Porting and blowdown

The go kart guy's running Yamaha KT100 engines run as high as 450 - 500 degrees. The go kart guy's running the clone class (harbor freight Predator engines) are pushing the same temps, and those are four stroke engines. 350 is a good temp. Cold cylinders don't make power.
 
Making good power now,so good in fact when I come rolling around the concrete driveway at the corner of my house in 3rd aND rolled on the throttle, I let off (back thumbed it, lol) 3 times before finally having to stop finding myself sideways looking at the house. My driveway isn't slick it is actually quite rough and really chews the rubber off the tires.

The needle (5j11-3.5)/ needle jet ( richer at Q-2) combo is still a bit of a compromise.
I am a bit lean around 1/4 throttle, but I think when my #30 pilot gets here and I get ajust a bit leaner across the board I should be able to go from clip 3.5 to 4 and start onto the needle taper a bit sooner clip 4 was mostly on at 1/4 but a little too rich a little over 1/2
I got a 330 I it now which is a tiny bit rich, and should be perfect after the pilot change.

I don't know about anyone else,but I like to run midrange rich as I can stand, helps avoid lean spots, especially this time of year when it is only going to get colder.

Hopefully after tomorrow, I will have everything where I want it, and can post my jetting numbers for this carb. I might spend alot more time experimenting with the needle/NJ combos as I have an O-0 NJ (quite a bit leaner) and several thinner needles, and the Q-2 NJ (current and a little richer) and the stock +some slightly thicker needles. I am going to keep notes just, so I can narrow it dow to a few choices to run back to back in the same conditions.
My goal is to not only find the best combination for my current setup, but to also gain an understanding of Mikuni needles and learn to be able to look at the various needles and specs both physically and on the chart and be able to choose a needle after taking a baseline with a given needle. If i can accomplish this then I will feel as if I can truly jet a carb basically from scratch. I am finally beginning to be able to feel/hear/know rich or possibly lean at various throttle positions and engine loads, and hope to develop this new found skill as well.
 
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Got my #30 pilot jet and my hour meter / tach this morning . pilot jet made a huge difference, idle is much better and needle came on up to clip 4, also got up to 340 main jet. On the way to the trails now.
With tach idle is set at 1400, it's laggy and digital but I did see 9200 rpm at at near peak

EDIT
spent about 2 hours at the trails, and put almost another hour and a half on the engine. The more and harder I ran it the more it come to life, 4,5,6 th passed by as quick as I could shift. I over shot my target by a little, and I am making more power than expected. Pulls decent from idle up to about 3250 where midrange stsrts.
From 3250 -5500 has a nice midrange grunt and the real power is only a clutch finger away.. at 5500 all hell breaks loose until a 8000 rpm shift, or a snappy 9200 rpm where the over rev dies off. The power band reminds me of a mid-late 90's cr125. That thing is faaasst now, picks up the speed as fast as traction allows.
Of course once I get new rear tires that will hook a little better I think it will be downright nasty on the trails.
I am thrilled with the width of the power band and it's faster than I expected.........
Nice mocha latte looking plugs, maybe a tiny bit rich but doesn't seem to hurt power much if any.
Thanks to
Blaster Forum
Ken O'Conor of KOR ACING
Joeak47
JvB
JusMe
Herpodol
AWK08
And anyone else I might have missed.....without your guys help, insight, wisdom, efforts, and calling me out when I was too far off base, this would have never been possible, I spent $100 over the cost of a basic top end job and nearly doubled my power. I have to spend the next free day I have putting in my HD clutch set, as well as order some tires, tires were useless under power through 3rd ,often 4th, and the clutch just can't take peak torque in 6th, even felt slippery in 5th.
Shock adjustments, and front hydros are my next areas of focus, until all of that's done it will still look rough.
JusMe you will be happy to see that I did at least go with some black duct tape, until I gat a cover.
 
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Nothing to speak of, ran into some issues, parked it ,waiting on some parts. Been working on the little CR80 I bought for my 10 year old so we could ride together, we got to ride once, first time either had left the yard, thefresh motor and the cr80.
Once everything is sorted , I will try to update.

