Resurrecting a XS400RJ for a friend of mine who just got her MC license

gpounce32768

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It only has 2500 miles on it, but sat indoors for at least 20 years (otoh water got into the tank rusted lots of holes in it) but having cleaned the carbs the bike is running great- everything else works. I opened up the AF screws a bit and balanced the carbs, doesn't seem like it really wants new jets but I could do it if strongly recommended.

New tires etc are coming, will clean and regrease all the suspension links when the wheels are off. When I do the fork oil are there any suggested tweaks to viscosity/amount? I did a Nighthawk's suspension a year or 2 ago and the win there was slightly more and thicker than the OEM spec to improve damping and stiffen them a bit... wondering if something like that would be suitable here?

Sure is nice to work on an almost new 40yr old bike lol; nothing rusted solid or beat to death- just gummy... OTOH that tank is going to be a pest... going for sanding & derusting, metal putty and POR15 and crossing my fingers.
 
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Not all putty is fuel-resistant. If you are patching a through hole, be sure to check what the label says.
 
copy that... got it from POR along with the prep/coating and rust dissolver- so its compatible. Apparently, before curing it can be easily shaped with a wet finger, hoping that I can feather the stuff on the visible portion of the tank.

getting the new tires on the wheels tomorrow...
 
Drained and refilled the forks- the caps are quite interesting. I found a light push on the plugs with an arbor press would afford access to the locking rings with a dental pick, getting them out is easy at that point (not like fighting with a circlip)- so for sure find a way to have a 3rd hand or similar to push them down. Oil was the usual dirty and smelly brew, put in the new stuff.

236cc's of 10w on the 82 XS400RJ

Once its on the road if it needs more damping I'll add some 15w- besides the greater viscosity adding a bit of oil should increase air pressure a bit when the fork compresses.
 
I had a moment of glory yesterday- strapped a temp bottle of gas to the frame and rode down the driveway- 1st time the bike has moved under its own power in 20+ years. lol, but the new rear went flat as soon as I started moving, I think the shop which put the new tire on kept the old tube which failed.

Its tedious to bleed the front brakes but they're maybe 70% there, enough to fiddle around in the parking lot across the street. The bike isn't tagged so I'm not going anywhere in any case. The new front brake pads needed some filing in the hole for the retaining pin. It looks like the proper pads but the hole is not quite right. Might be due to the off-brand manufacture... we'll see how they shape up in use. I still have the old OEM pads which could be a step up.

Engine is tough to start but runs well once going... a bit skeptical of the carbs still but might be the little temp bottle needs to be mounted a bit higher to push enough gas into the carbs for starting. It sure is nice balancing these dual carbs, so easy to reach everything- was a pain doing that on my old Bandit.
 
Filing the pad slide hole is fine for getting them to fit but do make sure it is filed large enough to slide freely, plus some wiggle room for heat expansion. You don't want it dragging when fully hot and everything grew from heat. Otherwise, congrats!
 
copy that, thanks! I got the fit to be approx the same as the OEM pads.

This weekend is prep for sealing and coating the tank... looks like its been blasted with a shotgun, a line of holes all around the outside and underside maybe at 1/8th of a tank or so- I guess thats where the old fuel and water sat for years. I've been poking all the rust bubbles with a small screwdriver, finding all the holes. Going to sand that whole line down today, shake a bunch of ball bearings inside and get the tank into the rust dissolver overnight. I ordered some paint which is supposed to match, so at least the repair won't look really horrible. I'm giving it a 50:50 chance of working...
 
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Whew a long haul getting this bike sorted. POR15 in the original tank was a complete failure- too much rust left for it to stick and even a couple seams are leaking also, so its a long term project now. I got an an ebay 83 maxim tank which is a sort-of fit- the pucks fit but its a bit shorter so needed some fabbing to make up a bracket to support the tail of the tank. The lines don't quite work but its passable. I had a body shop fix up the maxim tank good lord the $$$, but at least its a good tank and workable in the long term. As for the old tank I'm going to try soldering brass gauze over the lines of holes, then having a friend try fairing and painting it.

Went thru the carbs several times- needed new float valve seats and needles but the carbs are nice and tight now; left one was leaking fuel so choking out the cylinder. Power is noticably better. I eventually realized that it takes little while for the carb bowls to fill; with the diaphragms closed theres very little air venting out. So lesson learned; let the bowls fill before trying to start and the starting circuit needs the enrichener open and throttle closed. Given all that, the bike starts up nice and easy.

Both main jets were 117.5's so I drilled out the left to approx 127 as per the assymetric jetting these bikes seem to have.

The carbs in this bike are shorter than others I've seen on ebay etc, demonstrated by the airbox boots not fitting over the carb intakes- they dont' reach far enough out of the airbox. The ebay xs400 seca carbs are clearly longer, so the boots fit them. Otherwise the carbs seem identical. So the solution was to remove the boots from the airbox; pry them loose so both the mounting flanges are outside the box instead of one flange inside and one outside. That moves the boots 1/4" or so forward so they clamp onto the carbs properly. Probably they aren't as airtight as a proper factory setup, yet the fit is snug so its certainly better than before. I suppose a bit of silicone sealant around them wouldn't go amiss... something to do next time I have the carbs out I guess (lol, hopefully never) I'm inclined to think the boot seals and air filter are fairly important to increase the vacuum which helps improve the slide's responsiveness.

on edit- I'm inclined to bet these are '81 carbs which look shorter from the pics I've looked at, that year having a different airbox and longer boots.


I was about to call the bike roadworthy but the front caliper locked on me- master cylinder wasn't letting pressure back into the reservoir. I'll keep an eye on that, maybe try a different rebuild kit if it acts up again.


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I was about to call the bike roadworthy but the front caliper locked on me- master cylinder wasn't letting pressure back into the reservoir. I'll keep an eye on that, maybe try a different rebuild kit if it acts up again.

Did you replace the hose?

That type of lockup often happens if the hose deteriorates inside (can look totally fine outside) and the particles clog the small orifice in the master.
 
I haven't but been thinking about replacing them. It took a bunch of work to clear the old solidified brake fluid out, the hoses are now quite open and clean. But that said, if they're decomposing inside...

on edit; I see the apex brakes option, replacing the 2 lines w/ junction block with a single line. I think I'll do that- the 2 line idea seems silly.... the old OEM rubber lines are not filling me with confidence anyway.
 
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Changing the oil fooled me, I had thought opening the oil filter cover would drain the oil- not so- only a very little drains from there. The bulk of it comes out when the drain plug next to the filter cover is removed. Before I realized that I had about 6 liters of oil in the crankcase lol... so at least the engine got a good rinse.
 
6 liters - holy crap! Let that thing drip a while as there is probably a lot stuck way up inside that will take a bit to work its way to the bottom.
 
I haven't but been thinking about replacing them. It took a bunch of work to clear the old solidified brake fluid out, the hoses are now quite open and clean. But that said, if they're decomposing inside...

on edit; I see the apex brakes option, replacing the 2 lines w/ junction block with a single line. I think I'll do that- the 2 line idea seems silly.... the old OEM rubber lines are not filling me with confidence anyway.

You can't really tell if they are decomposing unless you cut them, but... 40 year old rubber... yeah. Not real inspiring. I replace them on almost every old bike I buy, just on general principle.
 
Put on a single brake line- HEL, brake feel is much improved. For the '82 xs400rj Seca, about 34" would fit better, I used 36" which is quite a bit too long and needed some extra routing to take up the additional length. Fittings are 10mm size. I put 20 deg "nod" angle fittings on both ends, with a single grommet. Preferable if the two fittings are 180 degree opposed eg hold the line horizontal, one fitting angles up the other angles down- mine were both the same direction so there is some twist in the line. 10 to 15 degree fittings would be better than 20 degree.
 
Just a followup for posterity- working on the last bug now, the bike is otherwise pretty well sorted. The issue is under some circumstances the master cylinder is not allowing pressure in the brake line to ease back into the reservoir when the brake is released- as if the piston seal cannot vent pressure back to the reservoir. I ran into something similar with my old Bandit's hydraulic clutch; due to a mod the piston couldn't retract far enough. I also found the front brakes essentially impossible to bleed without a vacuum pump, which makes me wonder if the two problems are related.

I've bought 2 rebuild kits- the parts looks the same as the originals and the problem is identical with all of them. Could I be missing a clogged small vent hole- or perhaps some other feature?


ps on edit; naturally answered my own question- there is a very small hole in a partly drilled hole just forward of the main fluid feed hole. The partially drilled hole is so you can find it... the hole is very small, and is clogged in my cylinder- that is how pressure in the brake line vents back to the reservoir when the brake lever is released. I cleared the hole with a #72 drill (.025" diam) which didn't bring any metal out, so the OEM hole is approx that diameter.
 
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ps on edit; naturally answered my own question- there is a very small hole in a partly drilled hole just forward of the main fluid feed hole. The partially drilled hole is so you can find it... the hole is very small, and is clogged in my cylinder- that is how pressure in the brake line vents back to the reservoir when the brake lever is released. I cleared the hole with a #72 drill (.025" diam) which didn't bring any metal out, so the OEM hole is approx that diameter.

That hole is what usually gets clogged by old crumbling rubber.

So it was probably good you replaced that hose.
 
Only about 2500 miles on it but a million years of storage really made a mess. It starts quite reliably now, basically the bike just needs exercise.... its a nice ride tooling around the neighborhood... very plush and mild but it moves OK.
 
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