Upside down fork options

[ChristoT]

So, for Project Fazer, I plan to fit USD forks. So, what fits, and how much modification to the yokes does it require? Can, say, an R6 front end be chucked on with a bit of milling to the top and bottom yokes?


I know people have fitted FZS1000 forks, and Aprilia RSV Mille forks - any other easy fits?

[Fuzzy]

Well, the thing to bear in mind is that you want to keep the speedo sensor as this effects the running/performance of the engine. This narrows down the options somewhat, I reckon your best bet is either an overhaul of the stock forks (new springs + emulators) or Thundercat forks as per Punkstig who managed to get the sensor in there with minimal trouble.

USD forks look great but in this scenario they don't really make much sense imo.

[ChristoT]

Well, the thing to bear in mind is that you want to keep the speedo sensor as this effects the running/performance of the engine. This narrows down the options somewhat, I reckon your best bet is either an overhaul of the stock forks (new springs + emulators) or Thundercat forks as per Punkstig who managed to get the sensor in there with minimal trouble.

USD forks look great but in this scenario they don't really make much sense imo.

I thought the speedo sensor didn't affect the carbed version?

On my project bike, I have no forks to overhaul. I'm starting from scratch, basically. I intend to eventually fit something like a Koso RX-2 GP speedo anyway:

[Fuzzy]

It does afaik. Part of the same circuit as the TPS and the result is less than optimum performance. Not really sure what the solution is tbh, I've yet to see a convincing one anywhere.

[Ruby Racing]

Well, the thing to bear in mind is that you want to keep the speedo sensor as this effects the running/performance of the engine. This narrows down the options somewhat, I reckon your best bet is either an overhaul of the stock forks (new springs + emulators) or Thundercat forks as per Punkstig who managed to get the sensor in there with minimal trouble.

USD forks look great but in this scenario they don't really make much sense imo.

I've done some research on this, nothing conclusive yet though.


One option which I haven't yet tried is to use an Igniter Box from the Thundercat, as that model doesn't have a speedo sensor. Pretty much everything else seems the same, just need an extra block connector and to move some the wires around as the Thundercat has three connectors on the Igniter Box, the Fazer just two.


With regard to the speedo sensor, I bought a second hand Koso just like the one you've pictured. It had been installed in something and the previous owner had spliced in an additional wire from the speedo pick up. It's purely a guess at this point, but I reckon that goes off to the loom in the same way the OE does. So you effectively keep the standard set up and don't send the bike into fault code mode. I've yet to get that far down the road with my build, but I'll mention it on my build page when I have. Whatever, I intend to find a solution.


As for fitting USD forks not making much sense? Yeah, you're spot on. But if we had any sense we wouldn't be modifying a Fazer in the first place! We do it coz we enjoy the challenge and we want to create something unique. Well, that's why I'm doing it. Link in my sig if you're interested.

[ChristoT]

It does afaik. Part of the same circuit as the TPS and the result is less than optimum performance. Not really sure what the solution is tbh, I've yet to see a convincing one anywhere.

Could the TPS not be sent emulated data from a different Speedo sensor, run through a digital filter?

[ChristoT]

As for fitting USD forks not making much sense? Yeah, you're spot on. But if we had any sense we wouldn't be modifying a Fazer in the first place! We do it coz we enjoy the challenge and we want to create something unique. Well, that's why I'm doing it. Link in my sig if you're interested.

And that is why there is a Honda Bros 400 swingarm in my boot.

Interesting info on the T-Cat ignition box, but I'm not 100% sure I know what you're talking about! Could you please elaborate?

[Ruby Racing]

And that is why there is a Honda Bros 400 swingarm in my boot.

Interesting info on the T-Cat ignition box, but I'm not 100% sure I know what you're talking about! Could you please elaborate?

You do understand! You can get therapy for it, I'm pretty sure.


Well it's the ECU for the motor. It's only a theory at this point, but as the Fazer motor is basically a Thundercat motor, then it seems logical to assume you can use the Ignitor Unit from the Thundercat to replace the Fazer one. You just have to make sure you connect the wires up correctly as the TC Igniter Unit has three connectors compared to the two on the Fazer Igniter Unit. Just means you need an extra block connector and to change some of the wires around in the block connectors. I've had my electrician mate look at the wiring diagrams and he thinks it'll work.


But it might not come to that if running a wire (or wires) off to the loom from the Koso speedo sensor does the job. The Koso speedo sensor and the OE speedo sensor are just a sensor and some magnets, so if you keep the TPS in the loop there's a good chance you won't get any fault codes. I'm guessing when others have fitted aftermarket speedos they just run the wires from the speedo sensor up to the speedo. If you also maintain the connection back into the loom, there is a good chance you will avoid any issues. That's my theory anyway.

