Dgoodsy's xs400 maintain/restore/build thread

[dgoodsy]

Hello everyone,
I'm new here (obviously), and new to old bikes as well, although not new to bikes entirely. I grew up with a dirtbike, and had a newer street bike for a few years as well. This week I purchased an xs400 from a friend and have been on this site many times already looking for guidance, looks like a lot of help and inspiration here! I figured I would start this thread to document modifications, fixes and ask questions.

I'm not sure what direction I'm going to with this bike yet, I like the brat look and the cafe racer look but I want a comfortable efficient bike to bomb around the city on. Whatever i end up doing i want to compromise as little comfort as i can. So for now I aim to take care of missed/unknown maintenance, have it running reliably and go from there.

My first question: what year is my bike? It was sold to me as an '83, however it is a SOHC bike I believe, and the VIN starts with 4T5. Most links I found don't list those first 3 digits of the VIN but I found one that called the bike an '81 xs400h, which I have assumed correct. Can anyone confirm or deny this?

I have done an oil/filter change and made some cable adjustments so far, nothing too serious yet. It runs very well, even with the fuel that sat in it for the last 18 months. It could use some tuning though as it has a few issues. It seems to hesitate or misfire at low throttle angles around 3500-4000rpms, but as soon as I give it slightly more throttle it clears right up. It also idles way quicker warm than cold. If I set cold idle (warm enough that it idles nice with the choke off, but not fully warmed up yet) to 800-1000rpms (haven't looked up specs on what idle should be, just set it to what the engine seems to like so far) it won't come down below 2000, maybe 2500rpms after it is fully warmed. Maybe I just need to set the idle lower and leave the choke on longer, I haven't played around too much yet.

I have parts ordered to refresh the fuse panel, I should be able to do that next week. Since the fuse holders/clips were broken or weak someone had used tiny wires wrapped around the clips to hold the fuses in better. It should be no surprise that contact was intermittent at best. Also the main fuse had been removed and the 2 wires twistd together and taped up. I have used some female spade connectors and regular blade fuses as a temporary fix.

I also adjusted the clutch cable to fix the issue with the kick starter not engaging. I assume there is a Yamaha too to adjust the screw and locking nut inside the clutch side cover, but I don't have it. I ended up having to use an electric impact wrench to loosen and tighten the nut which seemed to work good although not what Yamaha would recommend.

The bike also may have a charging issue that I hope to test next week as well.

That's all for now

edit:

here are a few pictures of the bike at work today. Not the best pics but you get the idea.

 

[BDxs400]

Hey Damen, If you haven't already noticed this site allows the members to view or download the manuals for your bike. If im not mistaken there should be a vin number call out somewhere on that page that should help with figuring out what bike you have. Also post some pictures of the puppy and I guarantee someone here will be able to help you. I would definitely change the gas, then install an inline fuel filter to help keep the carbs clean. I know from reading around here majority of performance issues is due to dirty carbs so and good carb cleaning sounds like what you need to do. Your charging problem could be from an old battery might not be up to par, if im not mistaken not sure exactly why myself the charging systems on these bikes needs a full battery to actually keep charging the system. Im sure someone will be able to help us both there. but best of luck and keep the pictures coming everyone loves something to look at.

 

[dgoodsy]

Yep I downloaded some manuals already, haven't dug into them too much yet. I have searched for vin decoding threads and found a bunch, maybe I missed one.

I noticed the bike didn't have a fuel filter and figured someone removed it, didn't realise the bike may have come without one. I got a jerry can of fresh gas for the bike. Is it recommended to run sea foam fuel treatment? Hard on anything in the carbs? I'm tempted to, just to see if it clears up the hesitation, but not if it will ruin rubber in the carbs.

