watkins Posted October 22, 2005 Report Share Posted October 22, 2005 First day out at glamis and first ride with noss head with 21cc domes. Bike ran awesome for about 2 hours ans then all of a sudden the power dropped ans then it finally died. Tried kicking it over and it felt like there was no compression. Pulled the head and both pistons were missing a chunk in the front of the piston in the same exact spot. Just finished rebuilding it and am concerned about what could have caused this... Jetting is a little rich, but I was juat running pump gas. Could running pump gas with the increased compression caused this... I just am trying to cover all the bases before I ride tomorrow, I also checked for air leaks and didn't find anything Quote Link to comment Share on other sites More sharing options...
watkins Posted October 24, 2005 Author Report Share Posted October 24, 2005 (edited) Ok.. now the sucky part. Rebuilt it out at Glamis, fired up on the 2nd kick, was running like a champ using 20/80 of race gas and pump.. then bam... loss of power and I was only going like 1/2 throttle. Got it back to camp with only 1 side running, pulled the head and the left piston has a hole right through it, also the plug from the left side had a piece of it missing (the part that you gap), and these were new plugs that i just put in. The right piston looked fine. I have a few questions now..... 1. What could be causing this? Heres What I have checked so far: Checked the carbs & Jets, running dynojet needle 4th clip from blunt end & 320 mains. Checked for airleaks.. sprayed the bike down before I tried breaking in the new top end with Carb Cleaner and it didnt rev at all. Checked the Timing plate to see if it had come loose.. still right at +4. 2. Where do I go from here? The cylinders look great, no scratches or anything.. can I just purchase a new piston and slap it in or will I have to have it bored out again? Edited October 24, 2005 by watkins Quote Link to comment Share on other sites More sharing options...
dlnoss Posted October 24, 2005 Report Share Posted October 24, 2005 With +4 timing and 21cc domes you do need at least premium pump gas. Do you know what the compression was before the problems? Does the top of the piston looked like it's been beat on with an ice pick? Quote Link to comment Share on other sites More sharing options...
watkins Posted October 24, 2005 Author Report Share Posted October 24, 2005 (edited) With +4 timing and 21cc domes you do need at least premium pump gas. Do you know what the compression was before the problems? Does the top of the piston looked like it's been beat on with an ice pick? 429013[/snapback] Initial blow I was running premium with no race gas. 2nd set of pistons I was running 20/80 Race Gas & Premium Both pistons were at 156psi before 1st blow up.. didnt measure it after the 2nd (didnt have all my tools). First set after inital blow look like they were beaten up pretty bad with an ice pick on the exhaust side of the piston. After the rebuild during the break in the left piston was fine except for the dime sized hole dead center, the rest of it looked good and the right piston looks fine.. Edited October 24, 2005 by watkins Quote Link to comment Share on other sites More sharing options...
batoutofshell Posted October 24, 2005 Report Share Posted October 24, 2005 Sounds to me like the pistons are slamming into your plugs? Quote Link to comment Share on other sites More sharing options...
wayfst Posted October 24, 2005 Report Share Posted October 24, 2005 check your crank and then your cdi box. if your timing slips it can take out your engine quick. feeling for you bud! Quote Link to comment Share on other sites More sharing options...
87sheerips Posted October 24, 2005 Report Share Posted October 24, 2005 Sounds to me like the pistons are slamming into your plugs? 429030[/snapback] I agree. Quote Link to comment Share on other sites More sharing options...
watkins Posted October 24, 2005 Author Report Share Posted October 24, 2005 check your crank and then your cdi box. if your timing slips it can take out your engine quick. feeling for you bud! 429043[/snapback] Sorry for the stupid question to follow, but how should I check the crank? Do i need to split that cases (hope not). Also how should I check the CDI? Clymers doesnt list any testing procedures. How/Why would the pistons be slamming into the plugs? I will make sure I get pictures of the pistons for you. I am sure that will help in diagnosing this. Quote Link to comment Share on other sites More sharing options...