I did get new tires 20x12x8 NANCO 606 generic hole shots $125 shipped and 21x8x10 Wanda journey directional fronts $95 shipped. All are 4 ply the fronts kinda look like an itp tread pattern as well.
New chain and cogs 14t 41t
2 inch rear swingarm extension
HD clutch kit installed
Also got an entire front hydro setup off of a 660 raptor, got to finish modding the spindles to fit. $85

Once the new tires went on in place of the bald 18x10 tires (still had 14/40 gearing), the higher effective gearing, extra bite of the tires and clutch. Seemed to really drag it down , putting the 41t on the rear. if that doesnt take care of it I can go back down to 13 (40 or 41)
Anyone who has ever dragged a street stock with a manual trans knows the effect of clutch slippage and on dirt wheel spin is nearly the same.
Once I get everything squared I will see if I can do a more in depth update, maybe some pics and such.

Reguards
Dan Da Man
 
Nothing to speak of, ran into some issues, parked it ,waiting on some parts. Been working on the little CR80 I bought for my 10 year old so we could ride together, we got to ride once, first time either had left the yard, thefresh motor and the cr80.
Once everything is sorted , I will try to update.

I did get new tires 20x12x8 NANCO 606 generic hole shots $125 shipped and 21x8x10 Wanda journey directional fronts $95 shipped. All are 4 ply the fronts kinda look like an itp tread pattern as well.
New chain and cogs 14t 41t
2 inch rear swingarm extension
HD clutch kit installed
Also got an entire front hydro setup off of a 660 raptor, got to finish modding the spindles to fit. $85

Once the new tires went on in place of the bald 18x10 tires (still had 14/40 gearing), the higher effective gearing, extra bite of the tires and clutch. Seemed to really drag it down , putting the 41t on the rear. if that doesnt take care of it I can go back down to 13 (40 or 41)
Anyone who has ever dragged a street stock with a manual trans knows the effect of clutch slippage and on dirt wheel spin is nearly the same.
Once I get everything squared I will see if I can do a more in depth update, maybe some pics and such.

Reguards
Dan Da Man

I run 20x11x8 Sedona Bazooka's. Very similar to what your talking about (4ply and a holesshot knock off) with really good results. No use of spending the extra money when these cheaper tires do the same thing.

Gearing is something you have to play with untill you find what works for you. 13/40 is what I run here, but I ride at slate dumps, and the foothills of the mountains.
 
Got my stuff back, put it together found out I had 21cc not 19cc head, ring end gap seemed large, definitely was over the minimum, first start up I noticed some piston slap, at this point I am trying to be optimistic figured the lower compression head and larger endgap was an effort to prevent problems with cold starts etc.. I was kind of insulted that it was deemed necessary to keep compression down and clearances up, for a motor going to someone who is well aware of expansion rates, dangers of lean jetting, warm up period for forged pistons etc. I had intended to run 95 or 100 octane out of the pump.
Went through hear cycles,and did some might riding around the yard. etc.
I did not mention the above and kept telling myself it must be as it should be.
In the mean time I adjusted my exhaust timing which I have already detailed.
Did a couple more heat cycles just to be safe, rode around e yard some more basically lightly repeated the first part of the break in cycle.
Get to the trail ride gently for 30 minutes, all seems well.
After it has cooled, go back out this time I ride it pretty much normally with the exception of no extended wot, but I did really get the rpms up for the first time, ride for an hour or so and notice everytime I ride easy for a while, it seems a little weak, until I accelerate fairly hard through a few years a couple times, then the power comes back. This is the first time I start to see through the rosy colored glasses and admit to myself that something is just not right. I went back to the parking lot , checked to see if it was hot, checked the plug, made sure the wheels turned freely and the brakes weren't sticking to note there. Let it cool for another 30 minutes. Start it up and now with only 3.1 hours its really noisy, as everything breaks in the piston has a nasty slap. I warm it up as for quite a long time and go out on the trail to get an idea of if it is for sure piston slap, and if it will stop when warm, it doesn't quiet down unless I run it harder tan I care to with any strange noise.

