Cub Porting...dyno numbers

[TurboBanshee420]

i would like to keep my 30 pwk's on there if you guys think it will run better...lemme know

[dajogejr]

Don't take this the wrong way...but for what you're trying to do, IMO, you're better off with a set of stock cylinders and a 4 mil crank.

 

I've said this a million times. You can take a top fuel dragster to the grocery store, but there are more practical ways.

You're trying to "detune" a cylinder meant for open duning and drag racing. Low end and midrange really don't come into effect there.

 

I agree 100% with you that making bigger holes isn't the answer. However, the cubs have BIG HOLES...so, you're working backwards.

 

I couldn't give you port timings or specs for what you're trying to do, because...to be honest, I didn't use either of my cubs in the manner that you are trying to.

 

My 4 mil was a duner that I ran at the drag strip more than the dunes (stupid me didn't put a lockup or override in it...so, kind of a waste, but I learned a lot about it, what it can and can't do) and my 10 mil has ONLY been a straight line drag bike. 95% of the time at the track, otherwise a straight line at the dunes. After running it for 2 years cleaned up by me personally, I had it ported by Kevin @ HJR. It lost a little mid, but DEFINITELY gained on top. It revs forever now. Not what you need....

 

Off the subject, on your turbo bike, isn't there an ignition you can buy that will record what the bike is doing, to play back later on a laptop for diagnosis?

 

If you really want to try and do this on a cub, here's my challenge to you. Fuel Injection.

 

I don't know how much you know about (I admittedly don't know SQUAT) but I know Kevin Gigot can make them run.

I know you want to do your own work, kudos for that, really. But with a little help from the outside, I'd bet an EFI cub would be a lot closer to what you're looking for than what you're trying to do.

 

It's still gonna be a top end screamer, there's no way around that. But I'd bet EFI can somewhat smooth it out and keep the power a little more tractable with a better delivery...or at least your best chance at a better power delivery.

[TurboBanshee420]

ok...don't take this the wrong way either....but are you even reading my posts, well at least the part where I said I'm only running the 2-1 until I can afford some drag pipes? All the trails i ride ARE straight line WOT type riding. Very rarely do I even get into some woods, since there aren't much around. I only want a BROAD power output...well...as broad as I can make it anyways.

 

I know what your saying bro..you said it well. But i still think your misunderstanding my intentions. I want all mid-TOP end. I realize the cub it a different game, but not far from what I have now... considering what else is out there. I wish I could dune it, but the closest thing we have here is the sandy shore of lake Ontario...lol, not that I haven't been there before.

 

If these are only good for all balls drag racing then....BINGO....I'm all about it, since thats all we really do out there anyways.

 

Problem with such a peaky bike is the gearing I run...the shearers I ran for a while would fall out of power before I got to the bottom of the next gear when up in 4-5-6. Not so much that is was a pain...but noticable. Hence why I'm looking for a bit wider, usable power. I had to rev the shithole out of it to get into the power in 5th and 6th so it would continue to pull hard.

 

as for efi cub...sounds fun. It's really easy to do when your pressure range isn't 50-300kpa...lol...however I had some problems getting enough rpm to get the system to register without elec start. I would have to use a haltech or similar. Megasquirt has limits on odd applications like these. No elec start really is a problem there. I could just as easily use the cdi for ign...on a NA engine it would be no prob. The boost blows the weak cdi spark out...hence y I needed an HEI(DIS) ign system...50k volts and 6 amps!!!! Thats enough to kill your ass good!!!

 

but yeah...take another look at it now and see if you can give me some pointers here. I'm not really going the direction your thinking.

[dajogejr]

Alrighty then.

 

Ditch the Rocket Idea. Get CPI pipes. Between terrible past ownership, bird shit welds, etc., I wouldn't use them, period.

 

The reason I assumed you were trying to neuter it was you asked if 30mm carbs would be better than 34PJs...

 

blowit and/or firehead can probably give you ball park port specs and timing. As said, they're pretty close as is.

