Kiwi's 750 Sport race conversion

[Kiwi Rider]

Hi guys, there doesnt seem to be a lot of traffic on the forum around the 750 Sport model so thought I'd start this thread.
I'll try not to make it long winded

So I got the bike cheapish with 48,000km on the clock, dead rego and highly 'modified' appearance with the lower fairings missing due to a prevoius crash. I was looking for a pre '89 bike to turn into a classic racer. So thats the plan..

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It ran a bit rough on the test ride but the frame seemed straight and the motor sounded OK. Firstly I fit new fuel pump, coils, leads and plugs +caps. That improved the running a bit.
It had an oil leak on the LH case cover so I took it off and fit a gasket. At the same time I did an oil and filter change. Kinda weird having that extra little drain plug underneath the gauze filter housing?? My bike has an aluminium sloted head plug in there that is really tight on the thread. Is this standard? I'm going to need something I can drill like a hex head to get lock off wire through it.

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I've decided to stick with the original carb for now even though I know its not the best set up apparently. I sent it away to a Weber specialist outfit and they did a real good job cleaning it up and checking everything over. They found lots wrong (butchered!) with it so at least I know it is stock spec now. Looks like new now!

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During the process of fitting a new fuel tap and inline filter I discovered there was no return line to the tank. I found it a bit fiddly trying to fit all this up near the tank with frame rails and the rear timing belt cover in the way so I have lowered everything down.

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So the bike is still a bit fluffy off the bottom just revving it on the side stand. I havent done the valve clearances yet though so I will start chasing that issue once those are done. I had a '93 750SS for about 10 years once so I'm kinda familiar with the engine and know how to do the valve clearnces. I did read that the stock fuel pump can over pressurise the carb and that an inline regulator reducing it down to 3psi helps. But feel free to throw any ideas my way. I need to get it out on the road for a proper ride test. Thats all for now.

[deswoodau]

Hi Kiwi, welcome to the forum and good luck with your restoration \ mod project.

There's some good threads on the forum detailing Weber tuning.

The auxiliary venturi update from 3.5 to 4.5 helped smooth out the flat spot. I also stepped up my idle and primary jets too.

[Kiwi Rider]

Thanks for the tips Des. I will spend some more time searching the forum about the weber when I get a chance. I'm looking forward to geting it running sweet. I forgot to mention that I replaced the timing belts as well. Every piece of rubber on this bike looks old!

[deswoodau]

I've had mine for over 10 years now and in most part it's been fairly reliable and great to ride. I had a Weber float failure last year which resulted in flooding, unable to idle and oil contamination. Seeing the Weber uses a pressurised fuel feed, your needle valve and float must be in perfect working order along with a good quality fuel line and clamps.

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[Kiwi Rider]

Its been nearly three months since I updated this thread but there has been work going on! I had a bad fuel tank leak at the front mount plate that took two attempts to fix and I lost enthusiasm for the project there for a while... But I'm back up to steam now as I have a race meet which I wish to participate in a fortnights time. I wont have time to get any cosmetics done bar a rattle can paint job once I finish removing the previous owners wrap design, so I've just been concentrating on getting the mechanical bits sorted:

I started at the rear of the bike by removing the rear swing arm to get two cracks welded up and when I put that back in I fit a new Hagon shock. Unfortunately the Hagon shock is 5mm shorter than the OEM one despite being listed as the correct model for this bike. This has done nothing for my race geometry (opposite of what I want) so I've pushed the forks 10mm through the triple clamps to compensate. Not ideal as I'm losing ground clearance here!

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I wanted to lower the gearing but I couldnt find alternative size sprockets here in NZ so I bought a 41 tooth 520 pitch aluminum blank and lathed the center to suit the sprocket carrier and drilled the bolt holes to match. Weighs nearly a third of the OEM steel sprockets weight. Fitted new chain and front sprocket as well. You will notice in the second photo that I also cut off the pillion peg mount. Can re-weld it back on in the future if need be.

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While I had the rear wheel out I fit a new Shinko tyre and I gave the rear brake a clean up and fit new pads. I did not refit the rear wheel hugger.

