Drag Anyone? - What To Displace

The question - If I may I would like to draw from some of your experience. I need a builder and kit for a drag Banshee. We run 300 ft, on dirt. What would be the best kit for this and who should I get to do it. I am thinking of any where from a stock bore 350 to a full 500 stroker. Reliability is not a concern, pure raw speed is. Give me lots of INTELLIGENT opinions, idiots need not apply!! It will also be ran on alcohol.

The response - Displacement is ALWAYS preferred over other ways of gaining power. Perhaps you should find out what the rules are for a/the class you intend to run in and build it within those boundaries. Certainly the 350's don't run with the 500 to 600 cc strokers do they? Having said that, I see no reason why a fully modified 350 cc Banshee motor can not be modified to make in excess of 110 hp at the rear wheels - though over a narrow range of RPM. The guys that drag race them (RZ350's) are making that kind of power.

If I had a 500-600 cc twin it better put out in excess of 135 HP and have a wider powerband than the 350 or I'd find a different engine builder. I'm thinking of a Yamaha 701 cc watercraft engine that I saw dynoed. It was highly modified and put out 110 HP at a "pokey" 7140 RPM. I wondered what it would do at a more respectable 8000 or even 9000... Either way - big or small nitrous oxide is a MUST, and welcomed with alcohol. But why stop there and not go for a nitro burning, nitrous assisted package?

And don't kid yourself - reliability is ALWAYS a concern. If you can't finish a race you can't win it. Pure raw speed will be achieved with the lowest vehicle weight, the best hook up the tires can provide, the most CC's allowed and above and beyond all else - someone who can drive.

Rick - not trying to sound like an idiot

I'm not going to claim to be the engine guru, but here's my thoughts, and hopefully I won't come across as a an idiot either. The old saying there's no replacement for displacement. Often in larger displacement motors, longer swept volumes are obtained thru longer con rod lengths. This kills the motors ability to rev to the moon. That's why I've seen some 400 something motors (I'll be primarily speaking Banshee's) spank on some 500 something motors. The bigger motor can't rev to keep up with the other smaller motor. Example LT500's big displacement tons of torque off the line, but generally, not able to rev out to 9500 rpm and survive.

I've seen a 420 stroker, on alky, injected, claimed by the owner to put out 100 rear wheel HP, at 10,500 RPM's. And I watched him race all weekend long schooling people. So we know that this can be done. Rick is right about the RZ350's, for years those bikes have been well into the triple HP numbers!!!! The constant battle of a two stroke--gain more on top, lose it on the bottom isn't nearly a problem if drag racing is your thing. I've heard of grass drag snowmobiles, that with the clutch tuned properly and complimentary massive port modification, have a powerband that's only 2 to 3 HUNDRED.... RPM's wide.

So what am I rambling on about. There's a motor package out there that will fit your needs. Who should do, there's a ton of shops out there. Several here local that I know of. A bunch in So. Cal..... Who's the best...... who ever is going to listen to your needs and not just say box it up, send it, and we'll ship it back to you with what we think is best for you...... I HATE THAT!!!! My feelings are to find someone to do the machine work, and find someone who does nothing but port modifications. Each jandra allows them to focus, and hopefully perfect it. I've got a URL of a excellent port grinder who does just that focuses on port modification, intake and exhaust systems. A consummate professional who really knows his stuff. Email me if you're interested in that. As for who to do your machine work, that would require some time on the phone, asking. Maybe some shops don't want to do only the machine work, they want to sell the whole package, but you won't know unless you try.

Backcountry - not trying to sound like TOO much of an idiot.

Go to http://www.trinityracing.com and follow the 2-stroke performance links. The biggest they have is a 570 cc kit. I have read of some kits that actually go in the 600's, but I think they involve custom jug castings. I think YFS200 mentioned something earlier about a 100+ HP Banshee hill-shooter. I'll try to look for that URL.

Marc

Let me qualify my statement about displacement. Don't get me wrong, bigger is better, but what is crucial is a BALANCED package. One that finds the "in between" ground. If you're going to spend $$$$$$$$$$, probably around $3000+ for this....... better make damn sure that it fits what you need. I can't emphasize enough about making these race shops do what you want, not what they THINK best. I hate condescending race shops that try and tell you how you should ride and a motor setup isn't what you want.

One other item. Custom exhaust. Never can be beat. Production pipes are some engineers best guess at what works best. For what state of tune? Try to design a pipe that will fit the broadest range of tunes, it comes out pretty mellow. Some pipe designers are better than others. A key to better performance is to custom build a pipe that fits exactly your purposes. You know exactly at what RPM range it is designed to operate at, because it has been matched to fit your porting exactly!!!! Think of it this way you pay bank for motor mods, but leave the stock 26 mm carbs on, yep it'll run and ride ok, but it's not to it's fullest potential until you add let's say- 35 mm or 39 mm carbs. The same applies to pipes. Sure a production pipe works, but is it the best? No!!! Go with a custom pipe.

