edgehanger Posted August 20, 2014 Report Share Posted August 20, 2014 So I rebuilt this stock motor and for some reason the left side is showing a lean condition both at idle and WOT. I can only come to two possible conclusions which are either it has an air leak that the leak down test is not showing or something is wrong with this cylinder and i'll tell you why I suspect the latter. Background of the motor: Engine had to be rebuilt because it overheated real bad and completely sprayed piston everywhere in the engine on the left side. I thought it was just a blown head gasket because I see the paint removed from the cylinder on the outside where the water seems to came out and ran down. one of the worst I've seen. So I go with fresh bore, wisecos, hot rods crank, new seals/ gaskets. pretty routine stuff at this point. On idle the right plug is wet, the left plug not so much. Take it for a little blast and right side is rich with a dark brown/blackish plug, left side looks lean with a hot looking greyish/black plug. Bike starts and idles fine, No bogging, sounds good, runs good, no back firing but it does sputter a little from the big jets I put in trying to figure out what gives. Seems to fall of the pipe a little at times. I know it won't last long like this. I took cylinders back off and the left cylinder looks like its been ran awhile, already removing some of the hash marks like it's wanting to seize, right side look brand new. Mods: No porting, pro circuits, k&n filter, airbox with lid no snorkel, stock carbs, VF2'S, 320 mains should be too rich, 25 pilot, carbs are synced, everything else stock. Stock needle, clip in the middle . What I've done so far: Swapped reeds from VF2 to stock, Swapped heads, swapped carbs, swapped pipes to fmf, verified water pump is working right, rejetted, numerous leak down test and it passed with flying colors, ran it with snorkel on at which point it wouldn't even get out of it's own way(too rich), compression test (about 135 both sides warmed up). Still left side is leaner than the right. Only thing left to swap is the cylinder. Questions: Could it be leaking air only when it's running? Did the cylinder overheat so bad that it has some damage I can't see causing a lean condition? Water not circulating good on the left side? I've seen about three mysteriously lean bikes that passed leak down test but it is usually lean on both sides evenly with no air leaks so we just give it the bigger jets that it ask for and run it. Ever seen anything like it? Can electrical cause a lean condition/overheating or detonation excluding timing? Quote Link to comment Share on other sites More sharing options...
trickedcarbine Posted August 20, 2014 Report Share Posted August 20, 2014 Up the pilot....... Quote Link to comment Share on other sites More sharing options...
camatv Posted August 20, 2014 Report Share Posted August 20, 2014 pressure test the cooling side to the cap's rated blow off.. its a lot like a leak down test on the internals of the motor except you are testing the internals of the cooling system. sometimes there is a head gasket leak but because of the coolant in the motor if the head is leaking into the coolant passages it may not show with only a 6psi leak test. the caps are usually around 10-17psi blow off. i pressure the coolant system to about 12ish. did you also flat test the cylinder? it could be warming up and warping enough to start eating coolant. ?? if your leak tester is one of the ones that has just a single sided gauge and pressure port. switch the sides when you leak test it. i run a t fitting between the test plugs and the p gauge is fitted in between the 2 intake plugs Quote Link to comment Share on other sites More sharing options...
edgehanger Posted August 20, 2014 Author Report Share Posted August 20, 2014 I know the pilot might be too small but it still wouldn't explain the left side running so different. As for my leak tester, its the home made kind with the rubber plugs that go inside of the intakes and exhaust with one side having the gauge and the other side having the hose with the bulb that i got from the drug store to pump it up with. I will definitely pressure test the coolant system and i didn't check the cylinder surface to be flat. I will post my findings. Thanks for the help Quote Link to comment Share on other sites More sharing options...
edgehanger Posted August 21, 2014 Author Report Share Posted August 21, 2014 So I got the tester on it and it holds at 12 to 14 psi but it slowly creeps. Manual says it should holp for at least a minute, it doesn't drop a full psi in that minute but it does creep. So I warm it up and re-test it and no change. I crank it with the tester on and I can see the needle move but not bouncing around. I zing it up and the needle fluctuates a little up and down. I know as the engine heats that the pressure will rise but if I zing it up the needle drops then raises back up as it heats up. Is this just the coolant moving around in the system or it shouldn't be doing this? When I tore it down the bike had overheated so bad that both of the rubber plugs in the bottom of the cylinder were fried like they had been in an oven. I mean shriveled up and broken, completely useless. When I was cleaning the melted piston and carbon out the exhaust I went ahead and hit both exhaust with some 80 grit drum rolls and grinding stones and a little emory cloth with my slotted mandrel, trying to be careful not to remove much material but just to smooth it out after the scratches I put in it while cleaning. Could this be the issue? Quote Link to comment Share on other sites More sharing options...
edgehanger Posted August 22, 2014 Author Report Share Posted August 22, 2014 Well it turns out that there is an air leak that can't be detected with a 6 or 7 psi leak down test. The bottom crank case has 4 spots on the bottom that have epoxy in them and they can leak. I remember talking to jeff at fast a while back about these when he told me that they re-epoxy these. So I happened to just look under the bike checking for any kind of leaks and as I shine my light under the engine I see a wet spot that shouldn't be. It was right at the epoxy under the left side of the case. So I wipe everything clean and go on a couple blast and re-check it and sure enough it's wet again and it smells like gas. I'm going to put some epoxy over it and see if it improves. Quote Link to comment Share on other sites More sharing options...
do-work-son Posted August 22, 2014 Report Share Posted August 22, 2014 New cases are cheaper then ruin a weekend and destroying a motor. Most shop will do the work for a few hundred bucks if you don't wanna and cases can be found for about $200 so less than $500 should be able to fix it right. Just my .02 cents though Quote Link to comment Share on other sites More sharing options...
edgehanger Posted August 22, 2014 Author Report Share Posted August 22, 2014 I don't think the cases are damaged. The cases come epoxied from the factory so, I think it has just worn out in that spot so I'm going to re-epoxy it and check for leaks. Quote Link to comment Share on other sites More sharing options...
sheerider11 Posted August 22, 2014 Report Share Posted August 22, 2014 The cases come epoxied from the factory What? Quote Link to comment Share on other sites More sharing options...
edgehanger Posted August 22, 2014 Author Report Share Posted August 22, 2014 Yea. Look up under the cases, there are 4 spots right up under where the crank sits. It's either epoxy or some kind of glue. Quote Link to comment Share on other sites More sharing options...
wayne_smith97 Posted August 22, 2014 Report Share Posted August 22, 2014 Sounds like someone made an attempt to fix the cases after a catastrophic failure. Quote Link to comment Share on other sites More sharing options...
sheerider11 Posted August 23, 2014 Report Share Posted August 23, 2014 Yea. Look up under the cases, there are 4 spots right up under where the crank sits. It's either epoxy or some kind of glue.No. There's not. You have some other issues you need to figure out. Quote Link to comment Share on other sites More sharing options...
edgehanger Posted August 23, 2014 Author Report Share Posted August 23, 2014 http://i1176.photobucket.com/albums/x336/edgehanger/DSCN4306.jpg What's this? Quote Link to comment Share on other sites More sharing options...
slobanshee Posted August 23, 2014 Report Share Posted August 23, 2014 my 3 cases have the same epoxy looking stuff. Never noticed it before Quote Link to comment Share on other sites More sharing options...
sheerider11 Posted August 23, 2014 Report Share Posted August 23, 2014 Well I went out to the garage and looked. I see what your talking about. I poked at it with an awl. I'm not to sure it's epoxy. I have a set of junk cases. I'm gonna drill those holes Quote Link to comment Share on other sites More sharing options...
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