Restomodding?

[Billby]

G'day all, billby from Queensland here.
I am looking for advice,knowledge and experience so I can do up my kawasaki zephyr 750 C1. It is currently in pieces in my shed and at this stage I think it needs close to a full rebuild. The forks and rear shocks are rusty, is there an upgrade that works like a cartridge kit or is the damper rod system sufficient? Fork brace?
Is there a 320mm front brake conversion with 4 spot calipers? Rear brake upgrade?
Big bore engine kits? Or fitting a turbo to it?
Frame mods like bracing and gussets?
And lastly cosmetic enhancements like belly pans.....
Thanks everyone,
Billby

[Freddy]

G'day all, billby from Queensland here.
I am looking for advice,knowledge and experience so I can do up my kawasaki zephyr 750 C1. It is currently in pieces in my shed and at this stage I think it needs close to a full rebuild. The forks and rear shocks are rusty, is there an upgrade that works like a cartridge kit or is the damper rod system sufficient? Fork brace?
Is there a 320mm front brake conversion with 4 spot calipers? Rear brake upgrade?
Big bore engine kits? Or fitting a turbo to it?
Frame mods like bracing and gussets?
And lastly cosmetic enhancements like belly pans.....
Thanks everyone,
Billby

My thoughts ..... (based upon my D1 so I can't say with 100% certainty how a C1 may possibly differ)

Absolutely no need to do anything to the frame. Kawasaki have done all the strengthening for you, it is probably the greatest strength of the bike.

Fork brace .... if you stick with the right side up forks, absolutely essential, like any bike with em. But it must be a well engineer one, and fitted with great care. A bad one will make matters worse e.g massively increase 'stiction'.

Damper rod forks sufficient for what? Sufficient if you just want to putter around the neighborhood. Positively dangerous on fast back roads, railway crossings etc, when they completely lock up. The options available range from modified damper rods (Racetech emulators) through to full cartridge replacements, or retrofit UDF's (careful with that option, can radically alter the geometry). I run emulators and are very happy with them. Turds of things to get right, but once done, work well. Getting the spring rate correct is essential.

No need to worry about a rear brake upgrade, other than a lighter than OEM disk from EBC and their pads. The OEM disk is unnecessarily heavy (adding to unsprung weight).

I can only speak for a D1 which I know has upgraded from brakes to a C1. I run stock pads on stock discs (still the original disks after 190,000 kilometres) rebuilding the calipers EVERY brake pad change, and they have all the stopping power I need.

Personally, I would only fit a big bore kit if I couldn't source OEM 2 oversize pistons (I doubt you'll find 1 oversize as the pistons were used in a lot of previous models and have been used up by those owners). This is assuming it needs a re-bore, which it will. I have heard people say engine vibrations have increased significantly after fitting a big bore kit, and that only stands to reason as the crankshaft would need to be re balanced for such a radical change. If you want to have the crankshaft re balanced by all means go for it. If you thinking you might want the power of a turbo, you've got the wrong bike.

You haven't mentioned the rear shocks. That is the biggest bang for the buck change you can make. Wilbers triple clickers piggybacks are the way to go IMO.

Bellypan on a retro naked ..... YUK! You did ask.

P.S. My last thought, keep it neat and tidy and looking original as much as possible if you ever want to at least get some of your money back.

[Freddy]

One more thought .....

Unless the frame is rusted and needs repainting, consider just getting it going with basic maintenance e.g new fork, engine, oil, brake fluid oil etc, and restoring it in manageable 'chunks' while continuing to ride the bike. That way motivation is maintained, and there is pride both seeing and enjoying the progress.

Seen WAY too many people who pull their bike down to the last nut and bolt, a big effort initially but that fades and it either never goes back together, or by the time it does the project has turned into a chore and they have essentially lost interest before they ever get to ride it. Only a very small minority seem to be the exception.

[Billby]

Thanks for the reply, this bike was acquired in pieces to start with. A bit of a failed project from someone else. So I plan to poke on with it as money permits but I don't want to do things twice and the expensive way. So... I'd like to keep the forks looking standard, is there a preferred replacement cartridge that works best? And I only might fit a turbo because I can, knowing it's not a sports bike. And to have something unique as getting my money back on it isn't a concern

[Shedman]

I agree with Freddy, I'd put it together first and get it running, who's to say that everything is there and nothing is missing....... other than the person you bought it off? It won't cost you anything other than oil and filters if it is complete and you'll get a feel for how it goes together and comes apart before you put any expensive new paint on it. I'm pretty sure that most of us have bought a "complete" bike in boxes only to find parts are missing, usually the hard to find parts.

[Freddy]

And I only might fit a turbo because I can, knowing it's not a sports bike. And to have something unique as getting my money back on it isn't a concern

Just for the sake of rolling the topic along ....

The engine is obviously air cooled. Fitting a big bore kit (810cc being the common kit) will significantly raise the compression ratio which in turn significantly increased combustion temperatures. THEN, stick a turbo on (I assume there is no room for a large intercooler as per a car to cool the heated compressed turbo intake air) and you further increase internal temperatures with a heated air intake, and an even greater compression ratio (more air forced in). THEN you ride the bike in Summer Queensland temperatures, lets assume Brisbane with an average 29C Summer day temperature (obviously plenty days hotter than the 'average').....

See the potential problem.

[Billby]

Yes,that was a thought. Also would the clearances have to be changed, like on the crankshaft and or the conrod to piston? A better/more powerful oil pump?
Isn't this motor closely related to the GPZ750 turbo and the KZ750 turbo? Wiseco also do a lower compression piston kit, that is the link to putting a turbo on it for me.

[Freddy]

Yes,that was a thought. Also would the clearances have to be changed, like on the crankshaft and or the conrod to piston? A better/more powerful oil pump?
Isn't this motor closely related to the GPZ750 turbo and the KZ750 turbo? Wiseco also do a lower compression piston kit, that is the link to putting a turbo on it for me.

Good point .... but regarding a GP750..... "To build the turbo, Kawasaki did not simply add fuel injection and a turbocharger to a standard GPz750 motorcycle engine. Some parts are exclusive to the "turbo", such as low-compression (7.8:1) pistons, stronger gearbox internals, a modified oil pan with an extra oil scavenge pump". You can just about bet that a different camshaft may have been used.

Don't be dazzled by HP or quarter-mile figures in assessing performance. A street bike preforms best with good wide mid-range torque and smooth throttle roll on. I'd be a bit skeptical that a turbo is going to give you that. I'd expect it to be all WOT performance which isn't the great on the street. People put GPZ750 cams into a Zephyr. I'm not keen on that idea as I reckon you must give up mid range torque to push the bigger HP number at WOT. If there was some magic camshaft that could do both its would have been standard in every engine years ago. Variable cam timing is the current solution to this eternal challenge.