[Fuzzy]

Could the TPS not be sent emulated data from a different Speedo sensor, run through a digital filter?

In theory yes, that makes sense. In reality it'll most probably be more trouble than it's worth, for me it would be anyway. The thing is you can achieve a great effect in other easier and cheaper ways.

I've been following Ruby Racing's build which is simply fantastic, but way beyond my and most people's capabilities. Of all the foccers here, he's probably one of the best placed to figure it out so I will continue to follow the build for that reason amongst many others.

However, nobody has achieved a simple solution yet and the bike has been on the market since 98' so I guess what I'm saying is, if you go down the USD route be prepared for a lot of work! Sometimes there is virtue in keeping things manageable, something like that can potentially become a drain on time and money - and that often ends up being detrimental to the whole project.

Having said that I totally get the enjoyment to be had from taking on such challenges and admire you guys for pushing the boundaries!  If either of you do come up with a good solution I imagine I will be amongst the grateful who will follow with upgrading the forks.

 

[Ruby Racing]

I've been following Ruby Racing's build which is simply fantastic, but way beyond my and most people's capabilities. Of all the foccers here, he's probably one of the best placed to figure it out so I will continue to follow the build for that reason amongst many others.

Very kind words, thanks Fuzzy. But certainly not beyond yours or anyone else's capabilities. I had never used a lathe before starting this project, now I can. I'm not very fast using it mind! Plus I will have to get a grown up to help with some of the build, like welding on a new subframe.


I don't know about best placed either coz electrics are just like magic to me, I just went into my project determined to find a solution. If I do find the answer I'll be posting a separate topic on the subject as I can see from the research before starting my project that this has been a problem for some time.


Glad you're enjoying my build thread.


Back to the original question and I would suggest looking at bikes that ARE NOT sports bikes for your USD forks. I'm pretty sure most of those options will be shorter than the OE forks and if you fit them then you're dropping the front end, which changes the bike set up and you lose ground clearance.


I would look more at the super nakeds for your donor forks. The Fazer forks are approx 720mm long measured from the top of the fork to roughly centre of the axle. I've used the front end from a KTM Super Duke 990 as they are the same length and were the same distance between top and bottom yoke. I've used the KTM yokes and this will have altered the front end geometry as the offset is less than OE so this will change (increase???) the trail figure. I'm not sure if this will cause instability (I'll find out!!!), but it may do. The swing arm should allow the rear wheel to be in the same place as OE, however it is a little shorter so I won't be able to move the rear wheel back as far as OE. Using the yokes from the donor bike may or may not cause problems and if it does then you may need the expense of custom yokes.


In addition the KTM yokes I've used, because of the reduced offset, means I have less lock and need new lock stops welded onto the frame. This isn't a problem for me as the lock is not much worse than a sports bike now.


Other bikes I thought suitable were the following:


Aprilia Mille 2001 at 735mm
Yamaha Fazer FZ1 at 720mm
Aprilia Tuono Mk2 at 730mm

[Doddsie]

I remember this bloke saying that R1 forks were a pretty straight forward swap but the wheel spindle caused a few problems. Dunno how (or if) he got round the speedo sensor problem though.

[ChristoT]

Ruby, It's the ignition box you refer to that's confusing me. Is that the reg/rec?

[Paul]

My speed sensor packed in twice, but I didn't notice any drop in performance when it was broken.


I struggle to see why the speed sensor would affect the advance and retard of the ignition.


I can see how engine revs, and throttle position could be used to alter the advance and retard, but not the speed sensor.

[Punkstig]

Before I made changes to the speedo drive I was running with the sensor unit cable tied out of the way, but before doing all this I did some 'performance' tests after sticking the unit out the way I did comparable tests and there was NO performance issues with the sensor not in use.
The only problem was when taking the engine over 10,000 revs a fault code would then display, this could only be corrected by switching off the engine, one would assume whatever speedo you attach if the sensor isnt attached it would display the error code.

As for front ends Christo don't even think about milling out the yokes, you want to buy the entire front end including wheel and possibly calipers if not getting R6/R1, and then swap out the stem!

[Ruby Racing]

Ruby, It's the ignition box you refer to that's confusing me. Is that the reg/rec?

No it's the Igniter Unit which sits in the tail of the bike, near the brake light. It controls all the electrical functions of the bike, like an ECU in a fuel injected vehicle.


The R/R sits on the left just behind the headstock and controls the electricity being generated by the stator (I think!).