I get home contact Ken tell him whats going on, he immediately mentions the fact that I had adjusted the exhaust timing, and suggests that I pull the exhaust and have a peek. I do everything looks normal still a lot of crosshatch marks, e machining marks on the piston are clean and sharp wit the exception of the very bottom of the skirt. I send him the pics, and he tells me that he doesnt see anything that worries him and I must just not be used to the ring of the head without the top two rubber pieces.
Knowing what piston slap sounds like, and no longer willing to convince myself that all is well. I pull the head notice that the piston moves side to side both ways fairly freely. Since a digital caliper and feeler guages is all I have to measure with and I haven't pulled the jug yet I use the feeler guage and find .013" between the crown and cylinder wall, definitely not a standard measurement but I felt it was large enough to be concerned about . I am also able to put .008" of an inch up through the exhaust port and past the piston skirt. I send Ken more pictures and he tells me that he sees no wear, and he bored it to a .003" clearance, and since it was cut right and not worn there is no problem just irrelevant measurements.

Since Ken is getting really defensive, I remind him that I haven't said he done anything wrong (yet) and that I figured it more likely that I made a mistake, and I would take his for for it and at least measure correctly.

In the mean time I ask several questions as to if this or that could cause a .005" increase in clearance ,in what is now 3.7 hours (2 hours riding), without showing any signs of excessive wear.
I pull the head and send pictures of a .007 feeler guage ( the .008 is a tight fit since feeler guages are flat and cylinders are round, the piston and cylinder are acclimated at 72 F , the feeler giage has been in my pocket, each of these conditions would indicate a smaller than actual clearance.
At this point it is blatantly obvious to me (and later verified by a local machinist) that the cylinder clearance was bored and honed to no less than an initial .006" or more. Even if I were able to find other mistakes, which I expected and checked for, it still could not have caused the piston clearance to grow to tripple the recommended and double what Ken decided to use.

I do some more measuring and find a top and bottom edge bore diameter of 66.52. Which is what is expected within the small area I am able to measure with a caliper, l also find the piston is 66.32 at the skirt which is .20mm or .0083".
Once again accuracy is only good to .001 but even with that said it is still clear. I am furious inside that not only has tis happened but that I was told to run it its OK, that I couldn't measure, that Ken doesn't make mistakes ( I later take this mean it was no accident). Etc. I hold my breath show pictures of piston measurements, information Ken that I have found the problem and that even though the piston seems to have a normal taper it is around .005 five thousanths smaller than expected and than the bore will correctly support. I state that it should have been caught and thank him for "helping me find e problem".

With a lot of questions unanswered I find a local machinist, who takes a look and tells me it didn't wear to .008" clearance, it didn't shrink equally from top to bottom , and if the port chamfer would have been bad enough to cause .005" wear, it would have snagged a ring almost immediately. I leave the cylinder to sit and acclimate.
At this point although I am not proud of it I let Ken have it there is no doubt now that not only did he not cut my head to the spec I requested so I could run 95 or 100 octane pump gas, but that there was no way he could have measured the piston and not know if was undersized. Running that motor could have caused it to grenade lock and possibly injure or kill me or my children, I can't believe he would treat me this way, etc.
Ken tells me that he nor wiseco has ever made a mistake and anything other than me doing something wrong was impossible, Ken apparently never has or never will make a mistake, so he must have given me a near stock compression head and a huge piston clearance on purpose. I ask him if he had even sent out the parts I had ordered on the 14 when I first mentioned it, he said we were done he would not ship my order (he did refund the parts order).
Since then I have been made out to be an idiot, hardware, informed that Ken was a staff member here at BF, that none of my conversations are private, I have had messages deleted, been taunted for being an engineering student, called a know it all, etc. Of course my 25 years mechanic experience, now expired ASE certs, a working knowledge of all of the math and physics behind how a 2 stroke works, 4 other multi cylinder rebuilds (4 stroke). Means nothing.
Whats worse any mistake I could have made would not produce these results, the only way to get that much off a cylinder that quickly is with a boring bar. No one not even Ken can create .005" wear without anywear.

I am sure by the time I have typed this I have already had at least a couple posts ripping on me trying to discredit me , making all kinds of wild claims, but the fact is I was done wrong , not with the mistake , but with an arrogant and ignorant attitude, that showed me Ken O'Connor thinks he is incapable of making a mistake, and will trounce any one who doesn't agree.

