i don't know your rules....
are you building a gs 450 chassis or installing a 450 engine in a GS500 chassis?

if the second....
why not re-sleeve the GS to make it a 450+1mm
a thicker sleeve will make a stronger cylinder.

look at the different kat600/750/1100 and oil cooled gsxrs and build a set of big bore carbs they came as 36,38, and a canadian edition had 41's if i remember

if you are spending stupid amounts of cash..... 450cc dirtbike engine into a 125 GP chassis or 250 GP chassis is a better way to spend cash....about 100-150 # lighter and more HP   look at barebones racing site   sick bikes there

I'm actually planning to install a GS450 cylinder block between a GS500 top and bottom end. Really cheap, simple solution. Not super expensive either, until I start springing for race oriented parts.

Rules for the class permit pretty much any build that meets the safety specifications, so long as it's 2 cylinders, and 450cc+1mm overbore or less.

I've never been terribly happy with the petcock solution I have for the GS. The Motion Pro inline shut-off valve works fine, but the stock dual pickup is clunky, and makes simplifying the fuel system for maintenance, performance, and reliability rather difficult. Also not satisfied by the Pingle solution; I don't care to spend $130 on a piece of bling that's going to sit behind the frame and fail to add much performance to the bike.

Doing some research, it looks like the Yamaha YZ250 petcock is a direct, bolt on fit for the tank. Good deal, since it's a mechanical 3 way petcock, with a downward facing nipple. Not confirmed, but the fuel spigot does appear to be about the same as stock, which seems fine for race use on the GS. Gasket cross references to be the same as the R1. Cross referencing the R1 petcock against Pingle's adaptors indicates that the bolt spacing is the same as for our GS500. Gasket is very very similar, pretty much the same. Cost for the full kit is ~$15.

Planning to buy one, experiment. Will post a new thread if it works out.

And hey, if someone still wants a bling petcock, we can still buy the Pingle YZ250 valve.

Piston tools arrived. When I have some time, I'll start bolting things together to see how it's all going to fit.

Lots and lots of Hi-Res pictures, yes?

Thanks.

Quote from: Mauricio on October 12, 2011, 03:06:56 AM
Lots and lots of Hi-Res pictures, yes?

Thanks.

+1

Hi burning 1,

                     Interested in your post,  my project is very similar with the gs500/ gr650 engine. I know you saw my post on balance shafts, and a couple of points.
       I am of the firm opinion that removing balance shafts is the wrong way to go.  I have modified and rebalanced cranks before and I am aware of the effects.  It works very well if done right.
       Removing the balance shafts will drastically increase crank and bearing loads, which you are going to do in spades anyway with the mods as is.
       Lighter reciprocating parts pay dividends, but require the crank to be rebalanced, which requires the balance shafts modified to suit.  Partial assembly of the engine and someone with a balance table, in a perfect world.
        Also  I have a couple of 425 4valve/cyl heads. I was hoping there would be some advantage in valve area, to be had, but  Not much.  Works out about the same as the 500 head I have, I can dig it out if you would like to know.  I have not flowed them yet but will be happy to let you know what I find, if you are interested.  I am still working on the crank #'s if you are interested in my findings I am happy to share info.

Regards Ian

valve diameters on the 425 head?
lift of the cam?
CC of the combustion chamber?
as compared to a gs500???
a set of FJ1200 /kz1000 pistons.....compression ratio compared to a stock GS500? with a smaller combustion chamber of the 425 head....

still cheaper to install a 450 single into a 125 or 250GP chassis (sub 275#)  but we all are farquin crazy and do what we do

Hi Harlton,

Yeah, the small valves on the 8 valve heads is something I've seen mentioned elsewhere. I'd be interested in playing around with a 4 valve head, but as mentioned above the exhaust routing issue is something I don't want to deal with right now. I've been idly thinking about cutting down and swapping in a GS1100 16 valve head, but I have too many 'unknowns' as it stands with this project. A GPZ head might also be an interesting option if it could be made to work.

Took a look at the balancer shaft again... It's a heavy sucker - 5-10lbs, and lots of inertia. I kind of figured that pulling it would do bad things to the crank bearings, but the weight savings seems to be worth it, and I've known a lot of other racers to successfully perform the mod. One other aspect of the removal is that I have an otherwise good engine with a seized balance shaft.

Would not just pull the shaft though... If I do the mod, it'll be going to the guys at APE for a pro rebalance/lightening job.

BTW... Did anyone notice that the latest GS500F models get updated rods in the parts fich? I'm very very curious what's changed.

BTW: Just ordered a rack of 4 GSX-R 750 smooth-bore flat slides from the UK. Will document the process of fitting them to the GS. The carbs were stock on GSX-R 750 models, and can be had for less than 200GBP. Should be good for improved throttle response and a little power on our bikes...

Yeeeeah. Dibs on the two left over.

But only if it works... 