For WOT Trails, race fuel is the ticket. Methanol would be good for a 5 to 10% increase...but the 200% more fuel consumption just doesn't make it a very viable option unless you wanted to carry an Exxon/Mobil tanker on the back...

 

Not to be a dick...and not like I'm holding big top secrets, but if I posted everything in my motor, you could go to walmart and buy it.

And as you fully understand, the numbers alone (timing, etc.) are only half the battle. Shape and tune, as well as overall combustion chamber design and efficiency will get you where you want.

 

To get off the subject but on the same topic, with all this power are you prepared to upgrade the swingarm, suspension, clutch and tranny as well?

 

An override solves that problem of falling off the pipe, btw....bang gears, stay in the meat of the power.

[TurboBanshee420]

as this WAS my turbo engine....I have it all already. I was planning for 120+hp.... it will handle the cub easily....

ti-moly chain and sprockets

direct drive lockout with 4 washers (pancake too)

+4 swinger modquad tubular

blah blah...u get me

 

everything short of shift cam mods.

 

btw...not a fan of the pj's though they never did me wrong...still not a fan. My 30's woke it right up when I ditched the pjs...I'm guessing because they were just straight-up too much for a stock cyl 4mil...even with the shearers

[dajogejr]

PJs are like blondes.

Kinda flaky...some people get them and love them, some are just turned off by them.

 

I like the PWKs better, and in my opinion, a 4 mil cub will handle 39PWKs all day long.

Badassbanshee 479 has always run 39PWKs, gas then alky on his 4 mil and it's always ripped.

[TurboBanshee420]

I'd like to end up running 35pwk's with the cub...CPI (*wink*) pipes and maybe even try some of this e85 shit....no race fuel for me since i have a 6gal tank that tends to be empty by 3am everytime...meth sounds fun too, but I'm not crazy enough to ride the trails that way. I like to just kick and burn ass outie...no foolin around with the high end side of banshee-izms...lol

 

I think it's time for bed. goodnight(day) gents. chat on the flip.

 

Thanks!

[dajogejr]

I'd like to end up running 35pwk's with the cub...CPI (*wink*) pipes and maybe even try some of this e85 shit....no race fuel for me since i have a 6gal tank that tends to be empty by 3am everytime...meth sounds fun too, but I'm not crazy enough to ride the trails that way. I like to just kick and burn ass outie...no foolin around with the high end side of banshee-izms...lol

 

I think it's time for bed. goodnight(day) gents. chat on the flip.

 

Thanks!

 

If you're running out of fuel at 3AM with gas, you'll be out by 12 midnight or earlier with E85. Which...may or may not be a good thing.

 

 

[No Limit Powersports]

I would like to see a dyno sheet where the rockets are so broad never really seen any dyno testing done on them. Also what was the port timings on the motor you ran shearers on? Pipes are built around the motor so every motor will like a different pipe and shearers small bore inframes are built around a motor that had 197* exhaust and 130* of transfer. I can assure that only doing intake work and nothing else is not going to gain you anything, possible even loose power cause if you open them to much your going to lose velocity.

 

Raising your exhaust 1mm (assuming this is a 68x58 cub with a 115 rod and 573 pistons) will put you 201.5 on the exhaust thats really really tall exhaust and that motor will need a revy pipe to make power (like the shearer) or something custom built. Your cub out of the box is 197* 130* which are really good numbers for what your doing. Dont get me wrong i clean up everything i build, and there is alot of power still left on the table but its not in the intakes. That doesnt mean i dont do intake work on my cubs bc i do but thats not where you are going to make the power at on a cub.

[J-Madd]

I have only a cleanup port, and no case porting on my 421, and it runs 4.0s - 4.1s all day long in 300 ft with 185 lb rider (plan on getting into the 3s next time out if the track is good). I don't know that it would pick up my e.t.s with porting.

 

I'd just bolt it on and go for what your doing.

 

Btw, I've had some bad luck riding Cubs WOT on long roads. I couldn't really cruise because it leans out at half throttle (this could probably be fixed with a different needle, I guess). If you go WOT for a few seconds, then eventually have to let out, again it will lean out. I locked a 392 and 421 up like that before I decided to only drag race them.

