Chain alignment for non-stock wheel

[rosso75]

So I'm working on a Thunderace swingarm conversion, and trying to figure out which direction I want to go with a rear wheel.  I've looked at several threads where the crush drive was modified, along with other parts, so as to get the rear sprocket to align with the front.  I can't help wondering if it wouldn't be easier to just use an offset sprocket.  The crush drive is there to serve a purpose, so why mess with it? 

Am I missing something obvious?

[Pat Conlon]

If you deviate from Marc's installation shown here:
http://www.fjmods.btinternet.co.uk/MarcRittner.htm

According to Marc's measurements, the unmolested cush drive will add 0.195" to the outward offset on the chain in relation to the counter shaft sprocket.
Therefore, instead of using the oem Honda VF1000 offset sprocket, which has a offset of 0.070", you will need to special order a custom sprocket with a offset of 0.195+0.70= 0.265"....or about ~1/4" offset on the counter shaft sprocket.

I believe Sprocket Specialists can make you such a sprocket. Don't forget to specify the sprocket's countersink relief necessary for the bolt and locking tab to fit on the shaft. I would go ahead and order custom 2 sprockets to have 1 on hand when time comes to change out the worn custom sprocket.

What is unclear to me, is what this 1/4" outward offset will do to the clearance of the 530 chain inside your c/s cover. You may need a XJR sprocket cover.....others can chime in here..

On the plus side, you will have more room between your chain and the back tire.

Hope this helps.  Cheers!

[axiom-r]

I can give some insight here... I mounted a 1/4" offset sprocket from PBI and indeed the stock engine cover would not clear it.  Randy sold me a kit for the XJR cover that included a longer clutch push rod and a longer shift shaft.  The XJR cover has a corner on it that must be removed to easily go on and off past the FJ frame.  I used a hand held grinder and just buzzed the thing- no sweat.  The result was a totally stock looking engine with the 8mm wider cover, push rod and shift shaft.  None of the parts were difficult to instal the clutch basket did have to come off though.  It was an opportunity to get those wire like clutch retainer deals out though.

Once the offset sprocket was done I was able to mount a 6" wide wheel with no clearance issues at all.  I felt like this process was easier than machining a hub or cush-drive.

Do it- you will be happy!

tim

http://www.fjowners.com/index.php?topic=3148.60

[Pat Conlon]

Very cool Tim, thank you....Your bike is sooooo bitchen. It was great to meet you in Porterville. 

[rosso75]

I already have the VF1000 sprocket on the bike.  In reading my original post again, I wasn't too clear.  I was refering to the possibility of using an offset rear sprocket.  If I have to machine stuff, it just seems more logical to me to machine what I need to offset the sprocket.  Modifying the crush drive seems to me the equivelent of cutting a coil spring to lower your car.  It works, but I wouldn't think it's really the best way to do it.


Something like this

[axiom-r]

Very cool Tim, thank you....Your bike is sooooo bitchen. It was great to meet you in Porterville. 

Thanks Pat-  really good to meet you and the others guys too. I had a great time!  Wish I could have gone on to CO but it wasn't in the cards- next year though!

Rosso75- careful with the rear offset as no matter which end you offset you have to deal with the issues it creates.  The countershaft sprocket can be done with the method and kit I used- not sure how you would deal with the clearance of the rear sprocket next to the swingarm...  Anything can be done if you think it through and man are you going to love the updated wheels!

Keep at it!


tim

[rosso75]

not sure how you would deal with the clearance of the rear sprocket next to the swingarm

The object would be to offset the sprocket inward, rather than cutting / machining the crush drive.  The swingarm wouldn't be an issue.

[Pat Conlon]

If I have to machine stuff, it just seems more logical to me to machine what I need to offset the sprocket.  

You will only have to machine the cush drive once..... rear sprockets, on the other hand, need replacing....

Do you want to go thru this exercise every time you need a new rear sprocket?  Do it once and get it over with.

[fj1289]

Rosso,

I think there is a minor misunderstanding.  You are in no way removing the cush drive nor changing it's function at all.  You are merely machining the mounting surface for the sprocket by a small amount.  If you really wanted to get into it, I'd say it would minutely IMPROVE the way the cush drive operates due to putting less of a side load on it by moving the sprocket slightly inboard. 

This mod has been very thoroughly researched - and I'll also say that when Marc Rittner "re-did" this mod, he was very meticulous.  If you need further verification of his thoroughness when modding things - you should see his 200 mph Aprilia - the fastest 2 cylinder motorcycle in the standing mile - anywhere. 

Offset countershaft sprockets are an option - and really needed for a 6 inch rim.  An offset rear wheel sprocket would be a one-off part to solve a problem that does not exist. 

Cheers,     
Chris

[axiom-r]

not sure how you would deal with the clearance of the rear sprocket next to the swingarm tire

The object would be to offset the sprocket inward, rather than cutting / machining the crush drive.  The swingarm wouldn't be an issue.

  Got ya- I was thinking of that the wrong way- but the issue is the same only with the other side (tire side).  The offset rear sprocket is an interesting approach.  I have not read about anyone having done it that way yet...  I would check to see if you can get a small enough sprocket and still get the offset you need- they are mostly for dirt bikes and therefore have a higher tooth count I think.  I dropped to a 38 tooth in the rear and I need to go lower still to get the RPM's back down to where they were stock at 70MPH.  Even though you are fitting a larger rim the over all wheel diameter with modern rubber mounted will drop slightly compared to stock FJ's - this will raise your RPM's and fuel economy.... gotta adjust for that in your gearing. If you mount that 44 tooth (shown) she's going to be a monster off the line but no fun to ride for the whole weekend!

tim

[rosso75]

I find it interesting that I got all this response, and all these suggestions, and nobody even knows (or asked) what wheel I'm using.  As I mentioned in the original post....I'm trying to figure out what direction I want to go with a rear wheel.  The logic of the question was simply, in a perfect world, wouldn't it be better to keep the cush drive intact?

Anyway....

I know there are several wheels that are bolt-in, or close to it with some mods.  Me personally,  I tend to go with the "make what you got fit" approach, rather than the "buy more parts" approach.   I just happen to have an '03 954rr wheel laying around, so that's what I'm working on.

Among other things, my concern right now is the width of the wheel and the alignment of the sprockets.  I know...useless without pictures.  I'll try and post them tomorrow.  My concerns regarding the cush drive are still legit, I think, especially now that I've taken the stock FJ wheel apart.  The rubber dampers in that hub are HUGE, especially on the power side.  I'm assuming it was engineered as such due to the FJ's torque. 

That being the case, I just can't justify modifying what would already be a smaller cushion against driveline shock.  Every wheel mod I've seen already has smaller rubber in the cush drive, and in some cases you wanna cut them down further?  It may work, but what kind of stress are you putting on other driveline components?  As I said, I'm of the opinion that the cush drive serves a purpose, so why screw with it if you have the option of offsetting the sprocket instead?

I'll get pics up.  It just happened to be on my mind at the moment, so I figured I'd post up something.

I appreciate all the input

[Pat Conlon]

So I'm working on a Thunderace swingarm conversion, and trying to figure out which direction I want to go with a rear wheel. 

^^ This was your opening statement.

Pardon me. I assumed that you were also using a T-Ace wheel with the oem bearings for correct axle diameter which fits the axle blocks which fits the swing arm....

Re: Altering the cush rubbers; I agree with you.....We never told you to do that. Again, in the Mark Rittner write up, it clearly shows that you don't alter the cush rubbers at all. You simply remove 0.195" from the *face* of the cush drive....where the sprocket sits (you gotta remove the sprocket studs first)

Re: Offset sprocket; My point was simply that this step, shaving the outside face of the cush hub, is no big deal. You only need to do it once.

If you plan on using a different rim (sounds like you are) all bets (and measurements) are off.

Best of luck.

[fj11.5]

should look great once fitted , what width is that 5.5" ?

[rosso75]

6 inch.....190/50-17

[fj11.5]

sweeet , will be awesome , one fat arse end