creamsickle Posted June 7, 2006 Report Posted June 7, 2006 ok so im running a 4mill cub with 35pwks and a noss coolhead with 18cc domes. the timing is advanced 5 degrees, the cylinders have been decked on the bottom in order to make it more of a dune bike, and for some reason it really hasnt been running good. I did a compression check and both cylinders were at 175psi did a leak down a little while ago and it checked out. I am runing c12 race gas and using the torco gp7 oil. when I checked the plugs the left cylinder seemed to be running leaner then the right and the plugs were both yellow. the left was like canary yellow, weird coloring. never seen a yellow plug. I am running engine ice and am wondering if that could be leaking in and causing it to become yellow rather then carmel. my jetting is 52 piot and 162 on the main. before you get into the power it has a bog. like all banshees but the bog is kinda funky, almost like the main is way too big. but just a slight bit different, more choppy then a fat main. but the plugs look like they are lean I cant figure out what the problem is. anybody have any ideas? I will probably be pulling the cylinders to check the gasgets and will be throwing in a thinker base gasget to bring it back to the normal cub port timing. Quote
dajogejr Posted June 7, 2006 Report Posted June 7, 2006 Boy....does this all sound familiar.... I've had to have the head surface and base surface decked on my cub. It was sucking air at the bottom, and leakind coolant at the top... Both surfaces were uneven out of the box...to my dismay. Got it sealed up....and my flywheel had bad (broken) magnets inside. Ran GREAT on the dyno...took it out in real world...(rainy, wet and muddy) and had some more problems. I'm in the middle of getting bigger carbs now, same as you....and getting everything in the ignition re-tested and Ohm'd out. Also...my squish out of the box was a little tight. You may want to have that checked and measured as well... I'm not trying to start a war of words, but...for a motor that was supposed to be bolt on and go...it's been more bolting on and not enough go... Sorry I can't be of much help...but I'm going to keep an eye on this one...and know you're not alone in this one brother! Best of luck!! Quote
rebelbanshee2 Posted June 7, 2006 Report Posted June 7, 2006 Instead of pulling the cylender to check the gaskets do a leak down test so you can know where its leaking for sure..if it is. Quote
dlnoss Posted June 7, 2006 Report Posted June 7, 2006 Was the squish clearance checked when assembled? With the decking, 'standard' Cub dome clearance might not be right for that engine. It could effect the lower RPM power. Quote
creamsickle Posted June 7, 2006 Author Report Posted June 7, 2006 Was the squish clearance checked when assembled? With the decking, 'standard' Cub dome clearance might not be right for that engine. It could effect the lower RPM power. I already did a leak down test and it checked out. a leak down test wont test the inner oring so I will still ahve to look and see if its gone bad. the bike makes great low end power. it dynoed at 52ft lbs of torque at like 6500 rpms. im running the paul turner pipes. my problem is that I cant get it jetting right cause of this weird ass yellow plug. I had a builder deck it and assemble and cut the domes so it should be all up to specs. but I will have to see. im goign to throw the thinker base gasget on to bring up the port timing again and then see how it runs. I really dont want to go get new domes and get them cut but if it is the head clearance thats my problem well then I guess I dont really have a chance. Quote
cdwood37 Posted June 7, 2006 Report Posted June 7, 2006 This is the exact same problem i am having. My plug was a yellow color and i have a bog right in the middle until i get up into the higher rpm range. How do i do a leakdown test? Quote
creamsickle Posted June 8, 2006 Author Report Posted June 8, 2006 yeah the whole yellow thing is really gettin me messed up here. if anybody has any knowledge of this please help. yeah it kinda seems like my bike has the same problem as yours. Quote
creamsickle Posted June 9, 2006 Author Report Posted June 9, 2006 so I took the head off and found that there was some greyish yellow buildup on my pistons the left was worse then the right. I can scrape it off with my fingernail. not realyl sure but I think its from a coolant leak so im going to change out the orings and clean off the pistons a little and give it a shot. anybody have any advice on how to clean then off. http://i15.photobucket.com/albums/a390/kcpoager/6357a415.jpg Quote
addicted Posted June 12, 2006 Report Posted June 12, 2006 so I took the head off and found that there was some greyish yellow buildup on my pistons the left was worse then the right. I can scrape it off with my fingernail. not realyl sure but I think its from a coolant leak so im going to change out the orings and clean off the pistons a little and give it a shot. anybody have any advice on how to clean then off. http://i15.photobucket.com/albums/a390/kcpoager/6357a415.jpg I am having similar problems with my 421 cheetah. My plug was yellow and it was getting too hot. I suspected a coolant leak also so i checked the o-ring groove depth and found that they are too deep. there is not enough squish on the o-ring. You may want to check yours. Quote
WinNuke2003 Posted June 12, 2006 Report Posted June 12, 2006 Weird...my plugs always burn a dark yellowish orange, and they are very even. Get a pic of the plugs Quote
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