Bonneville America Forums Forums Technical Forums Performance Mods HP Increase

After reading past posts regarding Horsepower increase, I gather that a big bore kit (904), carbs, exhaust, and port/polished heads is the best combination. But installing cams can be tricky and costly (not sure if it's worth it for only a 3-5 HP increase). Any other suggestions?

What type of carbs are most popular with this upgrade and what can on expect to spend total on parts (excluding cams)?

THANKS

JMHO but everything you do should be directed to make more torque and give you a crisper throttle responce.And you will get the most bang for your buck buy dropping down one or two teeth on your countersprocket. Al

I know it's always a "later" thing, but sooner or later, I will be doing a dyno run with my Speedmaster, with CRS carburetors and re-ground cams. Besides the carbs / cams, it has Freak / Pipes, so I'm truthfully expecting at least 65 Rear Wheel HP, but we'll see.

You need to look for near 70HP. I hit 66HP with 50 Ft lb torque with just pipes, freak and carb tune on 18 tooth sprocket. I'm hoping to see near 75HP and a big increase in torque with what I have.

Thanx again....
Jango, where do you get the BB for around $400?

Bellacorse has had them on sale now and then. Seems like they do that now and then. Jump on it next time as you will always get your money out should you decide not to upgrade. Keep an eye out, some are usually aware of any great sales and do post it.
www.bellacorse.com

Has anyone actually done a dyno run after the big bore. I havent seen one posted as yet.

I'm not sure I get all this "more HP/Torque" stuff. Why not just buy a bigger,smaller, faster bike? Shields up, Scotty!

there was a post earlier about turbo's for haybusa's. So it just never gets powerful enough or fast enough.

70HP would rock, wonder what wheel torque would be with the 44T rear sprocket I got on her. Still need to augment my jet / needle selection, in case tuning is recommended for better performance.

Quote: I'm not sure I get all this "more HP/Torque" stuff. Why not just buy a bigger, smaller, faster bike? Shields up, Scotty!

Actually, I have a modified Sprint RS. When I crave speed, we gone!! Bonnie's a great bike in a different way and it would be nice to enhance her beauty with a few cool mods!

SCOTTY, I need more power!! lol

Slightly OT; sprockets...someone told me to go up on the rear not the front. I have never heard anyone here say that and I know there are some who know the math for why. So what would be a respone for such a claim of which is better?

ed

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Why not just buy a bigger,smaller, faster bike?

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Cause we love these bikes, and some of love to tinker.
Most of all, cause we can!!

Pat, I read your Bio on the modifications...not sure if you're running CVKs or Mikunis (I remember before you had a hellofatime with Mikunis)?

Also, I assume you have stock cams and what is a guestimate price for head work?

--R

I'm thinking that cams would be near the bottom of the mods list. If you divide the power by displacement, then multiply by 650, you come out near 50 HP, 5 more than the 650 Bonneville in it's best factory trim. That tells me that the stock cams are pretty well optimised, so there is not likely to be a lot gained without a significant loss elsewhere in the operating range.
Now, *AFTER* a lot of other mods, this would be a different matter, which is why I say move different cams to the bottom of the list, but don't take them off.

rich,
Back to the stock CVKs with 160 mains (gonna drop them down a bit I think), 42 pilots, thruxton needles, freak.

I had Steve Seeley do my heads for $100 cash, I'm sure he would do the same for anyone else. Took about 4 days to get them back. I have seen shops advertise the same work for upwards of $500 as well.

If you want more torque, yes the cheapest way is drop a 15 or a 16 tooth sprocket in the front. Or, if you want real measurable torque, throw the wiseco kit in.

The mikunis are excellent carbs, but I could never get mine to run right. I have since talked with a few others with them and they told me that they ended up going way down to 130/140 mains in them to keep them from flooding the motor with too much gas. And disabling the accellerator pumps. Seems this still defeats the purpose. I wish they had around a 38mm mikuni carb that would fit, I bet that would be the ticket.
But I can honestly say that I got more from the big bore than from any carbs setup. Maybe when I stop sending all my money to Brent and Bill Gately, I will try and fab up a pair of the FCR39 or 41mm carbs. They look like they may be some fun too.

Pat, speaking of BIO, I noticed beer at the top of the list...looks like Home Brew!

Absolutely homebrew. My garage is not for cars. the bike lives there as does my entire brewery.

No, I think everybody has skirted around that issue. Its basically all heresay. We go through this discussion every couple of months or so. Nobody actually goes out and dyno's the bike but THEY know its faster than anything so they must have gained 20-30 HP.

Some recommend the BIG BORE, some recommend the cams first, some recommend the carbs first. Its all worthless until someone dyno's their back after each mod, which nobody does.


Fryguy

I have the Mikuni's with the BB (and Bub slash cuts). The accelerator pumps are on! I am meaning to get it to a dyno, but life has a funny way of getting in the way. When I do get it there, I will post. (Hell, I don't think I've posted at all in some time - barely have time to even look at this site these days. Then again, if I get some time, I'll probably go ride...that's why we have these things, right??).

Totally understand. Riding IS more important. It just cracks me up is all.


Fryguy

What are you talking about FRYGUY?! I just put Kuryakyn grips and pegs on my bike and I know that I picked up at least 10hp, maybe more!

You must have put on the space-age, light-weight "gofaster" edition of those grips and pegs!

Did you dyno?

I removed the snorkel.
TB Pipes air screws 4 turns.
Stock Jetting.
17 tooth front sprocket.
Leaking front sprocket seal.
2004 Speedmaster,Yellow & Black tank with chipping paint.
I got a dyno reading two weeks ago of 64.1 hp.

Thats a very nice Dyno reading. Its good to have a basline reading from when you start. This way you know what you add when you started and how much your gaining after each mod. I'd like to see some Dyno runs from people who have had performance mods as well.


Fryguy

AHA! That's why you shouldn't do anything untill the breakin is finished. I couldn't get a before dyno run because the pipes and anti-AI kit went on at about 160 miles, and the junk came out of the airbox maybe 40 miles later.

I forgot to mention.
I have the AI removed.
The bike just turned 4000 miles.
Also have the oil temp gauge from Brent.
Oil temp reads around 180.

Recent speed mod I've done is concave rear view mirrors (objects are closer than they appear) -- now things zoom away from me much faster than before. Guessing 20 more HP.

I guess you are right if you are looking in your mirrors when you crank it on.

that's nothing I put moon air in my tires and dyno'd at 84.6753hp!!!

gee, and all this time I've been filling my tires with helium.

OK
I am sorry I posted.
I see where this thread is going.

just a temporary side trip...
I actually have enjoyed the serious side to this post.
I, personally, have been trying to "re - think" my quest for more HP. So far I have removed AI, Uni filter, removed snorkle, Triumph off roads, re jetted. Not really feeling the results I think the bike is capable of. Thinking of a different exhaust (not sure I like the TOR sound) and maybe Freaks. Does anyone think that the change in exhaust/intake over what I am running would make a significant change?

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Thinking of a different exhaust (not sure I like the TOR sound) and maybe Freaks. Does anyone think that the change in exhaust/intake over what I am running would make a significant change?

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Yes!

I had TOR's with the Freak.I switched to Epco's and there was a big difference in power.The Epco's give much more power and better sound.

I think you will probably gain some noticable power with another exhaust system. The TOR pipes are a compromise made to make the local customers happy without getting too many of them locked up for disturbing the magistrates' sleep, cracking windows and frightening small children.

By the way, be very careful to oil the unifilter according to the directions. Over oiling can restrict the air flow and cost you a few HP.