As for the charging system, the battery is new as of 18 months ago. It was left in the bike outside over this past winter (maybe 2 winters?) With no trickle charger on it. It had enough juice to turn the motor over a few times, but not enough to start the bike without boosting it. I have only measured battery voltage at idle and it was 11.5, shortly after the bikes first start in 18 months. The bike died just down the street from the house later that night and wouldn't start again (I didn't try very hard, it was late) I assumed it was the ignition fuse not making good contact, but it did show signs of a very low battery. I'm wondering if the ignition box/module/igniters ( i am not familiar with the ignition system on these bikes obviously... Yet) won't operate when battery voltage drops below a certain point and that's why it died suddenly without hesitation and didn't want to start again before the battery was charged again. I put the charger on for the night and it was charged in the morning so I removed the charger but didn't start it. When I went to start it that evening it cranked quickly and started right away. I rode it a few times, and the last time it wasn't so eager to start. Charged it again overnight and it fired right up again this morning. Without having tested anything it seems like the battery is okay, just not getting charged up. I will look into it more soon and do some more conclusive testing.

As for pictures I don't have many, will try to get some decent ones up here soon. It's not a looker compared to many I've seen here!

 

[BBS360]

Stock bikes come with a fuel filter in the tank and little filter screens in the carbs. External fuel filters are aftermarket but a good idea. Easier to monitor and replace.

I normally point people to the History thread for VIN prefix checks but it doesn't list a 4T5.
There's a 4G5.

 

[dgoodsy]

Yes, the history thread i have been through. this is the only link I have found that lists a 4T5 VIN number
https://merrittmotorcyclesalvage.com/pages/yamaha-model-code-identification

edit: pictures added to the original post in this thread.

 

[BBS360]

There are some VINs that were used that don't fit the usual model codes. Seems like Canada tends to get the odd codes. Mine also has an odd VIN and even has non-standard parts for the year.

That site says it'd be an 81 H and it fits with the pictures.
It has the ape hangers so it's post-79.
The 82 SOHC had black styling so it's pre-82.
It has wire wheels, drum brake front & rear, and the non-cast pillion bar so it's a Special II (H vs SH).

 

[dgoodsy]

OK, well that's good enough for me, I will call it an'81. Thanks!

The backlights on the gauges are not functional either, found that out riding last night. I will have to figure that out soon as well.

 

[dgoodsy]

So I got the fuse box refreshed tonight. It was in rough shape so I kludged some stuff up last week just so I could ride the bike.

Kind of embarrassing to show that but it was better than when I bought the bike. The main fuse was removed and the corresponding wires were shorted and taped together! Also if you look close you can see some tiny wires used to help the fuse holders make good contact with the fuses. They didn't work very well (surprise) and I broke one of the holders trying to bend it to squeeze the fuse tighter. So I put some female spade connectors on those wires and connected them to the appropriate size spade fuse for the time being. Not pretty but it worked.

So today I took the fuse box out, removed all the wires and fuse holders and broke/dremelled anything that protruded from the floor of the box to get a nice flat floor.

I snipped off what was left of the old fuse holders, stripped some wire back and soldered to the new fuse holders I bought. I test fitted the block of fuse holders on the main fuse box several times as I cut, stripped and soldered wires to make sure wire lengths were approximately correct. I didn't get it perfect but I'm happy with it for now. I used some adhesive lined heat shrink to protect the solder lugs and to help the joints survive the bike vibrations better. (Seems like it will help in my head, time will tell if it will help or not.)

Added some machine screws to hold the new fuse holder in place. ( I used #8-32 screws because I had them handy. I had to drill out the fuse holder mount holes so the screws would fit, then grind the heads of the screws down so they wouldn't interfere with the fuses. I could have probably gone to home depot, got #6-32 machine screws and avoided those "mods")

And remounted the fuse box. It's not perfect but I will fell a lot more comfortable knowing the fuses should make good contact for a while now.


Also one fork seal started leaking quite a bit, enough to get fork oil on the tank and side cover. The seals looked dried out when I bought the bike but weren't even weeping. I have new seals ordered and on their way, hoping to get that done before the weekend. The bike is parked until I get that fixed.

 

[BBS360]

Fuse box looks good. A lot of people switch to blade type automotive fuses. Supposedly they're more reliable but with all new parts it should work well. Just make sure there's nothing that could possibly contact the bare fuse holders and short to ground.

