Building a 372XP Big Bore With 272XP Piston

[davebull]

How do you intend to cut the squish band and how much do you need to take out?

Pretty funny after mentioning you'd ordered 5 x 272 pistons in the other thread for pop ups You'll have a few spares now

I went and seen a guy in Sydney, he's going to cut the squish for me for $100 using cnc, he can also do a popup for me for $30 but I don't think that will work.
I was planning on taking out a little over .045
I'll give him the current squish reading with 372 piston and then just give him the lot and he can work it out,
He pretty good with 2 stokes, he's built race bikes race kart motors and bike saws.

 

[davebull]

How do you intend to cut the squish band and how much do you need to take out?

Pretty funny after mentioning you'd ordered 5 x 272 pistons in the other thread for pop ups You'll have a few spares now

I was on YouTube the other night checking out your vids, you've got a nice 7900!! I think I won't one now after seeing it pull a 42" bar!!!
I'm only guessing it is you on there though?

 

[MCW]

I was on YouTube the other night checking out your vids, you've got a nice 7900!! I think I won't one now after seeing it pull a 42" bar!!!
I'm only guessing it is you on there though?

Yeah I'm the main culprit there.
Funnily enough the 7900 pulling that 42" bar buried in Redgum is actually way less powerful than the pop upped one that Brad Snelling has built me since. That one has over 600 hours on it now and is still pulling 210psi compression

 

[Mastermind]

I forgot the pics of the grinding......







I still don't like the way it runs.

 

[Jacob J.]

I still don't like the way it runs.

You should be able to fix that...

 

[morgaj1]

Very nice ones these are.

What, are you Yoda now?:tongue2:

 

[Mastermind]

You should be able to fix that...

Yeah........I figure you're probably right. :msp_wink:

What, are you Yoda now?:tongue2:

No. I'm Randy. R A N D Y opcorn:

 

[Jacob J.]

Yeah........I figure you're probably right. :msp_wink:

I usually am...

 

[Mastermind]

I usually am...

That's weird for a hillbilly too huh?!?!? :msp_unsure:

 

[davebull]

I still don't like the way it runs. [/QUOTE]


If you would like to part with that cylinder, I've got a nice little home for it on my 372...
I've got $$$ :msp_biggrin:

 

[Mastermind]

If you would like to part with that cylinder, I've got a nice little home for it on my 372...
I've got $$$ :msp_biggrin:

200.00 and shipping

 

[davebull]

200.00 and shipping

Sold randy, I just sent you an email
Cheers Dave

 

[davebull]

Yeah I'm the main culprit there.
Funnily enough the 7900 pulling that 42" bar buried in Redgum is actually way less powerful than the pop upped one that Brad Snelling has built me since. That one has over 600 hours on it now and is still pulling 210psi compression

If I ever get a 7900 that's where I'll be sending it,

Or mastermind..

 

[MCW]

If I ever get a 7900 that's where I'll be sending it,

Or mastermind..

Can't go wrong either way

 

[wyk]

No. I'm Randy. R A N D Y opcorn:

MY GF tells me the same thing.

Nice work on those ports, btw.

Oh, hey, my GF also tells me that as well.

 

[ckelp]

Randy, my 1000's of hours of inexperience made me think of could it be the ignition timing be off for your half baked saw

 

[wyk]

Randy,

How much blow down are you running on that BB?

 

[Mastermind]

Randy,

How much blow down are you running on that BB?

About 20°

I just put a different piston in it.....

 

[wyk]

About 20°

I just put a different piston in it.....

Thanks for a quick answer! I got one in front of me right now and was running the numbers.

 

[Mastermind]

This is weird........I got a notification......but no one has replied.

Good thread to bump though.

This 272 piston in a 372 BB was a waste of time. I didn't have anywhere near the grunt that a full circle piston had. Case compression suffers with the 272 piston, it takes up less volume in the case...

Another case of the original designers knowing more than a redneck with a grinder.