Bonneville America Forums Forums Technical Forums Performance Mods Which Mod Next??

Hello Folks. I have a used TBA with Bub Pipes. Removed AI myself and not sure where to go next. From what I can glean from the posts, if I improve air flow then needle and/or jets would be in order. What do you folks recommend? Thanks in advance

ditch the airbox and get some K&N filters, rejet, you'll be good to go. for a while...

45 pilots, 135 or 140 mains to start

Thanks for the quick reply. I'll check out Haynes etc for replacing the air box and check into carb mods, thanks again

http://newspeedmaster.com/html/airbox_removal_kit.html
http://www.dinqua.com/Triumph/carbs1.html
you dont need to buy a Haynes, this site is a fountain of information. save money for mods!!

thanking you again, Surely appears good info. I just read a note where a guy built his own support brackets for the K&N. I best focus on the kit, thanks

If you remove the air box it is a good idea to do exhaust too. Both need to be done to gain the full effect.Air/fuel can only enter as fast as it can escape the other side. Don't have to really loud of you don't want to but less restrictive yes.

Appreciate the reply. Former owner replaced stock exhaust with Bub pipes, so its breathing fairly well on that end. I removed the AI. Will tackle the air box soon. Thanks again.

Since you got it used, there is a good chance you have the older engine. If so, anything you do to get more air to pass through the engine will give you startling power gains. If you have the later 865CC engine, nothing will do much until you change the cams unless you intend to add a turbocharger. The exhaust valve timing on the later engine is terrible for other sorts of power mods, but ideal for supercharging.
Once you've done all else, if you want to have even more power, you can get big bore kits. You can go up to about 904CC with bolt on kits. There are a few bikes bored to over 1100CC, but you have to modify the crankcase bores for that.

Thanks Greybeard. I've been reading all info from previous posts. Very helpful. Its a TBA 2003 model, obviously a 865cc. Its been a long time since I have had Triumphs, the bikes I use to ride vibrated allot and were 650 and 750's. This is a nice machine, but a little sluggish. So if I understand your note, I will not realize much improvement removing air box and fiddling with the jets due to the cam timing, correct? What bolt on's are you referring to for 904CC? Thats really not much of a jump. Be waiting for a reply and thanks in advance.

Geezer, if your bike is an 03' TBA it is a 790cc (NOT 865cc) so you have the good cams and will notice a big difference with mods etc. The 865cc came to the speedmaster in 05' and the TBA in 07'.

It's best to start with all the add ons as greybeard mentioned (pod filters exhaust needles jets etc.) and then if you still need more power like I did, get a wiesco 904cc BB kit and port the cylinder head to get somewhere like a 40-50% increase on stock!

its not all about cc's but also the compression jump you get and it is a much better piston (forged) with bigger valve reliefs for oversized valves

Frank

Hey Geezer,if its a 2003 model then its 790cc not 865cc

Nick

OOOOOPPPPPS!!! I can't believe I replied with 865cc. Guess I seen the review of newer models and the numbers stuck in my head. I have removed the AI and have Bub pipes, so I'll work on the air box next and carb. By Pod filters is that same as Freak mod? You guys are keeping this old Geezer straight and coments well appreciated..

The Freak (from newspeedmaster.com) is one (probably the most popular) method of utilizing the pod filters. But there's the "Ghetto Freak" (basically hacking up the stock air box to make room for the filters) and a few battery-relocation methods (the hacked stock battery box bracket utilized by Brokenfixed and others, and I believe Boogieman has a bracket for sale as well). In late '02 I designed and built my own battery relocation box.

The only two issues with just simply removing the airbox and calling it good is (1) the gaping hole in the right side of the bike since the airbox is what the side cover mounts to, and (2) keeping mud and road grime from being flung onto everything by the rear tire. Otherwise you don't really "need" anything more than the filters.

Buy the Freak and come to the Ga. rally in may. Bring it with you and maybe Pete will install it for you, right Pete?

kennymc and friarjohn, appreciate the reply. I just was reading an article on dinqua www site on amal carbs and big bore kit. From what i can see, he has the pod filters exposed from the carbs. I'll check the bikes right side out and see where this is leadng. Again, thanks for the notes.

PODs are just the filter. The FREAK comes with those, and an under-seat arrangement that blocks crud from the rear tire, hold a "tool box", has attachments for the side covers and the cheese graters. Most FREAK type kits come with jets as well.

The 03 TBA has the 790cc. I am doing it a little at a time. Started with AI. Moving to EPCO's with Uni Filter & Velocity Stack at air box mouth with rejetting beginning with 130 mains 42 pilots. Airbox will probably come off, but want to do it in increments, to get a feel for the bike

Has anyone compared the Freak to the Britsh Customs puts out?

x2!

I passed on the freak with my 790, just pipes and a modded airbox as Dinqua suggests. Not enough bang for the buck for my wallet. If I ever found a used one, maybe I'd go for it.

One reason you need either a Freak or similar kit or to at least keep parts of the original airbox is that the airbox in installed through a rather large hole in the rear fender (mudguard). The right sidecover is attached to the airbox as is the starter solenoid. So, you could simply make a support to keep the carburettors from sagging, but you also need to plug the hole in the fender and find a place for the solenoid. The bike will look a little odd if you don't remount the side cover or replace it with something that looks like a vintage oil tank. Hmmm... an auxiliary fuel tank might be a good thing in that spot, you could probably get another 3/4 gallon there.

heard nothing but bad things about it

Frank

I sure have not compared the airbox mods yet. Just educated myself a little off the www wrt Freak. Will look at Hittman and Cowtipper suggestion this evening. Thanks Guys. There is only one thing I know for sure, in 1976 I paid 700.00 British Pounds (about $1100.00) for a brand spanking new Bonneville. Cowtipper, like your sig and the symbol. More later, thanks for the inputs.

