Zongshen Sierra: XT 600 speedo experimentation

ChillRider · 06-09-2021, 04:00 AM

So....my ZongShen Sierra's speedo has started drifting in the last few months, and it's probably on the way out.

It first started squeaking (that went on for months), then after a top speed attempt that nearly drove it off the scale, something must have broken and it suddenly went from indicating way more than the actual speed to indicating less than the actual speed...

The odometer also is gradually losing accuracy: first, it was pretty dead-on, even with the speedo's antics, when accounting for the different front wheel diameter than stock. However it started drifting too, first to 93% of actual distance, then to 85%, and last time I checked it was at 75% or so

As you can imagine, this has left me almost stranded for gas a couple of times...

I figured, since the Sierra's instrument cluster is a clone of the Yamaha TW200/XT200/XT225, and a Tanaka instrument cluster for the XT 600 looked pretty similar (similar to this one) and was reasonably priced to boot, I ordered one, expecting that at least the speedo would fit, although the entire assembly is compatible with the existing mechanical mounts (not so with the electrical one, and no tacho cable on the Sierra...)

Indeed, the speedo was easy to remove and fit into the existing frame with no modifications and even matched the existing speedo cable. I adapted it to the lighting harness with some spade terminals, and I have a spare "OIL" indicator light as well...

It did work, however it's way off (indicating slower speed/distance), probably because the XT 600 uses a lower speedo worm gear reduction at the wheel= higher speedo cable speed.

Is there anything I could do to adapt the speedo cable's speed, e.g. some inline gear multiplier, some internal calibration or an electric speedo drive that could be calibrated?

Alternatively, by hacking my old speedo open, is there anything I could -realistically- check and fix by myself? I have some experience working on tape decks, but I reckon the only remotely similar thing would be the tape counter

ChillRider · 06-14-2021, 06:23 AM

Hmm...after going for a longer/faster ride, I realized that even the new speedo has exactly the same deviation as my stock one: the odometer indicates 3/4s of actual elapsed distance, and so does the speed (with a reluctance to go above 80 km/h indicated and a weird wraparound effect when I do), exactly as my old speedo did.

Also, it didn't fix my needle bounce at all. Testing the old speedo with a drill and a different cable (which however I cannot mount on the bike), showed a smooth operation and no needle bounce at all.

So now I start wondering whether the problem is the speedo cable itself, or its sheath

**JerryHawk250** · 06-14-2021, 07:31 AM

Did you lube up the cable? Any kinks in the cable?

ChillRider · 06-14-2021, 09:44 AM

I did lube the sheath 6 months ago and replaced the inner cable (sadly, I could not install a new sheath because it had a defective fastener at one end, and it just wouldn't thread where it was supposed to...so I just used just the cable from the new sheath). I even used some Moly DX paste (despite the name, it's not moly based, it's a white lithum-based grease). Maybe it wasn't really up to the task, who knows...

Kinks....nope, used the existing routing fasteners as the old one. I will try to fill the thing with gear oil this time, and see how that goes.

franque · 06-14-2021, 01:10 PM

I'd check to see if the gears in the wheel are okay (assuming a mechanical speedo), they could be missing teeth.

ChillRider · 06-15-2021, 06:39 AM

At first I thought about mechanical damage/stripped teeth too, but spinning the old speedo with a drill (and a different cable) resulted in butter-smooth operation, no needle jumps etc., while the new speedo mounted on the bike behaves exactly the same as the old one...bumpy needle, slow odometer and all, so maybe the real problem lies elsewhere (cable, sheath, or even the worm drive at the wheel).

franque · 06-15-2021, 11:29 AM

I'm talking about the worm drive at the wheel.

ChillRider · 06-15-2021, 02:18 PM

Yup, that's what I was afraid of...

I will have to push the bike on the curb with the spindle gear removed and check it every quarter turn of the wheel or so, I suppose.

Though, if teeth were stripped, wouldn't I be hearing all sorts of nasty noises down there? The spindle gear is some type of metal...(bronze), dunno if the rest is plastic.

franque · 06-15-2021, 04:51 PM

Not necessarily, they're pretty small, so it might not make a big noise. Also, the engine is between you and the sender, which I would imagine drowns out a lot of noise.

ChillRider · 06-16-2021, 03:55 PM

Well, I pulled the Speedo drive's core out to inspect the ring gear. TBQH it looked like a flat, greasy mess everywhere, and yet it still meshed and turned the core somehow... and that's about as mush as I could tell without taking it apart.

Long story short, I washed the core in some mineral spirits, and poured some SAE 90 gear oil down their Speedo drive and the first portion of the speedo cable. That seemed to have some effect, as the bounce was reduced somewhat and indicated speed went up a bit.

Well, I'll try the cheap fix, remove the cable and flush + relube it.