If there's that much oil flow you might want to check the condition of the o-ring/gasket around the fork spring stopper. I need to track some down myself.
OEM part #: 1L9-23114-00-00
There's also a Honda part that appears to be the same, more common, and much cheaper. I'll post it tonight when I get home.

 

[dgoodsy]

I saw lots of people go with the blade fuses and maybe I will later, but for now I appreciate the stock appearance. I can put the fuse box cover on and you can't tell it’s modified. Also I was originally looking for a blade style fuse box but the only ones I found that I liked were too expensive, too big or required a minimum purchase of 50 or 100 wire terminals and a tool to crimp and install them which is more of an investment than I want to make right now.


If the holding strength of the fuse holders is any indication there should be no issues with inconsistent contact, I have to use a small screw driver to pry them out since I can’t do it with my fingers (which is concerning if I need to change one on the side of the road). Also these fuse holders are better protected against accidental shorting out than the factory ones now that I have the solder lugs covered with shrink wrap. They have plastic bodies around each fuse that make any shorting have to be pretty much intentional, one of the pictures above shows it fairly well.


Good to know about that o-ring, is it inside the inner tube/ fork rod, or is it the one on the top of the rod, just under the cap near the handlebars? I am not terribly familiar with the forks and their internals and I am not making a lot of sense of the partzilla part diagram. If that o-ring failed, how would it contribute to excessive leakage past the main fork seal?

 

[BBS360]

Ah. I didn't realize the cover would still fit. Maintaining the OEM appearance is nice but it can be almost impossible with blade fuse boxes.
I did manage to make a custom blade fuse box that fits but it was a fair bit of work and I'm not sure how well the soldered connections will hold up to vibration. Time will tell.

As for the o-ring, after double-checking the parts diagram the advice was premature. It's in the very top of the forks right by the handlebars.
It'd be a totally different area for leakage than what you're seeing and probably less likely to leak.
I don't think you need replacements.

 

[dgoodsy]

Yes the tops of the forks are dry and that parts diagram is making sense now. Yesterday I popped the top rubber covers off to see if I was going to have trouble removing the metal caps when I actually do the job. The caps did move against the springs below them fine, however the area between the caps and covers show corrosion, one side worse than the other. Moisture obviously has gotten underneath the covers, I hope that doesn't cause any issues getting that cap and o-ring out and back in without damage.

I have watched this video and will have it handy as I replace the seals, the jobs does seem straightforward. I am aware how "straightforward" jobs go though.

 

[BBS360]

Yeah. My forks were pretty rusty under the covers and the caps didn't move much. I dropped a little bit of rust remover in there.
Tapped them the next day with a screwdriver and hammer and got some movement. Took some careful digging to get the clips out while compressing the springs.
The o-rings I was talking about above looked to be in good condition but one got stuck on the way out and tore slightly.

Maybe put some light lubrication in there before trying to remove the springs and be more careful than I was letting the springs pop out the metal cap. Releasing the cap slowly, maybe rocking it around a bit might help.

 

[dgoodsy]

Thanks for the tips, I will be cautious. I'm hoping to hit the rust with a buffing wheel or wire wheel on a dremel before I attempt to remove the caps.

 

[BBS360]

Well I just got back from the shop in town with new o-rings. After some research online I discovered that:
1. Yamaha part # 1L9-23114-00-00 is expensive and a strange size. 19.4mm ID x 2.8mm cross section.
2. Honda part # 94608-40000 has the exact same weird dimensions.
The shop had the Honda rings. They look and feel identical and at about 2.50 CAD each they were a much better deal.

Will be putting them in this weekend.

Fingers crossed that you won't need them but I wanted to put the info up on the forum for anyone else that might need them.

 

[dgoodsy]

That's good to know, thank you!

I actually got my forks resealed and put back on the bike yesterday.

Here is what the tops of the fork tubes looked like underneath the rubber top cap.