Look up the ghetto freak too. You can mod your air box to keep the stock look and use pods. The air box just becomes a mounting point and tool box as well as staying in place to act as the lower portion of rear fender. I used the Freak and don't regret it although after I bought it and saw what it consisted of I saw that I could have made it easily for about $10 plus cost of pods and jets.

Hi,
I'm running a '07 TBA 865cc and I've been tinkering around for a while getting to set up I'm comfortable with for now.
AI & Snork gone, TBS with a shim (might remove), 42 and 130 jets, Uni and Short Spec Spares (still baffled.. ).

I was thinking of fitting a freak kit shortly but this thread is the first I've seen that mentions the limited impact of removing the airbox on the 865 motor. Is this really not worth doing without a cam change?
I'd really like more torque (i know, wouldn't we all.. But I'd thought the freak kit might get a significant improvement.

Appreciate your thoughts whether this is worthwhile.

Cheers

To give you an idea about the later valve timing, Thunderbike was thinking of not offering their pipes for the 865 because they made so little difference in performance. There was a very long thread about that including some charts of their results working with that engine. As best I can remember, the intake timing was not changed much, but the exhaust valves close something like 3 or 4 degrees before TDC. On the bright side though, that valve timing is ideal for turbocharging.

Thanks ton. I am just about to the point where I need to look at a bike that has the Freak Mod. I'll ask around the local dealership and see. Same with me, If I see something I am more inclined to try and build it. I just finsihed a 14 ft tandem axle enclosed trailer to take the Bike with me, Saved over 1/2. Can send pic if anyone is interested.

Meant to reply to your post, computer operator farkel.
Thanks ton. I am just about to the point where I need to look at a bike that has the Freak Mod. I'll ask around the local dealership and see. Same with me, If I see something I am more inclined to try and build it. I just finsihed a 14 ft tandem axle enclosed trailer to take the Bike with me, Saved over 1/2. Can send pic if anyone is interested.

Well, the price is sure right and it sounds like a reasonable incremental initial start. I am assuming drilling the holes and with the pipes already opended (Bubs) things will be breathing better and may warrant a mild jet/needle change. Sound reasonable?

yup... Give Pat's jetting calculator a whirl. It will get you close.

Assuming stock needles, no shims, 42 pilots, all the snorkels still in tact, elevation at or near sea level, and the original paper filter (wheh!) you should be close to a 135 main.

I see you and Frank have mod's for Mikuni carbs. Are they a considerable better option than the Triumph CV?

only reason i got them was because i now have 904 and headwork, with the stock motor it did start better, idle better, and just plain feel better. but very expensive and i showed no peak gains on a dyno. but from what i hear going to mikunis on a 904 bike is like going from stock cc's to a 904

Frank

thanks Frank, I am assuming there was an appreciable gain in performance when you upgraded to 904...correct? That mod has interested me for some time. Do I understand correctly you had Mikuni's on prior to 904 upgrade and it seemed to run better, but dyno revelaed no big gain? Sorry if I missed your point.

There are both pros and cons to changing out the carbs. First of all, let me say that there really is not a huge gain in power, just performance. That means it runs better, starts better and has faster response. But on a dyno there are small increases.
Frank has the Mikuni 42mm flatslides (with accelerator pumps, that need to be disabled) from Bonneville Performance (about $1200+ but also includes airbox eliminator assembly, cables and controls), I made my own set of Mikuni 36mm flatslides (no accelerator pumps) from a pair of carbs I bought from Pro-Flo for about $300. A new throttle cable, a 6" piece of aluminum channel for a brace and new air filters since the stock/freak K&Ns ones no longer fit. So I got about $400 into mine. Plus many hours of dicking around making the cable and drinking. Member biker (Ed) has the same carb setup as mine and I basically copied his. Neither of us has had any problems whatsoever in over two years of running them. And parts are a dime a dozen at pretty much any mc shop in the world. They are nothing fancy and I do have to use two chokes to start it, but only when when ice cold, but no biggie to me. I do still need to do some more jetting work but it's snowing and the snowmobile is taking priority now.

Thank You much for the detailed reply. My brother-in-law runs Mikuni and he suggested changing. I think more cause he has them on his Harley. Being semi-retired, I normally default to things I can do myself. I weld/fab whatever I can in my modest garage, TIG/MIG/Stick/metal break. So, a bracket for the carbs does not appear to be a big challenge. I may start looking for a reasonable used set....any leads or areas I may try? Thanks for taking the time to reply. Inputs well appreciated.

Thanks Frank, you guys are setting me straight and I am much obliged. I see you have 42's and Pat 36's. Not sure what that means in relation to 904 kit or stock for that matter, guess just a matter of juggling jets for the right combo. Both of you testify to better performance and thats noteworthy. I tried Pro-Flo www site (Pat got his carbs there), but no soap. Some kind of tech or admin farkel. Well, I shall proceed incrementally as Pat suggested and drill holes first. But since I love to tinker, I imagine that won't last long.