1995 Blaster piston slap? or somthing else

[paulrizik04]

gizzy2014

im hoping that is the problem. i have a small scratch already there but cant feel it. it was bored out 3 seasons ago and i did the break in stuff and maybe rode it once after. the carrier bearings went out and it sat for a few years. i fixed bearings about 1 week ago. started up first time in 3 years on maybe 8th kick. i can still see some of the bore marks from when it was bored out.

does anyone else agree with gizzy2014 about the piston rings. i thought this could be my problem from the start. i just dont want to fix the champhers and reassemble thinking i fixed it only to find out i have to tear it apart again. gaskets time and money are at stake.

also could anyone tell me if an air leak could have caused the rings or piston to make the scratchs? i dont think so but i know i dont know enough to make the call. im figuring the only thing that could have made the marks is the piston or rings. thanks again. i will check back later

 

[jus_me]

Well by not getting into it to much and having a chemistry class, an air leak can destroy a motor. Quick or slow depending upon the leak. I'm very surprised no one else chimed in on here.. i can't seem to open the video so i can hear anything so I'm runnin blind.. I will try again... actually i have to many questions.let me see if i can listen first.... so after the bore and break in or during the break in you never had this noise?? I've yet to hear it..:-/..

 

[paulrizik04]

jus_me

try this

[http://s1362.photobucket.com/user/paulrizik86/media/PC300058_zpsc1045412.mp4.html]url=http://s1362.photobucket.com/user/paulrizik86/media/PC300058_zpsc1045412.mp4.html[/url]


and this

[http://s1362.photobucket.com/user/paulrizik86/media/PC300057_zpsd4766a2e.mp4.html]url=http://s1362.photobucket.com/user/paulrizik86/media/PC300057_zpsd4766a2e.mp4.html[/url]

i have never heard that noise before. its a metal on metal sound. i had a hard time hearing it in the video i made anyway. im gonna have to make a better video with the sound more clear. i just thought of something. when i kickstart the bike i can feel resistance( metal contact) cant hear a sound sometimes but almost feels as if the piston was rubbing one side and it sounds like the piston shakes. the piston on the wrist pin bearing rattleing/scraping the inside of the cylinder

thanks again jus

 

[Blaner]

Ok, i never read through all the replies, so please excuse any points already covered.

Sounds like a heat sieze to me. Typical of a heat sieze is scoring on the cylinder and piston between the intake bridge.

This is caused by incorrect jetting and incorrect running in/heat cycles.

Can you BRIEFLY explain the following:

• What was your cylinder/piston clearance?
• what is your jetting at?
• What running in procedure did you use? Heat cycles?

A lack of a leak test and messing with the oil/fuel ratio was also not wise at this point. Next time, rather change your jetting to fix rich/lean (air/fuel ratio) scenarios and not the oil/gas ratio.

 

[paulrizik04]

Blaner

i dont know the piston/cylinder clearance. no micrmeter to measure. after bored out i bought the piston. i think the plan was .8 MM. i know it was supposed to be under 1MM. 3 years ago cant remember

jetting is all stock.

yes during the breakin peroid i ran all the heat cycles. took about a tank and a half and about 1 week.

thanks for your help blaster forum townsman

 

[paulrizik04]

i looked at the piston. the #'s still very clear. 573M06700

stock is 66mm and im at 67mm makeing me .40 over right?

im not sure if i should get cylinder honed/bored. i have these very small cluster of scratches i can see but cant feel. if this is the result of a scored cylinder/piston should cylinder be honed/bored? no other damage from what i can see but can feel clear metal on metal scraping if i move kickstarter through its motion. it has to be the piston/rings scrapping the scored/scratched surface. id imagine the scoring left cylinder out of tolarance and rings made contact.

blaner

you said, " Sounds like a heat sieze to me. Typical of a heat sieze is scoring on the cylinder and piston between the intake bridge."

when this happens where the scoring takes place does it reveal where the air leak could be? because the scoring is between the intake bridge does it give me a clue that maybe my leak is close. im working on getting nipple capped for the carb where oil injection line was. i was just wondering about another leak somewhere other then the uncapped nipple cause i have seen this bike run well for years with it never capped. Strange. i also know that the leakdown test will reveal any and all leaks so making one is my next step.

i know i write alot but im hoping something clicks for someone reading and replying to my post that helps get my blaster back on the trails. thanks everyone

 

[paulrizik04]

so after some lite reading through my clymer service repair manual. i learned that the piston to cylinder clearance is supposed to be much lower. more like .03mm to .04mm not the .8mm i thought. im not sure if i noticed when i did the top end but the rings are keystone which are tapered at one side. im not sure if i was aware of this when installed them. i will check them tommorrow.
according to this manual my rings may have moved (the pin on the piston for the rings) or the pins are loose. i will also check them tommorrow.

