Bandit Alley

MODEL SPECIFIC => SUZUKI BANDIT 250 & 400 => Topic started by: El Dopa on July 08, 2007, 06:25:31 AM

Title: tuning a '91 gsf400 engine for track - what mods are best?
Post by: El Dopa on July 08, 2007, 06:25:31 AM: I have just shaken hands on a deal to buy a 'parts' bike - a '91 Bandit 400. Hopefully i'll be picking it up next weekend.

I'm inclined to drop the engine and carbs out and tune the bejeebus out of them for use on the track.

My headers/cans are already upgraded. I'm upgrading my suspension as part of the overall project.

So what's a good place to start on the engine?

I'm thinking:

Rebuild the carbs with something from Factory Pro, probably a race kit.

Replace the airbox with pods.

Possibly one of Jay's bore-out kits.

What other suggestions does anyone have?
Title: tuning a '91 gsf400 engine for track - what mods are best?
Post by: Banditmax on July 08, 2007, 07:48:04 AM: Bigger valves in new radial seats ported and polished. long stroke crank with 460cc kit from jay giving you a 500. Some keihin fcr flatslides. That'll be fast when sorted.
Title: tuning a '91 gsf400 engine for track - what mods are best?
Post by: Bartjan on July 08, 2007, 08:42:48 AM: what will radial seat do when the valves arent radial? :stickpoke:
polishing the ports is a bad idea, cos the mixture get mixed worse compared to no polishing and you lose some power although its slightly better on the flowbench.

getting hold of the longer crankshaft takes alot of searching i think :wink:
Title: tuning a '91 gsf400 engine for track - what mods are best?
Post by: Banditmax on July 08, 2007, 10:00:43 AM: well get radial valves too then.
Title: tuning a '91 gsf400 engine for track - what mods are best?
Post by: gsxr400 racer on July 08, 2007, 12:12:44 PM: really no room due to angle, for bigger valves tried that route was going to be 1200.00 for valves and i wont even say what they wanted to charge for custom ti valves about the only custom thing i was going to do was have corrillo rods made for 800.00 that was the only company i found that would make them that small but my lightened stock rods are holding up OK with the big bore.
Title: tuning a '91 gsf400 engine for track - what mods are best?
Post by: El Dopa on July 08, 2007, 05:47:03 PM: OK, so putting the valve and the crank in the 'too hard' basket for the moment,

1) what exactly are flatside carbs?

2) Where do I get a set that fits the bandit?
Title: tuning a '91 gsf400 engine for track - what mods are best?
Post by: gsxr400 racer on July 08, 2007, 07:45:42 PM: http://www.okshon.com/v.cgi?YYurl=http://page13.auctions.yahoo.co.jp/jp/auction/r37615971

those are smaller than what i have but will work great for the road. I have 33 here is a pic of soem tmr a little diff than fcr but i can find the pic of my bike with the fcrs on.

(http://img459.imageshack.us/img459/6148/toshikun555img600x45011cj9.jpg)

they do make adapter for both to mount pod filters
Title: tuning a '91 gsf400 engine for track - what mods are best?
Post by: gsxr400 racer on July 08, 2007, 07:50:58 PM: there are a number that fit JC bought my old RS round slide race carbs (haven't heard much from him) with the big bore i think i could go bigger carbwise than 33 as soon as i stuck them on with the big bore they where really crisp like like i needed bigger carbs mine came from a Yamaha xjr 400 thats what they where bought for originally by a guy in japan for they went right on my bike no problem or spacing issues.
Title: tuning a '91 gsf400 engine for track - what mods are best?
Post by: El Dopa on July 08, 2007, 10:51:07 PM: Like these?

http://cgi.ebay.com/ebaymotors/keihin-flatslide-33mm-carborators_W0QQcmdZViewItemQQcategoryZ133200QQihZ002QQitemZ120139777264QQrdZ1
Title: tuning a '91 gsf400 engine for track - what mods are best?
Post by: El Dopa on July 08, 2007, 10:53:22 PM: Or these?

http://cgi.ebay.com/ebaymotors/zx7-zx9-keihin-fcr-carbs-flat-slides-BRAND-NEW_W0QQcmdZViewItemQQcategoryZ35587QQihZ007QQitemZ170129056424QQrdZ1
Title: tuning a '91 gsf400 engine for track - what mods are best?
Post by: El Dopa on July 08, 2007, 10:57:56 PM: Or these?

