Engine getting tired? Or am I just fat?

[MACHV]

Greetings Gurus,

I recently did a top speed test and ringing this 89 3CV out, it accelerates up to about 125 (GPS speed) and seeminly hits a wall and won't go faster.
Variables are:
36,600 odometer
Rider and gear comes to about 290 lbs ( suspect variable)
FZR 17 in front wheel.
GSXR 1100 17 in rear wheel.
New Mich PR 4GTs (180 rear)
New brake pads.
New chain.
New plugs.
Clean K&N air filter.
Drilled out air box.
Everything freshly greased.
Cobra F1s cans packed with Course SS.
MRA Touring windscreen w/o spoiler.
No luggage.
Running 18/38 sprockets (also suspect)
Does not smoke but uses almost a quart of oil in under 1500 miles.
Smooth road.
Fresh wax job and second fastest color.

How fast would you guess this bike "should" go if the engine was really healthy?

[FJ_Hooligan]

What jets/needles are in the carbs?

Are the carbs clean?

At 36K, the engine is barely broken in.

[krusty]

RPM @ 125?
Max RPM & MPH in 4th?
When changing from 4th to 5th what happens re acceleration?

[fj1289]

x2 what Krusty asked. 

If you've added gearing, it'll probably slow you down - lowers RPM for given speed, so less power available to accelerate with. 

Also body position?  How well tucked in?  Toes down?  Or feet flat with heels pushed down?   Elbows in?  Butt back on seat as far as you can?  Body tucked down just far enough to "catch" the airflow coming off the screen to try to smooth out the flow a touch?  Or flat on the tank letting the air go up and over and create more drag?  Touring screen = taller?  Bigger hole in the air AND more drag behind you from the "dirty" air not being able to come back together smoothly?   

Road perfectly flat?  Or possibly some slight uphill grade? 

Lots of variables!  Sounds like it's running well though

[Pat Conlon]

Compression #'s?

I agree with David, that engine should be fresh.

If your compression is ok, it sounds like you are running out of gas (main jet) but then again, you said rider and gear = 280lbs?

[Millietant]

Mine runs on 18/38 sprockets, has 80,000 miles on it and comfortably hit 135 mph GPS on my Garmin unit (speedo reads about 142-143 mph) two up with my top box on, with plenty more to come it seemed.

To be honest, these days I don't really bother with really high speed runs but on a deserted stretch of, shall we say...autobahn, at the end of 2018, I ran it up to that 135 and it just cruised along like it was out jogging.

Back when I was younger, and riding it at the Nurburgring, the speedo needle would hit the 165mph mark  down the back straight between the gantry and the exit lane no bother, as long as there wasn't a headwind - probably a real speed of between 150 and 155 mph which is about the best I'd guess anyone could hope for out of an "untuned" FJ (mind you, I'm just shy of 5'8" and weighed about 150lbs at the time - thankfully, I'm still only 155lbs, 15-20 years later  ).

[fj1289]

I'm 5'11" and 200 lbs, my son about 5'8" and about 140 lbs — he was 4 mph faster than me on the race bike on motor.  My best on motor was 158 mph, he ran 162 mph.  Size does make a difference too!

[Pat Conlon]

Unless it's a GPS unit, don't rely on your speedo, look at your tach, use the gearing table to determine your top speed.

[Millietant]

Unless it's a GPS unit, don't rely on your speedo, look at your tach, use the gearing table to determine your top speed.

Do you use Gearing Commander, Pat ?

[Pat Conlon]

Hey Dean, no, we made it easy....we have a separate File Section just for gearing.
Back in '09 Chris P put together 6 tables with different back tire sizes for mph vs rpm.
http://www.fjowners.com/index.php?topic=669.0

I use the last table for the 180/55 tire and 18/39 gearing.
Now, we know not all 180/55 tires have exactly the same circumference and that tire circumference changes as the tire wears down, so these calculated speeds based on rpm are just a very close approximation.
Still, much better than the wiggling needle of the speedometer.

Cheers

Pat

[Millietant]

I started using Gearing Commander because we had so many bikes in the garage (11 back in 2015) and I was always playing around with sprockets (and changing wheel and tyre's sizes) to get each bike's geaing to suit.

The other forums/groups I'm in don't have their own dedicated gearing data .......FJ Owners leads the way, as usual     

[ribbert]

Also body position?  How well tucked in?  Toes down?  Or feet flat with heels pushed down?   Elbows in?  Butt back on seat as far as you can?  Body tucked down just far enough to "catch" the airflow coming off the screen to try to smooth out the flow a touch?  Or flat on the tank letting the air go up and over and create more drag?  Touring screen = taller?  Bigger hole in the air AND more drag behind you from the "dirty" air not being able to come back together smoothly?  

A comprehensive list Chris, obviously you have researched wringing every last mph out of your bike, but......



....have you tried changing gears with your left hand yet?

Noel

[MACHV]

I have never actually speed tested this machine until recently. I was always satisfied with how fast it passed 100. But after the sprocket changes I decided to take it out onto the newest, smoothest road rural Illinois has to offer and see the results of 18/38. Again, I was surprised that it seems to go right up to 125 like its going to go right thruough and it's like it hits terminal velocity. Eventually will try the old gearing and see if the powerband is better used with those.

[fj1289]

Are you winding out 4th?  Try taking 4th to redline before shifting to 5th - 9500 in 4th should put you in the neighborhood  of 140 mph - then try shifting to 5th. 


Just a quick word — be VERY SURE of your surroundings!  Many years ago on a causeway (no side access) I got my 89 up to 136mph (per gearing, tire size, and RPM) and saw a car up in the distance...so I looked down at the tach, rolled out of the throttle, and figured I'd just coast down to a reasonable speed before I got to the car - NOPE!!!  He got VERY close VERY quickly!  Lesson learned!

Even at the Colorado Mile at a formal event - had to stay very focused on the finish line and the braking zone - 1/2 mile isn't much to slow down in at some of those speeds! 

[fj1289]

Also body position?  How well tucked in?  Toes down?  Or feet flat with heels pushed down?   Elbows in?  Butt back on seat as far as you can?  Body tucked down just far enough to "catch" the airflow coming off the screen to try to smooth out the flow a touch?  Or flat on the tank letting the air go up and over and create more drag?  Touring screen = taller?  Bigger hole in the air AND more drag behind you from the "dirty" air not being able to come back together smoothly?  

A comprehensive list Chris, obviously you have researched wringing every last mph out of your bike, but......



....have you tried changing gears with your left hand yet?

Noel

Well, yes!  But only using my thumb - on the air shift button on the left bar!

Cool pic - do you know the back story?  Where was this?