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Stormin' Mormon
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310 Posts
Discussion Starter #1
Currently im running one of boosted306's head kit and i dont know why i had to use a gasket in mine, he said a thin layer of rtv gasket maker would do the trick but i guess my block is different. with the gasket my squish is about .6mm but im only getting about 70psi. i thought maybe my piston rings were shot so i put new ones in and the compression is still the same.

I used a standard tool to test the compression but maybe these little engines require a special one? not to sure on that one, but i went ahead and threw in a rocket key and put my sparkplug back in and it did feel noticeably harder to pull. when i was testing the compression i couldn't screw the threaded part all the way down cause it was to long and would hit my piston so i threw some teflon tape on the threads and call it good. would that possibly mess with my readings? and speaking of compression. what is a good standard compression. i remember seeing cam say in a post that it can be anywhere from 130 to 200 :eek:.... is my bike effed? if i forgot to mention any upgrades i have done that would alter the compression let me know so i can inform you guys on what i got
 

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Banned
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21,744 Posts
When you installed the head kit ..........Did you use new rings and piston to begin with?

Sounds like you may have a reed sealing issue....................Look there

Ive never had my hands on a Sam built engine to test one out and Ive been dying to hear the compression numbers EPR has on his build ups but so far all I know is it has finger ripping compression and I know what that feels like on my engines;-lol.....................

This is the compression numbers on my 2 piece Zenoah head kit I built....I know its not reed inducted but you can see the numbers exist..............

 

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Stormin' Mormon
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310 Posts
Discussion Starter #3
yeah he included a piston that was port matched and it had fresh rings and then i broke the new head in
 

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Stormin' Mormon
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310 Posts
Discussion Starter #5
the squish was .6 and compression was 70psi and when i took the head off to put in the new rings on the squish was the same and the compression was still the same
 

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Stormin' Mormon
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310 Posts
Discussion Starter #6
When you installed the head kit ..........Did you use new rings and piston to begin with?

Sounds like you may have a reed sealing issue....................Look there

Ive never had my hands on a Sam built engine to test one out and Ive been dying to hear the compression numbers EPR has on his build ups but so far all I know is it has finger ripping compression and I know what that feels like on my engines;-lol.....................

This is the compression numbers on my 2 piece Zenoah head kit I built....I know its not reed inducted but you can see the numbers exist..............

geez... im quite jealous lol. i have a triple stage reed in it and when i took the reedblock out to clean it the seals seemed good, i can take another look at it, considering getting a gasket kit and replacing all the gaskets. once i check the reeds ill test the compression again and let you know where its at
 

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Stormin' Mormon
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310 Posts
Discussion Starter #8
I got the bbk about a year ago and when I installed it I broke it in with a tank full of 32:1 mix then 40:1 then 50:1 while taking it easy on the throttle and never leaving it at wot. once that was done I started upgrades like port polishing the carb, v stack, new cone filter, stiffer clutch springs. Triple stage reeds all that fun stuff. While doing all that some upgrade messed with my fuel to air ratio so for the most part I ran lean while testing the new upgrade. But the most id ride it was up and down the street then id adjust it. Would running lean do anything or just wear out the rings? All that running lean and getting upgrades was last year. This summer I got the fuel mix good and made sure my gaskets and seals were ok and cleaned up stuff, then I find out I have weak compression so I put fresh rings on and that's where I'm at. Hope the extra info helps.
 

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Trained Chimp
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364 Posts
Even my 2 stroke race bikes have never been leaner than 32:1. What oil do you use? If you use anything besides Castor. You were to lean. Castor oil doesnt burn it lubricates. The less expensive oils burn and dont lube as well. I would start by asking Sam what his compression usually is when he builds his motors. Have you done a leak down test?
 

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But who prays for Satan?
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6,571 Posts
Even my 2 stroke race bikes have never been leaner than 32:1. What oil do you use? If you use anything besides Castor. You were to lean. Castor oil doesnt burn it lubricates. The less expensive oils burn and dont lube as well. I would start by asking Sam what his compression usually is when he builds his motors. Have you done a leak down test?

Sam is SUPER SMART, I PM'ed him just a few days ago, Really nice too,
but his weekends are going to be more work than the week was pretty soon here!

NaSa.
 

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Stormin' Mormon
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310 Posts
Discussion Starter #12
Sam is indeed a wizard when it comes to these little engines. Id buy from him anytime. I quit doing 50:1 last summer and currently In my gas tank is like a 40-35 mix. I haven't been able to find fully synthetic oil, so just regular oil for dirt bikes. I may have done a leak down test but I haven't heard of what that is.
 

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But who prays for Satan?
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6,571 Posts
It could take as little as 2 minutes of "Fun" while @50:1 to "Spoil the PARTY"

Sorry for the bad luck, I would pull the head first, check for damage, then pull the cylinder to check it and the rings plus crank...

Should only take a few minutes! ;):thumbsup:

NaSa.
 

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Trained Chimp
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364 Posts
I by no way was questioning Sams work please dont take it that way.
I cant wait until I can afford one of his motors.
I was just saying thats a good refferance point.
I know from reading posts here that hes quite a guru. Lol I know he bench tests his motors.
I would think he knows where it was at when he was done with it.
As a matter of fact I want Sam to build a motor for me for my full suspened mb. For the next race.
Now for the leak down test. My compresion gauge(Snap-on) also has the abillity to hook a air supply to it.
You can then generally tell what is leaking. One way is if you can hear the leak.
Another is by how fast it looses preasure. One more is buy how much it holds.
 

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Stormin' Mormon
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310 Posts
Discussion Starter #15
I did that last night. All seemed good no scratches in the cylinder, piston looked good along with the crank. The rings looked ok but I threw new ones on anyways. I honestly think the tool I used is the problem cause its for a car and the threaded part is longer so I could only screw it half way and perhaps some compression is getting past it. Cause after the new rings and putting my spark plug back in the pull start was noticeably harder to pull
 

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Trained Chimp
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364 Posts
Ruffles,Most motorcycle shops sell Maxxim Castor 927 or 929. Its good stuff. Ive never seized,or prematurely worn out a motor. I had a kx250 with hundereds of hours on it. When we tore it down. All it needed was a good hoaning and rings. I know I didnt spell that right.
 

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Trained Chimp
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364 Posts
May I sugguest you make a spacer out of pvc or tubeing of some sort with flat rubber washers so yo get a real reading?
 

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Stormin' Mormon
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310 Posts
Discussion Starter #19
do you think using a crap ton of teflon tape will work? Ill tinker with the tool and if I still keep getting 70psi I'll tear down the motor and take pics..... Lets hope for the best :p
 
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