Rare Scottish Tree Badger Posted June 27, 2005 Report Share Posted June 27, 2005 BOLLOCKS!!!!!!!!!!!!! Here we go again. ......... Man, that's not even 7 hours on this rebuild! I can't afford this. ... But there's just nothing to replace that buzz of mid-gear, WOT powerband hit and pull. And then you knock it up a gear and go through it all again! ... I refuse to give up. Long story short: Same right cylinder, long WOT run over about a mile, came off the gas to slow down, and the right side started to rumble. About 3 or 4 seconds before this, there was just a split second stumble, but it came back strong (I think). ... Still turns over (by hand), hear clicking, and the plug's covered in little bits of alloy. (I guess piston ). The plug was also loose. ... Just like the last time. 'cos I'd just checked and tightened the plugs. (From two 15 min. MX track sessions). I'll get tore into it tomorrow, 'cos I went for beer tonight. Rare. Quote Link to comment Share on other sites More sharing options...
dlnoss Posted June 27, 2005 Report Share Posted June 27, 2005 WOT for a mile? I'd be suspect of leaning out, possibly detonation with the loose plug. Quote Link to comment Share on other sites More sharing options...
chris642 Posted June 27, 2005 Report Share Posted June 27, 2005 damn bro, you dont have the best luck in the world do you? Good luck, i wish we had places to go WOT for a mile, well there is sarco keep us posted! Quote Link to comment Share on other sites More sharing options...
thegroup Posted June 27, 2005 Report Share Posted June 27, 2005 im in the same spot with my 87 lt 250. got it about 2 mons. ago, blew it up 2 days later, got it back together, 2 wks, melted the piston again, did that 2 more Xs, and now its time to bore. i call up trinity and they told me what i was doing wrong, staying in the gas in top gear too long(1st 2-stroke, use to riding 4-pokes) Quote Link to comment Share on other sites More sharing options...
wayfst Posted June 27, 2005 Report Share Posted June 27, 2005 you have all the clues. look to your cdi box, it has killed your bike on the track with excessive timing (maybe a little theatrical, but you get the point). one way your cdi box fails is on high end instead of curving down, it continues to advance. the ones i have seen destroy the intake side of the piston. good luck Quote Link to comment Share on other sites More sharing options...
80overShee Posted June 27, 2005 Report Share Posted June 27, 2005 BOLLOCKS!!!!!!!!!!!!! Here we go again. ......... Man, that's not even 7 hours on this rebuild! I can't afford this. ... But there's just nothing to replace that buzz of mid-gear, WOT powerband hit and pull. And then you knock it up a gear and go through it all again! ... I refuse to give up. Long story short: Same right cylinder, long WOT run over about a mile, came off the gas to slow down, and the right side started to rumble. About 3 or 4 seconds before this, there was just a split second stumble, but it came back strong (I think). ... Still turns over (by hand), hear clicking, and the plug's covered in little bits of alloy. (I guess piston ). The plug was also loose. ... Just like the last time. 'cos I'd just checked and tightened the plugs. (From two 15 min. MX track sessions). I'll get tore into it tomorrow, 'cos I went for beer tonight. Rare. 386046[/snapback] I would have said that the problem came from the loose plug. Obviously a loose plug is going to cause a lean condition due to an air leak. The real question is, what actually caused the loose plug? I'd say make yourself a plug lock (weld 2 - 13/16 box end wrenches together) or buy an aftermarket one. Quote Link to comment Share on other sites More sharing options...
Koolguyson Posted June 27, 2005 Report Share Posted June 27, 2005 Dont do that. When a plug comes loose the bike is trying to tell you to stop abusing it. A plug comes loose because of detonation. You are either running too much timing, too lean, or your head is cut too tight. You could also be running a fuel that does not have enough octane in it. If you would, let me know your setup. Tell me what carbs, jetting, head specs, what fuel, what ignition, and what the timing on the ignition is set at. Quote Link to comment Share on other sites More sharing options...
bigboybanshee Posted June 27, 2005 Report Share Posted June 27, 2005 You could also be running a fuel that does not have enough octane in it. 386175[/snapback] That's the first thing that came into mind for me... Quote Link to comment Share on other sites More sharing options...