http://cgi.ebay.com/ebaymotors/keihin-41mm-fcr-flatslide-GSXR-CBR-ZX_W0QQitemZ120139842049QQihZ002QQcategoryZ35580QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
Title: tuning a '91 gsf400 engine for track - what mods are best?
Post by: gsxr400 racer on July 08, 2007, 11:36:28 PM: it may be worth a shot on the top ones for the f2 thats a good deal and the spacing might be real close

http://cgi.ebay.com/ebaymotors/keihin-flatslide-33mm-carborators_W0QQcmdZViewItemQQcategoryZ133200QQihZ002QQitemZ120139777264QQrdZ1

just have to make sure you dont buy down draft carbs as they are angled to much
Title: tuning a '91 gsf400 engine for track - what mods are best?
Post by: Bartjan on July 09, 2007, 06:03:32 AM: whats the difference with the normal carbs?

Ps. Banditmax do you know what radial valves are? difference with normal valves is that they open directed to the middle of the combustion chamber, so if you want radial valves there is need for more difficult rocker-arm-construction. since normal valves open in 1 direction instead of 2
Title: tuning a '91 gsf400 engine for track - what mods are best?
Post by: Banditmax on July 09, 2007, 06:39:08 AM: :duh: ill keep quiet
Title: tuning a '91 gsf400 engine for track - what mods are best?
Post by: gsxr400 racer on July 09, 2007, 08:53:52 AM: Quote from: "Bartjan"
whats the difference with the normal carbs?

Ps. Banditmax do you know what radial valves are? difference with normal valves is that they open directed to the middle of the combustion chamber, so if you want radial valves there is need for more difficult rocker-arm-construction. since normal valves open in 1 direction instead of 2

never heard of that one, would like to see some research or documentation on that one "radial valves"

carbs i have a a dyno print out to show the performance gains on a 400 with them.
Title: tuning a '91 gsf400 engine for track - what mods are best?
Post by: gsxr400 racer on July 09, 2007, 08:58:19 AM: (http://img20.imageshack.us/img20/16/gsxr400gk76awfcr33flatskz0.jpg)
Title: tuning a '91 gsf400 engine for track - what mods are best?
Post by: El Dopa on July 09, 2007, 04:30:34 PM: So the red line is with flatsides?
Title: tuning a '91 gsf400 engine for track - what mods are best?
Post by: gsxr400 racer on July 09, 2007, 09:09:28 PM: yes sir
Title: tuning a '91 gsf400 engine for track - what mods are best?
Post by: gsxr400 racer on July 09, 2007, 09:09:31 PM: yes sir=
Title: tuning a '91 gsf400 engine for track - what mods are best?
Post by: Bartjan on July 10, 2007, 08:58:12 AM: and what is the difference in the carbs?

picture of radial valves.
(http://www.mvagustausa.com/web-mvagusta/images/valve-280.jpg)
as you can see the valves are pointed to the center.

when the valves open there is more room to allow better flow (more distance to the cilinderwall), also the combustion chamber is a better shape so the combustion will be (slightly) faster.

the valves are exactly the same but the rocker arms need some special construction.

alot of 1 cilinder cross motors have these and so does the mv agusta f4
Title: tuning a '91 gsf400 engine for track - what mods are best?
Post by: Banditmax on July 10, 2007, 10:03:55 AM: i actually meant radial valve seats not radially arranged valves. So the are alot smoother than 5 anlge or 3 angle ones.
Title: tuning a '91 gsf400 engine for track - what mods are best?
Post by: gsxr400 racer on July 10, 2007, 10:21:01 AM: accelerator pump for taking off thats all you need to know race carbs the berries
Title: tuning a '91 gsf400 engine for track - what mods are best?
Post by: Bartjan on July 10, 2007, 10:48:04 AM: Quote from: "Banditmax"
i actually meant radial valve seats not radially arranged valves. So the are alot smoother than 5 anlge or 3 angle ones.