Backcountry--well okay maybe I do sound a little like an idiot.....

Custom exhaust is definitely worth it. Especially when doing a project such as this. Since the Banshee frame/engine combo is so much heaver than a TRX I wondered if you might not consider doing a 500 cc CR into a TRX frame. Estimates put the highly modified CR motor in the neighborhood of 80 HP and with alcohol add to that about 6 to 8 more. Add to that Nitrous and it would put you over 100 HP with a package that weight about 50 lb. less than a Banshee.

With more displacement, lower RPM's and fewer parts to buy it may be just the ticket to a fast way up the hill. I've seen a few VERY fast CR motored TRX's. The only complaint I've heard is that they vibrate a lot and will eventually vibrate the engine out of the frame. For a purpose build short distance drag motor I don't see this as being such a problem.

Rick

From what I've heard about dirt drags, tractor pulls, and all that good stuff, you basically want to spin the tires as fast as possible. Wouldn't that suit a big bore Banshee motor better than a single cylinder? Also, hasn't anybody tried making isolators for the motor mounts on those CR implants?

Marc

Some sort of isolator might help, but since the motor is not counterbalanced like a TRX or LT it will vibrate more. All things being equal - 100 HP will spin the tires of the properly geared CR very well. It may have a wider power spread too.

Rick

Actually your opinion does have merit. You have raced all the Banshees before and know what is the fastest. The Polaris is smokin', but not enough to keep me from suffering from attention deficiency. As for the 500, we blew the cylinder off the bottom end, and it never was as fast as it could have been. I called around and everybody recommended the Banshee over all others so I guess that is my next project. I just keep finding new stuff to do to the Polaris and I get delayed!

You guys are the ones I hoped to get responses from. The idiots are the ones that say what do you want to do blow it up. I didn't need that. I need you guys experience. And of coarse reliability is an issue, I just don't plan on running this thing on long trails and that sort of thing. I race and then park it. I am seriously thinking of going with a Pro-X cylinder (420). I think I can get around 90 hp with alcohol for under $3000, actually about $2500 for the complete set up. Thanks again. Do any of you know anything about Trinity's reliability?

Brandon

I NEVER trust anyone who won't tell me up front exactly what they are going to do to a cylinder or motor package - complete with port timing specs, final compression, any milling of the barrels top or bottom (or both), the parts used - complete with part numbers - and anything else they (feel) they need to do like machining the pistons. I want to know EXACTLY what they did. Experience has proven to me that many of the engine builders DO NOT keep a data base of records. They "wing it" to get it all to work. They have the theory, but the reproducibility is my question.

There are very few REAL secrets out there. The biggest secret might be the profit made from hiring low overhead workers to do the redundant work. Unfortunately while these owners pat themselves on their backs saying how great a job they're doing the $6.00 an hour employee grinds in a little too far and makes mincemeat out of a perfect piece. The owner can pat himself on the back if he is able to save the messed up piece. I've seen it a bunch of times. If he can't fix it, you can bet he'll tell you he decided to change the timing a little bit because it should work better...

When I started porting/engine building it took me a lot of time to get the time it takes to do it within an acceptable limit. After I got better at it I improved that time considerably. These days it is not uncommon for me to spend 40 hours to sleeve and porting a 2 cylinder Yamaha watercraft jug. Complete with lapping all the surfaces, custom machined pistons and domes. Add to that the the disassembly/assembly, and a careful leakdown test and you can see where the time goes.

Rick - not in it for the money

I like the new Pro-X barrels, that's the real reason that I want them. I am particularly partial to the porting done by Duncan. I guess though I will probably get CT to do the whole kit, they developed it so I figure they know more about it. I have friends that have gotten stuff from everybody. I don't know though, I may wind up with somebody else doing it. I still have a little time. Do you know anything about C&O racing, JD racing, or Port Magic?

Brandon

Hey did you still have the engine mount on the cylinder head attached when you blew the cylinder off the Suzuki. This is a common problem for zuki's, especially when you up the power. They make so much torque that when under stress(very common in drag racing) the engine can tweak in the frame a little and the cylinder head mount holds the cylinder better than the rest of the mounts so when the bottom shifts the top doesn't and boom there goes the cylinder. It sounds like you want a Banshee anyway but that may help with the zuki till you get a Banshee.

Dunerider

No, The head stay had been removed. The cylinder had always been weak. It is on its way to Trinity for a complete rebuild, bottom and top.

Brandon

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