Rare Scottish Tree Badger Posted June 27, 2005 Author Report Share Posted June 27, 2005 Dont do that. When a plug comes loose the bike is trying to tell you to stop abusing it. A plug comes loose because of detonation. You are either running too much timing, too lean, or your head is cut too tight. You could also be running a fuel that does not have enough octane in it. 386175[/snapback] I think that says it all. My set-up: Std. Mikuni carbs with K&N filter and pre-filter, lid removed. ... 300 mains, 25 pilots, 1.25 out on air screws, needle on #5 (richest). Premix: Silkolene Pro2 @ 33:1. The head is milled to 20cc and the barrels have MX porting (bored 1mm). ... Wiseco Prolites. ... Fresh rebuild showed 148psi @ 660ft. I've only just fitted the DynaFS recently and had jetted up from 270 to compensate for improved ignition and proposed timing advance. ... I ran the bike on the stock curve last w/e on an MX track for about 6 x 15 min sessions with no problems and plugs looked fine. (Rich if anything ... Dark chocolate porcelain and black base ring). Yesterday I wanted to try the advanced curves, so went to the track, (cruised back-roads for 3 miles to get there), and did one 15 min session on the stock curve, and the second on curve number one. ... After a 20 min break I checked the plugs and headed back, low speed to the road for 1/4 mile. Still on curve 1, but this time had it pinned all the way for the mile or so of fast road. I think I've caused this failure from a combination of errors: - I normally run 97 Octane, but for the first time ever I used 95. (All I could get). ... If I'd remembered about this, maybe I wouldn't have been so hard on the bike yesterday! - Curve #1 on the Dyna does continue to increase the timing in the upper RPMs as wayfst pointed out. - Not sure about this one? - My carbs are too small for this set-up to run top gear WOT for extended periods and 'leaned out' under too long running. (Drained the bowls - Is that "leaning out" ). But the bike would have died??? Ultimiately, I think I was jetted too low in the mains, and the plug colors were disguised from the MX type of running and not showing WOT running. I'll take it apart later, but expect to see more signs of detonation. Rare. Quote Link to comment Share on other sites More sharing options...
alcoholbanshee Posted June 27, 2005 Report Share Posted June 27, 2005 What is your squish at.....if you know. If not and you can still turn over the motor it might be a good place to start. Quote Link to comment Share on other sites More sharing options...
Rare Scottish Tree Badger Posted June 27, 2005 Author Report Share Posted June 27, 2005 What is your squish at.....if you know. If not and you can still turn over the motor it might be a good place to start. 386247[/snapback] I don't know? ... The bands were re-cut after the last piston failure. What do you mean by "... a good place to start"? And what am I measuring? ... Sorry, but this 2-stroke stuff has been a fast learning curve for me, and I'm only just touching on port timings and head design. Rare. Quote Link to comment Share on other sites More sharing options...
baddboyy21 Posted June 27, 2005 Report Share Posted June 27, 2005 (edited) I just had to send my engine back to Passion. My plugs kept vibrating loose and caused the bike to detonate. It started to melt the piston on the leftt side. I now have 190psi on the right and 165 on the left. Jim stated that when the plug comes loose on a high crompression engine, it loses its ability to disipate the heat. That causes it to detonate. I'm running 115 octane, with my set-up..only thing we have in common is the dyna ignition set up. I run on curve 3. But have been doing so for almost two years. Not sure if that may have been the problem or not. I definitely think your problem was from the plug coming loose. Edited June 27, 2005 by baddboyy21 Quote Link to comment Share on other sites More sharing options...
Nighty Posted June 27, 2005 Report Share Posted June 27, 2005 I quote: not even 7 hours on this rebuild + long WOT run over about a mile, I'm sorry harehope, send me some pics. Quote Link to comment Share on other sites More sharing options...
H250RHATER Posted June 27, 2005 Report Share Posted June 27, 2005 Jim at Passion set us straight about leaning out top end( after receving a ass kicking port job from his shop)we had to go up almost 90 thousands in jet size and run 110 octane., and 4 degrees in timing.She stays together and is the wildest ride we have aver had. Quote Link to comment Share on other sites More sharing options...
Rare Scottish Tree Badger Posted June 27, 2005 Author Report Share Posted June 27, 2005 Ok, I've taken it apart a bit and taken a few pics (4): * * * * The big end rod bearing has failed and both rings are siezed in their grooves. ... The damaged side of the head is the same color as the top of the piston; it just looks darker in the pic. So what failed first? ... Does that look like detonation, or has the big end bearing failed and the piston's been mashing against the head and the shock's loosened the plug? Or did it 'lean-out' on that side's carb, cause detonation, loosened the plug, and then bearing failure? Or even the advanced timing was enough to fail the bearing. BTW, this was an out of spec crank from an RZ that I took the risk on. I think I bring my own bad luck sometimes! Does everything look fine on the good side? All I do know is that this is going to be damned expensive to fix! Rare. Quote Link to comment Share on other sites More sharing options...
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