Hi Guys,
                     I agree that a unbalanced regards Lanchester shaft style, 180deg twin can be made to work not to badly.
     The first bike I ever tuned way back in 1979 was a Honda 500 twin 180deg crank, I put it thru police speed trap equip of the time at just under 125mph. It was quick, vibration wise I didn't find it unbearable, but it was designed to take the vibration.  I love my Nortons, and after carefull balancing and lightening  their quite nice and bearable.
     My point is, the next step is to smooth things out further and make more power, with less waste. There is also a fair amount of conversation on this forum about how bad the bike shook after removing balance shafts and sad tales of broken cranks and failed bearings. 
     Sure the balance shaft is a chunk,  but its moment is not so bad, especially after it would be lightened to suit the other lightened parts as it has to be.
     I'm not knocking a costs basis decision, and serious racing requirements are different to mine, I'm just  extending the discussion.
      I am sure that ape will do an excellent job, my dynamic balancer guy is also really good, I only static balance to ball park it. But he still cannot get me to the next place.
      I am aware of a place in the UK that dynamically balances partially assembled engines, as assemblies, so the moments balance each other out correctly, done on a balancing table.
     I felt sure with all the high level racing going on in the states, this service should be available somewhere. (hoping) If anybody reading this knows where, can you please let me know.
     That's all I have on the crank subject, sorry if I've gone on about it, I find it really interesting. So I will not post any more on this unless contacted.
     As to the cylinder head, and the other comment that was posted.   My point is if the potential valve size is limited as compared to the other head, your stuck, all it can offer is maybe more rpm due to the lightness of the parts, if it can be made to breathe. Cam lift and duration can be changed reasonably cheaply and easily, not so with valve sizes past a certain point. Compression ratio's are also fairly easy to adjust, so the valves have it, also important when it comes to porting.    I am also building a 650+ bike, but could be great on a 450 with higher rpm potential. After they gave a good boost in an apples to apples, 425 twin UK comparison.
     I've seen the cut down GSXR head thing done, still have the article. However  then you have to deal with oil cooling the head and the extra demands on the oil pump.
     I  Much prefer keeping it a simple air cooled if possible, and slightly larger sizes will go in.  The compression ratio works  out to about 11+ :1 when fitting it to the 500 with good squish, and if the breathing problems are overcome, there's good potential.  I can supply any details you wish if you are interested.
     The parts are all pretty much the same so cams, heads, barrels can all be swapped around with ease. I don't know of another Jap bike offering that, and it handles great, what more can anyone ask for, Oh it's really cheap to, I got the 8 valve heads with cams for $40 each, $20 without cams, whole 650 motor $100.

Regards Ian

Ian, your imput is very much appreciated. Just describing my thought process, and not taking it as an argument at all. Really looking forward to hearing how the 4 valve thing turns out... Are you doing this with a GS500 frame, BTW?

Hi Burning,
                   Thanks for the comment, I didn't mean argument in anyway, just that it is my position, sorry I'm originally from the UK so sometimes I use the wrong terminology.
       Yes to the second question I have a 99 gs500 frame, I've fitted conventional gsxr 600 forks, 2002 I believe and revalved them, and I'm re-valving an R6 shock as I got it free.
        If I can help in anyway with info I am glad to, I have a copy of Engine pro software and can run an engine for you if you wish, I already have quite a few done, but I am still working on finalising some flow #'s, but a good indicators, before spending money.
         As to the 8 valve heads, I am fitting one at some point to the 500 engine to see what it does.  A straight swap would be  nice, but the stock 8v cams would be to mild to be meaning full for the 500.     So I think a webcam regrind, but I'm looking at #'s, the fingers look a little frail.
    Thinking and  figuring on the other, originally I was hoping for 650, if I can move the valves to get a larger size in, but it does not look easy.
     A local scrap yard had a few of these heads last time I was there,(late summer) from a now defunct school and cannot sell them,due to lack of interest.
     Your 450 project is very interesting what kind of RPM are you thinking of, I've been following your posts.

best Regards  Ian

Mikuni RS Flatslides are here. Need a thorough cleaning, but seem to be in good condition otherwise. It'll probably be a while before I can play with them; I don't have a running engine to test with.

http://www.motorcyclespecs.co.za/model/suzu/suzuki_gs400s%2085.htm

i don't think these came to the us...... anybody up nort ever seen one?


I thought the 400X was the 8 V engine

have you considered using the early GS400 bottom end(ex: 77 gs400XB)   it is showing having a roller crank....

http://www.bikebandit.com/1977-suzuki-gs400xb/o/m6023#sch270649


it should be able to take much more abuse.  then big bore it....

Longer stroke though, which could limit peak RPM.

Although I'm throwing a lot of money on this bike, I'm hoping that I can encourage a few other people to campaign GS450s in the AFM. It's nice to build a monster 50+HP machine, but being able to get one on the track for less than $2000 is also a project goal.

and that affects RPM by how much?