Link to comment Share on other sites More sharing options...
stroking Posted June 13, 2010 Author Report Share Posted June 13, 2010 well the domes are 17cc and the compression is 184psi i'll have to get the squish later. Quote Link to comment Share on other sites More sharing options...
stroking Posted June 14, 2010 Author Report Share Posted June 14, 2010 well the domes are 17cc and the compression is 184psi i'll have to get the squish later. squish is .050 Quote Link to comment Share on other sites More sharing options...
J-Madd Posted June 14, 2010 Report Share Posted June 14, 2010 Are you talking about the Vito's cylinders, or just that you got the package from Vito's? I've got a Vito's 421 Cub and it uses the 0.060" base gasket. It has 110 mm rods and uses their pistons (9768 series or something like that.), OOF BB CPIs. It has 19cc domes, 175 psi, and 0.050" squish. I run 38 pwk airstrykers on it and it hauls pretty good. 4.07s in 300 ft; stock lightened chassis. Quote Link to comment Share on other sites More sharing options...
RadarRacing Posted June 15, 2010 Report Share Posted June 15, 2010 Ya I shouldn't have assumed it was their new "big block" setup. It may be a cub. I was talking about their stock style triple ported cyls. If you have one of those $25-40 laser temp guns you can ck cyl temps right after a 300 ft run. Just like a plug chop shut it off immediately after the run and roll to a stop. If the side of the cyl right at the top doesn't get up to 100 degrees it'll be rich. At 100 degrees you are getting close on the powerjet. Quote Link to comment Share on other sites More sharing options...
stroking Posted June 15, 2010 Author Report Share Posted June 15, 2010 yes,its the bigblock 421 i think its lean then because the cylinder and pipes get to hot to hold your hand on for 2seconds after 2 runs....and it bogs between shifts with a full override. and i have a 421cub here that you can make 5 passes on and still hold your hand on the motor as long as you want right after the runs. im starting to think PJ Carbs are not good for alcohol. Quote Link to comment Share on other sites More sharing options...
feelsoright03 Posted July 11, 2010 Report Share Posted July 11, 2010 I would definetly think about upgrading the carbs to some 39pwks and back the timing down to around 7. ~Teddy~ Quote Link to comment Share on other sites More sharing options...
Wheelman Chassis Posted July 12, 2010 Report Share Posted July 12, 2010 I would definetly think about upgrading the carbs to some 39pwks and back the timing down to around 7. ~Teddy~ i have pjs on mine setup is in my sig, mine revs perfect.. i got the carbs setup, but im pretty sure that the idle curcuit has some major work done. also if the choke/ idle knobsare too far out it will bog and not rev clean, Quote Link to comment Share on other sites More sharing options...
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