2003LimitedBanshee Posted October 24, 2005 Report Share Posted October 24, 2005 Sorry for the stupid question to follow, but how should I check the crank? Do i need to split that cases (hope not). Also how should I check the CDI? Clymers doesnt list any testing procedures. How/Why would the pistons be slamming into the plugs? I will make sure I get pictures of the pistons for you. I am sure that will help in diagnosing this. 429060[/snapback] To my knowledge the CDI box is a non-serviceable piece, thus you cannot bench test it to determine if it is faulty. If you have a bud with a bike, you could try swapping the CDI's. It sounds like DL Noss may be on to the problem you are having, since he asked for a specific condition which you reported you had. Sorry I don't know what these symptoms indicate, but it sounds like Noss might. You could run into piston/spark plug interference if you are running a stroker (don't think your mods listed that), or if you are running a plug with the wrong reach. Assuming you are running a BR8ES or B8ES, as long as the Noss head does not require a different reach plug (don't believe it does, Noss will be able to set it straight for sure) this shouldn't really be an issue. Quote Link to comment Share on other sites More sharing options...
Wallrat Posted October 24, 2005 Report Share Posted October 24, 2005 I'm racking my brain on this one. It sounds like detonation issues but if jetting is good and ur on race gas, that doesn't make sense. Is the hole in the piston from melting or does it look like it broke out? If you have a chip missing from the front of the pistons that's caused by catching on the exhaust port. Run your finger down the cyl wall into the exhaust port. The edge should be chamfered nice an smooth with no lip. My shee blew up last year cuz the shop that did the bore forgot to chamfer that port. Boy was that expensive! Took out the crank while it was at it. To check the crank you measure the free play on the rods and compare them to the specs in the clymers Quote Link to comment Share on other sites More sharing options...
watkins Posted October 24, 2005 Author Report Share Posted October 24, 2005 (edited) Well.. here are the pictures of the first set of pistons I blew on this trip. I will take pictures of the other set tonight when I take the motor apart again (2nd set is the one with the hole in it). Also, while we are troubleshooting the cause, what can I do to get the piston replaced. Do I need to have the clyinders bored out again or can I just drop in a new piston without taking the cylinders to the shop.. they are smooth as a babys bottom. Edited October 24, 2005 by watkins Quote Link to comment Share on other sites More sharing options...
fast500#12 Posted October 24, 2005 Report Share Posted October 24, 2005 check your water pump, that is what mine looked like when the water pump shit and since it is a recurring thing you might wanna check it out. my kx 500 did the same shit over and over againg when the impellar broke off the shaft. Quote Link to comment Share on other sites More sharing options...
Wallrat Posted October 24, 2005 Report Share Posted October 24, 2005 (edited) Yeah it looks like it overheated. Are the piston tops next to the exhaust port melted or chipped? Hard to tell from the pic. While you're at it you might wanna do the meat thermometer mod so you can keep an eye on your temps. I'm amazed that your cyls don't have any damage. Did you maybe forget to put coolant back in after installing the head? Edited October 24, 2005 by Wallrat Quote Link to comment Share on other sites More sharing options...
watkins Posted October 24, 2005 Author Report Share Posted October 24, 2005 Yeah it looks like it overheated. Are the piston tops next to the exhaust port melted or chipped? Hard to tell from the pic. While you're at it you might wanna do the meat thermometer mod so you can keep an eye on your temps. I'm amazed that your cyls don't have any damage. Did you maybe forget to put coolant back in after installing the head? 429132[/snapback] The pics are showing the exhaust port side. Quote Link to comment Share on other sites More sharing options...
Wallrat Posted October 24, 2005 Report Share Posted October 24, 2005 Yeah I know. What I mean is, are they melted or does it look like the pistons smacked something and got dented/chipped? Quote Link to comment Share on other sites More sharing options...
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