Ive been sitting here thinking and wondering the last few days what I could maybe do to my GS for some added fun. I know there are various racers out there that know some key mods and how to do them I was just wondering what those specific mods were and if any of you would be willing to go into detail about those mods. Im probley gonna end up keeping my GS for a good while so I might as well make her go fast. The thought of completly swapping engines has crossed my mind but there are alot of issues that come into play there, I dont really want to buy an engine then not have it fit, I would really like to try an SV650 engine though if I could find one cheap enough.
Found this which seems like a good place to start. Using this post for older threads.
http://www.gstwins.com/forum/viewtopic.php?t=14401&highlight=engine
http://www.gstwins.com/forum/viewtopic.php?t=13284&highlight=engine
http://www.gstwins.com/forum/viewtopic.php?t=12764&highlight=engine
http://www.gstwins.com/forum/viewtopic.php?t=6906&highlight=head+swap
http://www.gstwins.com/forum/viewtopic.php?t=6510&highlight=head+swap
http://www.gstwins.com/forum/viewtopic.php?t=6843&highlight=head+swap
http://www.gstwins.com/forum/viewtopic.php?t=6869&highlight=head+swap
http://www.gstwins.com/forum/viewtopic.php?t=8398&highlight=head+swap
http://www.gstwins.com/forum/viewtopic.php?t=9072&highlight=head+swap
http://www.gstwins.com/forum/viewtopic.php?t=9638&highlight=head+swap
http://www.gstwins.com/forum/viewtopic.php?t=14490&highlight=pistons
http://www.gstwins.com/forum/viewtopic.php?t=14401&highlight=pistons
http://gstwin.com/racers_corner.htm
Odd that you post this....just yesterday I was pondering the idea of some kind of hybrid bike/motor. Been thinking about the 4 valve head swap for awhile but have not bugged Bob about the details....yet. plus I have 2 engines that need to be put back together. One will be stock but the other will probably be total loss ignition and remove the counter balancer. Figure out how to add an oil cooler, not sure of the plumbing. I keep bugging my boss about moving another milling machine to work.....hmmm....
Yea Ive been reading through old posts for about the last 2 hours, read the racers corner deal too. I think Im gonna bore out to the 78 mm pistons, more then likely anyhow. Theres so many little thoughts about ideas and what not, like the 4 valve head you mentioned but theres not really any info on what parts you need or how to get it to fit, I guess you just experiment. Dgyver, did you ever figure out what the 78 mm engine you had was making for power?
No idea about the power of the 547 (78mm). It was JamesG's motor when it split a shim and put it through the head. Someday soon I am going to put my 555 (79mm) on a dyno. It is basically the same as James' 547, same cams, ign adv, etc. But first I am going to install the CR carbs that he was running.
Bob has posted some general info here before on installing the 4 valve head. I need to pick his brain for the details.
Here is some of the info I have collected from this site since I am not sure how long posts are archived:
madman Posted: Sun Feb 08, 2004 2:14 pm Post subject: head swap
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Well, the motor started as a stock gs motor. Then the cylinders were bored quite a bit to allow for larger sleeves. Total bore increase is 11mm per cylinder to 85mm. Then the counterbalancer was removed and the rotating assembly was rebalanced. That saved a lot of weight. Now, with my bottom end done, I am looking for a really kickass valve train setup. I could just port & polish a stock head, but I think I would get a significant gain from that by using a GSXR head. The mating surfaces of the 2 center cylinders match the GS perfectly. So, you cut the outer cylinders off of the head and camshafts. Then make a custom valve cover and adjust everything to spec. Theoretically a 4 valve per cylinder head should outflow a 2 valve by a lot. This coupled with a 156cc jump in displacement should equal close to 100hp, I think. The head will also allow the use of an oil cooler, since they came stock on the old GSXR's. So, what do ya think?
Reknelb Posted: Sun Feb 08, 2004 5:25 pm Post subject: Re: head swap
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Now for some useful info. The bandit 1200, the gsxr/katana 1100 and the gsxr 750 (up to 89) heads are all the same. I think they have different cams and perhaps different valve sizes (combustion chambers may be different too) but they are all oil/air cooled heads with the same construction so in theory they should all work. The cams are all interchangeable between models. The 750 cams are the best, followed by the gsxr 1100 and katana 1100, and the bandit 1200 has the mildest cams.
werase643 Posted: Sun Feb 08, 2004 8:47 pm
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look for a kanadian GS400 8 valve head from the early 80's..i think 81-87)
the damn thing will bolt on and all you should have to do is weld up the ex ports and bore them where a GS port is suppose to be.
just get a complete head with cams cam cover
the 400 exhaust pipes go right thru the down tubes on a 500
it is basically half of an old GS1150 head with TSCC
Bob Broussard Posted: Mon Feb 09, 2004 2:00 am
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The head I have is an 89 gsxr 750. There was one on ebay last week, but I decided pass on it.
