piston top clearing cyl top

headache
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headache 10/4/2014 9:13pm
10/4/2014 9:13pm
Squish needs to be around .038"-.040" for optimum performance
slipdog
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slipdog 10/4/2014 9:36pm
10/4/2014 9:36pm
This thread is getting Squishy
hillbilly
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hillbilly 10/4/2014 9:59pm
10/4/2014 9:59pm
If the piston was flush with the cylinder before you sent it off the compression will be so high it will burn a hole thru it from detonating even if the piston clears inside the head.

If it was protruding before gorr did his thing and it clears the head you can buy a 30 buck compression tester at advance autoparts and see what psi you have.

Ground the plug on the head or hold kill button,open throttle and kick till the gauge stops rising. About 220psi is all 93 octane can stand without preignition and detonating.

On the linkage,if the lower shock mount uses a bolt and nut it most times will only clear one way ,put it in backwards and it hits the pull link binding the travel.

JW381
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JW381 10/4/2014 11:38pm
10/4/2014 11:38pm
Did a backup squish test by threading solder thru the spark plug hole, I think it's good to go. Got the shock freed up (I think). Tired and sore, you'd think I rode it.

The Shop

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JW381
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JW381 10/5/2014 12:12am
10/5/2014 12:12am
Honestly, I'm not too worried. I doubted myself the first time I did my top end and that was a mistake because everything worked well. Granted I faced some hiccups today, I took my time and I checked the squish twice and it appears to be enough, the shock is fine I think I was just being a pussy and not putting enough weight on it without the subframe on. Gonna break it in good tomorrow and get a good seal and just trust that I did at least mediocre enough for it to run and not blow up.
Jakes Dad
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Jakes Dad 10/5/2014 4:27am
10/5/2014 4:27am
Jakes Dad wrote:
How a guy can take your cylinder and head, and start grinding and machining. Not knowing where the piston sits in the hole or at what...
How a guy can take your cylinder and head, and start grinding and machining. Not knowing where the piston sits in the hole or at what point the ex port opens is beyond me.
slipdog wrote:
???
How do you know how to adjust port timing when you don't know where it is to begin with. How do you know how to cut a head and chamber when you don't know where the piston sits in the hole at TDC.
dirtaddict 10/5/2014 4:43am
10/5/2014 4:43am
JW381 wrote:
I posted about this in race shop but I kinda need some input ASAP. Installing my new Gorr cylinder and the studs aren't even fully torqued...
I posted about this in race shop but I kinda need some input ASAP. Installing my new Gorr cylinder and the studs aren't even fully torqued yet and I noticed this. Is that part if the mod when Gorr mills the base ?

how does the piston look at the transfers when at bottom? should be in line , adjust base gasket to suit then get the squish right with the head
Cygnus
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Cygnus 10/5/2014 6:52am
10/5/2014 6:52am
Eric Gorr built that. You assemble it and go. Did he send 2 base gaskets? If not did he send 2 head gaskets. I doubt it. I'm sure it's gonna rip.
JW381
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JW381 10/5/2014 7:09am
10/5/2014 7:09am
Cygnus wrote:
Eric Gorr built that. You assemble it and go. Did he send 2 base gaskets? If not did he send 2 head gaskets. I doubt it...
Eric Gorr built that. You assemble it and go. Did he send 2 base gaskets? If not did he send 2 head gaskets. I doubt it. I'm sure it's gonna rip.
That's the post I need, I woke myself up an hour early all anxious. One set of gaskets. Checked squish twice, it's gonna be sick. Now hopefully I can hold on.
rcannon
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rcannon 10/5/2014 7:34am
10/5/2014 7:34am
The only way you woudl have trouble is if you had a really worn crank that let the piston travel up too close to the head..makes sense, right? I know Eric built hundreds of these for us over on Thumpertalk, and I dont recall anyone having a clearance issue.

As for holding on? Yea...Even with "better all around" porting, its very fast. You could say its easier to ride than the stock bike, which would be true, but the bike goes through the low end and midrange so fast, it is slightly terrifying.



roost251
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roost251 10/5/2014 8:01am
10/5/2014 8:01am
hope it all worked out JW381 and that you are roosting with a big smile on your face at Albany right now!!
slipdog
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slipdog 10/5/2014 8:02am
10/5/2014 8:02am
Jakes Dad wrote:
How a guy can take your cylinder and head, and start grinding and machining. Not knowing where the piston sits in the hole or at what...
How a guy can take your cylinder and head, and start grinding and machining. Not knowing where the piston sits in the hole or at what point the ex port opens is beyond me.
slipdog wrote:
???
Jakes Dad wrote:
How do you know how to adjust port timing when you don't know where it is to begin with. How do you know how to cut...
How do you know how to adjust port timing when you don't know where it is to begin with. How do you know how to cut a head and chamber when you don't know where the piston sits in the hole at TDC.
Who doesn't know, JW? You?

I know, Gorr knows, Pro-circuit knows, Varner knows... Can they vary a little, yes, but they don't vary as much as people on the internet will lead you to believe. Of course you don't just cut wildly on a cylinder you don't know, but do you really think Eric Gorr doesn't know the CR250 motor? I've done a lot of CR250 motors, I'm sure not nearly as many as Eric, and when everyone was finished and checked they came in right where my specs intended.

