Where are the 8 valve 750 folks?

[slow_heavy_750]

So, like everyone else who has to deal with winters, im starting to go a little nutty, and am finding myself wanting to do something to my bike before the warm weather hits. Im already doing a top end on my BSA, and im not sure if im going to keep my CB750 or not, so that leaves the poor 78 750.

Ive been searching around, and it seems most performance-oriented threads involve the 16 valve 750, and the ones that do pertain to the early 750s usually turn into a discussion about swapping a 1000 motor or bolting the 850 top end onto the 750 bottom end. I guess im a glutton and dont want to go down either of these roads


Currently I have a V&H 4-1 system, pod filters, and have gone down one tooth on the front sprocket. I am already planning on going to a 530 chain, and possibly going a little shorter on the gearing. I was also contemplating going with the dynatek electronic ignition (as well as changing to the appropriate coils. I know this isnt really a performance mod, but figure replacing the 30+ year old ignition wont hurt anything.


Im looking for ideas on what else to do. I was considering cams, but I cant seem to find any info/feedback on if its worth the change/money. Should i just break down and go big bore? Both? :-#


Im just looking for some feedback and more ideas from those who have modded the 750s and the results they have had. Again, id like to stay with the 750, as I have quite a few spare parts collected and dont want to start all over again..lol Any input would be greatly appreciated.

 

[chuck hahn]

well i have a 77 750B and a 78 750E..I though am not a mods kinda guy. Mine are bone stock all the way around..My album has pics of the 77. I just got done doing a full polishing of both the bikes engine covers and the forks. I also restored the original point and stator cover emblems. they both look nearly showroom new .Just waiting on the tanl for the 78 to get back from the paint shop and finish everything up..

 

[wkmpt]

'77 750B Here. Presently, mostly stock, only dyna ign. and bandit coils. Fairly well sorted, though I need to fix several broken exhaust bolts and then get the carbs properly synced. Going to upgrade the single front brakes to some degree or another before the next riding season comes around. Priority.

Future pipe dreams include but are not limited to: 4-2-1 exhaust, pods & jetting, some mild cams, progressive fork springs, Salty_monk's twin pot caliper and rotor upgrade for front brakes, fork brace, 530 chain, enhance electrical sys., train headlight. That's mostly it, and only the Shadow knows when the funds will be flowing enough to get cracking.

Have to admit I'm also one of those sods mulling about the idea a well-equipped 8-valve 1000 swap and a wider wheels with wider tires. If I did this I'd also like to install a beefier front end and have some frame bracing welded in as well. Maybe when my money tree starts to bloom, I'll just buy another bike and do one one way and one the other...

So there ya be.

 

[Detroit Diesel Man]

77 750B here too..my winter project...


John

 

[slow_heavy_750]

Have to admit I'm also one of those sods mulling about the idea a well-equipped 8-valve 1000 swap.

The more I think about it, the more I think this is the way to go. Only issue with this is I am having trouble finding a a complete 1000, nevermind just the motor. Oh well, just have to wait and see what happens.

 

[SqDancerLynn1]

Best bang for the $$$ is a 850 top end

 

[TheCafeKid]

Best bang for the $$$ is a 850 top end

Well, givin the choice I'd go with the 1000 motor over the 850 top end. Having said that finding a complete 1000 motor in good shape without paying a fortune for it might be tough. In that respect i'd go with the 79 850 top end swap. It's the easiest, as all you need is the jugs and pistons and wrist pins. You'll need a gasket kit of course, but the jetting between the two is nearly identical. It's an afternoon of work if you have all the stuff ready to go. The later 850 top ends can be used as well but require a bit more work as the cases need ground a bit to fit the jugs etc from my understanding. While it won't garner you the increased comp ratio that a true bore kit would, it yeilds you the same displacement at about a third of the cost depending on how much you pay for the part and the machine work (I'd suggest gettin the head decked and jugs honed by a shop to assure good breakin of the new rings.) All in all there are pleanty of HP mods you can do to the 8v 750, including turbo! The bottom ends are one of the stoutest of the GS series and the only to run straight gears vs helical like the other motors. They are bulletproof. Great motors and great bikes. I love em myself almost as much as my 1100ES

 

[slow_heavy_750]

I was contemplating on going with the 850 top end, and possibly shaving the head a bit to bump the compression. I can do the honing myself, so I wouldnt be paying for anything there. I need to talk to the parts manager at the shop I work at to see if we are set up with web cams. If thats the case and I can get a set of cams for less than retail I may go with cams and the 850 top end (if I can find one.)


We also have an 1150 in storage at the shop that I could probably get for real cheap...the downfall is im told it has an 1100 motor swapped into it...if that makes sense.

 

[spyder2120]

web cam racing cams. www.webcamshafts.com they seem to be able to go as far as you want to go. good luck

 

[Guest]

Will the 750 head gasket fit with the 850 jugs or do you need the 850?

 

[Spyderman]

Will the 750 head gasket fit with the 850 jugs or do you need the 850?

you'll need the 850 pistons wrist pins cylinders head gasket and head (Complete with cams and gears just to be safe)

 

[Guest]

you'll need the 850 pistons wrist pins cylinders head gasket and head (Complete with cams and gears just to be safe)

From my research (on this forum) my understanding was that the 750 head would bolt straight on to the 850 barrels. Is this not correct?

