Vroom's 79 Build Thread- scrambler/brat?


XS400 Addict
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SouthEast FL
Finally able to make some progress and decided it was about time to start a thread and track my progress:thumbsup:

I've done an intro somewhere else, so we can just skip that:doh:

The bike: 79 xs400, 12.5k miles when purchased, dual disk brakes
Location(for tuning purposes): South FL, so sea level at all times :shrug:

The day I got it...

Home at last. Removed the big screen right away:thumbsup:

Will consider selling the touring screen for the right price...:laugh:

First ride impressions:
1) Front brakes might as well be non existent:wtf:
2) Engine seems solid, revs well and steady idle
3) Clutch seems to slip when grabbing a heavy hand of throttle; but gets better as the bike warms up? :shrug:
4) Newer tires in good condition, but not the best quality
5) Starter button loose... then just popped off:doh:

Build starts... lots of research on here:thumbsup:

New ally buttons from KimbokoJoe... great quaility

Bars gotta go...

Trackers bars in and mirrors removed...:bike:

The tank was surprisingly clean inside, so I went ahead and dropped in a fuel filter and new clear lines...

Cleaned her up a bit and went for a ride:)

Picked up a spare fender and did a quick shorty fender... Thanks Volcom!

The plan was to make it flat black, but the more I see the tank, the more I think I may color match it in dark blue.

XS pods in 53mm size from MikesXS arrived:D

I should note that the 53mm size will fit both direct on the carbs and also over the H-pipe... that was a big question for me and hopefully it helps others:thumbsup:
Pulled off the carbs and they are pretty clean:D

Bad news is my carb boots are all cracked up! I had inspected them before orderign and they seemed fine, but the second I shook the carbs all the cracks appeared:banghead:

(trusty shop hound in the pic:laugh:)
I've heard of some people using sealant or something rather to fix them... any suggestions?

Pilot and Main Jet replacement went smoothly. 150 Mains and 45 Pilots.(132.5 and 42.5 stock).

I may still go with 50 Pilots later...:shrug:

I was also going to replace the wires, plugs and caps but ran into this little snag...:wtf:

How are the cables supposed to be switched out? Looks like they are glued in...:banghead:

Wrapped it up there... started right up and was running great:thumbsup:

Doing a front brake bleed and fresh oil on tomorrow. Getting ready for a vintage meet tomorrow night, so looking forward to some saddle time:D

Next stage is to get the wires on, with new caps and plugs... soon as I figure out how to deal with the wires being glued on:doh:

Also an oil change and clutch adjustment are in the card. I'm hoping that adjusting the clutch will help with the slip.
Those coils are the 77-79 4ohm coils and where stock for the bike.
xschris: Thanks! It's def got some more pep now. A lil popping here and there, but overall an improvement:thumbsup:

drewpy: Are you referring to the new clear lines? If so, no, the fuel line isn't pinched. It's got a slight kink in it, but not affecting the flow(at least not that I can tell anyway :shrug:)

So does anyone know what I should do about the coils and wires? I already have the new wires, caps, and plugs and would be pretty irked if I can't put them on:doh:
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Items completed today:
1)Brake fluid flush and refill with new DOT3. Made a world of a difference:thumbsup:
-Not too surprising considering this is what came out:yikes:

It wouldn't surprise me if this is the oem fluid from '79:laugh:

2)Adjusted the brake lever, but I am pretty sure I will tinker with it again.

3) Removed all 4 blinkers and rubber supports. They were in perfect condition, even the rubber mounts. Almost felt bad pulling them off, but I have no intention of keepin blinkers on her. Made me realize how much I really need to chop off that rear hoop and change the headlight mounts...
-Willing to sell the blinkers if anyone is interested:D

4) Removed the oem chain guard. It was mint too:thumbsup:
-Had to remove the rear shock to get it out. Only afterwards did I realize the shock on the other side was on backwards... will have to remove and rotate it in order to adjust preload:doh:

