1qwk421 Posted June 14, 2007 Report Posted June 14, 2007 (edited) ok so i was riding today and i was at wide open throttle and my motor locked up on me and i went coasting for some distance and i tried to kick it over as i was coasting and yea and it was solid as a rock so when i came to a stop i kick again and it kick over like normal but it wont start im thinking a rebuild will fix the prob. but what is the cause of this thanks and by the way its a 421 cub 68mm bore and 4mill crank please help ....thanks Edited June 14, 2007 by 1qwk421 Quote
dajogejr Posted June 14, 2007 Report Posted June 14, 2007 My best guess is you ran it out of gas...and it seized up. Cubs suck gas like no tomorrow....and they suck alky even quicker... If you're gonna run WOT in any gear for more than a few seconds, you need to find ways to get more fuel to it. Larger Float bowls, dual pingle, a fuel pump/carb setup...etc. Is this a gas or alky motor? Quote
1qwk421 Posted June 14, 2007 Author Report Posted June 14, 2007 My best guess is you ran it out of gas...and it seized up.Cubs suck gas like no tomorrow....and they suck alky even quicker... If you're gonna run WOT in any gear for more than a few seconds, you need to find ways to get more fuel to it. Larger Float bowls, dual pingle, a fuel pump/carb setup...etc. Is this a gas or alky motor? its a gas motor i have 38 mm pwk on it do you think the jeting is wrong? Quote
bigboybanshee Posted June 14, 2007 Report Posted June 14, 2007 Your jetting was probably fine, what Dave is trying to say is you didn't have enough fuel in the carb bowls to feed the engine, and it ran lean, locking it up. :thumbsup: Most people that run cubs either put bigger carb bowls on there, or a fuel pump, or both to make sure the engine gets enough fuel so it won't run lean. It's also recommended to drill the hole out bigger in your gas cap, to help the gas flow quicker to the carbs. Quote
dajogejr Posted June 14, 2007 Report Posted June 14, 2007 its a gas motor i have 38 mm pwk on it do you think the jeting is wrong? Even if the jetting is spot on, a long WOT run will run the carbs out of gas... The jetting plays a part when there is enough fuel in the float bowl to feed the motor...at the rate you're sucking down fuel at WOT...it doesn't take long to empty that float bowl, especially on a 4 mil cub. It's possible it's lean on the jetting....too. But, IF you're gonna hold it WOT...you'll need not only clean and proper jetting, but a means to get more fuel to the carbs themselves... Quote
1qwk421 Posted June 14, 2007 Author Report Posted June 14, 2007 Even if the jetting is spot on, a long WOT run will run the carbs out of gas...The jetting plays a part when there is enough fuel in the float bowl to feed the motor...at the rate you're sucking down fuel at WOT...it doesn't take long to empty that float bowl, especially on a 4 mil cub. It's possible it's lean on the jetting....too. But, IF you're gonna hold it WOT...you'll need not only clean and proper jetting, but a means to get more fuel to the carbs themselves... alright i have too fix that prob so i just went out a kicked it over and it fells normal but its popin and sputering but no start up ? Quote
bigboybanshee Posted June 14, 2007 Report Posted June 14, 2007 I'd go ahead and check the compression Have you pulled the plugs yet to see what they look like? Quote
dajogejr Posted June 14, 2007 Report Posted June 14, 2007 Yep, stop running that bike. If something is damaged, running it is only gonna make it worse... Quote
1qwk421 Posted June 14, 2007 Author Report Posted June 14, 2007 I'd go ahead and check the compression Have you pulled the plugs yet to see what they look like? compression test results left cylinder when your sitting on the bike is 135 psi and right cylinder is 0.......... Quote
dajogejr Posted June 14, 2007 Report Posted June 14, 2007 You're gonna probably find a real nice hole in the piston, broken crown, ring land, etc. Either way you slice it, pull the motor out, split the cases and have the crank checked too... Be a waste of time and money to put fresh pistons in and have a chunk of metal waiting to waste a crank bearing...if it hasn't already.... 135PSI is really low for a 4 mil cub unless you're in really high elevation...I'd be curious to see what that side looks like as well, post up some pics.... Quote
1qwk421 Posted June 14, 2007 Author Report Posted June 14, 2007 You're gonna probably find a real nice hole in the piston, broken crown, ring land, etc. Either way you slice it, pull the motor out, split the cases and have the crank checked too... Be a waste of time and money to put fresh pistons in and have a chunk of metal waiting to waste a crank bearing...if it hasn't already.... 135PSI is really low for a 4 mil cub unless you're in really high elevation...I'd be curious to see what that side looks like as well, post up some pics.... yea i live in florida so not so high of elevation and im not sure what cc are in the cool head but yea i tearing it apart tonight will deff post some pics thanks guy for your info Quote
1qwk421 Posted June 15, 2007 Author Report Posted June 15, 2007 yea i live in florida so not so high of elevation and im not sure what cc are in the cool head but yea i tearing it apart tonight will deff post some pics thanks guy for your info so i just spent the last 45 min. tearing my engine apart and looks like the cylinder with no comp was slaping around pretty bad and the rings were pretty much welded to the piston and it looks like the pistons are going to have to be replaced and no broken or crack pistons so i dont think i have to touch the bottom end ......i took some pictures but i cant get them too upload because there to big and dont know how to make them smaller .... Quote
RIPRuck Posted June 15, 2007 Report Posted June 15, 2007 so i just spent the last 45 min. tearing my engine apart and looks like the cylinder with no comp was slaping around pretty bad and the rings were pretty much welded to the piston and it looks like the pistons are going to have to be replaced and no broken or crack pistons so i dont think i have to touch the bottom end ......i took some pictures but i cant get them too upload because there to big and dont know how to make them smaller .... Resize the pics in MS Paint and save it. Or use photobucket which will size them up! Quote
dynodon Posted June 15, 2007 Report Posted June 15, 2007 Where in Fl. are you at ?? I would agree that you ran it out of fuel, causing it to run lean. I have billet bowls, BUT, I also cut off one of the floats. That way I know I wont ever run out of fuel in the 300` that I run. Dajogejr. Is absolutely correct. My 421 cub SUCKS alky like its going out of style!!!!! Quote
1qwk421 Posted June 15, 2007 Author Report Posted June 15, 2007 (edited) Where in Fl. are you at ?? I would agree that you ran it out of fuel, causing it to run lean. I have billet bowls, BUT, I also cut off one of the floats. That way I know I wont ever run out of fuel in the 300` that I run. Dajogejr. Is absolutely correct. My 421 cub SUCKS alky like its going out of style!!!!! im in fort myers cape coral area so could i just cut one of the floats off and still run in the woods and run around on the street with no prob? or if i do that its just a track bike ? Edited June 15, 2007 by 1qwk421 Quote
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