Power_Man Posted April 13, 2017 Report Share Posted April 13, 2017 Had a odd experience the other day. When for 2nd rip of the season on the Cub. Went a few miles, all was good. Hammered down on it for a hundred yards or so, and when I let off it started backfiring a little. Gave it a shot of gas and back fired a tad more. So pulled over and checked stuff out. The stator side ceramic of the plug came loose. The plug was tight, but the ceramic moved up and down. Swapped plugs and took it easy home. Doesn't look like any ceramic was missing. How ever that cylinder is 6ish PSI lower than clutch side. I don't know if it was much different last year. Could just be a coincidence. What would you guys do? Seems to run start and run fine. Quote Link to comment Share on other sites More sharing options...
spurdy Posted April 13, 2017 Report Share Posted April 13, 2017 Had a odd experience the other day. When for 2nd rip of the season on the Cub. Went a few miles, all was good. Hammered down on it for a hundred yards or so, and when I let off it started backfiring a little. Gave it a shot of gas and back fired a tad more. So pulled over and checked stuff out. The stator side ceramic of the plug came loose. The plug was tight, but the ceramic moved up and down. Swapped plugs and took it easy home. Doesn't look like any ceramic was missing. How ever that cylinder is 6ish PSI lower than clutch side. I don't know if it was much different last year. Could just be a coincidence. What would you guys do? Seems to run start and run fine. Not sure on the compression issue. Could be from sitting over the winter and rings a little sticky?? Broken ceramic on a plug is a sign of detonation. Sent from my iPhone using Tapatalk Quote Link to comment Share on other sites More sharing options...
Power_Man Posted April 13, 2017 Author Report Share Posted April 13, 2017 Not sure on the compression issue. Could be from sitting over the winter and rings a little sticky?? Broken ceramic on a plug is a sign of detonation. Sent from my iPhone using Tapatalk Can detonation come from lean condition?It's jetted for a little warmer weather. Quote Link to comment Share on other sites More sharing options...
J-Madd Posted April 13, 2017 Report Share Posted April 13, 2017 Deto for sure. Borrow a scope and look or pull the pipe and feel of piston crown and ring land, etc. Sent from my STV100-1 using Tapatalk 1 Quote Link to comment Share on other sites More sharing options...
J-Madd Posted April 13, 2017 Report Share Posted April 13, 2017 Can detonation come from lean condition? It's jetted for a little warmer weather. For sure Sent from my STV100-1 using Tapatalk 1 Quote Link to comment Share on other sites More sharing options...
Power_Man Posted April 13, 2017 Author Report Share Posted April 13, 2017 Thanks guys. I'll throw some fatter mains in. Quote Link to comment Share on other sites More sharing options...
ClaudeMachining Posted April 13, 2017 Report Share Posted April 13, 2017 Sorry but, lean/rich and detonation are connected?? Quote Link to comment Share on other sites More sharing options...
Power_Man Posted April 13, 2017 Author Report Share Posted April 13, 2017 Sorry but, lean/rich and detonation are connected??I don't think rich and detonation are. Think I'll also check my timing. Don't want to rebuild this slut again Quote Link to comment Share on other sites More sharing options...
ClaudeMachining Posted April 13, 2017 Report Share Posted April 13, 2017 I mean that timing/Domes and octane are usually linked detonation, not lean jetting... Envoyé de mon SM-G935W8 en utilisant Tapatalk Quote Link to comment Share on other sites More sharing options...
tfaith08 Posted April 14, 2017 Report Share Posted April 14, 2017 Lean mixtures will contribute to detonation. Quote Link to comment Share on other sites More sharing options...
bansheesandrider Posted April 14, 2017 Report Share Posted April 14, 2017 If it is lean, it is running hot in the cylinder. If it is hot in the cylinder, it will detonate. Quote Link to comment Share on other sites More sharing options...
ClaudeMachining Posted April 14, 2017 Report Share Posted April 14, 2017 Guys,i understand that. But usually, when your engine is detonating, you look at timing/comp/fuel before jetting. Do you often fix detonation problem by rejetting the engine? Quote Link to comment Share on other sites More sharing options...
spurdy Posted April 14, 2017 Report Share Posted April 14, 2017 Guys,i understand that. But usually, when your engine is detonating, you look at timing/comp/fuel before jetting. Do you often fix detonation problem by rejetting the engine? Actually, as temperature drops we feed more fuel through the PJ circuit to richin up the motor to prevent deto. Now depending on his warmer/colder span, that could very well cause his issue. Although you are right, typically, timing, comp, etc. but we only have limited info to go off of here. Broken ceramic = deto Info given was temperature change. Can only add together using the variables given to come to a logical conclusion. Anything else is speculation. Sent from my iPhone using Tapatalk Quote Link to comment Share on other sites More sharing options...
registered user Posted April 16, 2017 Report Share Posted April 16, 2017 (edited) Guys,i understand that. But usually, when your engine is detonating, you look at timing/comp/fuel before jetting. Do you often fix detonation problem by rejetting the engine? adding in more fuel is a poor way to try and fix the problem. the root cause is usually something else, timing/fuel/comp like you say. adding more fuel is just a aaron rogers hail mary with 1sec left on the clock, in hopes that it might some how work. theres a handful of other things you forgot to mention claude. poor chamber design (most folks probly have to large of squish gap), head and plug cooling is shit (the reason im against the coolhead style heads), sufficient cooling around the exh passage as it will otherwise just pack more heat back onto the piston, the stock pump impeller im not convinced will push enough water at a fast enough rate, depending how experienced the porter is the transfers might or might not have some cooling on the piston top Edited April 16, 2017 by registered user 2 Quote Link to comment Share on other sites More sharing options...
J-Madd Posted April 17, 2017 Report Share Posted April 17, 2017 adding in more fuel is a poor way to try and fix the problem. the root cause is usually something else, timing/fuel/comp like you say. adding more fuel is just a aaron rogers hail mary with 1sec left on the clock, in hopes that it might some how work. theres a handful of other things you forgot to mention claude. poor chamber design (most folks probly have to large of squish gap), head and plug cooling is shit (the reason im against the coolhead style heads), sufficient cooling around the exh passage as it will otherwise just pack more heat back onto the piston, the stock pump impeller im not convinced will push enough water at a fast enough rate, depending how experienced the porter is the transfers might or might not have some cooling on the piston topRU - what squish clearance is too big? Is 0.060" too much on a 58mm x 68mm motor? I know its not optimal, but do you think it leads to deto? Sent from my STV100-1 using Tapatalk Quote Link to comment Share on other sites More sharing options...
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