Maybe I was confused by your original post, but you seemed to be insinuating that because JW was confused with how his motor goes together, somehow Gorr doesn't know what he's doing.
JW381
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JW381 10/5/2014 8:39am
10/5/2014 8:39am
Loading up now dudes, I'll let y'all know! Woohoo
JW381
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JW381 10/5/2014 3:24pm
10/5/2014 3:24pm
Ran good! Smooth and strong after about 7 little things kept fucking up like my float and clutch cable. Need to get bike turning better but it was fun, it's been a while haha. Jeffro was out there on his RM, it was a good (albeit HECTIC) day.
JW381
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JW381 10/5/2014 3:34pm
10/5/2014 3:34pm
I also did kind of a harder break in like people around here swear by. Warmed it up and went thru all the gears a few times then basically just started riding and tuning.
Cygnus
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Cygnus 10/5/2014 3:37pm
10/5/2014 3:37pm
JW381 wrote:
I also did kind of a harder break in like people around here swear by. Warmed it up and went thru all the gears a few...
I also did kind of a harder break in like people around here swear by. Warmed it up and went thru all the gears a few times then basically just started riding and tuning.
That's how I've always done it. Warm it up and make sure there are no leaks and loose stuff then ride it like ya stole it
Jakes Dad
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Jakes Dad 10/5/2014 3:53pm
10/5/2014 3:53pm Edited Date/Time 10/5/2014 3:53pm
slipdog wrote:
???
Jakes Dad wrote:
How do you know how to adjust port timing when you don't know where it is to begin with. How do you know how to cut...
How do you know how to adjust port timing when you don't know where it is to begin with. How do you know how to cut a head and chamber when you don't know where the piston sits in the hole at TDC.
slipdog wrote:
Who doesn't know, JW? You? I know, Gorr knows, Pro-circuit knows, Varner knows... Can they vary a little, yes, but they don't vary as much as...
Who doesn't know, JW? You?

I know, Gorr knows, Pro-circuit knows, Varner knows... Can they vary a little, yes, but they don't vary as much as people on the internet will lead you to believe. Of course you don't just cut wildly on a cylinder you don't know, but do you really think Eric Gorr doesn't know the CR250 motor? I've done a lot of CR250 motors, I'm sure not nearly as many as Eric, and when everyone was finished and checked they came in right where my specs intended.

Maybe I was confused by your original post, but you seemed to be insinuating that because JW was confused with how his motor goes together, somehow Gorr doesn't know what he's doing.
My last rebuild found out a Wossner rod kit was .010 shorter than the Hot Rods which I normally have my guy use. .010 is more than I would have wanted. Had to send the head out to get recut. Bought a RM cylinder that had the base cut, when I gave the info to my guy he said something was up and had me measure port heights where we found it.
These are common things that can happen to anybody, why I feel it is smart to know where things are at before sending them off to be ported or machined.
jeffro503
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jeffro503 10/5/2014 5:28pm
10/5/2014 5:28pm Edited Date/Time 10/5/2014 5:29pm
JW381 wrote:
Ran good! Smooth and strong after about 7 little things kept fucking up like my float and clutch cable. Need to get bike turning better but...
Ran good! Smooth and strong after about 7 little things kept fucking up like my float and clutch cable. Need to get bike turning better but it was fun, it's been a while haha. Jeffro was out there on his RM, it was a good (albeit HECTIC) day.
Good to finally meet you today Justin! Going to take me a while to figure out how to ride one of these 2 strokes again , but damn it sure was fun Re-learning it today!

Hey i was going to ask you about your clutch and I forgot. Did the end of the cable just slip out of the little lever arm inside the case? I saw you ride again after I had talked to you. And wasn't sure of the issue and figured " I guess it wasn't the shifting arm " ( after I saw you riding again ). Is that what it ended up being? I couldn't think of anything else it could have been. Glad you got your bike figured out.

I'll have to get you up this way for some Woodland practices. They are a good time , even though I know that's quite the hike for you.

Pit Row

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theonlinelegend 10/5/2014 6:43pm
10/5/2014 6:43pm
I just got to ask. Did you ever contact Eric Gorr before you drilled the holes in the piston? I can understand the reasoning behind it, but I'd think if it needed to be done. One would think a master engine builder would mention it or already have done it. Just wondering why you didn't communicate with them about the piston and the squish.
JW381
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JW381 10/5/2014 7:04pm
10/5/2014 7:04pm
Jeffro, Yup that's all it was, I was so relieved haha. But then my last moto I noticed we forgot to re tighten the adjusters so the slack kept increasing to the point where I just stopped using the clutch for a few laps then pulled off. It was a day of struggles.

That RM is nice man, I'd love to trek up for a woodland ride soon! Just gotta make sure that CR of mine is working properly .

Legend, I tried to call Gorr about the piston clearance, but he had started his weekend already. I didn't call about drilling the holes because it's a necessity if you have an exhaust bridge (that has not been relieved) and a forged piston. So I did what was necessary for the pieces I had in front of me.
JW381
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JW381 10/5/2014 7:08pm
10/5/2014 7:08pm
And Jeff, it was nice to meet you too buddy!
jhansen510
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jhansen510 10/5/2014 9:01pm
10/5/2014 9:01pm
Glad you got to ride justin! I was wondering if you made it or not as I was at the track today. Sundays and mx just go together!
jeffro503
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jeffro503 10/5/2014 9:51pm
10/5/2014 9:51pm
Right on Justin. Glad you had fun and you made some good progress on working some of the bugs out. That CR will be an awesome bike as soon as you get those things ironed out. Beautiful looking bike too!

I plan on hitting Albany again next weekend as well ( probably Sunday ). I'll be bring the RM again so I can have some more seat time on it. I wanted to get some riding done on that before i whipped the Kawi 450 back out. I just got that FMF mega-bomb exhaust system and a new JD Jetting ecu programmer and some other goodies......she's gonna be a beast. I could barely hold onto that RM today from not riding in 4 months. That KXF woulda killed me!

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