Here's the deal. The 4 inner stud holes lineup perfect. The outer 4 need to be relocated outward a bit. The GS head gasket works fine. The cam chain slot on the gsxr head is longer than the cylinders. So you need to fill it in at the rear. The GS cam sprockets will fit on the gsxr cams, so you can use the GS chain and sprockets. The bolt holes need be redrilled 1mm bigger (better yet slot them for degreeing).
The cam lobes need to be relocated for a 180 degree crank (Megacycle cams can do this). Might as well get higher lift at the same time. You'll need hardened rocker arms (Megacycle again) Valve spring set.
The inner cooling chambers normally drain down the stud into the lowerend on the gsxr. The GS studs are open in front (major oily mess ).
Fill in the drain holes and drill other holes so oil drains into cam chain area.
Then you need to make end plates to seal the the sides of the head.
These need oil passages to oil the cams and rockers through the rocker shafts. And you need to make drain lines to drain the cooling oil.
I went the extra step of installing a second oil pump in the sump, driven off the transmission. The oil goes from the pump to the oil cooler (B&M Supercooler) then to the valve cover. It fills the cooling chambers in the head and then drains back down into the motor.
The original pump does the lubrication. I tapped into the plug just below the igniton cover. It goes into the side plates and into the rocker shafts.
I'm running Carrillo rods and JE pistons. I had the pistons designed for the gsxr head. The exhaust cutouts needed to be cut forward a bit more. That's why I broke the first head
The weak link in the crank seems to be the right side rod journal where it connects to the outer weight. The drive gear is helical. This flexes the crank and snaps it eventually.
I've milled a slot for another thrust bearing into the cases in an effort to limit the movement in this area. The bearing shows definate contact, so it's doing something (time will tell )
I have pictures of all the mods. Was planning on putting them on my website www.gszilla.com but i've been too lazy to complete the site.
Email me for the pics and more details.
There's other things, like gsxr cylinder studs (APE). Stronger and equal length. GS studs are different lengths.
By the way how rich are you?
Hmmm, thats some good info that raises alot of questions. How streetable do you think a 78mm engine would be? Would there be any durability issues with the crank breaking? Those are my two biggest concerns, with the latter of more importance. Thanks for all your help so far dgyver, I think its cool to talk about stuff like this. :cheers:
Honestly I do not see any real issues with streetability of a large bore motor. The problem of breaking cranks seems to come from a combination of high compression and chopping the throttle at high rpms. The flywheel's mass is more than the crank can handle. Keeping the compression down (ie: not milling the head) should reduce this.
The only other issue I can think of is the extra heat with the air cooled motor. As long as it does not run too lean then it should not be a problem.
My 79mm motor actually idles better than the 74mm and the 75mm motors that I ran. A little of that I contribute to plugging one of the holes in each carb slide. No more high idle hang.
Yea those are good points that make sense. Im still contemplating on how much modding I want to do, I contacted a guy on some turbo's but he seems to want too much for me. Also found an 89 head on fleabay but it didnt have any cams, what do you use for cams if you mod the head, GSXR stock and then mod them?
I am not sure about the cams. I have just recieved several e-mails from Bob this morning about his work on the 4 valve head swap. Haven't had time to read through it all. 4 e-mails with plenty of pics. The cams is one question I need to ask him.
I would be happy to get any head to work with, just in case I screw up.
After reading over Bob's e-mails, looks like gsxr cams are used:
"The cam lobes need to be relocated for 180 degree crank. Megacycle knows how to do this. The stock GS cam sprockets and chain are used. You need to enlarge the sprocket bolt holes to 7mm for the cam bolts."
Send those emails my way, t_netsch@hotmail.com :thumb: Thanks. Also you mentioned above you were going to run different carbs, what bike did they come off of?
How big is your in box? With pics the e-mails are 2.7mb, 4.8mb, 3mb, 2k
If you need a bigger one I have a few gmail invites. Just check and I have 50 invites!!!!
250 mb is the size of my box.
this is all very interesting, any chance i could get a forward of those emails? what a collection of knowledge for future engine projects.
I don't have a problem with forwarding them but I would like to get Bob's permission first.
No problem, just let me know either way. I actually tried to send Bob a message last night but Hotmail was being dumb so I dont know if he got it. Ill wait to see if I can just get yours and save Bob some work. Thanks again. :thumb: :cheers:
Wow, look at this thing, amazing. Sweet engine Bob :thumb:
(http://www.gstwins.com/gallery/albums/userpics/10021/normal_000_0029.JPG)
wouldnt mind seeing some of those emails and pics myself, and yes. get bobs permission first.. im thinking of the earlyer GSX head from the 80-82 750 and 1000 myself, might not be quite the frankenstein, but then who knows.
