ATV Drag Racer Forums banner
1 - 17 of 17 Posts

·
Registered
Joined
·
246 Posts
Discussion Starter · #1 ·
I am waiting on a email from the tuner with the a/f but I am in the process of loading the hp chart.

It made 68.55 hp and the tq didnt read

the mods include 392 cub cylinder no cleanup +4 on the timing plate with vforce 2 reeds and 39mm pwk's, shearer sb inframes on 110 octane, blaster pistons long rod crank, and off ther shelf domes i need the correct ones cut so the squish is over .70

the tuner kept on saying the tip in was lean so I needed a richer needle.

with a 48 pilot dek needle in the middle position and a 152 main it was too rich on the a/f meter it was 10.5 so he kept dropping mains down to a 135 main and the a/f ended up being 12.5

This doesnt sound right to me with such small mains and the needle being in the richest position.

Can anyone shed some light.
 

·
Registered
Joined
·
246 Posts
Discussion Starter · #2 ·
If this needs to be moved to the dyno section by all means move it but I just figured it would get more hits over here.
 

·
Registered
Joined
·
767 Posts
That head chamber is so far out of whack that more than likely it just cant burn all of the fuel you were putting to it, hence the need for less volume.

I would not try to do ANY tuning until you get the dome situation handled. Anything else you do right now will more then likely be useless once a correct dome design and squish is done.
 

·
Registered
Joined
·
246 Posts
Discussion Starter · #4 ·
QUOTE (bubba297 @ May 14 2009, 04:11 PM) index.php?act=findpost&pid=42575That head chamber is so far out of whack that more than likely it just cant burn all of the fuel you were putting to it, hence the need for less volume.

I would not try to do ANY tuning until you get the dome situation handled. Anything else you do right now will more then likely be useless once a correct dome design and squish is done.

Bubba, I have spoken with noss about domes. whats your turnaround time on a set and what measurements do you need? pm me a price and time if youd like
 

·
Registered
Joined
·
246 Posts
Discussion Starter · #5 ·


Thats the best I could get with the camera phone I am waiting on the email with the a/f
 

·
Registered
Joined
·
246 Posts
Discussion Starter · #7 ·
QUOTE (fast guy @ May 14 2009, 08:54 PM) index.php?act=findpost&pid=42618you need to try puting the timing up more and see what hhappens

The domes are wrong we lost power at +5 +3 +0 It looked like +4 was the sweet spot but im gonna get a set of correct domes and get it retuned
 

·
Registered
Joined
·
767 Posts
Hey Chugger, I use a good friend of mine in Oklahoma to cut my domes, but it isn't noss.

Nate McCoy (sponser) can do them

Tim at Titan Racing can do them

You definitely need someone who understands what they are doing and knows exactly what you have, and what you want. The chamber design is a big key to power output. Notice the dyno graph how erratic the line is coming into the power range of the pipe. If jetting is correct, I can only see that being ignition or your dome.
 

·
Registered
Joined
·
1,534 Posts
or use banshee stroker pistons.. is your deck hight zero??

my pump gas t-5'd stock cylinder'd short rod 350 made 65 hp... and had a nice flat curve..

most gas banshee's dont seem to like much more than +4 timing.. at least what i have seen..

get your squish down to .45 and then put that 152 main back in it and try it again..
 

·
Registered
Joined
·
246 Posts
Discussion Starter · #11 ·
My pistons are in the hole a few thous at tdc but from what dave at noss told me thats typical with the blaster pistons. He is fixing me up with a set of domes. very good guy and informative as is this site too.
 

·
Premium Member
Joined
·
1,953 Posts
Chugger Are you using a 54mm stroke LONG rod crank? If not disregard what I'm saying.
I had a 392 cub and had a long rod (115mm) crank and if you use a 573-MO-6800 blaster piston which is what you are supposed to run with that setup you end up having about .073 squish with a standard cut dome.
I dont know if you have the long rod crank or not I'm assuming due to you using the blaster piston and not a 68mm bore banshee piston. With that setup you'll have say 18 or 19ccs in your dome and then you have like another 2.6cc in the bore above the piston and end up with low compression even with an 18cc dome. If you call Nate Mccoy he can fix it for you or he has a piston he sells that is .031 longer from pin to dome and fixes the 392 longrod length problem if that's the case. You will then need 68 bore banshee domes to go with it. I would swap cranks if it were me and go with a stock rod crank. I fixed mine by milling .032 off the base of the cylinder.
 

