New Rebuild Already Shot

[No Limit Powersports]

Ok here we go. I just got this bike back together and it already blew up wtf!! To start its a 02 with a noss head 19cc domes cpi inframes, vito power pistons, mild port, vforce 2s, kn no lid,wiesco crank welded and trued, 360 mains with stock pilots and aftermarket needles(not sure what ever came in kit) clip on third down from the top no washer. Alright the problem is that b4 the last rebuild the motor was not ported and we were running vitos ss. It ran fine for about a year then broke a skirt off of the right side. We tore top end off sent it to the porter so we decided to go with the power pistons. We found a air leak on the bottom of the air box between the filter and the carb so we fixed that but sand did get in the motor. Cylinder was fine slight hone and new pistons and rings and we were back in buisness. We flushed the crank with diesel and installed all new gaskets. Brake in was about 10, 20-30 min rides complete cooldowns. After breakin was over the bike wouldnt run in the power band at all after alot of frustration I found that the little black box below the flywheel that picks up the spark was loose so i tightned it and it ran great.

 

Now last night we were riding and one side went dead so we tore the head off and found a hole burnt in the top of one side the other side is perfect WTF. I need some help Im scared to just fix it and go on because i no its going to do it again. My porter guy thinks that its a possibly a bad crank seal on one side causing a air leak and hence a lean condition, what do you guys think. Also is there a spec on that little black box and is this a possiblility. What would you guys do next????? This sucks cause its my roomates bike and now he thinking abouts selling he shee because its costing to much money .

[fixitrod]

If you had metal in the crank case it very possible the metal destroyed the crank seal. You have an air-leak somewhere.

[SDD]

Where is the hole in the piston? Close to the exhaust side or in the middle?

[No Limit Powersports]

Pretty much in the middle

[boonman]

Which side of the engine? stator side, or clutch side? Andx the location of the hole would be good to know. if it is detonation, there will be a hole in the middle of the piston. A hole 98% of the time indicates detonation. If you were lean, it would 98% of the time melt the piston near the exhaust port, and smear it all down the side of the cylinder..... Either way, it sucks. Now, with blowing debris in the crankcase, you may have had some shit in the lower bearings.... This would be bad. Flushing it out, I would use about 5 gallons of diesel or kerosene, or whatever. And still, I wouldn't even bother. Iw ould split the cases. It's not worth trashing a crank. You need to blow it out. Anyways, a lean condition on one cylinder can provoke an already present detonation problem to rear up it's ugly head in a premature fashion. What kind of fuel where you running? What elevation? If it is the stator side cylinder, it could be a crank seal or base gasket. Or an intake boot. On the right side, it can't be the crank seal, because you would be sucking oil out of the tranny..... Only place for air is the base and the intake boot... You pickup coil should be gapped at .020". (pronounced and read "twenty thousandths) If your spark isn't adequate, you could have detonated. If the timing was a little goofy, it could have detonated. If you are at or near sea level with 19cc domes, you may need higher octane fuel. This would be a detonation prone situation.....

[No Limit Powersports]

The hole is on the right piston Ill try and post some pics of the piston to show where its at. We were running 93 octane with yamalube 32:1 in south east kansas so probably between 2 and 3000 feet above sea level. The pickup coil is probably not right but wouldnt this cause a lean condition on both sides??? Timing set a 4 degrees. Not to say it isnt but we used all new gaskets. Would a leaking oring on the head cause this or would it just not run?? Also I was told after a port job you could lower you domes down because the porting would lower the compression is this not correct??

thanks for all your advice

Edited May 27, 2004 by bansheestang

[lincster]

I doubt this is the main problem, but with the port job, 19cc domes and it being bored out, you should be running at least 50/50 race gas.

Did you check your compression before it burned up?

[No Limit Powersports]

No I didnt check the compression probably should have its only bored .02 over. The only thing Im thinking is that if it was that it would have took longer to blow and there would be signs of detonation on the other side, correct me if im wrong. Also I was running 20cc domes and went to 19cc after the port is this wrong or would the compression not drop after the port job?

Thanks for the advice

[Blacksmith]

I don't know what your altitude is, but at 3000 feet the vitos power pistons will make over 150 lbs of compression with 22cc domes. By my way of figuring, that would put your compression with 19cc domes at over 190lbs. That is way too much compression for pump gas. If you have any advance in your timing it would make things even worse. If you went from a super stock piston which increases your exaust duration and lowers your compression to a power pistion which increases your compression with a taller deck heigth, while at the same time putting on smaller domes, I am sure detonation from too much compression is your problem. Put that baby back toghther and get some 110 or 112 octain race gas and you should be good to go. Make sure you clean everything out of the bottom end for your rebuild.

[TheBansheeMan86]

alright well i didnt read your entire post or everyone's replies, but i'll tell you a story.