 

[j mcq37]

Let us know what you find out, I'm interested to see what happens and hope you find the problem. So you can get back on the trails.

 

[paulrizik04]

will do

gonna graps some tools i need for the job and stop at the hardware shop and make a leak down tester also. i need to champher the two ports that were missed. what tool is used to do this? gonna google it. later all. tommorrow feels productive already!

 

[Blaner]

Yes, with a cylinder bore clearence of unknown measurements and gunning for 0.8mm, there is a excellent chance of the ring rotation.

Ring rotation occurs when you have a loose bore. You see, the rings are under compression by the cylinder they run. This keeps them compressed. However, on a 2 stroke, everytime the rings move passed a large port such as the exhaust port, this confining cylinder is compromised, due to a huge opening. This then decreases the pressure on the rings and they bulge out into the port. As the piston moves up or down and the rings reach the top of the port, they are gently squeezed back into position.

No, if your bore is too loose, the ring gap will enormous when the rings bulge out. this could allow for dislocation of the rings and allow them to override the stopper pin.

I hope you can also see how vital proper port chamfering is in this scenario. You need the port edges to gently guide in the rings. If you do not chamfer the ports, they will snag a ring.

Something else I picked up on the lack of a plug on the oil feeder on the carb. You SIMPLE HAVE TO BLOCK THIS! you cannot expect anything more than failure if this is open. You could theoretically run it open if you "over jet for it" but thats about as wise and Suntanning where I live.

A heat sieze cannot tell you where a leak may be. The intake is the cooler side of the piston and the exhaust the hotter, the piston heats up and expands at different rates and different amounts. For some reason, they seem to sieze like that when they get too hot. Too hot is caused by excessive air. Most probably from an airleak. The open oil nipple on the carb is probably your major contributor.

 

[paulrizik04]

yo right on blaner this is exactly what i was looking for. i bet my rings are rotating and getting snagged on the unchamfered ports. i will have them cleaned up before reassembly. i bet the oil feeder on carb was plugged(dirt,mud,grim) before. a while back i cleaned carb very good my float was out of whack and used to overflow fuel all the time. so i fixed it but i bet i cleaned that nipple not realizing it should be plugged although not with dirt,mud,grim lol) so i will make sure its plugged before reassembly. i hope its the main and/or only air leak.

im going to buy a caliper and a cheap bore gauge. ohh and some feeler gauges. im going to check my piston to cylinder clearance at several points. then gonna go to hardware shop and buy/make a leakdown tester to find /fix any and all leaks. i hope my seals are good. much more work then i want to get into right now.

blaner you da man! lol thanks evreyone for your help i will post back shortly
later all.

 

[paulrizik04]

alright

cylinder bore i measured in locations my clymer manual specified but instead of measuring 2 spots i measured 3. and labeled each set a title of Top,Mid, and Bottom.

Top - closest to the head

67.04 66.92 67.10

Mid

67.03 66.08 67.01

Bottom

66.94 66.75 66.87

Visual Scratch

66.92

just above and below the scratch to find the depth of the scratches

67.01 66.92

the piston

66.58 66.53

so as you can see my cylinder bore is all over the place
im shocked that my piston measured .5 mm small. the numbers on top of piston "573M06700" and mean that its supposed to be 67mm right?????

so i take my small piston measurment and largest cylinder bore measurement and subtract to find the piston to cylinder bore clearance right???

66.53mm - 67.04mm = .51 mm which is within the .8mm i told the guy at the machine shop so my bad there. my clymer manual says piston to cylinder clearance should be 0.035mm - 0.04mm and service limit of 0.1mm

i really regret telling the guy the wrong tolarance. 0.03 - 0.04 seems like it might be hard to achive even for a machine shop. can anyone verify this is the correct tolarance i should be looking for?

i checked the rings and the writing is faced up as described in intall guide so rings are in correct and not upside down. i will have leak down tester complete tommorrow. plugging oil plug on carb.

 

[JBRoc01blaster]

Most machine shops want the piston before they bore the cylinder, which kind of sucks because boring .010 over might not always cut it depending on gouging/scratches. Fortunately most reputable places will allow you to exchange pistons/rings as long as they are not used ! The reason the machine shops want the piston before boring the cylinder is to assure perfect piston to cylinder clearance. Piston sizes can vary slightly depending on manufacturer, especially with expansion. For example a forged piston will expand significantly more than a cast piston when the engine reaches operating temp.

