ultimate short track motor?

[cjcrete]

Hey guys looking for some imput here, I'm in the market to build a mean reliable short track/play motor. We race on smaller flattracks and need the hard pull coming out of the corners to keep up with those big torq 4 pokers. Some say 4mill some say 7mm, Powervalve motors may be out of the buget. What advantage will a stroker give you over a stock bore? Also wondering about what motor builder? 12 port design? maybe another port design? Short track motors are all together different I need smooth usable power from low on up. I race with a couple of high hp banshee's now (80-90)and they dont impress me much! by the time we hit the corner there power is just starting! no good!! and there power is like a switch! very hard to control. Thanks

[slopoke]

I admire what you are trying to do. It may be costly though. A banshee is not happy with anything "short". I'm not saying it can't be done, it just is asking it to do something it don't know how.

[cjcrete]

I admire what you are trying to do. It may be costly though. A banshee is not happy with anything "short". I'm not saying it can't be done, it just is asking it to do something it don't know how.

 

 

Maybe there's a reason 2 strokes are no longer a player in the mainstream tt short track wars. Or are they? Lots of r&d into these 4 pokes now Is there any tricks left for the banshee? I just can't seem to let go of these bikes!

[slopoke]

dunes and drags is where they are in there zone. Forestrokes generate such low end and a broad range that you would spend alot of money just to be close. JUS MY OPINION. The problem lies in that the banshee makes its horse power in a relativley narrow band. A thumper is very broad banded it pulls hard down low. Like you said a banshee has a nothing or balls to the wall switch. You can broaden the power band but it still will not compare with a thumper. Like I said it is very hard to make a banshee work in a short distance effictively. There are some awsome trail bikes out there but I don't know how they would compare on a small flat track with slow corners. If you are not careful when the power comes on you find yourself headed the other way. This is all just MY OPINION. I'm sure someone will have more to add. I'm just telling you my experience, not saying it can't be done but not practical. If it was a long flat track may, this might be a different discussion.

[kubitza123]

If money wasn't a problem i'd say a powervalve cheetah or something like that maybe?

[cjcrete]

for a very small short track it is very difficult to get a banshee to pull off of the corners like a 4-stroke. You can do it but if there is a budget in mind it generally can't be done. The crank (7MM or 10MM) is a grand by itself. Then you have to trench the cases and then find someone to port and build the stock cylinders to match. I would not use the cheetah or the cub cylinders for this type of motor, I have had both the cheetah and the cub and neither one could compare to the bottom pull of my stock cylinders. I know you can get more top end out of the ceetah cylinders but Iam making solid top end power but the smoothness and torque make up fo it.

 

another thing to consider is the gearing. Gearing is very critical to getting the banshee to run with the 4 strokes in a small, tight flat track environment. Then no matter what you do to a motor if you can't ride it then you are still going to get your ass kicked by whatever is on the track. If you are racing a pro caliber rider on a 4 stroke good luck but a Banshee in the right hands is lethal on a flat track.

 

 

Thanks lobo, I agree on the rider & gearing, my set up now always does very well against the competition i'm always running top 3-4 with a piped banshee and a good chassis setup!! Now i'm not running with farr, ogden and little 4 sure but there is some 450's with 500cc's that can run! Does it mean the higher you stroke your bike the more low end you will produce or the other way around? I see alot of 4mils around. and a few 7mils I think with a healthy powerplant under my seat this bike could be danger

[Snopczynski]

4 mill motor, resleeve the cylinders, and drop the exaust ports down lower than stock. Run a set of pro circuits on it, and a lot of compression.

[jbooker82]

I would do a dune ported 4 mill, gear it low to keep the rpms up, and a dunable override. So you can bang gears without touching the clutch or letting of the throttle.

 

If your wanting to go bigger skip the 7mm and go for the 10mill. The cost of the cranks, and trenching the cases cost about the same.

[cjcrete]

Back in the day before the old 450's came around who was building all the top riders banshee tt motors? I here stallworth has built some pretty nasty WINNING proven motors. How about duncans technology they just won pikes peak 09 on there banshee do these guys have a leg up on the rest????

[Snopczynski]

Im a little lost here. He wanted to know how to build a torque motor that pulls hard, so people are recommending Dune ports, 16/38 gearing, and trinity pipes? Im fucking dumbfounded!