:duh: miscommunication

i agree with making the valve seats "round", other things to do are:
- "edging" the combustion chamber, which means rounding all other edges, to speed up the combustion process
- setting the squish/quench clearance correct, the smaller the better (hp wise) but they shouldnt touch the head ofcourse (if your planning on using titanium conrods it can go smaller cos they strech less at high rpm)
- raise the compression ratio

btw are you gonna use race-fuel?
Title: tuning a '91 gsf400 engine for track - what mods are best?
Post by: gsxr400 racer on July 10, 2007, 12:40:49 PM: Quote from: "Bartjan"

- setting the squish/quench clearance correct, the smaller the better (hp wise) but they shouldnt touch the head of course (if your planning on using titanium con-rods it can go smaller cos they stretch less at high rpm)

This is a bad misconception as there is a limit and a rule of thumb and if you go beyond it you loose HP, I used to be 2mm beyond what the norm is and it really was not beneficial your pistons burn real clean on the edges but you also run into predetination issues this becomes worse when you start milling stuff off of 2 strokes. 30 thousandths has become my bench mark for alot over the years i have found if i go more than that i start to go backwards for example ( 30 piston to head, 30 intake and exhaust to piston ) Now others may go more but this is what i like and i am just a lowly engine builder not a expert by any means
Title: tuning a '91 gsf400 engine for track - what mods are best?
Post by: gsxr400 racer on July 10, 2007, 12:42:18 PM: also i believe when you mess with squish is when the heat starts coming into factor hence the gsxr 1100 radiator im messing with
Title: tuning a '91 gsf400 engine for track - what mods are best?
Post by: El Dopa on July 10, 2007, 08:44:48 PM: OK, all the stuff about porting/polishing/changing the shape of the combustion chamber is way, way, way out of my league.

Plus which, would I be correct in thinking that most of that stuff is the cherry on the cake - the stuff you think about once you've done your major mods?

So the main mods I'm thinking of are one or a combination of:

1) Flatsides
2) 442cc kit
3) gsx400 crank

(assuming I can source/afford all these....)

The overbore with the bigger crank should give near enough 500cc, right?

Any problem using the overbore kit with the bigger crank? Jay?

Also, dumb question about flatside carbs - do you need to rebuild them with e.g. a Factory Pro kit, or are they 'good to go' as is?
Title: tuning a '91 gsf400 engine for track - what mods are best?
Post by: gsxr400 racer on July 10, 2007, 09:16:55 PM: im happy with the 442 and flatslides but with a crank has to be amazing yes they will work with the crank there is enough room
no need for factory pro once you have race carbs and they have 4 orings versus how many in the b4 carbs?
Title: tuning a '91 gsf400 engine for track - what mods are best?
Post by: El Dopa on July 10, 2007, 10:05:26 PM: Thanks Jay, you're a blimmin' goldmine of information.
Title: tuning a '91 gsf400 engine for track - what mods are best?
Post by: Thief400 on July 10, 2007, 10:40:25 PM: Quote from: "Bartjan"
whats the difference with the normal carbs?

Ps. Banditmax do you know what radial valves are? difference with normal valves is that they open directed to the middle of the combustion chamber, so if you want radial valves there is need for more difficult rocker-arm-construction. since normal valves open in 1 direction instead of 2

:shrug: :deadhorse: :storm:
Title: Re: tuning a '91 gsf400 engine for track - what mods are best?
Post by: bsodders on October 09, 2011, 12:27:52 PM: Old post I know but, is the GSXR 400 crank different than the Bandit. I'm sporting a 76a and I'm trying to source big bore parts. Strangely I've found the crank but no rods or pistons. Any ideas?

Thanks
Title: Re: tuning a '91 gsf400 engine for track - what mods are best?
Post by: bsodders on October 09, 2011, 03:06:49 PM: Also trying to clarify what the components for the bb kits are? Where are they supplied from? Part #'s- and has anyone tried the gsx 550 crank yet?

Thanks
Title: Re: tuning a '91 gsf400 engine for track - what mods are best?
Post by: Chris H on October 09, 2011, 06:01:26 PM: Hi, GSXR gk73a is same crank as B4 but 76a is different. Bandit has helical primary gear and gk76a has a straight cut primary gear so you need the correct clutch also. Ive read but never seen that the 76a SP may have larger diameter main shells but without seeing the two im not sure, worth keeping in mind tho.
One of the old members (Bartjan i think) tried to stroke his B4 using gsx and early gsxr (longer stroke) but could never get any that fitted due to the differing primary gears.
Ive built a motor using TTS JE 440 pistons but Jay use to sell a kit based on OE pistons of some kind, probably 500/550 or 600, the JE use FZR600 59mm ring sets so start there.
Title: Re: tuning a '91 gsf400 engine for track - what mods are best?
Post by: bsodders on October 09, 2011, 07:18:42 PM: Thanks, as usual just trying to find what actually works and what's a headache.

B