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FJ Dragbike Project

Started by fj1289, March 22, 2010, 12:39:45 AM

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Quote from: fj1289 on March 24, 2010, 10:33:35 PM
About the lockup – I talked to Orient Express about a month ago.  Late last year they sold the last FJ lockup they had.

This thread was a hit on google and brought me to the site, loving your work man. I'm afraid it was me that got that last lock up but painfully slow project progress means it has yet to be used in anger. Should be up and running by christmas, 1500cc FJ turbo, injection with a tickle of gas for when it gets a little squirrely, sorry about the chassis.

Dangerous Brothers Racing


awesome use of a katana , love those things, , first big bike I rode the day I got my full bike licence  :yahoo:
unless you ride bikes, I mean really ride bikes, then you just won't get it

84 Fj1100  effie , with mods
( 88 ) Fj 1200  fairly standard , + blue spots
84 Fj1100 absolutely stock standard, now more stock , fitted with Fj12 twin system , no rusted headers for this felicity jayne


Havoc - great build!  Post up more pics and details in a project thread - looks like lots of good ideas to learn from!  What front end are you using?  (wondering because of the Yammi blue dot calipers)

I'll be evil and post up pics of the clutch I ended up with instead!  Tim will machine more hint hint!  Would be a great clutch especially trying to launch that turbo!  That's the first blow thru setup I've seen on an FJ. Thinking you'll have more than just 230 with even 5 psi of boost! 

With luck I'll get a chance to get out to the strip on Saturday and start over with the clutch and suspension tuning. 


Finally made it out to the track!

Made the 3 1/2 drive (each way) on Saturday to get to Albuquerque dragway. First time to this track -- Good track - nicer than the others around here, but was hoping for something closer to Bandimere in Denver.

Great to be back at the track again!  Felt very rusty after a   two year layoff - but had a good outing all things considered.  Made a little progress on the rear suspension setup and had another electrical gremlin that took a while to sort out. Only got three passes on - an 1/8 mile pass, an aborted pass (lost the ignition system after the launch due to electrical issues), and a 1/4 mile pass just before they closed the staging lanes. 

Good news - no injuries to the bike or me!  That was actually a fairly large concern after a two year layoff and knowing the rear suspension and clutch not sorted yet... There's also no such thing as "taking it easy" on the launch either - at "go time" it has to be WFO and throw the clutch away - or risk burning up the clutch pack. So in the end I'm pleased with the results -- have a good starting point for next season. 

Bad news - still don't have a good suspension tune. Spun hard every launch - tightened up the adjustable linkage for each pass and added some preload -  the shock bottomed on each launch causing it to spin hard until I backed off the throttle. 

Made some progress - the short times (60' and 330') improved enough to match my best street bike times (so a lot of progress still needed!). Last run was the best 1/4 mile to date -- but still about a second off where it should be by my best guess. 

Best pass this time out:
60'     1.689
330'   4.472
1/8    6.654 @ 113.51
1/4   10.142 @ 139.04

Previous best on the dragbike:
60'     1.905
330'   4.753
1/8    6.955 @ 112.00
1/4   10.504 @ 130.89

Best pass on the streetbike:
60'     1.667
330'   4.489
1/8    6.891 @ 101.94
1/4   10.795 @ 124.67

Density altitude was right ar 5500'. That puts the sea level corrected time is around a 9.5 @ 147

Did get some video this time out - will have to figure out how to post it. Waiting on the GoPro to make it back with the rest of my gear - will be fun to get on bike video next season. 


I hear ya man!   Sounds like some pretty decent numbers even without the setup issues.  :good2:



Been a while...but here's a couple videos from the outing at the end of October.  Disclaimer - amateur video operator!  (And even more amerateur video uploader!)

Here's the first run -- my first run in nearly 2 years!  I backed out after the 1/8 mile.  You can see the tire spin start from the launch.  The rear suspension is still set too soft and bottoms on the launch and causes the tire to spin. 


Looks like the first video may have worked...

Here's the third run from the day.  Adjusted the suspension link and shock preload to help stiffen the rear end - still spins through first gear, tried to feather the throttle to let it hook up. 

This is the adjustable suspension link.  Now it is adjusted nearly to the end of the forward adjustment range (which stiffens the suspension).  I'll order a stiffer spring this winter to help get the suspension dialed in and hopefully put the LinkPro toward the center of the adjustment range. 


Excellent. I have been looking forward to seeing it being used in anger. Sounds awesome   (popcorn)
Dangerous Brothers Racing


i love the sound of a FJ being ridden in anger!  :good2:

Just my experience but i found raising the rear ride height helped tighten the rear suspension and reduce weight transfer for nice hard launches with the front wheel about 6 inches high and just a bit of wheelspin.



Second pass shows it more clearly.  The tail drops and stops before the tire gives up.  If you've got the shock adjustment range left, you can slow the compression damping some, but that's going to make it harder to stick right at the line.

I used to have a really good link that showed how to tweak the pivot changed how fast the rising rate changed, and per usual can't find it right now.  >< Looks like you're on the right path though.


Yes - and that suspension action is a lot better than when I started!  I'm using an ultra high tech bright yellow zip tie around the shock shaft to show how much travel it is using   :good2: 

I need to get the serial number off the shock so I can call Elka and get the spring specs.  I'll try about 30% or so increase in spring rate to hopefully put the LinkPro back toward the middle of the adjustment range.  Right now the shock is set so compression damping is about 1/3 of the range from the min setting, and the rebound is about 1/3 of the range from the max setting.  A little more preload than I'd like on the spring since there is little static sag right now.  The rear ride height was also increased a small amount on the last run (didn't reset rear ride height after adjusting the LinkPro forward after the first run).  Would have been nice to get a couple more runs in that day...

The sound out of the open sidewinder definately makes people notice!  It's just a little fat right now due to the altitude - I think it will sound a bit "sharper" after tweaking the Lectrons!

Looks like I'll be moving to Colorado this spring!  (Just waiting on the formal job offer  :yahoo:)  Will be nice to make Denver my home track -- it is a really nice facillity. Even up there, I think this should go deep in the nines once I get it setup properly   :diablo: 


i'll be a very happy man if my bike is half as fast as yours!  :wacko2:
You can't turn a pig into a racehorse... So lets see how fast we can make this pig go!!


Quote from: backstreetheros on January 26, 2013, 02:17:17 PM
i'll be a very happy man if my bike is half as fast as yours!  :wacko2:

I think you will definately have a traction problem with that hard tail setup!  But is will be great for leaving your mark on the street! :diablo:  Keep up the good work on your build  :hi:

Swapped out the shock spring today - original was a 650 lbs/in rate -- put in a 950 lbs/in spring.  A 950 lbs/in spring is a WHOLE LOT more difficult to work with that a 650 lbs/in one.
Moved the adjustable link from the 2nd mark to the 14th mark (out of 16) and it still feels stiffer than the last setup (moving the link back softens the suspension).  The change in spring rate seems to be a bit more than I intended, but think it will work...the timeslips will tell the tale   (popcorn)

Here's my new suspension setup tool:

Was able to pull the shock with the bike still on the sidestand!  Add or remove air from the ball as needed to take the pressure off the shock - easy as pie!


Been a long time (much too long!) since I've updated this thread. Finally had the opportunity to get to he track last night for a Wednesday evening test and tune session at my new "home" track - Bandimere!  I love this track - definitely a world class facility. It's a huge change from my first track - a little 1/8 mile strip in North Florida. Loved that track too (Emerald Coast Raceway) for all the people and everything I learned there, so I was bummed to find out last week Emerald Coast had closed. 

I managed to squeeze out the time to FINALLY make the first outing of the season. I knew it would be less than ideal since I'd be getting a later start than I wanted.  At 4:00 PM when the gate opened I was still at a local credit union trying to figure out how to get a cashiers check so we can close on our new house (today)!  I've been living out of suitcases for nearly five months since retiring and taking a new job in Denver CO.  Finally got our old house packed up and the family moved out into a small apartment a month ago. Since I don't have a garage yet, all things motorcycle are packed in my utility trailer - another less than ideal way to go to the track.

Finally got everything to the track and pulled into the pits around 6:45.  Unload the trailer, get the dragbike out, grab all my gear, and get through tech pretty quickly.  I'm in the staging lanes by 7:15 and hoping to get three runs in before closing at  9:00 PM. In the lanes I'm behind a beautiful 57 Chevy (2 door of course!) - full interior, perfect body work, looks like a show car with the exception of the "cheater" slicks , racing number and decals on the windows, and battery cutoff in the bumper.

The line is going slow. Seems the track is hooking real well (probably due to running the Mile High Nationals here last weekend). Problem is, a good hooking track reveals the weakness in streetcars. That results in broken parts and oil downs...and track clean ups and a long time to wait to make your runs.

Finally get to make my first pass. I'm lined up with a Colorado State Trooper (sponsors of the test and tune nights) squad car (driven by a cute female trooper!) 

After a long wait, its my turn!  Get the burnout done, make sure the bike is in first gear, and stage.  Watch the lights come down, and next thing I'm thinking is that I'm really slow releasing the clutch and getting the throttle to WOT...and I know it won't be a good run.

Ran the full 1/4 mile (mostly because I had lined up against the State Trooper), roll out, and pick up the time slip.  Don't even look at it as I ride off - then I see the scales. Stopped to weigh the bike - 695 pounds with me on board and three gallons of race gas.  460 without the rider. Good for the bike, but crap!  No wonder the leathers are tight!  Time to start running again...

As I leave the scales I notice the edges of the rear tire covered with oil!  And then see the entire under tail coated with oil. No oil coming from the engine - whew!  Pop the seat and see the oil has blown out the filter on top of the catch bottle on my breather setup.

Ride it back to the pits and pull the seat and side panels. Look at the clock - it's 8:40. Holy crap!  Almost an hour and half for one run. Oh well, back to work - open the drain on the bottom of the catch bottle - nothing comes out?  Pull the hose off the breather and oil runs out of there.  Grab the catch bottle to remove the air filter and there's a puddle of oil where I laid down the bottle...huh?  But I'd already opened the drain and got nothing...

Then it dawns on me -- the compressor drain fitting I used is meant to drain water from an air tank (and usually with some pressure in the tank).  So, every time I've tried draining the catch bottle,  the fitting has been too small to allow the oil out. Over time it has continued to fill with oil - which explains why it pushed so much out this run, and why the problem has been getting worse instead of better as the engine gets run in more.  Glad to figure that one out - really don't want to tear down this engine already - don't think it's got 10 full passes on it yet! 

Cleaned out the catch bottle and the rest of the oil on the bike.  It's after 9:00 now and the track is closed.

Might as well look at the time slip now...yep, lost at least three tenths on the launch - forever on a dragstrip! 

60'          1.908 
330'        4.700
1/8         6.897 @ 112.85
1000'      8.796
1/4        10.418 @ 138.30

Should be easy to improve on those numbers next time out! 

The General

`93 with downside up forks.
`78 XS11/1200 with a bit on the side.
Special edition Rocket Ship ZX14R Kwacka