[Kiwi Rider]

Front end: Brakes

Big upgrade here, I fit a new Brembo master cylinder and got braided lines made to suit. It looks like I got my hose lengths correct luckily. I pulled the calipers apart for a deep clean and new seals. The ceramic pistons were in really good shape. I ordered a double banjo bolt with bleed nipple attached (second pic) as I have found from experience this makes bleeding up a whole lot easier. The lever travel is only 1/2" and very firm. I fit Newfren sintered pads as well. I hadn't used this brand before but they are Italian so kind of in keeping and they appear to work well. I'm real happy with the brakes on a road test but the track will be the acid test. You will see from the photos I need to make a mount bracket for the aftermarket reservoir!

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While I had the front wheel out I fit the new Bridgestone S21 in size 130/70/16 which I believe is the same front tyre as the original CBR900RR Fireblade.
This caused an issue with clearance for the front guard, so I had to raise it half an inch using spacers under the fork brace which supports the guard. Front end turn in has improved a lot with the more rounded tyre profile.

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[Kiwi Rider]

The previous owner had lost the original fork brace so I made a new one out of 6mm thick aluminum plate. Note my temporary spacers/packers underneath it to allow for the 70 profile front tyre. At the same time I removed the forks for fresh oil and seals.

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The LH clip on was bent so I straightened that, gave it a paint job and removed the LH switch block at the same time. I also fit a span adjustable clutch lever.

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[Kiwi Rider]

I had a spare Woodcraft folding tip for a gear lever floating around my race supplies box so that got fitted. Theres some slop in the linkages I need to address at some stage too.

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The clutch was not disengaging fully but after a few test runs up the road and a couple of bleeds it has come right now.

After doing some reading on this forum I decided to purchase an inline fuel pressure regulator to see if that would improve my running. I found a 1-5 PSI jobbie on AliExpress for not much and it has definitely helped. I have it set on 3 PSI but TBH it doesn't seem to change much if you adjust the knob in either direction. I want to check with a pressure gauge just what my actual fuel pressure is but it's definitely helped fitting this device. The bike is starting a lot quicker too.

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I think that is about it for now. Still a few small things to sort and a bit of tarting up and wiring off to do before race day, but I'm on track hopefully. I think I will put the fairing back on for the races as it covers that big ugly oil cooler and the fairing mount arms. The long term plan is to purchase a F1 style fairing kit and seat/tail unit. I'm enjoying myself mostly which is the main thing eh. Hope I haven't bored anyone

[Mc tool]

I spose now that you have your brakes sorted probly not the best time for me to remember that you can get adaptors to fit the Brembo 32/34 4 pots off the SS onto your bike . Sorry 'bout that

[Kiwi Rider]

I spose now that you have your brakes sorted probly not the best time for me to remember that you can get adaptors to fit the Brembo 32/34 4 pots off the SS onto your bike . Sorry 'bout that

I'll keep that in mind and give the stock jobbies a go for now, cheers for the info. The idea with this classic racing gig is to ease of the pace a bit and stop fracturing bones and being off work!

[Mc tool]

When I got my Paso I thought the brakes were pretty good , maybe not the strongest , Then I got the SS

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and like way better and the plan was to get some on the Paso but then I got to thinkin that I thought the Paso brakes were great to start with so in the end I didnt bother .

[Kiwi Rider]

Nice bikes the 750SS, I had a '93 model (aluminium swingarm, wet clutch) for about 10 years but its so many moons ago now I can't remember how good the brakes were. Given that I had traded up from a '77 Darmah they probably felt freakin awesome by comparison

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[Tamburinifan]

"I ordered a double banjo bolt with bleed nipple attached (second pic) as I have found from experience this makes bleeding up a whole lot easier."

+100, really makes you life easier.

Keep up the good work!

[Kiwi Rider]

I managed to find a M12 x 1.0 pitch hex head drain plug bolt in stainless steel on ebay. I got two because they were cheap.

https://www.ebay.com.au/itm/27549945214 ... 6352740269

I drilled a hole in one of them for wiring off and put a copper washer under the head and job done.

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[Kiwi Rider]

Painting

The tank was covered in a mixture of wrap and paint and took a bit of removing. It's been knocked about a bit and has had some rough repair work done in the past. I didnt get too carried away with my prep, just enough for my rattle can paint job to stick! I will get it professionally done in the future.

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The fairing parts are in poor condition but the front guard came up alright:

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