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GS450 Tachometer Drive Problem

Nessism

Nessism

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Just joined and need some help, please!! :oops:

Bought a 81 GS450EX for $200 bucks that was sitting since 1988 when it was parked. Got it started okay and now I'm working though some issues the previously owner created years ago.

Tach cable was missing so I bought a new one. Tried to attach it at the head only to learn the drive gear was missing. Pulled the valve cover and noticed that the exhaust cam does not have a gear per say to drive the tach. I checked ebay and saw photos of an 83 camshaft and that one seems to have a proper gear on there to drive the tach. Could someone please take a look at this photo and tell me what's going on?

Thanks.

Ed
 
Last edited:
tach drive

tach drive

Go to bikebandit.com and look at their parts fiche. Looks like you are missing the following parts:

19: GEAR TACHO DRVN [NT:10] 411255-99 $20.55
20: TACHO DRIVEN GR [GS1100ED] 490250-001 $14.71
21: SEAL BAND 490260-001 $2.62
22: OIL SEAL [GS1100ED] 472446-001 $4.25


Good news is that the parts seem to still be available. I stole Bike Bandit's pic of the parts, cropped it (too large a file) and attached it here. Maybe you will be able to see it.

ian
 
Problem

Problem

The thing I'm concern about is the gear on the camshaft; it doesn't seem to have any teeth to drive the other gear.

Ed
 
very odd, it looks like the drive spirals have been machined off the cam shaft.
 
So where the cable attaches is just an open hole? Is it blanked off? Was there something in the hole? In other words, is it supposed to be like that? It does look like the tach drive spirals have been removed. Weird.

But maybe they never existed. I believe that some later models used electronic tachs, but it would seem that you've already established that the tach drive parts should be there on yours. Maybe this bike is wearing a camshaft, head, or engine from a later model..?
 
The tach has the hook up for a cable and the hole in the head contained the housing for the tach gear, only with a bolt plugging the hole instead of having the gear in there.

I honestly don't understand what could have happened. The tach drive gear on the camshaft is ground down very uniformly - not some hack job on a bench grinder. it almost likes it is suspose to be like that.
 
It appears to me as well as though the drive spirals on the cam itself have been machined off. Odd. Never seen that before.
 
Owning an GS450ex -81 myself I can only tell you that it is not supposed to be like that. You will not get a tacho to work with that cam ever again.
What pussels me, like the rest here it seems, is the finish. If the tacho gear locked up and wore out the drive spirals, you would normally get a worn out groove, not completely blank out.
My opinion is that it was machined off, but you should definetly take off the sump and check the strainer for metal filings.
 
Could the drive teeth have been machined off to reduce rotational mass? :-s
 
the only reason I can come up with, is that at some time, possibly on another bike the cam was machined so that they could use the exhaust cam on the intake side to boost performance.
some bikes have more lift and or duration on the exhaust cam, and putting a exhaust cam on the intake side makes for more power.

I have seen this topic on the SV forum being done with SV650's

the tach drive spiral would not clear the casting on the intake side.
 
Bummer

Bummer

My $200 project has yet again slammed me in the wallet! Never again will I purchase a non-running bike! :oops:

Anyone have a camshaft and tach drive gear they want to get rid of for cheap? [-o<
 
Focus Frenzy's post makes more sense than anything else I've seen on this... Reducing rotational mass by that amount would be akin to a sprinter trimming his toenails .125" shorter than normal for the Olympics. Not really a whole lot of difference there. Not a criticism... just a comment on the amount of mass removed.
In retrospect though, it doesn't seem to my tiny mind that the exhaust cam would provide the desired effect installed as an intake cam. I am simply flying blind with this statement, but it seems to me that the exhaust side would not have as much duration or lift as the intake does already... burnt fual/air charge, less to remove from the cylinder than went in. I KNOW that in almost all cases, the exhaust valve is smaller than the intake for this very reason.
G'head and prove me wrong though 8-[ It for sure won't be the first nor the last time that happens :)
 
DaveDanger said:
Focus Frenzy's post makes more sense than anything else I've seen on this... Reducing rotational mass by that amount would be akin to a sprinter trimming his toenails .125" shorter than normal for the Olympics. Not really a whole lot of difference there. Not a criticism... just a comment on the amount of mass removed...
Click to expand...

I agree with you, but this assumes that someone's actions are based in rational behavior.:) For instance, Olympic swimmers (men) and other athletes are known to shave all of their body hair in hopes of going faster. I haven't seen too many hairy sprinters, and they may do the same. I have noticed that after the trimming and shaving, some seem to wear heavy gold chains.:-s
 
I can actually see some logic in the shaving of body hair in swimming. Hair extending out into a fluid would induce a tremendous parasitic drag on a body trying to slide through with minimal resistance. removing the amount of weight (mass) involved in toenails (or tach drive spirals) for rotational mass reduction seems a bit over the edge.
As woozy as it may make ya'll feel to hear it... I come home from softbal games most evenings during the summer and peel the sweaty uniform on the back deck and do a few laps in the pool for the refreshment factor. I absolutely KNOW that the only reason that I splash when I enter the water instead of a silent slip beneath the surface... is due to the fact that I'm hairy as a grizzly and nearly the same size. Instead of "skinny-dipp'n", I "Chunky-Dunk" :-D
 
TMI, Dave. Too Much Information. WAY too much information! :)


Getting back to the topic at hand, it looks like the best option is to plug up the hole so oil doesn't squirt out, button it all up, ride the snot out of it and enjoy yourself. Forget about the tach -- it won't make much difference to your enjoyment. Your $200 was well spent.

If you simply can't live without a tach, there are any number of electronic tachs that should work fine.

Or just put a big smiley face sticker over the tach to remind you why you're riding instead of walking or driving. Or remove the tach and sell it on eBay.
 
Ebay has a pair of cams for $29

Ebay has a pair of cams for $29

and another for $39. I'm still for plugging the hole and riding.
 
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