rf900 gsxr750 hybrid

[reknelb]

Im looking for some info on doing the rf900 bottom end with the 750 head on a 93 gsxr750. What exhaust should/can i use? Should i get an rf900 cdi box? Really any info that people can share would be helpful.

[richardgs1000]

I did one a few years back and your best option is to start with both engines as you need gsxr oil lines sump oil pick up and a few other bolt on part, as far as exhaust the only difference between 750 lump and 900 lump is about 10mm of extra height I used aftermarket 7x7r headers on mine and it worked a treat

[reknelb]

I do have both engines. What yr zx7 did you use? Would the gsxr750 exhaust still fit then? The gsxr exhausts are getting hard to find. right now i have stock headers with yosh slip on. I would like to find a full system. Did you use the 750 or 900 cdi?

[richardgs1000]

standard gsxr electrics and cdi I think you end up with a spare pink wire which restricts the 900 in lower gears so just tape it up I never tried standard gsxr headers but if you have enough clearance below frame should be fine as its bolting to gsxr head anyway. the headers I used were of a zx7r and would assume any 7r (not zxr) aftermarket headers would fit as long as they are not welded at collector box as spacing may be different

[reknelb]

Thanks for the info. I was a little worried about the 13500 redline on the 750 cdi. I was thinking of a dyna ignition. What were u using for carbs? If they were the stock 38mm, do you remember your jetting?

[reknelb]

Oh....dont be afriad to post more pics if you have them lol

[richardgs1000]

il be honest never needed to rev much above 11000 revs as the power dropped off above that , standard carbs modified airbox (more holes in the back took ages on dyno to get right but was around 135bhp at rear wheel

[richardgs1000]

[captain chaos]

Dec 21, 2014 16:16:39 GMT reknelb said:

Oh....dont be afriad to post more pics if you have them lol

don't be afraid to post your location in your profile lol

[reknelb]

Thought I already did? Buffalo , NY

[reknelb]

Pulled the 750 engine tonite, I will update this thread as the project continues.

[reknelb]

When you say you used the 750 sump, do you mean you changed the oil pan and pickup? (The screen on the end of the tube behind the oil pan)

[reknelb]

The rf900 engine i bought came with out the counter shaft sprocket cover, the starter and the generator/alternater. Ive purchased the cover and other clutch parts needed to swap to the hydraulic setup. You need the sprocket cover, slave cylinder, hydraulic line, and master cylinder with lever. You may also need the actuator shaft that goes into the engine if it didnt come with the engine.

So far ive swapped out the oil pan and pickup to the 750 one. The starter was a bolt on swap. The alternater did not swap directly. I had to pull the starter clutch assembly out and swap the last gear off the 900 assembly, and use it on the 750 assembly so I could use the 750 alternater.

So im running the 750 oil pan, starter, alternator, and starter clutch/alternator drive (with the 900 inner most gear).

[reknelb]

Disassembled both heads, the rf900 intake valves are 1mm bigger so my my buddy cut my seats to accept the larger intake valves into the 750 head. The exhaust valves, springs, retainers and keepers are all the same on both heads. He also did some porting. we are going to use slotted cam sprockets and put another 750 intake cam on the exhaust side.

Unfortunately the clutch on the 750 is totally different then the 900. I have a brand new clutch and springs in the 750, and the 900 clutch is whooped.

[richardgs1000]

I simply swapped complete 750 head cams etc had no issues what so ever