[blowit]

We have faced these same problems many times in the shop over the years. Guys want to go faster so porting is the first thing on their mind. It is important to either elect components that will work well with the porting or install new components on the existing setup to improve the performance. Just stepping out of the 34PJs and Dynoport pipe cann offer a large improvement in the topend.

 

Like I said, doing anything to the port of a Cub most certainly means stepping into drag only territory because the timings of the Cub are already at the "hot dune port" area. Porting the Cub will most certainly sacrifice mid power to put on the top. If you want your cake and eat it too, get into power valves. To be honest, I just cannot understand why people would buy a cylinder without them unless to strictly drag race.

 

Here is my recommendation, clean up ALL the ports, install CPI or Shearer pipes, move to a 35mm PWK carb, work A LOT with the head to ensure you are getting proper combustion, ride it..... I really do not think this build is warranting porting. Like I said, any more timing on the exhaust is asking for disappointment from the owner unless racing.

 

 

 

 

B

[TurboBanshee420]

fair enough...

 

Is there anyone out there who doesn't dune/drag only these cylinders?

 

Nik cylinders have a perticular problem with heat soaking. I always loved iron liners for this reason. It sure doesn't take long to swell up under full load. Newer sleds are running very wide pston to wall clearances for that reason.

 

Guess I'll just run them and see what I get...

Edited July 23, 2009 by TurboBanshee420

[blowit]

fair enough...

 

Is there anyone out there who doesn't dune/drag only these cylinders?

 

Nik cylinders have a perticular problem with heat soaking. I always loved iron liners for this reason. It sure doesn't take long to swell up under full load. Newer sleds are running very wide pston to wall clearances for that reason.

 

Guess I'll just run them and see what I get...

 

 

 

Thermal conductivity properties and cost are the primary reasons for OEMs using Nikasil. It is really a PITA for the back yard rebuild though. Heat soak is really a fact of life in an engine cylinder. Thermal conduction is much better in Al, than Iron and allows for lower operating temps. There are many advantages of Al blocks but rebuilding can be a bitch.

 

I am not sure why sled OEMs are running wider piston clearances. A plated bore cylinder typically expands faster with the piston and has natural lubricity properties thus allows tighter tolerancing. That being said, forged pistons create big problem there. The lower silica content in forged pistons and poorly aligned molecules from forging makes then grow in strange ways.

 

 

B

Edited July 23, 2009 by blowit

[Snopczynski]

Any mid-top pipe on the market will be better for that motor than the dynoport 2 into 1 exhaust. With the 2 into 1, your gonna have an extremely narrow power window. Unfortunately the power is gonna turn on and off like a light switch.

 

We have two 7 mill stroker bikes running around with those cylinders. They have been resleeved and had the exhaust ports dropped on them for more low-midrange power. We built them for those tight trail holes we climb out of at the dunes. They are not built for wide open dunes. One of them puts down about 94hp with pro circuits and twin mikuni 30mm carbs, which isn't too bad for being configured as a trail bike. The other one is running a single carb and those damn pt mids, he was putting down about 87 hp.

[okbeast]

Well to offer some not-so-technical advice, I have ridden my 421 cub everywhere. It's been on trails, dunes, dragstrip, riverbeds, you name it. I'm running shearers and 35pwk's now but haven't had much ride time on the 35's, still trying to tune them in. I've rode it with T-5's and 34pj's with 13/42 gearing and it ripped. Was it tuned down? Yeah. Do I feel alot more power with the Shearers, yeah. It has lost a little down low but with the 13/42 gearing I gained some of that back.

 

I recently switched to 14/41 gearing and haven't gotten to ride it hard because of some WOT bog issues but it definitely feels like it pulls higher and harder. I'm still not convinced on the gearing though because I can't launch in 2nd now which I love to do. Might go back to a 13 front and leave the 41 rear or maybe a 40 rear. I'll just have to play with it some to get exactly what I like.

 

Hope this helps ya. If I were you. Do your clean-up ports. Put on whatever setup you have and ride the damn thing. When you can get some mid-top end pipes throw 'em on.