Thunderbird Sport Gearing.

I don’t know if a previous owner altered the sprockets on my bike and made it low geared but I don’t particularly like a bike revving it’s nuts off on cruise.
Mine is at 4250 rpm at 60mph and 7000 rpm at around a 100 mph, with only Bout a 1000 revs to go. I’d be happier if the revs were down to 3000 for 60 mph to give a less revvy 80 mph cruising speed. Is my bikes present gearing normal? Has anyone gone up a tooth at the gearbox? My wheel sprocket looks about as small as I could go, so I’m thinking a dodge might be trying to get away with changing the smaller sprocket with one a tooth bigger while retaining the present chain and wheel sprocket.
Anyone else done this?

 

Cheers. Just looked on eBay for the front sprockets and see they range from 16 teeth to 20. Mine is probably a 16 tooth one, so I’ll be going for a 18 or 19.

 

Yes understood. It looks like there's a good inch of rearward rear wheel movement on the adjusters, and the chain and sprockets are all good. So for a £20 counter sprocket it looks like a possibility even I need to rivet in some additional chain.

It is also quite hungry on fuel so this might not only save on the buzziness but save a bit at the pumps.

 

Well that’s a crap design! After carefully removing the 8 mm headed bolts and gear change, and seeing engine/gear oil leaking out, it obviously involves changing the oil again. Just done that 200 miles ago so won’t be bothering with that for a few thousand miles.
A bit of a bugger just to confirm how many teeth are on the counter sprocket in order to buy one with a tooth or two extra.

 

Well I got sick of the bike buzzing away almost flat out at 100 and at over 4000rpm at 60 mph so I laid the machine over on a post to save my new oil pissing out and changed it.
It was a 17 toothed counter sprocket and I’ve changed it for a 19 toothed one.
Haven’t had it out on the road since the change but even going down the driveway it doesn’t need an up change. Perfect!
I can see why the gear change rod needs the support of a needle roller bearing as it comes from the R/H/S of the bike, but to need to lubricate it with engine oil seems a little excessive, when greasing it occasionally would have been more than adequate

 

Done a couple of hundred miles now and what an improvement. 1000 rpm less for the same speed as previously. I can only assume the previous owner rode and lived in town and didn't bother with going any distance on it.