GT535: what if we replace the engine with a pneumatic drill?

[mentalboy]

Can you retrofit a kickstart to these?

I don't think a large single cylinder machine can be fully appreciated until you've tried to kick it into life on a chilly winter morning...
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Make mine a Corona.

[stinkwheel]

Any I've seen had a kickstart from the factory. They kickstart no problem as long as the battery is charged.

One thing is though that if the battery isn't holding enough charge to turn it over on the E-start, it doesn't have enough to power up the EFI. So the kicker isn't really a backup, just a vanity feature on most of them. May be different on this one where the OP has retro-fitted a carb.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[blurredman]

Kickstart in itself is not a way to get around a flat battery. It's just a manual way of starting an engine. Unless the bike has an AC ignition then a kickstart is no use when you have a flat battery.
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CBT: 12/06/10, Theory: 22/09/10, Module 1: 09/11/10, Module 2: 19/01/11
Past: 1991 Honda CG125BR-J, 1992 (1980) Honda XL125S, 1996 Kawasaki GPZ500S, 1979 MZ TS150.
Current: 1973 MZ ES250/2 - 18k, 1979 Suzuki TS185ER - 10k, 1981 Honda CX500B - 91k, 1987 MZ ETZ250 (295cc) - 40k, 1989 MZ ETZ251 - 51k.

[Easy-X]

Yes, factory kickstart. I have tried kicking it over a few times but I'm not very good at it

While technically you could fire it up without a battery, my experience with trying the same on an old Triumph involves a fair few "primer" kicks to charge a capacitor and a really swift one to get it going. Adding a battery ups the odds of success and reduces the number of initial kicks to whatever's needed to get the carb interested in what you're up to. Something like half a dozen kicks, ignition on, swift one, 50% chance of success versus two or three, ignition on, swift one, 90% chance of success.

What a kick start really does is bypass the need for cold cranking amps. A battery might hold >12 volts but fall on its arse when trying to turn the engine over, especially in cold weather. I've fitted a lithium ion battery to the GT so while there's near infinite capacity in it to shred sprags it wouldn't fair so well in the cold. A kick start may still prove to be useful in the future

*edit for blurredman: these engines run a DC set up (as did the Triumph I cited). Converting to AC? Hmm, unknown territory. I'm not sure/if when Royal Enfield ran an AC system but not on their recent models, that's for sure. At the moment I'm using all standard parts so this is a Lego-brick job, nice and easy.
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Royal Enfield Continental GT 535, Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter

[stinkwheel]

[Easy-X]

Thank you, Mr. Stinkwheel. I'll just get that in pre-emptively

Sun came out this afternoon, "maybe I will run the oscilloscope over the pickup coil." And as I'm wrestling the plug loose the one from the stator plops out. Most likely I didn't push it in the whole way when messing with it yesterday but essential I was running around this morning just on battery charge I dare say if it was still the original lead-acid I'd have got stuck somewhere and got very good with the kick start very quickly. So yeah, glad I went to check.

Anyhoo, a quick AC reading shows ~3V peak-to-peak from the coil and the scope confirms that:

https://www.bikechatforums.com/files/screenshot_2025-10-12_170142.jpg

I've arrowed an odd looking peak that crops up. I took a video and it does look like this appears as 1 in every 24 when I counted. I doubt the tacho is built so clever it's looking for this odd peak, I suspect it just does a divide by 24 to get the RPMs.

As a bonus item I bought a cheap temperature gauge off eBay a while back that's been sitting in a drawer. The probe you're meant to screw into an engine case or radiator seems to read around 2 kilo-ohms at room temperature and if I warm it with my hands it starts dropping down to ~1.5 - a reverse coefficient thermistor. "I wonder what the one on the GT reads as?" 1.7 kilo-ohms on a warmish day, same sort of animal I guess Rather that try and fit the supplied probe I'll reuse the existing one, see what happens.

AFAIK the Hitchcocks carb-conversion kit recommends reconnecting the temp probe to the ECU purely for aesthetics. Plenty of people have left it disconnected, from what I've read, with no noticeable effect. I'd be curious to find out how sitting in traffic affects the engine and how quickly it cools down once moving again.
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Royal Enfield Continental GT 535, Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter

[blurredman]

[Easy-X]

I have loads of Arduinos and Picos lying about, how hard would it be to make a 1:24 multiplier?

For output a Pico has loads of PWN generators. For a feature so basic I had a hard job finding example code with a decent explanation. Anyhoo, I now have some code that basically goes: pick an output pin, set frequency and duty cycle, go! And seems to work well enough for 50Hz ~ 125MHz Red line on the GT is diesel engine speed so say 7,000rpms to match the gauge, 24 x 7,000 = 168,000 which a Pico should handle easily. The great part is the PWM function is fire and forget so it's not a problem if the frequency changes are a bit "lazy". Set 1000Hz and it'll keep doing it until you say otherwise.