 

[JBRoc01blaster]

I remember seeing that in my clymer manual as well and couldn't help but think that would be excessive clearance ! That's like having your cylinder bored .030 over and running a stock sized piston, sounds like a sure way to shatter the skirt real fast ! I asked my machinist who bored my cylinder for me about that and he said that you might be able to get away with that but he would not advise it !

 

[paulrizik04]

just found the box for the piston i installed. it shows clearance 0.05 its a wisco piston

so i need cylinder bored and new piston rings right?

i was thinkin i could just have them bore it again but at the smaller tolarance. i hoping i dont have to go to the next bore becuase of this. my smallest cylinder bore is 66.08 and largest bore is 67.10. the bore is supposed to be 67mm with tollarance of .05 so anything between 66.95 to 67.05 is ok right???
also have a service limit of .1 so anything after 67.10 is to far and will have to go to next bore size up right???? or is the service limit after the cylinder bore piston clearance making it 67.05 + .1 = 67.15???

if that was to confusing 67mm is bore size
67 + .1 service limit = 67.10mm

or is it

67 + .05 clearance + .1 service limit = 67.15mm

next piston size up is 67.25mm

my brain hurts. later

 

[paulrizik04]

JBRoc01blaster

im confused???

66mm is the stock bore right

66.25mm is .010 over stock
66.50mm is .020 over stock
66.75mm is .030 over stock
67.00mm is .040 over stock
67.25mm is .050 over stock
67.50mm is .060 over stock
67.75mm is .070 over stock
68.00mm is .080 over stock

im not sure if you can go .090 over on these

this is how i understand it. please someone correct me if im wrong i dont want to waste my $$$ if im wrong and buying the wrong parts.

 

[89blaster89]

JBRoc01blaster

im confused???

66mm is the stock bore right

66.25mm is .010 over stock
66.50mm is .020 over stock
66.75mm is .030 over stock
67.00mm is .040 over stock
67.25mm is .050 over stock
67.50mm is .060 over stock
67.75mm is .070 over stock
68.00mm is .080 over stock

im not sure if you can go .090 over on these

this is how i understand it. please someone correct me if im wrong i dont want to waste my $$$ if im wrong and buying the wrong parts.

yes you can go .90 over but i wouldint even waste my time doing it, i would just buy a new cylinder or big bore sleeve it

 

[Blaner]

Ok, firstly well done. Im glad you taking this seriously!

Next, you need to know that you have two kinds of pistons, cast alloy, and forged alloy. Wiseco make forged pistons while almost all the others are cast.

Cast pistons are more prone to shattering and need a tighter bore clearance (0.03mm) while forged pistons require larger clearances (0.05 - 0.07mm)

The reason for this: Cast pistons tend to expand in response to heat in a more uniform matter, meaning heat is distributed well throughout the piston as it heat up, in return, the piston keeps its dimensions well.
Forged pistons tend to heat up differently, they expand on the exhaust side before the intake side does and this causes the piston to get out of shape. A very tight bore on a forged piston will result in it heat siezing.

When you get your cylinder back from a machine shop, the piston should be almost an exact fit. You know its right when you cannot fit the piston into the bore with the skirt first, it should almost be too big, but put it in dome first and it should slide it as if it is sinking into putty.

Piston sizes do vary, and so will your bore, remember that you have a worn cyinder and bore so your measurement will be very wierd.

I suggest you go for a 67.50mm piston and get the cylinder bored to either 0.03mm-0.05mm for a cast piston and 0.05-0.07mm for a forged piston.

I like 0.07mm for my wisecos.

Remember to give your new piston to the machine shop together with your cylinder.

Remember to clean the cylinder properly with dishwashing liquid on paper towel before assembly.

Use new gaskets

Do all this, and a leak test, plug the carb, do proper HEAT cycles and you should have a stunner of a bike.

 

[paulrizik04]

yo blaner thanks for all your help i understand everything you mentioned above jsut have a question.

my piston is supposed to be 67mm but when measured its 66.53. i have read that other people have got wiseco pistons that were marked the wrong size also. you suggest going to 67.50mm which is .060 over stock right. cant i go to 67.25mm which is .050 over to save nxt piston size for next time?

thanks for your help again.

 

[Blaner]

Indeed you could, you need to look at those figures there and maybe take your cylinder in to a prof engineering shop and let them tell you. Sometimes those scratches dont come out with the next size up.

If you can, go 67.25mm and save a life for the motor.