gregrob Posted June 21, 2009 Report Posted June 21, 2009 Well we were out beating on my duner today and the right cylinder let go. Melted the ground strap and electrode completely off the plug and starting melting the threads. That cylinder has ZERO compression, will not even make the needle on the comp tester flicker... lol Dont know what happened but I will be inspecting everything as I tear it apart for possible causes. It was only the right side. The left side still has good compression, and the plug looked great when we took it out. I'm starting to wonder about this thing because every single time I have had a problem where I've been too lean, it's been on the right hand cylinder. Like maybe there is an air leak at the cases, or crank seal or something. Definitely going to be watching that very closely as it goes back together. Only changes to the bike from last wknd were I advanced the timing from +4 to +8 and opened the powerjets 2 turns to compensate. The bike was beastly in the bottom/mid range but felt like it bogged just a tad on top, so I closed the powerjets 1 turn, and made a few more runs. It pulled clean all the way through the powerband, until this happened. Only problem I have with blaming jetting, or timing is the fact that the left cylinder is cherry. No problems at all, plug looked great, still has good compression, etc. Bike is HJR dune ported 4mil with 19cc domes and this happened at about 8500ft elevation, so the compression was extremely low for methanol lol... Running 35.5 mikunis with a 55pilot and .103 mains. Bike has been running like this for a long time and hasn't had a problem until now, so either something happened to cause a big air leak and pull that cylinder lean, or just the RIGHT side didn't like the new jetting/timing combo... Other option is that the right bowl got sucked dry. It was in 6th at WOT when this happened. Damn it was running hard before it let go. I just gotta get back to that point and get it to live and we'll be good. Still had fun mobbin the hill climbs with Rippen and crew on the other bike though. Any ideas are appreciated. I'll be in with neat-o carnage pics later. Quote
rubberneck Posted June 21, 2009 Report Posted June 21, 2009 before you tear it down, do a leakdown test to rule that out. Are you running a pingel? Cap gutted? Quote
shanYE west Posted June 21, 2009 Report Posted June 21, 2009 Ok.. I could have swore someone was taking bets on how long it would take before it blew up. :shrug: Quote
FireHead Posted June 21, 2009 Report Posted June 21, 2009 Ok.. I could have swore someone was taking bets on how long it would take before it blew up. :shrug: That was Loco.... Quote
2strokespirit Posted June 21, 2009 Report Posted June 21, 2009 Hole in piston means detonation.. So to much timing advance, BUT if there is no airleak and you can't find any other issues, your cdi is starting to fail.. Quote
mopar1rules Posted June 21, 2009 Report Posted June 21, 2009 you don't give more fuel to compensate for more timing. that's just a bandaid. you need higher octane fuel for higher timing advance. also, you may of had a air leak on the right hand cylinder, and then when you advanced the timing another 4 deg, it just compounded and wiped that cylinder out. hole in the center of the piston means timing to high and deto. Quote
C&B Posted June 21, 2009 Report Posted June 21, 2009 mine was bad crank seal/bearing on the right side. Are you running stock bearings and helical gears (SPELL??). Same set up not alky though. Do a leak down man, then youll know for sure. If not, Id say detonation as mentioned before. Quote
gregrob Posted June 21, 2009 Author Report Posted June 21, 2009 Ok.. I could have swore someone was taking bets on how long it would take before it blew up. :shrug: Different bike dude. Loco wants me to blow up the fast engine. I'll say this nicely the first time. Please offer constructive input or don't post in my threads. Quote
gregrob Posted June 21, 2009 Author Report Posted June 21, 2009 before you tear it down, do a leakdown test to rule that out. Are you running a pingel? Cap gutted? Good idea. Yes on pingel and gutted cap. Only thing I dont have is billet bowls because I haven't found any for these smaller mikunis. Quote
bonbon Posted June 21, 2009 Report Posted June 21, 2009 Did you get the head off to see what it looks like? I bet you have an air leak somewhere on that right cylinder. Quote
gregrob Posted June 21, 2009 Author Report Posted June 21, 2009 you don't give more fuel to compensate for more timing. that's just a bandaid. you need higher octane fuel for higher timing advance. also, you may of had a air leak on the right hand cylinder, and then when you advanced the timing another 4 deg, it just compounded and wiped that cylinder out. hole in the center of the piston means timing to high and deto. It's on methanol. Don't get much higher octane than that. and yes you do add fuel when you add more timing. It's always best to go rich, then work your way down. This wasn't a jetting/timing combo issue as I stated in the opening post. The left cylinder is fine. Something happened on the right to cause it to go lean, start detonating and torch the piston. I just need to find out what. Quote
gregrob Posted June 21, 2009 Author Report Posted June 21, 2009 Hole in piston means detonation.. So to much timing advance, BUT if there is no airleak and you can't find any other issues, your cdi is starting to fail.. I would think too much advance would hurt both cylinders. Of course one could go before the other. Besides +8 is totally reasonable on a methanol bike, especially at my elevation. What makes you think CDI? Wouldn't that affect both cylinders as well. Not saying it couldn't be, I'm just curious to hear your reasoning. Quote
gregrob Posted June 21, 2009 Author Report Posted June 21, 2009 QUOTE (C&B @ Jun 21 2009, 01:41 PM) <{POST_SNAPBACK}> mine was bad crank seal/bearing on the right side. Are you running stock bearings and helical gears (SPELL??). Same set up not alky though. Do a leak down man, then youll know for sure. If not, Id say detonation as mentioned before. Thanks, I'm suspecting my crank seal too. This was all new from HJR last year, but still could be bad I guess. Stock bearings but straight cut gears. Quote
gregrob Posted June 21, 2009 Author Report Posted June 21, 2009 Did you get the head off to see what it looks like? I bet you have an air leak somewhere on that right cylinder. Not yet Jon. Might tear it down this week but I'm pretty busy with work. Might have to wait til the wknd or after I get back from chi town Quote
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