It's sad really I had really built Ken up in my mind as a good guy , someone you could trust, I was soo confident in his work that I didn't even go get a good caliper and measure myself before installation, as this was the only way I would have had a chance of getting things fixed and done right. My lesson is learned ,always recheck anyone's including your own work, never trust an advertisement, and when it comes to money people will rip off their own mother these days.
It's not the $150 bucks thats peanuts, its the principle that if I would not have had the sense to park the bike , instead of keeping on riding it as Ken suggested myself or one of my children could have been seriously injured especially if it locked up at 70mph and it for sure would have locked up prematurely and unexpectedly.
There is no doubt that Ken is capable of excellent wor, and is seen as kind and fair. I cannot say why he chose to go this route with my job, too proud to admit mistake, too slick to get caught, or maybe he didn't like me doing my own work above and beyond the basics without buying his exclusive templates, I was strongly encouraged nu!erous times to buy them.
Either way I am out $150 and my bike sits with the top end off a cylinder that needs bored and a head that although functional doesn't suit my needs. Ken's only only offer of relief was to pay to ship my piston to an acquaintance of his at Wiseco so the could confirm? There is no questionit is 3.5 thousandths of an inch smaller at the top and 5.5 thou smaller at the bottom and the bore measures 66.52 -66.54 from front to back side to side top to bottom. Neiter shown signs of wear.

So now that you all have had a week toget a plan together, you can rip ream, and say whatever you want to discredit kemas an idiot a maniac or whatever. I rarely say much and even in this case being mostly sure what had happened I didn't point the finger until my suspicions were verified by a machinist which Ken would have been aware of, had he not cut ties and asked that I not contact him, although he proceeded to send messages to me
 
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A few questions are in order, and I'm just curious...

If I understand correctly, you pulled the cylinder after it had some break in time/ riding time on it, and adjusted the exhaust timing? Why did you adjust the exhaust timing (raise the exhaust port) in the middle of the break in? ...or did I just read that wrong? Or... do you mean the porting you did? If so I understand.

You mentioned above that you measured .013 between the piston crown and cylinder? the pistons are tapered and have more clearance at the top than the skirt (I know you know this)... this is what I get when I set piston clearance on a cast piston to .0015 ...just saying its not a know all tell all.

Something isn't correct here...
I just measured a brand new wiseco piston that I have for a blaster. Its a 67mm piston (4th wiseco over size), part number 573M06700. It measures 2.622 at the very top edge above the top piston ring, and 2.635
(10mm up from the bottom) at the skirt. Thats a .013 (13 thousandths) difference. What does your measure at, and what size over bore is your piston?

You quoted above... "There is no question it is 3.5 thousandths of an inch smaller at the top and 5.5 thou smaller at the bottom". I'm a bit confused here.

Where are you getting 95 to 100 octane at the pump? Seriously... I know of no fuel station, at least near me that sells 100 octane. That's aviation fuel territory.

Did you specify a 19cc chamber? Please explain how you measured it. There is nothing wrong with a 21cc chamber what so ever for pump gas. The perfect squeeze for 92-93 octane pump gas. Just saying

What base gasket are/were you using?

What was the compression when you tested it after your rebuild? break in?

What compression tester did you use (brand) ...This is important.

What are you using to measure the bore? The reason I ask, is because I have super accurate stuff here.

What was your ring end gap?

What is the timing (stator) set at, or is it a stock stator plate with no modifications?

Not to sound redundant, but did you do a leak down test BEFORE break in? What were the results? Did you do one before tearing it down again after the problem? If so where was it leaking?

Please post some quality photo's of the piston ...top, BOTTOM (under the crown VERY important), and all sides with good lighting.

Please post the same of the cylinder with good lighting. I need to see the port chamfering.

Pictures of the plug too with good lighting.


Lets see what we come up with. Not stirring the sh*t here, just need to know a few things to see what happened.
No discrediting, or defending.

Anything is possible. Its a funny little world we live in.
 
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It's pretty simple Joe. He screwed his assembly up with filthy hands and a bunch of piston shards in the bottom end and wore the piston down. The funny thing is, he's measuring the cylinder bore and calling it perfect but telling me I didn't measure the piston. Are you f*cking kidding me???? I bore cylinders without measuring pistons. No way!!!!! Best excuse I can make for this minion is he's an engineering student. What's the difference between God and an engineer? God doesn't think he's an engineer. DB is only looking for his work for free. Everything that was done in my shop was perfect, to spec, and delivered in a timely manor. I encourage anyone that's even looking at this midgets post to go back into this thread and read how f*cking impressed he was with my product. Bottom line is ..........I sent him a world class product and he's not even capable of doing a CLEAN top end rebuild. I have a big target on my back guys. Take your best shot db.
 
