SpeedRacer88 Posted October 17, 2011 Report Posted October 17, 2011 long story short i had to help pull crank a raptor in the woods. my temps were already creeping up in the slow trails by the time we got it cranked i looked down to see 245 degrees on the temp guage. i turned it off and let the temps drop. i then noticed my left plug was loose. i tightened it let temps drop to 175. i hit a str8 road temps started to climb again pinned in 4th gear!!! i slowed the revs and it dropped. i pulled and checked the impeller all good. tried to limp home when i felt it seize. got it home pulled the head to find to nice chocolate pistons and plugs except left side through the rings and the other side broke off on the edge. i wanna know is this all because of the over heat or do i have different problems? Also i have our last big ride next sunday and i'm almost flat broke does anybody have a good set or (1) blaster 68 piston i dont have enough for a new set and its my last ride of the year i just want to get through this last ride Quote
BigRed350x Posted October 17, 2011 Report Posted October 17, 2011 You may have a lean condition on top of the over-heating. Why risk further damage for one last ride? Take the time and tear it down and fix the problem the right way. Don't shoot yourself in the foot just for one ride. Post up pics of your pistons and plugs and we can give you more help. Quote
SpeedRacer88 Posted October 17, 2011 Author Report Posted October 17, 2011 i will post pics tomorrow morn i check my plugs regularly and when i pulled the head the left side was the worse( the side with the loose plug) but the plug is a nice chocolate this is the first time i ever had a plug come loose the right side looks perfect both plug and piston just a corner of the piston crown broke off. the bike has been together a month and i already put about 30hrs on it according to my trail tech this is the first problem i have had. also the first time i have ridden on a trail that slow and first time i ever pulled cranked anyone and also the first loose plug Quote
SpeedRacer88 Posted October 17, 2011 Author Report Posted October 17, 2011 actually im uploading pics right now Quote
SpeedRacer88 Posted October 17, 2011 Author Report Posted October 17, 2011 picture link http://imageshack.us/g/851/leftnc.jpg/ Quote
4MiLLDraGSheE Posted October 17, 2011 Report Posted October 17, 2011 What do you mean by plug was loose? It was backing out? I dont know much but would think u were running her lean and had some deto? Quote
SpeedRacer88 Posted October 17, 2011 Author Report Posted October 17, 2011 What do you mean by plug was loose? It was backing out? I dont know much but would think u were running her lean and had some deto? Yeah i thinks thats what that usually means but it's never happen before I checked for air leaks no blown seals or boots I had just changed plugs before the ride so I'm thinking I just didn't tighten it well enough i only had a set of regular pliers handy Quote
4MiLLDraGSheE Posted October 17, 2011 Report Posted October 17, 2011 Yeah but i would think detonation would cause the piston damage. Musta been running lean or ran outta gas. But im no pro might have been another cause. Quote
Jereme6655 Posted October 17, 2011 Report Posted October 17, 2011 ever heard of "dieseling" its when motors get so hot that the fuel will just start ignigting itself. and if say that piston cracked it would create a hot spot on the dome and that spot could cause it to ignite the fuel on its own. Also it could cause it to ignite at the wrong times which would be detonation......detonation is what causes plugs to back out!! barrow a quad from a friend and ride that.......its not worth damaging a bottom end just to make it one last ride. Quote
SpeedRacer88 Posted October 17, 2011 Author Report Posted October 17, 2011 Im not wasting a bottom end I found all the fragments and if not I have threebond to split the cases just no pistons Quote
LS3 Machine Posted October 17, 2011 Report Posted October 17, 2011 I just checked the pics. Ash white spark plug electrode plus poc marks on top of the piston equals detonation. You probably have been running a bit lean all along, but towing the craptor was more load than normal. The engine got hot which leads to detonation. I would put in new pistons, and up the main jets at least one size, and also raise the needle at least one clip. Then ride and check your plugs and powerband. Do it right the first time. Quote
SpeedRacer88 Posted October 17, 2011 Author Report Posted October 17, 2011 The plugs look white in the pics but I promise you they are both dark brown it have been runnin more than a lil rich I have 168 main and 55 pilot my plugs had spots of ash because of the avgas so I upped the jets unaware of y they plugs were still ashy at the time and I just never dropped the jets back down after hjr told me Quote
SpeedRacer88 Posted October 17, 2011 Author Report Posted October 17, 2011 I have read on here somewhere about the cause of the pistons breaking right at top back lip (both sides) they both chipped at the top toasted the intake exact same spot and size i read somewhere on here about reading pistons and I think it was dajogejr who explained it Quote
BigRed350x Posted October 17, 2011 Report Posted October 17, 2011 Looks like detonation and lean to me. I would have told the raptor guy that's what he gets for having a 4-choke and let him push-start his junk next time. lol Quote
LS3 Machine Posted October 17, 2011 Report Posted October 17, 2011 I just checked your mods: 421 Cheetah Cub Play Port by HJR Chariot Head 165psi Shearer Inframe Exhaust VForce Delta 2s 35mm PWKs w/ pod k&N & Boss Intake Hotrods 4 mil long rod crank w/ Tz bearing Hinson basket with straight cut gears Lockout Cutch Timing +7 Shift Star, Rod, & Drum mods +4 Swingarm What I believe happened is this: +7 timing, combined with 165 PSI and ported, equals a need for race gas. AV gas might not be high enough octane for your setup. Jetting a little rich does not mean you don't have to worry about having enough octane to prevent detonation. I would back down to +4 timing when I put new pistons in if I were you. (Consider race gas, or bigger domes as well) Also remember, the temps just got a lot cooler, and the air is more dense, leading to a leaner condition for your bike. The load of pulling another quad is also a lot different than just you hauling ass alone. I think these factors lean to the detonation and the broke piston. Ive blown motors before, and I know what it takes to do so. Good Luck and keep us posted. Quote
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.