06-09-2021, 04:00 AM	#1
ChillRider Join Date: Jun 2020 Location: A small country with a funny name Posts: 164	Zongshen Sierra: XT 600 speedo experimentation So....my ZongShen Sierra's speedo has started drifting in the last few months, and it's probably on the way out. It first started squeaking (that went on for months), then after a top speed attempt that nearly drove it off the scale, something must have broken and it suddenly went from indicating way more than the actual speed to indicating less than the actual speed... The odometer also is gradually losing accuracy: first, it was pretty dead-on, even with the speedo's antics, when accounting for the different front wheel diameter than stock. However it started drifting too, first to 93% of actual distance, then to 85%, and last time I checked it was at 75% or so As you can imagine, this has left me almost stranded for gas a couple of times... I figured, since the Sierra's instrument cluster is a clone of the Yamaha TW200/XT200/XT225, and a Tanaka instrument cluster for the XT 600 looked pretty similar (similar to this one) and was reasonably priced to boot, I ordered one, expecting that at least the speedo would fit, although the entire assembly is compatible with the existing mechanical mounts (not so with the electrical one, and no tacho cable on the Sierra...) Indeed, the speedo was easy to remove and fit into the existing frame with no modifications and even matched the existing speedo cable. I adapted it to the lighting harness with some spade terminals, and I have a spare "OIL" indicator light as well... It did work, however it's way off (indicating slower speed/distance), probably because the XT 600 uses a lower speedo worm gear reduction at the wheel= higher speedo cable speed. Is there anything I could do to adapt the speedo cable's speed, e.g. some inline gear multiplier, some internal calibration or an electric speedo drive that could be calibrated? Alternatively, by hacking my old speedo open, is there anything I could -realistically- check and fix by myself? I have some experience working on tape decks, but I reckon the only remotely similar thing would be the tape counter
	0

06-14-2021, 07:31 AM	#3
JerryHawk250 Moderator Join Date: Oct 2016 Location: Houma, La. Posts: 11,588	Did you lube up the cable? Any kinks in the cable? __________________ 2023 Lifan Lycan 250 Chopper 2023 Venom Evader 2022 Lifan KPX250 2020 Kawasaki Vulcan S (Sold) 2004 Honda ST 1300 2016 Black Hawk 250 (sold) Keihin PE30 carb,125 main,38 slow.Pod filter,ported & decked head 10:1 CR,Direct Ignition Coil,15/40Sprockets,NGK DPR8EIX-9,De-Cat,Dual Oil Cooler,Digital Cluster 2016 Cazador180 XL 2014 Coolster150 JerryHawk250.com My YouTube Channel
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06-14-2021, 06:23 AM	#2
ChillRider Join Date: Jun 2020 Location: A small country with a funny name Posts: 164	Hmm...after going for a longer/faster ride, I realized that even the new speedo has exactly the same deviation as my stock one: the odometer indicates 3/4s of actual elapsed distance, and so does the speed (with a reluctance to go above 80 km/h indicated and a weird wraparound effect when I do), exactly as my old speedo did. Also, it didn't fix my needle bounce at all. Testing the old speedo with a drill and a different cable (which however I cannot mount on the bike), showed a smooth operation and no needle bounce at all. So now I start wondering whether the problem is the speedo cable itself, or its sheath
	0

06-14-2021, 09:44 AM	#4
ChillRider Join Date: Jun 2020 Location: A small country with a funny name Posts: 164	I did lube the sheath 6 months ago and replaced the inner cable (sadly, I could not install a new sheath because it had a defective fastener at one end, and it just wouldn't thread where it was supposed to...so I just used just the cable from the new sheath). I even used some Moly DX paste (despite the name, it's not moly based, it's a white lithum-based grease). Maybe it wasn't really up to the task, who knows... Kinks....nope, used the existing routing fasteners as the old one. I will try to fill the thing with gear oil this time, and see how that goes.
	0

06-14-2021, 01:10 PM	#5
franque Join Date: Nov 2017 Location: Marseille, France -> Conakry, Guinea Posts: 1,481	I'd check to see if the gears in the wheel are okay (assuming a mechanical speedo), they could be missing teeth.
	0

06-15-2021, 06:39 AM	#6
ChillRider Join Date: Jun 2020 Location: A small country with a funny name Posts: 164	At first I thought about mechanical damage/stripped teeth too, but spinning the old speedo with a drill (and a different cable) resulted in butter-smooth operation, no needle jumps etc., while the new speedo mounted on the bike behaves exactly the same as the old one...bumpy needle, slow odometer and all, so maybe the real problem lies elsewhere (cable, sheath, or even the worm drive at the wheel).
	0

06-15-2021, 11:29 AM	#7
franque Join Date: Nov 2017 Location: Marseille, France -> Conakry, Guinea Posts: 1,481	I'm talking about the worm drive at the wheel.
	1

06-15-2021, 02:18 PM	#8
ChillRider Join Date: Jun 2020 Location: A small country with a funny name Posts: 164	Yup, that's what I was afraid of... I will have to push the bike on the curb with the spindle gear removed and check it every quarter turn of the wheel or so, I suppose. Though, if teeth were stripped, wouldn't I be hearing all sorts of nasty noises down there? The spindle gear is some type of metal...(bronze), dunno if the rest is plastic.
	0

06-15-2021, 04:51 PM	#9
franque Join Date: Nov 2017 Location: Marseille, France -> Conakry, Guinea Posts: 1,481	Not necessarily, they're pretty small, so it might not make a big noise. Also, the engine is between you and the sender, which I would imagine drowns out a lot of noise.
	0

06-16-2021, 03:55 PM	#10
ChillRider Join Date: Jun 2020 Location: A small country with a funny name Posts: 164	Well, I pulled the Speedo drive's core out to inspect the ring gear. TBQH it looked like a flat, greasy mess everywhere, and yet it still meshed and turned the core somehow... and that's about as mush as I could tell without taking it apart. Long story short, I washed the core in some mineral spirits, and poured some SAE 90 gear oil down their Speedo drive and the first portion of the speedo cable. That seemed to have some effect, as the bounce was reduced somewhat and indicated speed went up a bit. Well, I'll try the cheap fix, remove the cable and flush + relube it.
	0