And after I hit them with I wire wheel on the dremel:

Not perfect but I felt much better about pulling an o-ring through there while trying to minimise contamination of everything inside. It took a bunch of wiggling and rocking to get the springs to push the metal caps out of there, but eventually they came out. O-rings and caps won't back in pretty decent as well. I could have stuffed a shop rag down the tube and hit the rust with a more aggressive dremel tool and really shined them up but I didn't think of it at the time, and I wouldn't want to damage the o ring sealing surface or the retaining ring groove.

I refilled them with 15-40w motor oil and they are more firm, which is good. After seeing the oil that was in there I think I will drain this new oil and replace it soon as well. If I decide I want a thicker or thinner oil I can change it up at that point. I will also keep an eye on the top of the forks to see if the top o ring leaks and if it does I will be using the info posted above. The old o-rings did look good, but sometimes all it takes is a disturbance for a good looking used o-ring to leak.

Took the bike for a test drive last night, and rode it to work and back today and so far the new seals are doing their job!

 

[trevingray9]

I would highly recommend investing in a high quality battery. I have used antigravity brand on my bikes and absolutely love them. I have an 8 cell antigravity in my 82 xs400 right now. I know a lot of people who buy cheap batteries and have nothing but problems with them or they just last a couple months and die. Definitely worth the investment, plus the antigravity brand batteries are made in the USA which is always nice. If you are going for reliability don't skimp on your battery choice and expect your electrical system to always be ready to go.
Also real good job on that fuse box repair you did. Makes me want to spruce mine up as well!
Cheers

 

[xschris]

Forks should have 20w fork oil in them.

 

[dgoodsy]

Thanks trevingray for the antigravity battery recommendation, I had checked out their website a few days ago. I might end up going with a battery of theirs in the future but before I do I have a bit of testing to do to figure out why my battery won't keep topped up. It holds a charge fine it seems as I can charge it and it will be happy to turn over and start a week later if I don't ride it, but on the other hand if I charge it and ride it a bunch on that same day it's voltage will drop until it barely starts. Seems like a charging issue, not a battery issue so I won't replace the battery until I know it's no good.

As for the fork oil I thought I read that 30w motor oil was fine. I have read that other have put motor oil in as well and played with different viscosities based on the riders weight and preferences. I had this motor oil handy and i plan on flushing and replacing it soon anyway so I used it. I will check out the manual before I flush and replace the oil in the forks, thanks for the heads up.

 

[dgoodsy]

So the other day I had the gauge out of their pods to replace the burned out back lights. I put them back together but didn't get to ride the bike. Today I had the bike running and noticed the tach acting funny. The needle only moves very slowly now. When I Rev the bike up, I have to hold the revs for a few seconds or more before the tach needle 'catches up', and the same when I let off the throttle.

I took it apart again, the tach drive cable seemed to go into the back of the gauge fine, I looked at the drive cable while the engine was running, it seemed to spin faster and slower with the engine speed normally (although hard to really tell). Any ideas what caused this?

I had the speedometer apart as well and haven't taken it for a test drive to see of the speedometer does the same thing after putting it back together.

edit:

http://xjbikes.com/forums/threads/speedo-and-tach-dissection-with-pics.15303/

I found the above link when google searching the issue. I imagine the xs400 tach works on the same principle as the XJ series of the same era, can anyone confirm this? The unfortunate part is that it looks to me like the xs400 tachs are not easily disassembled (judging by the bezel). has anyone found a way (DIY) to take these tachs apart?

(below is assuming my tach has the same innards as the xj series tach linked in this post)

The square end of the drive cable looks fine as does the square hole that cable drives. it seems that the needle shaft must have some resistance to motion that it didn't before. The tach worked fine before I had the drive cable removed so I don't think it is a lube issue, otherwise it would have gradually made itself known. I wondered if the needle shaft bearing had some debris knocked into it when I had the gauge upside down or sideways or something. It seems infeasible this would be the cause too, I imagine all the vibration and bouncing and shaking that the tach would undergo would shake any debris loose and it would eventually find its way into a spot where it would cause trouble. So I don't know. help please?