FJ2400 - Bonneville Land Speed Racer

[freakhousecustoms]

Does 15-20% slippage jive with what you've experienced?  If I remember correctly that was kind of the range I was expecting to see. 

Scott Guthrie has a series of articles where he talks about twin engined bikes and cars.   The simplified logic was for salt beds more weight = more traction and more power = more speed, so adding an engine gives you both!

15-20% jives... BUT - it is all hinged on the actual Salt conditions, which vary from year to year.

2014 - ZX14- I pinned the speedometer at 190mph, but when I picked up my timeslip, it read 167.563mph! :-O
Now this was my 2nd time down the Salt, ever, so I made the HUGE rookie mistake of simply PEGGING the throttle.  If I had just modulated my right wrist better, I should have seen 180-ish.    This was my first year, but everyone else said the Salt was WET  "worst conditions " they'd seen in years

2016 - I blew my bike up - only 2 runs no data collected

2017 - The Salt was like CONCRETE!  Records fell right and left.  I am still a n00b, but in my opinion, I would say MY bike had ZERO slippage (when both wheels were touching the ground... but that's another story)  I saw 130-131mph on a stock GS1100E motor and that's actually better than what the internet says it should run.  I only expected 120-125mph accounting for slippage.

2018 - First year with the dual-engine bike, had troubles with the bike itself, but the Salt was SOLID that year too, IF I had gotten my bike to run right, she would have laid down the 150-160mph I was hoping for, I am sure of it.

2019 - I am still pretty new to LSR, but even I can tell you that the Salt was WET!  On top of that, it was wet and the track was choppy.  VISIBLE ruts, which I had never experienced in my previous years,  I tried every single trick I had learned over the years and ALL my bike would do was slip.  I do NOT blame the Salt conditions for my "slow" speeds, but it definitely was a factor.  I would also say the slippage AND at a lower MPH than I expected.  I actually did the math just now and IF I expected 150mph then -20% of that is 120mph.  160mph - 20% is 128mph and I could not exceed 124mph.  I still consider 2019 a failure, but I feel a little better about it now. LOL

There are SO many factors that contribute to a successful (and SUPER unsuccessful) Salt run.  Compared to

[freakhousecustoms]

Nothing is set in stone yet, but I am getting very close to that time where I will need to make some decisions before/while I build this frame.

I've owned these FJ's for... 8 months now and today was the very first time I ever looked at the rear sprocket.  It's so CUTE! 
I have to count the teeth still, but the interwebs says it should be a 40T?  But if i'm lucky the one bike could be a 39T? Is that right?

If so, I don't see how i can go much smaller on a stock wheel...  is there a trick to running a 32T?  I mean, those bolts look pretty close to the chain already.



I'm used to a 630 chain and GS rear sprockets.  The smallest I have on hand is a 36T, but I'm definitely NOT going to run a 630 chain on the new bike


Option B is to run my ZX-14 rear wheel, and the pro would be that I could get a wider rear tire (190) and hi-speed tires are more readily available, but the con is that I would have to get an axle, swingarm and rear shock... $$$


Plan C would be using the Hayabusa axle, swingarm and rear shock that I also have... but no rear wheel... which is just about the same $$$ as getting the ZX14 parts.

I guess Plan D would be to have a conversion axle made to run the ZX14 wheel with the Busa rear bits... but again... $$$$ 

Honestly, I'd rather use the FJ parts if I could.  So any advice, tips and tricks would be greatly appreciated!

[fj1289]

Ok - as usual, a few ways ahead.  

My "solution" was purchasing a set of PM Chicane rims several years ago.  The rear has a solid aluminum drive hub so can take a very small sprocket.   Not all that feasible here.  

Of the other wheels you are considering, what is the smallest sprocket they can take?  I'm thinking none of them will get as small as you'll need.  

On your final drive solution, what's the largest "front" sprocket you think you can run?  May be a creative way to avoid the small-sprocket-needed-on-the-rear problem...