5) took a nice long ride:bike:
-Much more bottom end and more power throughout the rev range. I was expecting some flats spots but none to be found! I guess I got lucky on the first shot:thumbsup:
-Fiddled a bit with the throttle stop screw mid ride to get the idle right. 1.4k seemed just right
-Will probly tinker a bit with the idle pilot screws, but I intend to do an oil change to heavier weight before riding more. Considering the condition of the brake fluid, it could be bad to keep going on this oil...

low on pics today, but I'll keep at it:bike:
Not much to do with the coils wires. You can change the caps. As long as the coils test fine I would not worry. My 79 has 30k miles on the coils and still test fine.
Thanks guys:thumbsup:

I guess I am a lil irked that I got the XS wires from mikes XS and can't put them on now. I'll figure it out at some point in the near future, but I guess the caps and plugs will do. Any tips on changing the caps on the 79?

No rush on that though. I'll be focusing on an oil change and new seat setup.

I guess the plan is to go with 20w50 motorcycle oil since 20w40 is hard to find.

I've seen some posts about a battery switch but none seem conclusive for me. What is the minimum voltage and amps required to run my 79 xs400 and KEEP THE STARTER?
-needs to be solid battery(agm or gel) and ideally lighter, but more importantly smaller.
-my understanding is the stock battery is 12v/12amps... would any size 12v/12a battery do?
-If smaller is not an option(seems unlikely though it may be pricey) then it will need to be something I can put sideways, as I plan to lay it flush under the seat. AGMs can be put in any direction right?

Wish I had a full week to to just wrench on her...:doh:
To keep the starter you will need a 12ah battery. A 12ah gel will be a bit lighter and maybe a little smaller but not much. You can mount them any way but they still need air flow around them. They do make a micro 12ah battery but they are like $150 or some crazy price like that. Caps are easy to change , just unscrew the old ones cut a little off the end of the wire to get a clean fresh connection( make sure you still have enough length to connect to the plug) then screw the new ones on.
So after looking into it, looks like the options are a shorai for 148 or an off brand for less(though im not too keen on these) or figure out a better way to mount it....

My ideas are down to the following now:

1) create a smaller battery box with everything tucked int the same area(using a smaller batter) so there would be no need for rewiring, and the battery would only poke out a lil under the seat. I call this the $150 option lol

2) get and AGM battery and make a box that would do the sams as described above, but have the battery laying down. It would be tucked up as close to the seat as possible. So it would be a much shallower, but wider box and it would only stick down the width of the battery. Maybe a lil less than that thickness? This would be less cost but need the agm battery.

3) This option would be to relocate the battery to box at the bottom just above the swingarm. Remove the oem battery box and put something flat and think to hold all the electrical items. I've seen this done on some other bikes and I like that I would not need to change my battery and also could scale down the size later fairly easily. It would give me that "open" look up top that I am going for plus make the battery easily accessible. Just not sure how to mount the new box and how to extend the wires for the connection. Could I just add extensions to the oem ones? Might also swap for lighter agm with this option too, but no ned to rush on it.

What do ya'll think? 1, 2, or 3????
Got the oil change done last night:D

Picked up thee recommended oil:thumbsup:

Starting point...

Not as clean down hear as I would've hoped:doh:

Warmed her up then let the fluid drain...

This stuff was dark:yikes:

Pretty sure this is just regular old oil, which may explain my clutch slip:(

Out went the filter...

Out and new seals in...

Everything bolted back up and no leaks:thumbsup:
So went for a test run and the engine did just about everything better! Idle was smoother, revs were faster and more crisp, and just a lil less vibration(though not much lol).

Only down side is the clutch is still slipping substantially:banghead:
It got a little better after a long ride, and I am hoping it will continue to improve. Otherwise I will need to be new plates and HD springs... or maybe I just need to adjust the clutch? I need to find a good writeup on doing clutch adjustments:doh:

Does everyone have the clutch slip when first riding then improve with the engine warming?:confused:

Also, doing the oil I noticed the rear brake may get in the way of my "option 3" battery plan... I've seen it done on other bikes, but not sure about how to space it out on the xs...:shrug: