Hello! Just bought a 1985 xj700 bobber (vid)

Hello everyone,

So I just acquired a 1985 xj700 bobber, and i am already drooling over being able to ride this spring. This my first road bike! Paid $2100.

https://docs.google.com/file/d/0Bwk6x8d ... sp=sharing

How does it sound? Comments? How does the idle sound to you guys?
After reading threads about carbs sticking and all that, I figured someone may be able to tell from this video if something sounded way off.

She runs great and has lots of torque, engine was just rebuilt 5000 ago and starts right up!

The PO said it seemed the gas would run out on the quick side, with no speedo or gas gauge it was hard to estimate mpg. I wonder if the individual air filter pods and the custom 4 to 2 exhausts indicate some improvements made during rebuild that may sacrifice mpg and increase performance?


After reading tons of posts I plan on pulling the rear brake and inspecting for delamination before I test ride anymore. Maybe change the oil out of both the shaft and engine, and change the horn to something more....how do you say.. Fitting.
Looking forward to many rides on this beast.
Thanks for this awesome forum making this a hell of a lot easier for newbies.
Nick

 

Honestly?

I strongly suggest you check your valve clearances and then do a compression test IMMEDIATELY.

Depending on how "rebuilt" the motor was, it may be about 2000 miles overdue for a valve clearance check. Or it wasn't as "rebuilt" as you were told. More like sprayed black and screw it, it runs.

Even more importantly, it appears to have original brake lines. They have date codes printed on them, year/month. If they're over 4 years old, as in original, they need to be replaced ASAP.

Sorry, you asked for opinions and I'm simply being honest.

 

Dude don't be sorry, i like the bike and all but you arent insulting me! how else will I learn!

I'm not sure if this bike was supposed to sound like this or not.

 

I prefer the sound of a bike with mufflers but that's me. I think yours sounds the way it should with headers only.

Your horn sounds horrible because either you have only one, or only one out of two works. I hear only one note, each horn is supposed to have its own note. Also, it would be louder with two working horns.

There is a small screw on the back of the horn (if I remember well) that you could turn in or out to improve the sound.

 

Or bring the horn to life.

 

i like the look of it

 

Thanks I'll look into the horn issue too.
Hopefully it's adjustable!

Can't wait to ride this thing

 

Welcome, I agree that you are best taking Fitz's advice and making sure all's well with clearances & compressions (if the motor's properly rebuilt you shouldn't need pressure washer/donuts or even valve cover gasket if you're lucky) Even if you do, it's better than trusting someone elses engine work IMO. Would be interesting to see pictures of what the sparkplugs look like too.

Doesn't sound too bad for a custom exhaust AKA open collector box & pods, but it's 100 times easier to replace shims than it is to replace valves. Plus you get to see inside & judge for yourself how honest the seller was about the rebuild

Again welcome & nice looking bike 8)

 

Hey Slipnick, welcome aboard.

regards to this :
< quote >
I wonder if the individual air filter pods and the custom 4 to 2 exhausts indicate some improvements made during rebuild that may sacrifice mpg and increase performance?
< /quote >

Opening up the breathing ( both intake ( pods ) and exhaust ( 4-2 straights ) ) will require more fuel to balance the air/fuel mixture. So, in a general sense, doing both ends at the same time is good. But, I would submit that with this improved breathing, the PO possibly did the correct thing and jetted it correctly. Which this means you have bigger jets to accommodate the improved airflow.

This all means that there is probably more performance, and less MPG. The PO may have been fine with this, but it also opens the door to not knowing what's what in your motor, as mentioned by the other posters in this thread.

And, this also means that it's possible the PO didn't change the jets, which will mean that you are running lean. Lean is more air in the air/fuel mixture. Lean is bad in that more air means hotter running motor, which can wear things much faster, and also put holes in the piston ( had one ).

So knowing your jetting is important, as you have major differences in your fuel / air supply.

( my apologies if you already know this, I just wanted to be sure you were aware of what's happened in your bike, if you didn't know ).

You can check the plugs to see if they are light and dusty ( lean condition ) or if they are tan ( good ) or if they are black and sooty ( rich ). To further adjust, like BigFitz said, valve adjustment needs to be in order, then properly setting carbs, and I think a colortune is the key for properly adjusting the air/fuel mix.

hope this helps, and I like the looks of the bike. I'll have to listen later.

 

Thanks for the insight and kind words.

In the near future this inspection of clearance and compression is in the cards,
I have a mechanic buddy that can lend a hand with the technical stuff.
As for the spark plugs I planned on inspecting them ASAP and will report my findings. I'll also be checking for gasoline in the oil.

The sound really resembles an old muscle car to me. Which I enjoy.

 

Yes I like a nice rorty exhaust too, one you can feel not just hear :twisted: (ever seen 2 top fuellers go side by side? your eyeballs vibrate!)

Seems you're doing the right thing & reading up on what to look out for anyway so that's a great start, when you say ASAP you mean before you ride right? Would HATE for it to hole a piston on you 8O

When you know she's fuelling OK are you planning on more video footage? Me wanna hear some more 8)

 

The most recent po rode ~500 miles as is and had no issues.
Maybe I will bring it in sooner than I planned and have a look.
Of course I will be checking the plugs first.

An ounce of prevention...

And I absolutely will be recording more video dude. Coming from a 454 Chevelle I enjoy the rumble man.

 

Like you say, an ounce of prevention costs nothing in time or money to whip the plugs out and just see they're not bright white, specially with the mods you have (CV carbs can be finicky with pod filters, there's lots of debate on their use haha I'm not even gonna kick that hornets nest )

Fantastic I'll keep an eye out for the vids. Whats a 454 in English, about 7 litres?

 

I was told it was bored out a bit 30 over so probably more in the 462 range
It's was a 70s truck v8 so probably 7.2

Had to sell the thing for an apartment.
That's just how it goes !

 

I must say i love the sound, mostly because it sounds like my bike. Loud pipes save lives! From the video it looks like to PO removed one of the horns, there were originally 2. But its a nice looking bike

 

Skipnick,

Welcome. Slick bike.

Gary

 

Pull your rear wheel and check for delaminating brakes too....

 

Thanks for this detailed explanation. I am pretty green to the mechanic side of
Life but this all makes sense. So I will have to check my jetting, which could be indicated by the spark plugs being blackened, showing that I am running too rich. In which case I should go a number down or two on jet size until it burns clean.

 

Upload a video of your bike from your phone like i did!

I'd love I hear it.

I agree, this quiet bike stuff can't be safer.
Gotta upgrade the horns.

 

<quote>
Thanks for this detailed explanation. I am pretty green to the mechanic side of
Life but this all makes sense. So I will have to check my jetting, which could be indicated by the spark plugs being blackened, showing that I am running too rich. In which case I should go a number down or two on jet size until it burns clean.
</quote>

Well, that's the basics, but it gets a bit more detailed.

There are items that affect the air/fuel mixture :
1) air incoming ( air filters, carb shrouds, etc )
2) pilot jet ( for idle and low running)
3) main jet ( for normal running )
4) needle jet / needle ( normal running )
5) air/fuel screw ( fine tuning air/fuel mixture )
6) valves ( duration, lash, etc )
7) exhaust ( backpressure, or lack of it )


Here's a great bundle of threads from Chacal, the local parts guru and wiz:

http://www.xjbikes.com/Forums/viewforum/f=23.html

On that page of threads, this one in-particular is very informative:

http://www.xjbikes.com/Forums/viewtopic/t=27544.html

also

http://www.xjbikes.com/Forums/viewtopic/t=36344.html

This last one really shows the workings of the carb, so you get a 'direct' feel for what's going on or not. The link before has a carb section down in it that helps explain some of the symptoms of carb - mis - alignment.

-

To get back on your question about just changing jets, yes, you can, but you'll just be guessing unless you know how to verify and be sure you have the jetting set correctly. And if you're going to figure out how to verify, you may as well do the job right, and get it done correct the first time.


BigFitz has this awesome post about checking the valves, being sure they are in correct adjustment. Here's a super walk-thru :

http://www.xjbikes.com/Forums/viewtopic/t=14827.html