maximum speed

81 xj 650 h

so, my max speed seems to be about 80. 65-70 is normal acceleration. after that it's tough.

that's always been my max speed. the whole time i've been trying to fix the bike. so it don't matter what the carbs are set at. even when the bike ran like crap.

everything is fixed now but my max speed didn't improve. neither did m y gas mileage.

140 lbs compression in all 4 cylinders.

is the chip in the tci maxed out at that speed? is there any way to increase max speed. i've had a tci that ran like crap. and a replacement tci so now the bike runs like a champ.

back in teh day when the bike was produced. speed limit was 55 mph. so i'm wondering if the thing is even capable of anything faster.

 

I have had my 81 Maxim faster than that, so IN THEORY yours should also be able to go faster than that, although our speedos only show 80.. I estimate I hit about 95 or better before letting out of the throttle because the steering was getting a little wobbley and I didnt want to wipe out at 95mph, that would be BAD.

 

And now Snowwy begins the quest to do "the ton" !!

I think you're good for 110 MPH, check out "worldsfastestxj550"

http://www.xjbikes.com/Forums/viewtopic/t=7135.html

 

not on a quest to do a ton. but it be nice to have some accelleration on the freeway. i'm going to be toast with a passenger.

the bike runs like a champ now. but if it's capable of faster speeds. then i guess i still gots some work to do.

and it be nice to get more then 100 miles per tank. like my first bike did when it was brand new 25 years ago.

 

Generally speaking ...

As Miles per Hour --> Increase.

Miles per Gallon ---> Decrease.

 

yeah, but 28 miles to the gallon. isn't that a little pathetic. my 82 xj650 i bought in 84 got 60 miles to the gallon. i'm sure you all are getting wayyyy better mileage then my 28.

 

28 Miles to the Gallon ... ???

What are you doing?

Towing a boat?

 

:lol: :lol: :lol: :lol: :lol:

 

since there's a crack in the left muffler and a hole blew in the right muffler before she got to running right. i'm wondering if the mufflers are plugged. i've got aluminum plates for band aids right now covering the holes.

 

Wow!! 28mpg is not right. Neither is the 80mph. I don't think exhaust has much to do with it. Unless it is plugged pretty bad. I think I would be pulling the plugs and making sure your not running too rich. I would also check coils and wires and caps. Make sure all your connections are clean.

My old 81 650 would do 100mph 2-up and got 45mpg. I think you have some more investigating to do.

 

Mine's pretty much the same.

 

caps and plugs are new. plugs are golden brown now. coils throw spark up to 10mm gap. dealer tests at 6mm. so ignition is fine. i've either got a limiter somewhere. that previouis owner installed. flat cams. or plugged exhaust. and since i've got holes and cracks. i'm thinking plugged exhaust. to which i might want to fix before any more holes blow. and from the looks of things. can't just pull the mufflers off and test drive. the schematic shows the mufflers with 2 connectors each. into the headers. plus the crossover pipe.

wished i could just pull the baffles out. and see what happens on the freeway.

last year i had a 94 ninja 600. i took the 15 tooth front sprocket off and put a 17 tooth on. to lower the rpms on the freeway. it did 100 easily and averaged about 52 mpg.

 

Have you checked valve clearance?? It should have been done before the carbs were fine tuned. It's pretty time consuming but like everything else, it needs to be done to get maximum performance/mpg. out of these machines.

 

previous owner had valves adjusted, looks like 4 shims were used. carbs cleaned and synced, new intake and rear boots with gaskets. according to his repair ticket. but after seeing the poor quality of the work so far. who knows.

bike does sound pretty quiet now since the tci box was replaced. the old box was running advanced timing, sounded like loose valve adjustment. apparently it was pinging from premature detonation.

i know i never had the valves adjusted on the first model i had 25 years ago. sold it at 42k miles. but i don't think i ever maxed the bike out back then. but 60 mpg it was still getting when it was sold.

 

Have you done a compression test on this engine?

 

These motors get quieter when they wear. Quiet is not always a good thing. It would be worth a peek. "SOME" tappet/lifter noise is normal when they are adjusted properly.

There is a variety of opinions when it comes to the position of the cam when checking clearance. I for one like to position 180 degrees opposite the lifter/shim bucket. I've always done it that way and it works for me with NO Problems.

Something else I would check is the ends of the wires going into the cap. They get a little corroded. Snipping off a 1/4in and reinstalling the caps might be a good idea.

I'm just blown away how this bike doesn't have very much power and gets terrible mileage.

How many miles have you put on since the new plugs were installed? I've always had to drive a couple hundred miles before the plugs would give a good color reading. Unless it was running too rich. I know my 650 ran on the lean side and I could go 3 seasons without changing the plugs. And THEN, changed them just to do it.

 

forget the valves. they all checked out. and as far as i can tell. the lobes are fine also.

i've driven the bike about 500 miles so far. forget the plugs. caps. wires. and carbs also.

140 compression all 4.

has to be plugged mufflers. maybe i'll straight pipe the thing. and richen the jets. hehehe

 

Ok I could understand the exhaust could explain the "No Power" But how would it explain the mileage?? The fuel has to be going somewhere.

 

Power at Full Throttle is a function of how well the Main Fuel Jet Supply gets delivered.

IF, ... your Emulsion Tubes are clogged:
You are waisting gas ... because its getting sucked-in without atomization and not getting burned well-enough to make big power.

