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Jack15T

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Hey Folks, I have a 74 850 MK2 with a very erratic Tach. Any suggestions as to where I can send it for repair would be greatly appreciated. The cable is good. Cheers, Jack
 
I just rolled new bezel on my commando green dot. Wasn’t that hard just turned a peice of round timber in my metal lath for the face to fit into then g-clamp together. Slightly tapped the edge over then worked my way around by hand rolling the edge. I’m very happy with the end result looks factory correct
 
Could be a worn cable or the cable not sitting right, be the first things I be looking at, if its the gauge they do need lube, not much, I had mine rebuilt about 15 years ago the original speedo was damaged by the great fire of 83 and just recently the tac needle has dropped off and is sitting inside so got to remove the bezel to fix it, my speedo did the same thing a few months after the rebuild I took it back to the place that rebuilt it and they reinstalled it for free, I have it in the cabinet and using the Triumph Smiths gauge I been running after the great fire, a mate gave it to me after the great fire of 83 lol.
 
If you have a motorcycle which does not need to look original as a road bike, a good tachometer is the one on the Suzuki RG250 road bike. Later ones were electronic, but it is the earlier magnetic one to which I am referring. It is almost an exact copy of the tachos which were used on 1950s and 1960s European race bikes, except there is a small Suzuki 'S' on the face inside it. The rubber mount on it is an exact fit for the mount on my Seeley frame. The tacho is the required 2 to 1 ratio to suit the Commando motor, and the gearbox on the back of it is reversible by undoing two screws - just turn it over to the other side.
I have 3 of those tachos - they are cheap from a wreckers.
 
If you have a motorcycle which does not need to look original as a road bike, a good tachometer is the one on the Suzuki RG250 road bike. Later ones were electronic, but it is the earlier magnetic one to which I am referring. It is almost an exact copy of the tachos which were used on 1950s and 1960s European race bikes, except there is a small Suzuki 'S' on the face inside it. The rubber mount on it is an exact fit for the mount on my Seeley frame. The tacho is the required 2 to 1 ratio to suit the Commando motor, and the gearbox on the back of it is reversible by undoing two screws - just turn it over to the other side.
I have 3 of those tachos - they are cheap from a wreckers.
Many people probably do not know what the tachos on early race bikes used to look like. I was stoked when I found the RG250 tacho - it looks so genuine. My Seeley 850 looks as though it is from the era, but many people cannot see what I see. If it was in a museum, I would detect where it is non-genuine. For many people, if something will do the job, it is good enough. One of my mates said 'at least your bike looks right' . He got upset when I called it a 'shit-heap'.
A nut and bolt perfect Manx must be worth a lot these days ?
 
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One day my tach started to bounce. First I lubed the cable, didn’t help. Next I bought a new Venhill cable, lubed it per their directions... didn’t solve it. Sent my tach to Vintage British Cables in Canada. They refreshed it but didn’t think anything was wrong based on their bench test. They suggested I buy one of the cables they make on-site. Against their advice, I passed since I already had a new cable. Once I put my restored tach back on, it still bounced. So I replaced the tach drive and housing. Nope, still bounced. Finally, I bought a new cable from Vintage British Cables... and now my tach works perfectly, zero bounce!

They restored by speedo as well as my tach, beautiful work, my gauges work and look new.

 
One day my tach started to bounce. First I lubed the cable, didn’t help. Next I bought a new Venhill cable, lubed it per their directions... didn’t solve it. Sent my tach to Vintage British Cables in Canada. They refreshed it but didn’t think anything was wrong based on their bench test. They suggested I buy one of the cables they make on-site. Against their advice, I passed since I already had a new cable. Once I put my restored tach back on, it still bounced. So I replaced the tach drive and housing. Nope, still bounced. Finally, I bought a new cable from Vintage British Cables... and now my tach works perfectly, zero bounce!

They restored by speedo as well as my tach, beautiful work, my gauges work and look new.

That is very Good, useful info..
Thanks for sharing…
 
One day my tach started to bounce. First I lubed the cable, didn’t help. Next I bought a new Venhill cable, lubed it per their directions... didn’t solve it. Sent my tach to Vintage British Cables in Canada. They refreshed it but didn’t think anything was wrong based on their bench test. They suggested I buy one of the cables they make on-site. Against their advice, I passed since I already had a new cable. Once I put my restored tach back on, it still bounced. So I replaced the tach drive and housing. Nope, still bounced. Finally, I bought a new cable from Vintage British Cables... and now my tach works perfectly, zero bounce!

They restored by speedo as well as my tach, beautiful work, my gauges work and look new.

So, was there a substandard aftermarket (pattern) cable on the bike causing the bogus operation, or?
 
My speedometer bounced at different speeds even after lubing cable , gear drive and installing new cable.

Fully frustrated i call British cables, told them what i needed and they sent me a heavy duty cable. Much more robust than the normal cables i had bought before. First thing i noticed was trying to turn the inner cable by hand was difficult . There was what i believe a lot of resistance .. I made a call to British Cables and explained my concerns. The bery nice lady advised me that a properly lubed cable should have some resistance . The lube helps keep the inner cable from flopping around in the sheath .
I asked her what i should use to service my cables in the future. This is what they use .
I would recommend British Cables . I believe i paid $65 Cdn for my Mk111 canle
 

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So, was there a substandard aftermarket (pattern) cable on the bike causing the bogus operation, or?
Yeah, I was able to isolate the problem to the cable. The VBC cable came pre-lubed with Sil-Glyde, and Joni mentioned their inner cables are "wound correctly". Venhill recommends using gear oil, which I initially tried to use on their cable. After talking with Joni, I tried Sil-Glyde on the Venhill cable, but it didn't help. So perhaps there's something more going on than just the lube. Interesting comment by Ron on resistance since the tach bounce behaves like the cable is being overly twisted by the drive. At one point I suspected the cable drive bit wobbling in the drive gear since there is some play, even in the new drive gear.

Btw, a trick that Andy mentioned to help isolate a bad tach vs the cable or drive was to use the speedo cable to drive the tach at a low speed. It just reaches once I removed the soft ties and in fact my tach did spin with very little bounce.
 
Use an electric drill to spin the tach up to see if it is the problem or the cable. Counter clockwise rotation.
 
One day my tach started to bounce. First I lubed the cable, didn’t help. Next I bought a new Venhill cable, lubed it per their directions... didn’t solve it. Sent my tach to Vintage British Cables in Canada. They refreshed it but didn’t think anything was wrong based on their bench test. They suggested I buy one of the cables they make on-site. Against their advice, I passed since I already had a new cable. Once I put my restored tach back on, it still bounced. So I replaced the tach drive and housing. Nope, still bounced. Finally, I bought a new cable from Vintage British Cables... and now my tach works perfectly, zero bounce!

Same issue I had after a couple of seasons, same solution too. Don't know why, but the Vintage Cables seem to work better.
 
I've had more than 30 instruments restored by Vintage British Cables and I usually use their cables. 100% satisfaction with 0% issues. If you want to understand why they are better take the time to read their home page: https://vintagebritishcables.com/

Some things they can do for you that they don't talk about and that they don't charge extra for are:

Using your speedo or tach, turn it into whatever one you need. I buy up bad ones not worrying about what they are from and then say what part number I want.

Set the mileage to whatever you need. If you don't ask, they come back at zero, but for an actual miles bike you want to set to actual.

Look up exactly what speedo and tach you are supposed to have.

Repair them in almost any condition. The can must be good and the basic internals must be there but that's about it..
 
The tacho on my Atlas quit altogether one day after being intermittent on a few previous rides. I did the basic troubleshooting by spinning a cable core in my finger so see if the needle jumped, etc. Eventually I figured out that the cable core was a hair too short and the end had just barely engaged the tacho head. It was no longer square, rounded a bit. A couple of other cores in the drawer were also too short. So I cut a nip of cotter pin the right size and dropped it down the drive-end fitting to shim the cable up about 3/16". Tach now works fine as it ever did.
 
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