Bonneville America Forums Forums Technical Forums Performance Mods Southbay big bore

Just brought it home. New 904, porting, matcported the intakes, new clutch springs, fresh adjust of the carbs. UHMM
only 1/4 throttle so far, 50 to 90 mph different gears etc.It pulls really strong with a 1/4 throttle, can hardly wait to twist this bad dog. BIG jump in power ,I'm sure. Will have it Dyno'd after 500 -1000 miles. In the mean time, I'm smilin' like never before. Brand new bike!
Vic

$?

Dale,
It's not about the dollars. It's about the desire...

Oh, i know. I wasn't questioning doing it at all. I was actually wondering if i could afford it ! No so much for the tiny bit of extra CC's but for the forged pistons and higher compression ratio. That and the Tbike cam when it comes out would probably make for a killer power boost. Then again i suppose it would also require a HD clutch. I know the total would be astronomical, but i'm still curious.

iknowjohnny,
I think it would be fair to say that I got a great deal and leave it at that. Matt has been more than fair and extra helpful to me since I found him. He has seen alot of my dollars thus far and he has used my particular bike with the Thunderbike pipes as a tester to see what we get. I sure think we got a runner with all of our work! We'll see what the dyno shows. I will say that for anyone that may wonder if the bucks are worth it- I will say,"wonder no more! I can hardly believe the increase and I am still at 81 miles and holding at 0- 1/4 throttle and could get tickets all day long! Very impressed!
Vic

Vic,
Perhaps the best way to approach this is to ask Matt if he is willing to provide a price for those that might want to do the same. You don't need to devouge your price at all. Its really nobodies business but yours what you paid - But it could be some serious business to Matt if he wanted it.

..... the big bore , the head work with the match porting the intakes, the labor to do the work including the clutch springs, bring it back in 500 miles to check everything out and he will stand behind the work. Any problem, he'll fix. 1800.00
So we will bring to the dyno big bore, headwork, stage I cams from SB as well, air box, k and n filters , bigger jets (i can't remember-he wrote it down in his book) with 2 shims on the needle, no air inject, billet intakes and the T-bike pipes.
I was out again last night. Still 1/4 throttle maybe 1/3, taking it real easy. The best way to describe it is that the powerband is 100% across the board in any gear thus far at most any speed.
Vic

was your bike an 865 before because i am wondering if it would be worth the work and money to go from 865 to 904 or if i just need to jump straight to 994?

Bike is 03' started at 790. Went to 904. I like the 994 kit and don't have a cost thing. I guess I would just look at what I was going to do it for. All out speed power ,torque? Mine is fast enough now on the straight line and more than I can lay it over so far with out getting nuts on this style bike. Now, Thruxton? I will buy one this year and have him go as big he is doing at the time. 1140cc on a Thruxton sounds like something I need! Definitely going for the two horse stall.
Vic

Ok, i'm out ! I may consider the Tbikes cam when that comes out. 1/2 the cost, much easier to install, and about 8HP according to them. Not as much as the BB and all that machining i'm sure, but after the 8 to 10 i got with pipes and mods another 8 should put it well into permanent big grin territory.

I hope you will post all of your riding impressions and dyno numbers once you have the engine broken in. I have spoken and exchanged emails with Sean and Matt at Southbay a number of times over the last year or so and have decided to go with their 904 kit. Now I just have to get my engine torn down and sent away. You mentioned that you were using the billet intakes, how did you make them fit with the K&N filters. I bought a set a year ago from Mike at Bellacorse but found that they came off the engine at such an angle that I could not use my air filters or get my fake filter housings back in place. I am curious to know how you overcame this problem. Keep us posted.

they use forged pistons also? i would love to see performance and reliability numbers to compared to the weisco kit

Frank

LKR
The manifolds fit no problem. The right side air cleaner and brackets for the air box , and the chrome cover go without a hitch. The left side air cleaner needed to be modified so it doesn't hit the frame. Wasn't so much the angle but the mounting position for the aircleaners moves back about 1". Took the aircleaner and cut the rear off 1" and resealed it with back epoxy. The brackets and chrome cover worked fine.
Vic

Thanks for the reply. Do you by chance have any pictures that you could post showing the engine with the manifolds mounted and the covers in place.

lkr
There is a picture in my gallery of the right side with the cover on. No pic of the left side, but I can get on that soon.
Vic

Ok,
Was out for another 80 miles today. Hands down the most effective mod I have done. I am still being pretty short on the throttle , but I may have got close to half throttle a few times today. This bike is like night and day
compared to before. I am seriously looking forward to some hard shifting and compression braking going thru some of these canyons out here. The way it is pulling now without even trying is just the beginning I am sure. I also have found there to be a very distinct exhaust note to have developed with added compression. Lopier kind-of , it sounds like it will be quite poppy when I crack the throttle down the road.
Expensive? Yes. Worth it? You know it! I encourage anyone wondering about the big bore to find a way to go ahead and do it.
I am now a pair of 440's and fork springs away from my new Thruxton!
Vic

Vick,
Sounds like money well spent. I'll have to check out your gallery.