Ok - no other alternatives - modify the sprocket carrier and hub and get creative.  Random thoughts on that:

1. Narrow the cush drive as much as possible.   Turn down the sprocket mounting face on a lathe (good thing you have a friend with a lathe!).  Then trim more off the back side "dogs" on the cush drive.  Then trim the "webs" on the rim.  Then trim the cush drive rubbers to allow the whole thing to sink deeper into the rim.  You will probably need to trim the face of the wheel hub that goes into the cush drive too.  Is your friend's lathe large enough to check the entire rim into?  If not, how competent and confident are you with an angle grinder?!

B. WTF did I recommend all that - all it did was narrow the rim setup - still stuck with the same size hub and sprocket limitations - and misaligned the chain run?!!  Now, machine an adapter with a flange to bolt to the "old" sprocket mount, then extends out a little bit at a smaller diameter with a mounting face to mount a smaller sprocket.  This should give clearance for the chain for a smaller sprocket.  And should clear the swing arm.

Orange.  Another option - throw out the cush drive.  Trim the "webs" in the rim.  Fabricate a new cush drive that accomplishes the above.  You could even use a DIY liquid urethane motor mount kit to pour new cush drive "rubbers" to engage your new cush drive dogs.  

&.  Maybe some other solution?  Find an older Yamaha shaft drive rear wheel with the bolt on hub (most? all? later shaft drive rims used a cush drive system, so is not much different from the current issues).  Remove the gear drive hub and fabricate a new solid hub to mount a small rear sprocket.  If you use the dimensions from a PM hub, you can use the 109Z series sprockets from sprocket specialists.  

V.  I will try to get pics of the PM hub, and sketches of hub ideas.

Clear as mud?  I wonder what other ideas will get floated - there are some seriously smart, talented, and very experienced people on this board!




Also a QUALITY 530 chain will be plenty!



Another also - I have a Blackbird rim that could receive the above treatments - and accepts the FJ axle - and would mount a 180 wide (or 170 for a flatter profile) 17" tire.  Long story - the Blackbird rim is not a "typical" FJ mod - I bought it as a GSXR rim since it had been on the rear of a GSXR race bike.  Let me know if you are interested in it - it'd be willing to loan it for the duration of the effort.  

[freakhousecustoms]

Orange.  Another option - throw out the cush drive.  Trim the "webs" in the rim.  Fabricate a new cush drive that accomplishes the above.  You could even use a DIY liquid urethane motor mount kit to pour new cush drive "rubbers" to engage your new cush drive dogs.  

Clear as mud?  I wonder what other ideas will get floated - there are some seriously smart, talented, and very experienced people on this board!

Also a QUALITY 530 chain will be plenty!

1/B/Orange/&/V - LOVE that, because I do that as well. 

I didn't think of Orange.  Right?!?  I don't need "cush" on the Salt.  I've DIY'd my own urethane bushings (years ago), so it's not a monumental task.
Drag bikes don't even have a cush drive... and I'd like to roll this bike down the drag strip also.  I bet Pueblo would let me...

Thanks for the insight, my mind is now a'whirl with the possibilities.

[fj1289]

I modify quite a bit.  My basic tenant is to always try to make the mods on the least expensive, easiest to replace piece.  If not possible, then modify the most durable piece.  Don't want to get stuck with a one-off broken part you can't easily replace!

[freakhousecustoms]

Speaking of modifying...  I'm hoping you guys don't end up hating me after watching the next video.

The $500 bike was just that, a bike that was slowly returning to the earth, stored outside, sometimes covered by an awning.  The $1000 bike had been laid down... now I'm thinking on BOTH sides.  Definite evidence of a crash & slide on the right side, but now that it's apart I think it was crashed on the left previously and someone actually "fixed" the damage that time. 

I'll be using as much of the stock parts as I can for the build, and I already have plans to use the extra front end, wheels, brakes, etc in a future bike. 

[fj1289]

Other thoughts - you may want to find a late swingarm - they switched to steel at some point.  A little more weight on the rear wheel.  Also easy to weld tabs for bolt-on weights.  You may find someone willing to swap for one of you aluminum arms.

Greg Waters showed up for the 2015 or 2016 Colorado Mile with his bike still in Bonneville setup - I think his total weight for bike and rider was over 900 pounds!  Lots of weight IN and ON the swingarm.  

[freakhousecustoms]

Other thoughts - you may want to find a late swingarm - they switched to steel at some point.

WHAT?!?    Now that's a good bit of info to know.
Anyone want to trade?!? I have welded aluminum before, but it's not pretty - literally or structurally.  I've got a couple friends I can go to to do the bracing for me, but if the swingarm was STEEL?  That would make it so much easier.

It was always my plan to run BMST then the CO Mile the next weekend, but I could never keep a bike together long enough. LOL!  I was bummed when they cancelled the event.  I have Salt friends that run The Texas Mile, which I think is in March... and it's not out of the realm of possibility that I have this bike together enough by then... 

[fj1289]

Other thoughts - you may want to find a late swingarm - they switched to steel at some point.

WHAT?!?    Now that's a good bit of info to know.
Anyone want to trade?!? I have welded aluminum before, but it's not pretty - literally or structurally.  I've got a couple friends I can go to to do the bracing for me, but if the swingarm was STEEL?  That would make it so much easier.

It was always my plan to run BMST then the CO Mile the next weekend, but I could never keep a bike together long enough. LOL!  I was bummed when they cancelled the event.  I have Salt friends that run The Texas Mile, which I think is in March... and it's not out of the realm of possibility that I have this bike together enough by then... 

The second TX Mile event is usually in October each year .....

[freakhousecustoms]

The second TX Mile event is usually in October each year .....

Yes,  Oct never seems to work for my timeline after BMST.

[freakhousecustoms]

Episode 3 - I finally get the frames/engines mocked up, so I can get a good look at how the bike is going to lay out:

Click pic for video:

[racerrad8]

Gearing...

Chris had a lot of great suggestions. I think there is one was not expounded on as a viable option with stock parts and not have to do a ton of work.

I would suggest turning the wheel around and have the chain from the jack shaft to the rear wheel be on the right side. Have the jack shaft (engine) drive side be on the same side obviously, but run the jackshaft across the bike and drive the rear wheel from the opposite side. Then, the rear sprocket can be what you already have or that will fit the stock cush drive. The all you have to do the change gearing will at the output sprocket on the jack shaft.

You will just have to modify or fabricate a brake caliper brake and get a longer brake hose from the rear master cylinder to the caliper if you turn the wheel around.

Randy - RPM

[freakhousecustoms]

This is another fantastic idea!  Let's see if I got it right:

How big would I run the (4) front sprockets? Does that make a difference in this scenario?

I ran a jackshaft on the GloWorm, so building/setting one up isn't the problem.  But with the Juggernaut, I'm trying to get the wheelbase as short as I can.  The 3-4" I'd need to fit a jackshaft is what I'm trying to steal now while I'm building the frame.  Now, running a 9 foot long bike isn't a problem for me, but getting this bike to 9 feet or less is my current plan.  Definitely something I'd like to experiment with for a future build though.

[freakhousecustoms]

Just because you said "Jackshaft" - I had to share my "3 Chains" video:

[fj1289]

Is it feasible to increase the bore of the holes in the frame for the swing arm pivot shaft And weld in cups to hold roller bearings?  Then use roller bearings in the swing arm pivot?  And run the jack shaft as the swing arm pivot?

  Never mind - that would put the final drive chain run outside the swing arm

Another unorthodox idea - run the jack  shaft through the swing arm aft of the shock mount.  Again, would require some major welding to the swing arm...

Or reverse rotation camshafts and simply turn the engines around .... ok .... a little cost prohibitive probably....   and you'd have to figure out how to reverse the starter rotation ...