·
Registered
Joined
·
246 Posts
Discussion Starter · #13 ·
QUOTE (Radar @ May 18 2009, 01:26 PM) index.php?act=findpost&pid=43147Chugger Are you using a 54mm stroke LONG rod crank? If not disregard what I'm saying.
I had a 392 cub and had a long rod (115mm) crank and if you use a 573-MO-6800 blaster piston which is what you are supposed to run with that setup you end up having about .073 squish with a standard cut dome.
I dont know if you have the long rod crank or not I'm assuming due to you using the blaster piston and not a 68mm bore banshee piston. With that setup you'll have say 18 or 19ccs in your dome and then you have like another 2.6cc in the bore above the piston and end up with low compression even with an 18cc dome. If you call Nate Mccoy he can fix it for you or he has a piston he sells that is .031 longer from pin to dome and fixes the 392 longrod length problem if that's the case. You will then need 68 bore banshee domes to go with it. I would swap cranks if it were me and go with a stock rod crank. I fixed mine by milling .032 off the base of the cylinder.

Radar,
yes I do have a long rod crank and from my measurements I have the problem that you stated. Noss is trying to help me figure out a configuration if not I guess I will get some of those pistons from nate. So you are saying that the pistons from nate will correct my squish issues or are they like a standard big bore long rod banshee piston. I know that wsm makes a set will this work also is this messing with my port timings at all. All along I just thought I couldnt get a correct measurement at tdc i thought my caliper was junk.

Is there any other options I can do?

If i get the base milled I will prob jest get it ported as well by nate kill 2 birds with one stone.
 

·
Premium Member
Joined
·
1,953 Posts
Chugger the ways to fix it is

#1 The pistons and some domes from Nate they are a different piston than a banshee or blaster I believe they are .031 or so different from dome to pin. Might be a jetski piston???
I'd say that would cost ya under $300.

#2 Stick a stock 110 rod crank in it and banshee pistons and some banshee domes

#3 Or send it to Nate and have him port it and use the right combo and it will run hard.

#4 mill the cylinder. This is what I did but I wouldnt do it again. I'd send it to nate I was just trying to get my bike running in like a week.

Any of those should run right. Nate helped me on mine and he'll know exactly what you are talking about with a stock stroke cub and long rod crank.
 

·
Registered
Joined
·
246 Posts
Discussion Starter · #15 ·
Thanks radar,
David at noss is sending me some domes to try if I cannot get it ironed out with those nats getting a yell. I will prob get a set of those special pistons and domes or who knows might just send the cylinder to get it ported as well.

So is the port timing screwy with my setup as it is or is it fine just need the correct squish. Sorry somewhat new at this stuff I know the basics but trying to teach myself the the advanced mechanics of it.

thanks again
chris
 

·
Registered
Joined
·
240 Posts
QUOTE (Radar @ May 21 2009, 09:48 AM) index.php?act=findpost&pid=43654Chugger the ways to fix it is

#1 The pistons and some domes from Nate they are a different piston than a banshee or blaster I believe they are .031 or so different from dome to pin. Might be a jetski piston???
I'd say that would cost ya under $300.

#2 Stick a stock 110 rod crank in it and banshee pistons and some banshee domes#3 Or send it to Nate and have him port it and use the right combo and it will run hard.

#4 mill the cylinder. This is what I did but I wouldnt do it again. I'd send it to nate I was just trying to get my bike running in like a week.

Any of those should run right. Nate helped me on mine and he'll know exactly what you are talking about with a stock stroke cub and long rod crank.


I don't think #2 will work. I believe the 68 mm pistons for a stock crank/rod are a custom piston, not a banshee piston. The piston crown maybe the same as a Banshee piston, though...not really sure about that. I've had some bad luck ordering different domes for my 392, only to check the squish and it was 0.030''. Pretty scary.
 

·
Premium Member
Joined
·
1,953 Posts
You can get a 68mm banshee piston to run with a 110 rod stock crank no problem. I believe the # is 9768MO6800 any builder can hook you up that's a very common big bore 68mm banshee piston. Just need the correct 68mm bore banshee angle dome also. I believe you use a .022 or .020 base gasket. Just Call Nate he has all that stuff or any other good builder if you want they all have 68mm banshee pistons. The BB blaster pistons are 573MO6800 I went thru a few of them.

IT WILL RUN COMPLETELY DIFFERENT than it does now. Mine ran 1.98 60 ft times and bogged like crazy out of the hole ran at best a 5.4 at 64mph. That was when I first bought the bike and it was like that when I bought it.
 
1 - 17 of 17 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top