 

I guess my bike is some sort a freak of nature, cause I dont run any of that shit you mentioned. However, I can ride it in holes, on trails, and pull dunes on the Oregon coast. Then go down and drag race a Ported 350 with cpi's, drag port, and 35mm pwks and stomp a mudhole in his ass from the start to the finish line.

 

I have a low-mid motor that puts out 66.75 hp with a stock crank and ported cylinders on a crank dyno. I raced a friend of mine with a Trinity 4 mill motor, with Stage IV pipes, and 39mm pwk carbs, and it beats me by 1 bike length. I dont care what you say, Trinity dont know shit, and thats definitely not the way I would build a hard pulling motor with torque.

[cjcrete]

Im a little lost here. He wanted to know how to build a torque motor that pulls hard, so people are recommending Dune ports, 16/38 gearing, and trinity pipes? Im fucking dumbfounded!

 

I agree on the dune port, not so sure thats what i need! I would like to get this project rolling just need button down my combo and builder

[Snopczynski]

I agree on the dune port, not so sure thats what i need! I would like to get this project rolling just need button down my combo and builder

 

I say call Dave Roberts at ILR Performance. He built the motor in my uncles LT500 flat track bike, It hauls ass. All of Daves kids have won flat track championships on bikes Dave built. Not to mention he has a crank dyno in house, and knows how to build stuff with wicked torque.

[2strokespirit]

You don't need to lower a exh port to get low down power.. Get the blow down "in spec" and run a high transfer.. You will have TONS of low down power.. Agreed on the PCs.

[Snopczynski]

You don't need to lower a exh port to get low down power.. Get the blow down "in spec" and run a high transfer.. You will have TONS of low down power.. Agreed on the PCs.

 

You do need to lower it maximize the low end power you can get though.

[No Limit Powersports]

yes you are right, the 10MM crank is the same cost as the 7MM but the extra cost to make the stock cylinders work isn't worth it IMO. The 7MM will make tons more torque and with the proper port timing will be able to run high gearing and still pull hard out of the turns. I run 16-38 gearing on small 1/8th mile tracks and I haven't found a big bore 4-stroke that will out pull me, then once on a bigger track they don't have a prayer since they just don't have the top end like a banshee.

 

As for pipes I read someone said pro circuit or something like that??? I wouldn't run anything but Trinity stage IV pipes. I have done back to back dyno tests with all of them and the Trinity's are the best rounded pipe on the market. There are some that make more power and some that make just a tad more torque but trinity is the best all around pipe period IMO.

I know there are alot of Trinity haters around here but if they have a great product and it works that is all that matters to me.

 

I am not a huge fan of the 4MM motors. I just don't like have the piston coming out of the jug and having to cut the domes to make them work. Mine is resleeved with the sleeve sticking out of the cylinder then a spacer plate that takes up the area that the sleeve sticks out then I have zero deck height, bolt on the cylinder head and press on. LRD did the sleeving and spacer then we tweaked the porting to our specs. Call and talk to John at JSR Performance (316-733-1936) and tell him Steve with the E85 Banshee sent you and he can set you up with an identical motor as mine (minus the fuel injection). Trust me you won't be disappointed in the power of the 7MM. Everyone says go with the 10MM just because the crank is the same but the 7MM is a very potent combo and John has always built outstanding 7MM motors.

 

Oh and lots of compression is helpful it helps the motor get into the power quicker and if you think it won't rev out it will. Mine turns 10500 before it starts falling off on power and still will turn almost 12K in overrev. So if someone tells you compression won't let you rev it out they don't know. Also I run the Dyna box with custom curves which help with this.

 

LMK if you have any other questions but please give John a call and he can talk you through the whole setup.

 

All of the sleeves protrude out the bottom even stock, and if your talking about it protruding out the top putting a spacer plate isnt goint to make the sleeve flush because it will not move in the cylinder? A 4mm can be done with cut domes which in my mind is the best and let the piston pop out the top it doesnt pop out past the rings anyway so it makes zero difference. Another way is using a spacer which is just another place for a leak but will work just fine either way the motor needs to be ported to gain the benefit from the added stroke length.