I'm back from my country putt/break in ride. 800 miles now on the new big bore. Have given it quite a bit more of a workout. Haven't flat out gunned it yet, stiil kind-of creeping up on the throttle. I can only say that it was definitely the single most effective thing I've done. Going thru a cool canyon road in fourth gear , never shifted except up in the straights. The pull on this thing is simply evil. Yes, it's a cruiser. But it hauls the mail while your cruising. I think the next time out could be the real test. In the mean time, I am smilin' huge!
In the new year I will set up a dyno run and get us the numbers. Don't wait for the numbers to convince you tho if you have been looking to add cc's , do it! If you already have, then you know what I'm talking about.
Vic

congrates, keep us updated and lets see some numbers

Frank

Vic, if you have eight hundred miles on that big bore kit, it's as broke-in as it's ever gonna get... IMHO. Al

The verdict is in- screamin fast , super tuff pull. Up on the freeway it has as much as I need, in the canyons it's has everything I need. The 994 has the ability to literally fry the tire if you want. This 904 tho has everything I want for my all around riding. The front tire will lift off the ground if you get with it straight thru the intersection. I think it's just right for what I do with it. Now , my Thruxton (this years purchase) will go over the top. I will buy it and not pick it up until it's punched out to the 1140. I am doing some work that will allow that to be able to be done as one stop shopping. Build it and call me when I can pick it up. Would like to have EVERYTHING on it black except the spokes and the bars.
Next project tho-
Vic

well with that discription perhaps the 904 is the way to go for my thruxton since i plan to do track days and can't imagine all the power from the 994 going to the thin rear tire. did you go with new carbs or just rejet your stock ones? I also like how no machining is required with the kit. still i wonder why it doesn't have forged rods with it, i would trade for some forged rods and go with the hypeurectic pistons sorry about the spelling its early.

Bill,
Jets are the same, if I recall they were 145's with two shims on the needle. Plenty of gas. With the cams ramped quicker on the intake side and slower on the exhaust side it works well. The t-bike pipes , airbox out , intake manifolds it all makes quite the package of punch.
Vic

You can order Carrillo forged rods. Jojje, the guy in Sweden that drag races turbo Bonnevilles he builds, gets Carrillo rods for his bikes.

victorjr,

After I took mine out for the 2nd night on dry pavement, I realized this thing is now ferocious! I punched it and my front wheel came up a couple of inches, and I wasn't trying to do it (that's because I reinstalled the 16-tooth primary sprocket).

But, just viewing the spark-plugs after my little jaunt revealed that perhaps I'm running a bit rich (they were quite dark). I'm running 160 mains, stock 42 pilots, 2 needle shims, & 3 turns out on the air screws. So, I'd like your opinion. I've ordered the Nology coils & wires (this will create a hotter combustion chamber), and I could return to the 150 mains, and maybe even run one shim (or try the Thruxton needles with no shims).

What's your thoughts.

-BT

PS - I'm glad you can relate to this power increase because at least I know that you know what I am unable to describe with words (other than to say, "THIS THING COOKS!").

Hey BT.
I definitely relate. I've been around bikesw for awhile. Never added that kind of power in one fell swoop. Fresh rebuilds give a little boost, but this is just way to big of a difference to describe realistically. I have not seen the reads on my bike as far as the gas. Matt ran it at the shop before I got there and said the amount of fuel going in and the read at the pipe was right on, so he left it alone. I am not sure how many turns on the screws, but I have the two shims and 145 mains. I occasionally have a rich pop when shutting it off. If I clear it with some revs it won't happen. I think when th esun comes back out I will test by my riding with it the way it is, with one shim removed , and then the TBS needles with no shims. I'l get the best feel and go with it. Think it's fine now but need to make sure I'm getting all I can. Glad to hear you got a few miles on her and got to enjoy your work. Nice job and major kudo's to you. Myself, I just don't have the time. I would have it apart for 6 months. Now working two blocks from my house on the largest project our co has ever done with me in charge with this promotion along with. It's a 1,000,000 square foot mall project for Westfield. I just got take it to my friend at South Bay and ride it. Just got a weather alert over the tv - flash floods are imminent. >>>>>
Vic