 

last christmas i blew my top end, in oregon. my 'shee (at the time of engine's death): T5s, +4* vitos key, vito superstock pistons (forged, .020 over i think), 1/2" reed spacers, carbon tech reeds on lightly ported cages, K&N clamp ons, boost bottle (some dont like it, but when i took it off, i noticed a loss in bottom end, so im leaving it on), head milled 30/1000", and the ports have been lightly polished, but the port timing wasnt changed. i run 92 octane pump gas from shell mixed with torco smokeless oil. at oregon dunes (florence) its sealevel, i run 360 mains, toomey needles in the um... 3rd or 4th from the top, 4th i think. dunno what pilots or air screw settings off top of head, but it was jetted perfect, if not a little rich. oh, btw i had a toomey hush kit (for sound laws). i was cruising down the flats, grabbin gears, and about half RPM in 6th, i heard a *POP* so.... grr f*ck. it was saturday afternoon, florence yamaha just closed and wouldnt be open till tues so i was like f*ck it, threw it in the trailer and left it there, borrowed a friends spare 'shee. anyway, hole in the top of the left piston. NO sign of lean mixture. NO airleak. NO bad gaskets or seals. plug looked perfectly tan, oh temp was not hot or cold, nice out, and shee was mid temp, 160 i think. so, i actually dont ride much so the 'shee sat in the garage for a few months. anyway i was gonna do the top end myself, but my dad said he'd pay for it to get fixed, so i was like aight, and let Jeff Graves of Graves Motorsports go at it for me. hes a cool guy, knows his shit, and i know him pretty well. hes in seattle, WA so im like 2 hours from him. anyway he did my topend, i just went wisecos, and he did it for $400, done (i only took him engine). funny story though, i was gonna go pick it up one day cause i had to work the next few and wouldnt have time so me and my best friend left ellensburg at 4:30, jeff closes at 6. damn rush hour, usually takes 2:15 in rush hour, we made it in 1:30 lol average speed: 90, no cops the whole way, showed up at jeffs at 6 on the dot. didnt matter when we got there cause it ended up that wiseco fucked up and put a different sized ring in packaging that said it was what it was supposed to be, so jeff was like, well we can go drive to the wiseco distributor (30 min drive) for WA, OR, ID. pretty cool, he does it out of his garage, but has atleast one of EVERY part that wiseco offers, over $1 million in inventory so we rode with jeff and got the damn ring, went back to the shop, put the top end together. anyway, jeff told me the reason it blew was the metal just gave out. he said everything in my engine was advanced but my fuel. my compression was bumped up a little, ignition timing was advanced from degree key, exhaust timing was advanced from the cutout in the vitos pistons, intake timing was advanced from the huge ass ports on the vitos pistons (maybe not advanced, but is open all the time), and i was only running pump. he advised me to ditch the key, and run yamalube. i took his advice, to be on the safe side. now it runs awesome, no problems, even though i miss the fuckload of top end those superstocks give.

[hamuel]

same think happend to me on the left. side. I was told it was because the carb didn't get fuel for about a second a wot. or in other words it coughted

[boonman]

same think happend to me on the left. side. I was told it was because the carb didn't get fuel for about a second a wot. or in other words it coughted

If you blow a hole, it didn;'t happen from a lean condition. Now, here is the deal with porting. As the piston travels up, it is trying to compress the air/fuel mix. Now, with the ports raised, it has less travel when it is completely sealed from the ports. This will lower your static compression #'s. BUT, it will not change your compression ratio. So, on a guage, it will appear as though you have lost compression. So, droppping dome size gets your guage to read back up there, but if you had stock porting, with the same dome size, (19cc) your guage would read through the roof!!!!!!!!! Just knowing that there was a hole in the piston, tells me detonation.......

[No Limit Powersports]

The problem seems to be deeper than just a lean condition because one side is completly trashed and the other is perfect no damage at all. Boon you said it lowers the static compression? what does this mean? Do you think that I need to go back to a 20cc dome with pump gas or is the 19cc ok (guess i need to just check my compression when its back together). And if it is too high for pump gas any ideas why it only screwed up on one side??? Sounds like an air leak to me but doesnt an air leak usually give you an idle problem(i didnt have one)? Also you said that if it was the right side, which it is, that it would have sucked oil not air is this not possible even at wot that it could have sucked air? I appreciate all the help I think the best thing to do is just crack the case and replace the seals and bearings if they need it. Go all back together with it do a leak down test and a compression test and make sure. Boon what kind of compression do you recommend on pump gas?

 

Is it possible that the pickup coil not correct could have done this or would it be on both sides, also what about plug wire ends. just throughing ideas out there iam so confused

I know the rings were correct I checked the end gap.