The Pico pin output is zero to 3.3V which translates to ~1.6V peak to peak. I doubt that'll be enough to trigger the rev counter but you never know. There's also a 5V supply I can tap into which should bring things within spitting distance of the 3V p2p I saw from the pickup coil.

Next up, find a digital tachometer project. I can test it by feeding this first Pico project into it
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Royal Enfield Continental GT 535, Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter

[Easy-X]

To tap an RPM signal the GT currently splices into the pickup coil which as we've seen is ~3V p2p. I've ordered some bits so to start with I'll try and opto-isolator with a "micro-controller friendly" logic output. The specs say it can handle 5V reverse voltage so would 3V AC do it any harm? (with the appropriate series resistor, 200 ohm I think)

Alternatively, Hall Effect switches are very cheap. I'm wondering if I just glue one to the pickup coil there'll be enough "going on" to trigger it. The advantage would be complete isolation from the ignition electrics. For the output side I'm again going with an opto-isolator, the transistor sort, so I can experiment with various output voltages till I find what the tacho likes and also to isolate my Arduino or Pico from the bike electrics as much as possible.

From what I'm seeing of various tachometer projects, the Pico's PIO thingy (which I'm yet to fully understand) can sample frequencies. I already know the PWM system can generate frequencies so the actual CPU will act as the man in the middle and pretty much twiddling it's thumbs as its minions go to work
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Royal Enfield Continental GT 535, Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter

[Easy-X]

Gone down a rabbit hole

I'm trying to compare the engine we got in Europe that only came in Euro-3/4 flavours to the carb version sold in India and it's not easy to get hold of a parts list, Google continually wants to point me at Hitchcocks Anyhoo, I've tracked down a "retired parts list" and on the cover is a Thunderbird Twinspark which looks like the same engine but with a CV carb fitted. Finally! We have a winner

Stator and pulsar* assemblies are listed in two flavours 147058/A and 570720/A which only differ by mounting hole diameter - M6 or M5 bolts respectively. My GT has 570863 Visually 570720/A and 570863 look the same but the former has an extension cable. But! the 570720/A is also listed as the stator in a 2008, 500 Electra EFI so I'm still thinking the stator already on my GT will be fine.

As for the rotor, an EFI bike has the 24 pips on the outside, part 571062 for both the 2008 Electra and my 2015 GT whereas the non-EFI rotor is listed as 570606/A or 592237/A and has the single big pip.

tl;dr The internal engine differences between an EFI and non-EFI 350/500 engine is the only rotor and not the stator. I have one on order from India for the princely sum of £26, fingers crossed

*Royal Enfield's term for pickup coils.
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Royal Enfield Continental GT 535, Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter

[Easy-X]

Parts order turned up

I'm still weighing up whether to go with a Hall Effect switch or splice into the pickup coil output. The former means gluing a sensor somewhere and running an extra cable out the crank case whereas the latter requires interfering (in a very minor way) with the existing electrics.

I shall try the Hall Effect route first and the simplest is a unipolar variant billed as a digital reed-switch replacement. Regardless of orientation you can vaguely waft a magnet near it. I have the rotor but the big single pip doesn't seem magnetic enough to trigger it

There are some recesses on the rotor (see picture attachment) so I'm thinking glue a little neodymium magnet in the marked region. It's far enough away from the area the pickup coil is interested in and I doubt a gram or so will unbalance the rotor (feel free to slap me if I'm wrong!).

Of course, all this assumes fitting this older style rotor will get the engine running with the TCI box.
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Royal Enfield Continental GT 535, Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter

[Easy-X]

Spinning the rotor past the Hall Effect sensor works to generate pulses. How to mount it in the actual engine? The stator and pickup coil are bolted to the RH engine case with the stator obviously placed to sit inside the spinning rotor with the pickup out seeing the outside of the rotor flashing past.

https://i.ebayimg.com/images/g/B5oAAOSweZNlgBca/s-l480.webp

I can't find any decent photos to represent this so you'll have to make do with this:

https://i.ytimg.com/vi/OBGPH9I84Vs/maxresdefault.jpg

Anyhoo, there's nowhere around the outside of the rotor to hang a little transistor-sized sensor apart from the pickup coil shell. I think there's potential for electro-magnetic interference between the two

The other thing I've noticed is all the pickup coils for TCI units are cased in grey plastic and all the EFI ones are black plastic which hints the internals may be different. It's extravagant but to be on the safe side I've ordered the older style stator assembly (hopefully with the correct mounting holes!). I shall strap the sensor to the pickup coil, set something up on my workbench to spin the rotor and see what happens.

The bonus with this approach is if the Hall Effect sensor is a bust I then have a test setup for sampling the pickup coil output instead.
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Royal Enfield Continental GT 535, Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter