Hey...long time, no talk! I have a speedo-swap question:

[ERM83]

So, I'd posted about having a good mishap on the 80' SG, but was going to just replace the SG speedo (which was DESTROYED by a half-fallen tree) with the SF speedo at some point, anyway. Well, I finally did, but ended up breaking the cable nut that actually goes INTO the bottom to the 80...thought I'd try to sacrifice it, but NOPE...didn't know how to get a replacement nut. Being that I was putting the 79 speedometer on, I got the cable to replace the old one as well. EVERYTHING is working well, MINUS the speedometer. It runs slightly (say, 7-10mph) behind. I know how fast i'm going, based on riding that thing with the original on there for quite a while. Here's my question: what is off?? I tried to search through here, and I have no Idea. does the mechanism on the front wheel need to come off the 79, and be put on the 80?? I saw something about ratios...I'm just in the dark here. I know that a bunch from 78-81 fit, but what about the cables/wheel mechanisms??? if it's "plug and play", then is something going on INSIDE the speedometer??

Sorry if this post is jumbled, and nonsensical...I've been working A TON, and kinda sleepless, haha. this is a question for TOMORROW, when I've ACTUALLY gotten more than 3 sporadic hours of sleep!! haha.

thanks, everyone...

Eric

[DiverRay]

The grease in the "new" speedo is what, about 40 years old? It's probably hardened up a bit, and causing a lot of drag. ALL Yamaha speedo's from the mid '70's up should work. They are set up for the same revs per mile. The other problem MAY be the cable.
For the speedo, remove it from the bike, flip upside down and spray some silicon lube into the cable connection. Flip the speedo upright about 10 seconds after hitting with some lube so it does NOT flow into the faceplate.
For the cable, spend $20 and buy a new one. That way you don't need to worry about the inside of the sheath or the condition of the cable.
This is AFTER a good 6 hours or more of sleep!