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Discussion Starter #1
27 minutes ago · #1
2009 big bear 400 motor build
Figured I would post up a build that I'm currently doing for anyone else interested in making a little more ummff out of the BB.

As of right now, I have a epi comp clutch kit, k&n, hmf pipe, and warrior snorkel. The bike is on itp SS wheels and 29.5 outlaws. I tuned it with a sigma 6 jet kit using a aem wideband welded in the pipe. Current jets are 116 main and I believe a 22 pilot (not 100% sure have to double check) with about 1/8-3/16 shims under the needle. Has a lil bit bigger hole drilled in the slide and about 2 rings cut off the spring. AFR is [email protected] and light throttle at low rpms and richens up to 13.0 at light throttle high rpm and 12.2-12.4 @ WOT. (I'm at sea level in Houston)
Thing fires up instantly cold or hot with no choke and rips for having 29.5's and throws em around in the thickest of mud no problem.

I'm still wanting more out of the lil BB because I'm tired of watching my buddies that all have grizzlys and Kodiaks 660's and 700's ripping wheelies all the time through shit. Lol even tho most of the time I'm the one winching them out of mud holes.
The BB is just a tank of a wheeler.

Here's the plan and stuff I have ordered.
(Stock bore) Wiseco 11:1 piston for a warrior
Webcam #1617 grind cam (almost the same as 388 grind)
Spring kit with titanium retainers
Suzuki Ltz400 mikuni 36mm carb with raptor 350 manifold
Sigma 6 stage 1-7 jet kit
Head will also be ported as much as possible while it's off (I build and tune alot of racecars around here and I have ascess to a superflow flow bench for testing)

Only thing I'm not sure of right now and can't get any info on is a cdi box for these bikes that has a hotter spark curve?

The goal is to keep the reliability and improve the low end grunt and still add quite a bit of mid-range and higher end power but mostly focus on the mid-range because the clutch kit definitely jumps into the rpms much better then stock.
Parts should be pileing in over the week and weekend and should be ready to rock by next weekend. I'll keep you guys posted on the progress as I get cracking on it.
If any of y'all have anything to add, I'm all ears and would be greatly appreciated.
 

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CDI only times the spark, the coil makes it hotter. The only thing a CDI could do is make a multiple spark instead of single, and I think I remember reading that on anything but heavily modified single cylinder engines the gain is negotiable. I think the article was about single cylinder Nitro-Meth hill-climb bikes.
The coil is responsible for the intensity of the spark.
Bang for the buck there isn't much for gains you are going to find in the ignition system.

For Low end grunt be careful with your cam choice and your port work. Big Cams overlap the intake and exhaust events, at low RPM's this actually bleeds off compression, thats why big cams in cars idle rough and have vacuum problems. The point of opening up the ports makes way for more flow which is moist beneficial at High RPMS. Some of the builders have been know to restrict the intake ports to increase turbulence and velocity. The 'velocity porting' supposedly created more torque.

Dang sure a cool project!
 

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Discussion Starter #4
I agree with the porting. We're not getting too crazy with it. Just trying to get the low and mid lift flow #'s up a little which should bump mid-range torque quite a bit. Not too concerned with high lift flow #'s which would be more for just all out top end.
You are also correct with the valve events moving the powerband and bleeding off compression. On our race cars Ivo and evc points are crucial and are important to utilize all the nuts where the converter hits. On power adder cars it can mean you're bleeding off x amount of boost or nitrous right out the exhuast. On all motor cars it can really make for a really lazy motor if the valve events aren't correct.
I could have went with s bigger cam but it would have killed grunt off of where the clutch hits. No bueno.
As far as the spark, ignition timing is everything in a car. I tune them for a living and it's my understanding that the cdi is the "timing" at which it sends the spark to the coil in relation to tdc. Like the distributor or ecu in the car. If there was a way I could advance the spark a few * down low and in the midrange and just run better fuel it would help with the flat spot down there from running the bigger cam ect. 3* timing here or there Would make a huge difference
 

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Sounds like we are on the same page. Spark is much more critical in multiple piston engines, one lazy hole screws with everything, or if they are all off none are happy. Single cylinders not so much, if timing is off you feel it when its on its on. A hotter spark is a negligible difference on one hole. Back in the day they made a Roost Boost, it was a spark plug boot that had another little coil in it to boost spark. No one could prove any gains by using one. Bashing the idea with electrical theory is pretty easy. The magic booster was simply another coil(voltage transformer) a pair of non-contact copper coils designed to increase spark voltage. When voltage is stepped up in a simple step up transformer, without a doubt amperage lowers. So the intensity of the spark is increased but the ability for it to maintain the intensity is lost. So using that theory they could actually hurt performance, depending of course on the spark plug used and the coil wire.

All in all it is a single cylinder 2 valve engine, you are only going to get so much out of it. I read that you have already changed the ignition timing, so you've probably done the best mod on the ignition.

My advice, unless you are running nitrous, an air shifter, or crazy compression or fuel, keep the ignition stock. From the couple years I've been on this site there have been very few people that thought they got their moneys worth out of aftermarket ignition components.
 

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Discussion Starter #6
Thanks diggerz for the input. I'm not worried about hotter spark. I actually put a d9ea plug in it which is a step colder from stock. I have not found a way to play with the actual ignition timing for this particular bike, although that's what I was after until I got it running the other day. It's actually on the borderline for knock on 93 octane with the 11:1 piston.
When I was tuning the carb, any lean spots on the wideband made a audible clatter. I have since switched back to the factory modified carb due to not being able to get fuel through the 36mm @ heavy load low rpm, which was where the clatter was. Wideband showed about 16ish AFR and power was flat until it started to build rpm. One trip out to the offroad park and this became a huge problem in the mud. It's either fatten up the main jet to where she's in the 10's AFR wise up top to get mid 13's down low or 16's down low to get 12's up top.
Mind you, this is full throttle. Common CV carb crap. I tried every trick in the book and there was noway around it. I was fighting a never ending battle with a carb that was too big to pull enough vaccume or airspeed to drive the fuel up the main jet until the engine got up into the rpms.

I put the smaller stock carb on and it's night and day difference but there will always be the leaner spot at lower rpm and heavy throttle/load.
Right now it's 11's up top and 13's down low. I can live with it and knock is gone but still going to throw some 110 in it and move to a pumper carb before I take it out again.
Bike is definitely a different machine!
 

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One of those Edelbrock pumpers made for the warrior might be a good bet.
 

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Discussion Starter #8
The Edelbrock carbs are pretty hard to find. I went with a mikuni 36-38 pumper. Don't have it on the bike yet. I have a guy working on a GR for the big bear. Will do the pumper and GR in about a month when he gets the first test units made.
 
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