 

[Benstyle]

The first part of your post is slow, the next part heavy... start shaving some weight off the beast. Drill everything you can. See if you can find a blank for the kickstart hole and remove the associated mechanism. This way you aren't spending much, just putting holes in things. The tail section on these bikes can't be light either.

 

[Nessism]

From my research (on this forum) my understanding was that the 750 head would bolt straight on to the 850 barrels. Is this not correct?

The head is the exact same part number, or so I'm told (please check the part numbers for yourself to verify).

 

[Postman_Pat]

Hi all, thought I might share some thoughts on how to go about improving the ol' 8 valve 750s - and some examples of what I've done to mine. I'll try and post a photo here in the next few days if anybody's interested.

Engine

Definitely consider going the GS850 top end route, much better option than putting in a GS1000. The GS1000 engine WILL require you to fabricate new engine mounts. The bare minimum you will need to convert to 850cc is a good set of pistons. There's plenty of meat on the 750's cylinder liners - all you need to do is overbore and mount the new pistons and, there it is. You're actually better off retaining the 750 camshafts - they have a higher lift on the exhaust cam than the stock 850. The 750 camshaft is also worth seriously considering as a retrofit for the GS1000, for those that are interested.

Carburettors

My bike is currently running standard 750 26mm carbs with the standard airbox. No jetting changes - nothing. I haven't yet tried this myself, but also consider fitting a set of 28mm VM carbs from a GS1000S. They should be a bolt-on fit.

The change to 850cc was a really great move. More power, lower down the rev range - just perfect.

Chassis

Swap the weedy 35mm forks of the GS750 with those from a GS1000E. A great move and pretty simple to do. You'll need the lower steering stem bearing from a Yamaha SRX600 - that's all! It all bolts up perfectly once you've replaced the lower bearing. The GS1000 forks are shorter, but this isn't a problem - these GS's have VERY conservative steering geometry to begin with. Your GS750 instruments also fit perfectly on the top yoke. You'll also need the brake system from the GS1000 (rotors & calipers) - the discs and calipers are lighter too. Also see if you can source a GS1000 front wheel - it's 500g (over 1lb) lighter than the 750. Remember, reducing unsprung mass gives the best improvements to handling. My 750 is currently running a 1983 GS(X)1100 front wheel - lighter again than the GS1000 item.

At the back, consider swapping the standard steel swing-arm of the 750 for the lightweight box-section aluminium swing-arm from a GS(X)1100. It's close to 2kg (nearly 5lbs lighter) and a very easy conversion. It's also approx 20mm (3/4") longer than the 750 item, so it will lengthen your wheelbase, but you can adjust the rear axle to its forward position to keep it close to your 750 wheelbase. My bike has the rear wheel from a 1984 GSX1100EFE (GS1150 in the States). Here in Australia the '1150 came with an 18"x3" rear wheel, so this means I'm able to run a 130/80x18 tyre.

A 530-pitch chain conversion is obligatory if you want to save weight. I use a 16/45 sprocket set-up.

Other things to consider if you want to reduce weight:

- Do you really need a centre stand? While you're getting rid of the stand, also consider getting rid of the grab rail under the seat.

- Spend some time modifying the tail light bracket and licence plate holder. Replace these steel items with aluminium - they're not highly stressed items so going with aluminium is OK here.

- How about a fibreglass front fender to replace that big steel item? You'll need a brace across the forks to keep things in line, but you can possibly attach the fender to your new brace. I'm considering doing this in the near future.

- The head light brackets - depending on how handy you are in the workshop, why not make them out of aluminium?

- A lighter battery tray perhaps? I've made mine out of aluminium - it works well.

Just some quick ideas there. All the mods I've done haven't altered the basic look of the bike, just made it lighter and faster. In short, there are a lot of opportunities for weight reduction on the 750 - Suzuki really did overbuild the machine.

I know a lot of people will say "If you're going to go to this much trouble, why not get a modern bike?"

Well, if you're like me and you're really attached to your 750, then who cares what they say. Why throw something away if it can be improved?

 

[Guest]

Some good info Postman Pat. Thanks for going to the effort of typing all that out.

Glad to hear the 850 mod is worth the effort. Got some 850 cylinders (not sure what year, fingers crossed...) and pistons ready to go when I get a spare weekend - just need one more set of rings.

It seems I too am hopelessly attached to my GS 750.

 

[slow_heavy_750]

Pat-

Awesome post, definitely gave me a few ideas. I think at this point im going to focus on shaving some weight. The front fender is already off (doesnt fit with the current tire on there.) Im just going to keep my eyes open for the 850 top end and see if I can find the parts locally (because im sure shipping would be rediculous.) I already plan on converting the chain/sprockets to 530, and ive also been keeping my eyes open for the 1100 swingarm, but so far no luck...

 

[Detroit Diesel Man]

Nice post Pat...thanks..alot of what you mentioned Ive done and am planning on a few more things...I get the "why not buy a new bike" line from people at work alot...but yeah I like the old GS's and I dont want a cookie cutter bike like everyone else has...thanks for the post and tips!


John

 

[cyclefvr2]

would a 850 jug punched to 1000, with a 750 ,ported /polished head,and smooth bores fit,and work?
hehehe

 

[dlanes]

I just picked up katana forks wheels and brakes for my gs. I also got 850 jugs and pistons for swapping on in the spring