Camshaft differences between 85 700 and 84 GSX 750SE (pop up Katana)

[Guest]

So I've been trying to determine the differences in the engine between an 84 pop up Katana (GSX 750SE) and an 85 GS 700. Looking at the parts Microfiches at www.CMSNL.com (because this is the only place I've found an online parts fiche for an 84 Kat) shows the same part number for the intake and exhaust cams on the 84 Kat and the 85 GS 700. However, there is no parts listing for the 85 700's intake and exhaust cam sprockets.

My question is this: How likely is it that these two engines share the exact same intake and exhaust lift and duration numbers? The cams themselves are the same according to the parts fiche. How would a difference in tooth count on the sprockets affect intake and exhaust? In other words, if the teeth are different between the pop up and the 85 700, would one potentially make more power than the other?
Further research reveals the same cam chain and same number of links between the two models. This leads me to believe that intake and exhaust (or really, the whole head) is the same between the two.

So if the 84 pop up is listed as a 750, and the 85 is listed as a 700, probably the only difference between the two engines would be a slightly shorter stroke on the 700, right?

At the base of this quick n' dirty research is the haunting rumor I've heard that Jap market bikes (at the time) were mandated by the gov't to be limited to 77hp max. So if the engines are the same (except of course the slightly shorter stroke), the differences in power could possibly be attributed to carburetion?

I'd like to look into some reasonably cost effective ways to wake up my pop up Katana without having to resort to engine swaps or other super complicated ($$$) tomfoolery. I'm not against putting on an exhaust and rejetting if I could find a decent pipe at a decent price.....

Could you guru's enlighten me please?

PS - Looks like the igniter unit is the same as well.....

[Smokinapankake]

So looking at the carb parts fiche on CMSNL.com for the 84 GSX 750SE Katana and at Alpha sports for the GS 700, I'm finding differences in every air/fuel mixture determining part (Jet needle, needle jet, pilot air jet, etc...). This leads me to believe that the biggest difference between these two models is indeed carburetion. The only thing that appears to be the same is the throttle valves at 135. The one thing I couldn't find on the GS 700 that I could find on the Katana fiche was the pilot screw. Prolly due to emission regulations that may not have been present in Japan. It was listed as 1-5/8. I'm assuming this to mean # of turns out from bottom.....

Can anybody give me some idea as to what the horsepower ratings are on the 85 GS 700 and if possible what they really are on the 84 750 Katana?

I seem to recall reading somewhere that the 85 700 was listed at somewhere around 85 horse; and if the rumors are true regarding the Katana; well then the difference in hp is really negligible. Even more so considering the engines are approaching 30 years old and could be clapped out.....

Can anyone confirm the rumors about the Japanese regulations regarding horsepower in their domestic market motorcycles?

Maybe someone besides me will find this info useful or interesting....
Any help you can give is super appreciated!

[Smokinapankake]

Well I've answered my own questions about the camshaft sprockets. They are indeed the same for both intake and exhaust between the Katana and the 85 700. So the heads would have to be the same.

If I were to get a pipe and a jet kit I would be wise (probably) to change all the carb guts from my 84 Kat 750 for those out of an 85 GS 700. Then, the instructions and jets, etc... that came with the jet kit would be reasonably accurate. The airbox is the same as that of the 85 700 as well. Only difference I can see (aside from the carb guts) is the exhaust. But I can't imagine that big of a difference between the two as far as restriction / breathing qualities go....

To sum it all up, what are some reasonably affordable changes I can make to my 84 Katana to liven her up? Compression is good at about 145 across all 4; valves are all in spec, carbs are working properly with fresh O-rings. No vacuum leaks anywhere (yet).

Thanks for the help any of you can give!

[Billy Ricks]

If you can get your hands on a set of RS34 flatslides they will wake the bike up nicely. A set of VM29s would be a good choice as well. The VMs were the hot mod back in the day. When I installed my RS flatslides I had clutch slippage which was not there before due to more power and quicker throttle response. Instead of waiting for the slides to rise with vacuum your right hand controls the slide. Probably the most bang for the buck you can get, especially for a bolt on item.

[Smokinapankake]

Thanks Billy. So what motorcycles did the flatslides or even the VM29's come on? You know, to aid in ebay searching....

[gearhead13]

A set of .340 lift web cams would be a bolt in for a for sure increase in HP and torque. I ran the 1100 34mm carbs on my 750.
Flatslides didnt come stock, dont know about the 29's

[Billy Ricks]

Thanks Billy. So what motorcycles did the flatslides or even the VM29's come on? You know, to aid in ebay searching....

The RS flatslides are aftermarket.