tgbanshee Posted August 28, 2007 Report Posted August 28, 2007 (edited) Hi guys. First off I would like to say you have a great forum here. I picked up my first banshee about 2 months ago and have been riding it happily ever since. It pulled hard, started on the first kick, and never knocked or pinged that I could tell although this is my first 2 stroke. It has FMF Gold Series pipes w/ Powercore 2's, Pro Flow intake w/ K&N filter, and the previous owner told me he jetted it for the pipes and had rebuilt the top end 20 hours ago along with a 10 over bore. Over the weekend a friend was riding it and said that it started acting like it was out of gas. When he came to a stop, he said the kicked was stuck and it would not kick at first, then he got it to kick but it was making a metallic slapping sound so he pushed it back to the house. I arrived shortly thereafter to find my wonderful toy sick as a dog. I pulled the head off that night to try and see what was going on and the right side piston and dome looked as if they had been scraped clean with a wire brush, whereas the left side is black with carbon buildup which is what I would think it should look like. At the top and bottom of the stroke, the right side piston has some vertical play and that is what the metal slapping sound is. Also the right side piston does not come all the way to the top of the cylinder deck (see photos). I'm thinking the wrist pin bearing or the crank bearing spun and/or the connecting rod is bent. I'm going to pull the cylinders off completely sometime in the next few days as soon as I get the chance to see where the problem is. iHopefully I don't need a new bottom end but if I do, I'm thinking about calling up the guys as FAST Racing and doing a stroker kit. I also have to figure out why the motor is running the way it is so any input you guys have would be greatly appreciated. Also the pistons say 0.50 on them and I measured the cylinder width to be 2.536" left side and 2.538" right side which seems to be closer to a .020 over bore than a .010, so this guy has me wondering if he knew what he was doing. I would assume the 0.50 on the pistons means +0.50mm/.020 over bore piston but correct me if I'm wrong. Thanks for the help! Left side Right side - that is as high as the piston goes during its stroke now domes Left dome - seems to be a lot of nicks on this dome Right dome Edited August 28, 2007 by tgbanshee Quote
dajogejr Posted August 28, 2007 Report Posted August 28, 2007 My guess is the bore/machine shop didn't have the pistons when they were bored. That is critical in my opinion....mic the pistons, mic the bore...and get tolerances in check. I've seen a LOT worse...and you're a smart man for not neglecting that motor and pushing it back to camp instead of being a hero... Buy the pistons, take them to the machine shop with the cylinders, and have them machined to spec that way. I'd bet the left side had one of the following, if not more: Air leak plugged carb And it can't be a .010 overbore..if he used Wiseco pistons. They go from Stock to .020 for the first bore, ask what kind of pistons, they could've been cheap junk. At this stage, I'd tear it down to nothing and go through the cases, the crank, everything and check it all out...just to be sure! Quote
jbooker82 Posted August 28, 2007 Report Posted August 28, 2007 Running lean could cause the crank berrings to get ate up. Wich would allow the piston to hit the head like the pictures show. That is also why the piston doesnt go all the way up. The roller bearing on the crank is ate up so it wont push the piston up to TDC. I would do the stroker while your at it. You will need to have your cylinders ported for the stroker crank as well. Then get a noss head with cut domes for the stoker crank. That is a much better option instead of haveing a spacer plate inbetween the cylinders and the crank case. Quote
ellison445 Posted August 28, 2007 Report Posted August 28, 2007 I concur and I bet they didnt have the pistons as well. Or it was already .010 bore and they just slapped some new pistons in without a bore or hone.. My guess is the bore/machine shop didn't have the pistons when they were bored. That is critical in my opinion....mic the pistons, mic the bore...and get tolerances in check. I've seen a LOT worse...and you're a smart man for not neglecting that motor and pushing it back to camp instead of being a hero... Buy the pistons, take them to the machine shop with the cylinders, and have them machined to spec that way. I'd bet the left side had one of the following, if not more: Air leak plugged carb And it can't be a .010 overbore..if he used Wiseco pistons. They go from Stock to .020 for the first bore, ask what kind of pistons, they could've been cheap junk. At this stage, I'd tear it down to nothing and go through the cases, the crank, everything and check it all out...just to be sure! Quote
