Need help with gearing please?

[Tuneforkfreak]

I noticed on my first ride I was continuously trying to grab another gear that wasn't in the box. I think my bike is stock gearing 17/40 and that seemed to put me around 3 grand at 55 MPH . I'd like to be cruising at 65 or 70 but don't want to wear out the engine to do so. ( I'm not sure what safe RPM's would be for this bike) Can anyone tell me if they've made gearing changes to achieve the same cruising goal and if so what I should be shooting for if anything? I don't care so much about low end but I don't want it to struggle to get going and burn up the clutch either. Any info would be much appreciated.

[Pat Conlon]

Start with a 18 tooth countershaft sprocket (aka drive sprocket)

http://www.rpmracingca.com/products.asp?cat=39&filter=Sprocket

See how you like that....

Then play with a 39 or 38 tooth rear sprocket.

Here's some gearing tables to give you an idea of your results.
http://www.fjowners.com/index.php?topic=669.0

[Tuneforkfreak]

  Cool man thanks so much! That's exactly what I was thinking,I looked for that sprocket all over but didn't think they went above 17 T. Got that ordered along with some other stuff RPM had like the side cover grommets. I hope my chain is long enough now.

[Pat Conlon]

I hope my chain is long enough now.

You will be fine with the 110 link chain.

[jr1349]

the stock gearing on my model xjr is 17/38, some others had 17/39 & 18/38, bearing in mind we use 17" wheels with modern tyres, the 18T front is what everyone does, and imho, it makes very little difference.

I now use 20/37 gearing on the road for 116kmh @ 3500rpm, which is about 70mph I think, I'm sure someone will set me straight on the mph.
I had the 20T custom steel front sprockets made in the US, had to have 5 of made as they wouldn't do a run of one, I've still got a couple of new ones left, was only about $150 for the lot from memory, ill dig up the name of the mob who made them if anyone is interested, I'm pretty sure they are a pretty well known sprocket manufacturer over there, but also, I'm pretty sure a 21t, or possibly even 22t, front sprocket will fit fairly easily, there's mobs of room in there, and 1 tooth makes about 2-3mm difference in radius from memory.

the 37t rear is custom made in oz by chain gang, they wouldn't make me a custom front sprocket at the time but now I believe they do so next time I'm up for chain and sprockets ill hit them up for a 21 or 22 front as well, after I've double checked my measurements.
I would have had a 36t made for the rear but the clearance on the rear sprocket bolts will be nil with one of these.

however, and this may interest some of you with 17" wheel conversions and who like fuel economy as well, fz1 and r1 rear wheels, and the like, usually come with a smaller pcd for the bolt pattern on the rear sprocket than what my xjr has, and you can purchase 35t sprockets for them straight from JT's for bugger all, so what does a 18/35 JT sprocket combo cost I ask, well my 16/46 JT combo that I use for the drags cost about $50-60 aus.

as far as how high first gear gets for standing starts, well that comes down to what your comfortable with I guess, I do have to actually bobble the clutch a little in order to coax mine of the line, and its a little worse on hill starts, but I don't find it an issue, unless your trying to have a drag from the lights, still, ill be happy to try a 21t front sprocket with my 37t rear with my next set of chains and sprockets.

food for thought maybe, well that's only if you blokes aren't aware of this stuff?

anyway that's where I stand on gearing.

k

[charleygofast]

Check out the "Kookaloo and beyond" post and the 60 replies. I think we all have felt this way. FJs are revvy critters and like to "go fast".                                              Cheers, Charley.

[jr1349]

Check out the "Kookaloo and beyond" post and the 60 replies. I think we all have felt this way. FJs are revvy critters and like to "go fast".                                              Cheers, Charley.

is kookaloo and beyond a separate thread, I've seen a couple of threads about kookaloo, but I'm not sure what its got to do with gearing, feel free to steer me straight Charlie

k

[FJmonkey]

This site is fun to play with http://www.gearingcommander.com/

[charleygofast]

Check out the "Kookaloo and beyond" post and the 60 replies. I think we all have felt this way. FJs are revvy critters and like to "go fast".                                              Cheers, Charley.

is kookaloo and beyond a separate thread, I've seen a couple of threads about kookaloo, but I'm not sure what its got to do with gearing, feel free to steer me straight Charlie

k

Its in "what did you do to your FJ today" it sort of morphed into a gearing discussion.

[Tuneforkfreak]

Monkey that site is cool! Jr, I don't think you need to change gearing to find the Kookaloo but it may help in some cases......  I found a Kookaloo the other night, I was just riding along minding my own business,I turned the corner and there it was plain as day, just looking at me with a grin . It ran off in front of me quick as lightning but I was determined to catch it so I grabbed the twisty grip and off we went. That Kookaloo was so fast I barely caught it.  I've never  had Kookaloo before so I was curious to get a taste of it. I thought it was good! However, it was a bit greasy and it was covered in bugs. Yes Charlie, Revvy critters indeed

[novaraptor]

I'd like to be cruising at 65 or 70 but don't want to wear out the engine to do so. ( I'm not sure what safe RPM's would be for this bike)

It does feel like you are running at high rpms in the 70 mph range, but trust me, you aren't going to wear the engine out at those speeds... You aren't even at half the max rated output yet. But sure, the gearing can always be changed around a bit to lower the rpms.

[Tuneforkfreak]

I'm getting comfortable with it now, seems to be nothing to jump this bike into the 70 mph and you don't even realize it. Honestly it seems like 4 to 5 grand is where this bike really starts to make power.

[movenon]

I'm getting comfortable with it now, seems to be nothing to jump this bike into the 70 mph and you don't even realize it. Honestly it seems like 4 to 5 grand is where this bike really starts to make power.

  And you don't have to be on the brakes as much. 
George

[novaraptor]

I'm getting comfortable with it now, seems to be nothing to jump this bike into the 70 mph and you don't even realize it. Honestly it seems like 4 to 5 grand is where this bike really starts to make power.

If you like it at 5 grand, you're gonna love it above 6 grand..

[Bill_Rockoff]

At ~22,000 miles and completely stock, mine made peak torque at 7,000 rpm and peak power at 8,500 rpm.  I'll have to find my dyno chart and recreate my hp-vs-rpm spreadsheet from three computers ago to get other data points, but it's pretty strong at 5,000 rpm.

Gearing a bit taller wouldn't hurt anything.  I found the stock gearing on my '89 to be fine, but the conversion to a 17" rear wheel and 160/70 tire does spin a bit faster at the same speed so my effective gearing is shorter these days.  Maybe an 18T next time around would be the ticket.