[ChristoT]

Before I made changes to the speedo drive I was running with the sensor unit cable tied out of the way, but before doing all this I did some 'performance' tests after sticking the unit out the way I did comparable tests and there was NO performance issues with the sensor not in use.
The only problem was when taking the engine over 10,000 revs a fault code would then display, this could only be corrected by switching off the engine, one would assume whatever speedo you attach if the sensor isnt attached it would display the error code.

As for front ends Christo don't even think about milling out the yokes, you want to buy the entire front end including wheel and possibly calipers if not getting R6/R1, and then swap out the stem!

I'd be interested to find out whether that was just a quirk of your TPS, or whether the speed sensor really does muck it up. I suppose the only way to check would be to take a working FZS600, and do a few runs, including above 10K revs with and without the sensor connected, and check thinkls like revs vs a range of speeds, acceleration, etc.

[Punkstig]

Before I made changes to the speedo drive I was running with the sensor unit cable tied out of the way, but before doing all this I did some 'performance' tests after sticking the unit out the way I did comparable tests and there was NO performance issues with the sensor not in use.
The only problem was when taking the engine over 10,000 revs a fault code would then display, this could only be corrected by switching off the engine, one would assume whatever speedo you attach if the sensor isnt attached it would display the error code.

As for front ends Christo don't even think about milling out the yokes, you want to buy the entire front end including wheel and possibly calipers if not getting R6/R1, and then swap out the stem!

I'd be interested to find out whether that was just a quirk of your TPS, or whether the speed sensor really does muck it up. I suppose the only way to check would be to take a working FZS600, and do a few runs, including above 10K revs with and without the sensor connected, and check thinkls like revs vs a range of speeds, acceleration, etc.

Erm, that's basically what I did, I thought 'performance' tests would cover that!

[ChristoT]

Before I made changes to the speedo drive I was running with the sensor unit cable tied out of the way, but before doing all this I did some 'performance' tests after sticking the unit out the way I did comparable tests and there was NO performance issues with the sensor not in use.
The only problem was when taking the engine over 10,000 revs a fault code would then display, this could only be corrected by switching off the engine, one would assume whatever speedo you attach if the sensor isnt attached it would display the error code.

As for front ends Christo don't even think about milling out the yokes, you want to buy the entire front end including wheel and possibly calipers if not getting R6/R1, and then swap out the stem!

I'd be interested to find out whether that was just a quirk of your TPS, or whether the speed sensor really does muck it up. I suppose the only way to check would be to take a working FZS600, and do a few runs, including above 10K revs with and without the sensor connected, and check thinkls like revs vs a range of speeds, acceleration, etc.

Erm, that's basically what I did, I thought 'performance' tests would cover that!

Fair enough, sorry!

Did you do any with a different TPS though?

[Punkstig]

Why would I change something that's not broken?

[ChristoT]

Why would I change something that's not broken?

Well, I was wondering if the 10k error was due to a peculiarity of your TPS, or whether it held true for all units. That was sort of what I was thinking of.

[Punkstig]

Right, let me do this again-
My idea of performance tests-
With speedo sensor attached and everything else on the bike working fine apart from the plumb riding it

0-60 not bad, no where near as quick as the SRAD

2nd gear hard acceleration up to red line, not bad, no where near as fast as SRAD

3rd gear up to red line, same


Tests with speedo sensor tied out the way, but with magnetic hub still inside the sensor-

0-60, no difference to first test

2nd gear hard acceleration, no difference in acceleration, tacho shows error code when hitting 10K but engine still increases revs until hitting limiter.

3rd gear, same as above.


So, continued riding with speedo tied out the way using Thundercat wheel (120/60 tyre) in Thundercat forks, only issues found were over taking on fast roads would generally mean going over 10K and tacho showing error code until engine switched off.

Solution was to buy your wheel sensor filing down the plastic tabs to fit the T'cat wheel!

[ChristoT]

Good to know the performance won't suffer, but I was coming back to the error code. Is the fact that the code displays with everything working a peculiarity of your TPS?

[Punkstig]

Head-wall

[Deefer666]

From experience I can only comment that I used early R1 forks. You have to swap the centre stems and fit a spacer under the top yoke but you  get to retain the blue spot calipers from the 600 (ideal if you are on a budget). The other problem I know that others have had is that modern big sports bikes seem to have very short forks so you will need to check the length.

The downside is that your rev counter will show an error code due to lack of speedo drive but if you fit an aftermarket dash and take a feed from the coils themselves instead of the standard dash wiring you can eliminate this. There is talk of the TPS not functioning properly but I found fitting a Nikko G pack ignition unit boosted the power (it may of eliminated the TPS problem, but the difference in power loss if it actually does would not be really noticable)

[Hedgetrimmer]

I don't know about best placed either coz electrics are just like magic to me

Witchcraft! DIY = Don't Involve Yourself - i.e., get someone else to do it for you!