Clogged E-Tubes are a cause of low MPG.

 

Since everyone is standing around scratching their heads- -
I might as well suggest checking the cam timing might be off.
And the odd chance that the brakes are dragging; they are on my 750.

and for some entertainment- -

http://www.youtube.com/watch?v=jwieel03c-w

 

cam timing checked. i think the bike would run like crap all the way around if cam timing were off.

emulsion tubes were checked when i was trying to get the bike running in the first place. that led to the tci replacement.

thing that gets me. is we have a summit called parleys. heading easting out of the city. 6 - 8 percent grades. it don't matter if i'm driving around town or the summit. 80 is tops. and it's a struggle to get there. if i drop my speed while climbing that summit. say down to 60. i can forget getting back to 80. if i'm around town. it'll happen. but it kinda struggles.


the bike cruises along just perfect at speeds under 70. barely any throttle. it'll climb to 80 without much more throttle. but anything over that, forget it. open that throttle all you want but nothing happens. no spitting or anything. just sits there and cruises at 80. but has a tendency to drop off at the slightest uphill grade. unless the throttle is opened up quite a bit. it might hold.

it's like there's a limiter holding it back.

 

Well Snowwy,
When you get it figured out please let us know what you find or it will be like watching a 2 hour movie and then missing the last 15 minutes to see the outcome. I'm curious.......

 

i've already got holes in the mufflers. now that i've got the bike running. next chance i get i'll pull the band aids off and see what happens. see if has any more umph on the freeway breathing out the holes.

very first bike i had was a 72 yama enduro 2 stroke 125. top speed was 20. one day the muffler fell off and the bike took off and did 60.

momma was pissed cuz that was the sole reason i was allowed that bike. it had no speed. that was back when i very first got my license to drive. 1982

 

original coils? how bout wires? sorry if this was mentioned already

 

I can run my seca 400 all the way to the redline in 6th, which is just over 100, so there's gotta be something wrong.

I had a buddy who used to complain that his 500 ninja was too slow. I didn't have the heart to point out that he was 300 plus pounds, and that might have something to do with it.

 

unfortunately for me. i don't weigh anything over 220. and i'm 6 ft tall.

 

I am also curious to find out the issue here... keep at it!

 

Petcock OK? No kinks in the fuel line to the carbs? Clogged fuel filter? Sounds like a fuel limit issue not a spark or timing issue. if it was electrical you would feel the ignition retard a bit. It's not fuel injected so the computer can't controll the fuel delivery. See if the weak link is before the carbs... not after.

 

ok folks. here's an update

first got the bike. crappy throttle under 4k. max rev at stand still was 7k.

replaced the tci. got better lower rpm response now. much better driving conditions around town. got throttle ALL THE WAY to max rev at 9k. but still crappy freeway speed. and bike has to be warmed up a little for smoothest response on the lower rpms.

today i cut the mufflers off and put straight pipe.
crisp throttle response RIGHT OFF THE BAT. and NOW it snaps to 10.5k at standstill. without even warming up.

i tried the original tci and got the same crappy throttle results. so i'm sticking with the replacement.

STAY TUNED. i need to clamp the pipes down and i'm hoping to pick up some washers for backpressure and hopefully reduce the noise.

THEN I'M GOING FOR A TEST RIDE.

 

Have you checked your clutch adj lately?
The plates may not be seating at high speeds do to
ware or warping.
They may not be grabbing enough and the bike has
to work harder then it needs too. You may not feel a significant
slip. This may also account for your milage prob as the motor
must work harder to keep her going.

 

EDIT::::: thought the problem was solved but apparently not. straight pipe improved my gas mileage a bit. but top speed actually dropped.

i couldn't even gain speed GOING DOWN a 7 mile stretch of 6% down grade. 65 mph and that's IS ALL SHE WANTS. up hill or down hill.

someone posted a video of a suzuki with a limiter. now that i've got straight pipe on. that's exactly what is sounds like.

 

mine cruises up to 55mph smooth as can be. anything more than that get what i think is a chasis vibration. my spedometer has red line from 55 on up anybody know why? oh i get 60mpg with mine.

 

By any chance is this a reduced effect bike?

 

I had inadvertently turned the sync screw betreew 3 & 4
when I first bought the bike.
I had a very similar effect. She ran fair but would not
clime above 65, and there was quite abit of vibration in the mirrors.
Once I did all the proper carb cleaning and sync'ing she cleared
right up.

 

This is a real head scratcher...

Sorry if this has been asked but what ya got for an air filter? Also, is the petcock screen clear/in line fuel filter?

My Honda was like that too. She got up to 60 fairly OK, but after that she was gutless. I ended up removing the petcock screen, and putting in an inline fuel filter. Then I replaced the stock (old) air filter with a higher flow K&N. I had to run her through the colortune again, but now she climbs right up to 90 with no problem(with only 47hp I might add)

 

the red line at 55 was becuase the speed limit was 55 back then.

 

new vacuum line
new vacuum ports
new intake gaskets
new plugs
new caps
carbs cleaned and synced along with fuel switch
new shorter fuel line and took out fuel filter. direct gravity feed to carbs.
new mufflers ( although they're glass packs instead)
valve adjustment checked


we're now up to a speedy 85mph. has no problem climbing to or holding 85. and that's as far as she goes.

 

"new mufflers ( although they're glass packs instead) "
go up one size on the main jets