MDS2106 Posted August 28, 2007 Report Posted August 28, 2007 (edited) My guess is the bore/machine shop didn't have the pistons when they were bored. That is critical in my opinion....mic the pistons, mic the bore...and get tolerances in check. I've seen a LOT worse...and you're a smart man for not neglecting that motor and pushing it back to camp instead of being a hero... Buy the pistons, take them to the machine shop with the cylinders, and have them machined to spec that way. I'd bet the left side had one of the following, if not more: Air leak plugged carb And it can't be a .010 overbore..if he used Wiseco pistons. They go from Stock to .020 for the first bore, ask what kind of pistons, they could've been cheap junk. At this stage, I'd tear it down to nothing and go through the cases, the crank, everything and check it all out...just to be sure! Weisco does make .010 over pistons for the banshee. http://cgi.ebay.com/ebaymotors/Yamaha-Bans...sspagenameZWD1V Edited August 28, 2007 by MDS2106 Quote
dajogejr Posted August 28, 2007 Report Posted August 28, 2007 Weisco does make .010 over pistons for the banshee,thay also make http://cgi.ebay.com/ebaymotors/Yamaha-Bans...sspagenameZWD1V I guess I should've went to Wiseco's site..I always reference Magic racing, they don't have the .010 on their site... Thanks for the correction!! http://www.wiseco.com/PDFs/Catalogs/CB07/YamahaATV.pdf Quote
Justintoxicated Posted August 28, 2007 Report Posted August 28, 2007 Mine was bored twice when I got my weisco's too, maybe it's just safer after porting to bore out 2 sizes? Well Good luck with the next build you might as well split the cases and take some pictures of the crank. Was your crank trued and welded? You can always buy my stuff if needed Quote
FasterThanU90 Posted August 29, 2007 Report Posted August 29, 2007 the piston hit the top of the head wtf ur guys are retarded,.. no looks like u have sum detonation issues, and probly a bad bearing from either rod end, if u have a dial gauge check the crank runout and post ur largest piston to cylinder clearance Quote
tgbanshee Posted August 29, 2007 Author Report Posted August 29, 2007 Pulled the pipes off tonight and poured a nice pile of metal shavings out of the right pipe... I'll probably pull the carbs and wait until tomorrow or Thursday to pull the cylinders off and cry... Quote
jbooker82 Posted August 29, 2007 Report Posted August 29, 2007 you might as well pull the engine out. Lot easier to dissassemble on the bench. Your deffinatly not getting away with doing a top end. Quote
tgbanshee Posted August 29, 2007 Author Report Posted August 29, 2007 After I popped the head off, I pretty much gave up hope that I would be able to take the inexpensive way out on this one. I'll keep you guys updated with the status and what I find as I go. Also, if anyone knows a good machine shop in NJ or nearby on the east coast who could do boring, honing, check the piston-bore clearance, and possibly do a port job, please let me know. Thanks again for all the input. Quote
Justintoxicated Posted August 29, 2007 Report Posted August 29, 2007 the piston hit the top of the head wtf ur guys are retarded,.. no looks like u have sum detonation issues, and probly a bad bearing from either rod end, if u have a dial gauge check the crank runout and post ur largest piston to cylinder clearance Hmm at first thats what I thoguht but since it's only one cylinder and it kind of looks like something was bouncing around on top, I figure it could be something else. Quote
FasterThanU90 Posted August 29, 2007 Report Posted August 29, 2007 detonation causes the domes to pit up Quote
tgbanshee Posted September 1, 2007 Author Report Posted September 1, 2007 Well I finally pulled the cylinders off to take a look at the carnage... One f***ed up looking ride side connecting rod eh? Guess it's time for a stroker kit! Was thinking of keeping the stock cylinders (they look ok) and having them boring out when I get the pistons, then calling up the guys at F.A.S.T. Racing for a 4mil stroker setup w/ a welded crank, a NOSS head, and VForce3's. Let me know what you guys think. I'm not sure how far out you can go with the bore on stock cylinders, if anybody knows please educate me. Also, will I need to get new carbs or a single carb conversion with that setup or will the stockers do ok? I really would like to build the bottom end to be bullet proof so I will only have to do this once so if strokers are less reliable than a stock stroke crank, maybe doing a stroker setup isn't for me. I do mostly trail/field riding and occasionally go to the track. Thanks again for all the help! Quote
jmd0346 Posted September 1, 2007 Report Posted September 1, 2007 Well I finally pulled the cylinders off to take a look at the carnage... One f***ed up looking ride side connecting rod eh? Guess it's time for a stroker kit! Was thinking of keeping the stock cylinders (they look ok) and having them boring out when I get the pistons, then calling up the guys at F.A.S.T. Racing for a 4mil stroker setup w/ a welded crank, a NOSS head, and VForce3's. Let me know what you guys think. I'm not sure how far out you can go with the bore on stock cylinders, if anybody knows please educate me. Also, will I need to get new carbs or a single carb conversion with that setup or will the stockers do ok? I really would like to build the bottom end to be bullet proof so I will only have to do this once so if strokers are less reliable than a stock stroke crank, maybe doing a stroker setup isn't for me. I do mostly trail/field riding and occasionally go to the track. Thanks again for all the help! Did you clean it out any after you took the head off? It looks dry as a bone in there. I dont see any oil residue. Quote
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