Love the extended oilpan.
Bob said it is ok for me to share the info. Note that with the pics, these emails are about 10mb. If you need a bigger email box, I can send you an invite for a gmail account.
share share share!!
yay!
man does that engine look sexy.
Quote from: sprint_9Send those emails my way, t_netsch@hotmail.com :thumb: Thanks. Also you mentioned above you were going to run different carbs, what bike did they come off of?
I just sent the first e-mail.
I did not see that you asked about the carbs until now. They are Keihin CR flatslides with velocity stacks. Not sure if i want to add an airfilter or make a screen for them. I do not remember the size, but I think they are 39mm. Not sure if these came from another bike but I have seen them listed for other bikes. 4 packs sell for $200-400. They came with all the stuff I bought from JamesG. Still sorting through it all.
Cool, I saw somewhere else too, I think in one of those threads I linked to on the other page that some GSXR carbs would work. Bob sent me the emails earlier today so Ive been reading through them for a while now. The one thing I dont understand is how the cams are lubricated, Bob runs some lines up the front but is that just addtional to the inner oil passages or is it the main source of oil lubrication for the head? That is my main question I guess maybe Ill have to read it another 2 or 3 times, theres so much good info its amazing. Alot of craftsmenship went into that engine.
The CR carbs are not vacuum actuated so there should not be any lag time. I was having a slight hesitation when I was coming out of a turn at around 1/2 throttle and then slam it wide open. I was having to go to 3/4 then ease into WOT. I am hoping that with the CR carbs this lag would be eliminated since the slide is controlled directly by the throttle and not a vacuum. Plus they look really cool! btw...I have a 1/4 turn throttle.
I have been thinking about adding some ram air intake tubes to feed fresh cool air to the carbs. I know this is better than breathing the warm air coming off of the motor. Nothing fancy, just some kind of light weight flexible hose. Maybe cut holes in the front of the fairings to mount them.
I have not read over all of Bob's text too throughly yet. I am sure most of the parts that I do not understand would be answered by actually seeing the head and working with it....if or when I decided to take on this journey.
i would also like to see some pics please
moto_3bep@hotmail.com
Quote from: dgyverI have been thinking about adding some ram air intake tubes to feed fresh cool air to the carbs. I know this is better than breathing the warm air coming off of the motor. Nothing fancy, just some kind of light weight flexible hose. Maybe cut holes in the front of the fairings to mount them.
I have not read over all of Bob's text too throughly yet. I am sure most of the parts that I do not understand would be answered by actually seeing the head and working with it....if or when I decided to take on this journey.
Yea those are kind of the same thoughts I had, I think when I do my engine mods Im gonna rig up some sort of a cold air intake, I dont think it will hurt. We run a scoop on our sprint car with a plate type deal below the air filter to keep the hot air out of the engine, basically the same concept I want to use on my bike. After seeing all thats involved with the head swap I doubt I will end up doing it, Bob has his crap together, maybe if I got some spare parts to try it on I might think about it. I think at the moment Im probley going to go up to 78 mm pistons, perform some head work-perhaps port and polish, have megacycle cams rework my cam shafts, do my cold air intake, and maybe install some different carbs. :dunno:
Quote from: GRUi would also like to see some pics please
moto_3bep@hotmail.com
sent the first one
Another question I have been wondering about is what would you do for pistons, those custom pistons he had made up were pretty spendy I think. I wonder if you could use GSXR 1000 pistons?
thanks :thumb:
Quote from: sprint_9Another question I have been wondering about is what would you do for pistons, those custom pistons he had made up were pretty spendy I think. I wonder if you could use GSXR 1000 pistons?
Need to check the wrist pin diameter. The GS is 18mm. The gix1k uses 16mm pins.
4 valve head Suzuki's that use 18mm wrist pins:
80-84 GS750
87-95 GSXR750
89-97 GSX750F
80-83 GS1100
80-83 GSX1100E
There may be some others.
Wiseco makes a 74mm and a 76mm piston for the 88-89 GSXR 750 and 88-97 Katana that might work. They list a price of 124.95 for the 74 but dont list a price for 76. Wow just noticed the compression on both of those pistons is damn high, 13 to 1 for the 74 and 12 to 1 on the 76, I wonder if used in the GS if the compression would be that high?
The only real way to find your compression ratio is to measure it. I have been seriously contemplating swapping in the gpz1100 pistons. I got a friend that can bore the cylinders for free. So basically I would only have to pay for some parts. If I do that I will definitely check my compression ratio and take pics too for everyone to drool over. Haha