I'll add my input here, since both parties have involved me.


Got my stuff back, put it together found out I had 21cc not 19cc head, ring end gap seemed large, definitely was over the minimum, first start up I noticed some piston slap,

no, no and no again.

where have you up until right now, ever mentioned ring end gap was large ?
it's not in your build thread.
it's not in any of the conversations between you and I and ken.
never was this mentioned, sure looks like you're making sh-it up as you go.

*****************************************************************************************


you didn't ask for a 19cc head, the build sheet you filled out in your own handwrting says ...........

"18.5 cc ? (hemi or torroidial) or for pump gas"
cc.png


At this point although I am not proud of it I let Ken have it there is no doubt now that not only did he not cut my head to the spec I requested so I could run 95 or 100 octane pump gas

in another message I've seen you said "he gave me an almost stock head"
do you even know the cc of a stock head ?
you had no clue what you wanted or what works on these blasters.
he gave you what works and is what 90%+ of us run very successfully.
even if you can get 100 octane from a pump, it is not considered "pump gas", as was hand written on your build sheet.


***************************************************************************************


gotta luv this part of your "story", you're contradicting yourself, majorly.
between Nov. 5 and today

todays story
Get to the trail ride gently for 30 minutes, all seems well.
After it has cooled, go back out this time I ride it pretty much normally with the exception of no extended wot, but I did really get the rpms up for the first time, ride for an hour or so and notice everytime I ride easy for a while, it seems a little weak, until I accelerate fairly hard through a few years a couple times, then the power comes back.

Nov. 5
EDIT
spent about 2 hours at the trails, and put almost another hour and a half on the engine. The more and harder I ran it the more it come to life, 4,5,6 th passed by as quick as I could shift. I over shot my target by a little, and I am making more power than expected. Pulls decent from idle up to about 3250 where midrange stsrts.
From 3250 -5500 has a nice midrange grunt and the real power is only a clutch finger away.. at 5500 all hell breaks loose until a 8000 rpm shift, or a snappy 9200 rpm where the over rev dies off. The power band reminds me of a mid-late 90's cr125. That thing is faaasst now, picks up the speed as fast as traction allows.

Making good power now,so good in fact when I come rolling around the concrete driveway at the corner of my house in 3rd aND rolled on the throttle, I let off (back thumbed it, lol) 3 times before finally having to stop finding myself sideways looking at the house. My driveway isn't slick it is actually quite rough and really chews the rubber off the tires.

where's any mention of this running bad in your build thread posts ?
low compression ? piston noise ? excessive ring gap ? or any other of this nonsense you now speak ?
oh thats right, there is none.


****************************************************************************************

way before any of this, on Sept 21, you started a convo with me wanting to know how to clean the bottom end after your last piston shattered, and asked if spraying brake cleaner down into it would clean it out good enough.
at which time I told you to "split the cases to clean out the shrapnel and rebuild the bottom end".
then no mention in your build thread or to me about the bottom end at all, for 2 weeks, nothing.
yet you chronicled the rest of it in great detail.


then 2 weeks later on Oct. 6, magically the bottom end is done.

OK so I got the bottom end done, and am waiting on the money to send the top end off.

so, from sept 21 to oct 6, (2 weeks) you split the cases and cleaned, ordered and recieved new bearings, a crank splitter, an $80 tusk crank puller, yamabond, split and reassembled with all new bottom end parts,
yet no posts on the forum asking for advice, or messages to me on how splitting your first set of 2 stroke cases went, how you reassembled it, ect. ect ?
no mention of the bottom end at all, it just magically got done ?

I'm not buying it, at all.
****************************************************************************************

2 days ago you started a new "conversation" with me about this deal with ken,
I asked you some very simple questions to answer, including if you had actaully cleaned and rebuilt the bottom end.
yet you refused to answer even one of them............

you also had this top end off and re-ported the exhaust port, then re-assembled it (remember me asking about that in your thread ?)
1.you re-ported it based on it not running like you thought it should, BEFORE even tuning the carb 100% ? WTF ?
2.did you ever get the carb 100% ?
3.did you re-chamfer the exhaust port ?
4.did you clean it 300% no porting dust left anywhere ?
5.did you use a new base gasket ?
6.new or annealed head gasket ?
7.did you do heat cycles again ?
8.retorque head/base nuts after last heat cycle, again ?
9.did you leakdown test again ?


BTW......
What was the results of your compression test when you first installed the cylinder from Ken ?
What was the results of your compression test after you boogered up the porting more,
and re-installed it ?



your lack of cooperation, lack of provided info, tongue twisted contradicting stories, refusal to send the piston into wiseco on kens dime, your rant calling ken everything but a white man, accusing him of doing this purposefully to you, before he could ask you to send the whole top end back for inspection/remedy......has really limited your options here.





as for anyone calling you an idiot, I don't see that anywhere, nor is it needed,
you've done way to good of a job at that for yourself.




.
 
this is alot to read but
it is just 1 bump in the road that will happen when you are trying to experiment
as much as your are db.

i would have bought a comp gauge and tested it after fresh rebuild from autozone.
then went to a real atv shop to buy your b8es plugs.....not the bp8es plugs from autozone.
maybe the projection plug had no effect on it buttt i have witnessed at least -3 people on here that have had a problem with it in the air cooled blaster,add that to your carb problems ect...recipe for disaster:)

my top end showed signs of overheating when i purchased my last blaster.it read 121psi
i took it apart dremeled raised the exhaust port 1mm polished widened the exhaust port/put it back toghther and still read 121psi at least at kicking speed.
i sent the head to ken for the same mod he did to yours,put it back toghther and it read 148psi.And that was with a top end that def needed to be replaced..I had pics but on my other pc that died:(

at some point in this build there was going to be a snag and you have hit that snag
and i dont think you can blame anyone but yourself...At least, i would blame myself after trying to attempt such
difficult achievements. Best regardso_O
 
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I sent him a world class product and he's not even capable of doing a CLEAN top end rebuild.
A serious case of narcism, I believe.
IF piston charts where in the engine it should have left some evidence, at least in the bore or on the piston.
So maybe there will be some pics uploaded here to clarify things.
And you say db isn't capable of doing a clean top-end rebuild? I can not know, wasn't there with assembly but neither where you...
Lol I replace parts often(I abuse my toys) but never had this happend to me(and I do rip it when it's cold:oops: with a forged Wiseco piston 0.0020/0.051mm clearance ) that it could wear out this much in so little time, with out damage to piston/cylinder... such clearances can not come through wear without leaving evidence!
And if I believe he had ordered an 19cc head and got an "world class" 21cc cut out?
I believe mistakes are going to be made sooner or later, by everyone!
Sad that an unsatisfied customer is being referred as : midget,minion and has filthy hands...
I'll hope that K*R will stay delivering good work in majority, because if something is wrong, see how you get treated....
And you know why db didn't screw you right along when he did get his cylinder back! because he had taken contact with you to get things straightend out, what didn't happen.
That is the reason why he didn't complain on bf before, to give K*R a chance to resolve the issues.
 
WOW! There are some obvious holes in the story.
Seriously... you didn't rebuild the bottom end after a fragged piston? Say it isn't so...please.
Its possible the cases could have a minor crack (air leak = lean) from a piece of piston pressing it outward (bottom of case), or inward toward the counter-balancer (inside the case) where you can't see it.
Like I said above, a 20cc, (21cc), 22cc, and 23cc hemi head works great with all the pump gas I've used, and without issues, and without detonation.

I say ... "Hmmmm"
 
Why would you install a fresh new top end that has the bottom end full of old broken piston :eek:
Better split that case before you even consider running it again
 
if it was your local shop that did the cylinder work.
it would be the same story unfolded.
everyone on here OFFERS there advice
it is up to the individual to proceed with the actual work.

members on here that have seen it all since bf was created know when
someone knows what they are talking about and people that don't know what they are talking about.

if you think you can proceed better without the help of us then so be it.
 
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If that fresh top end was installed on a bottom end that was flushed out after fragging a piston, its very possible that the crank is well worn and perhaps what you hear is "clicking bearings" and not piston slap. Its a possibility.
Something to check.

My personal blaster that I purchased used had a 66.25mm piston stuck in a 66.50 bore and ran great. It was a bit noisy, but not as noisy as you would think considering that kind of mistake.