XS850 Master Thread

Hey Folks!

Proud new 81XS850H owner here. My bike is mostly complete, but not running. Presently sorting out electrical as I have voltage to the coils, but no spark & will post here with progress, etc.



In the past there were a couple sites dedicated to the xs750/850/1100 that are now defunct. Sadly, a lot of good info on these bikes was lost. As part of my learning process for this project, I've been digging up as many manuals and old docs as I can find.

Fortunately, this XJ forum is still here and these XS850s are very similar to the XJs & this forum has already proven to provide a wealth of information that has helped me with my XS850 so far... So, unless the mod's object, I'll continue to post about my XS850 project bike here.

I also re-drew the 850 wire harness so I can actually read it. PDF linked that below.
https://drive.google.com/file/d/1ltME7Haalzln_nmkipxKpJ4veYf_dRlj/view?usp=sharing

 

A recent, separate, thread covered the XS850 carb, which is the Hitach HSC34. It's a CV carb like the XJ's, just larger and also quite different.

Find more detail on the HSC34 Carb here: https://www.xjbikes.com/forums/threads/hitachi-h34c-carbs.122059/#post-687263

 

XS/XJ SERVICE BULLETIN:
There is a known issue with 1st & 2nd gears on these bikes where the gear dogs become worn and rounded.
This causes 2nd gear to pop out, especially under heavy acceleration. The issue is illustrated below.



Linked here is the full guide in PDF form:
https://drive.google.com/file/d/1GUevqs-LMGkY8Qjb7AKYthwaqQIm9WYU/view?usp=sharing

This is a repost of a guide that was hosted on XS11.com, recovered using wayback.archive.org.
All credit to the original authors.

 

The issue is with assholes doing clutchless changes.

 

Repost/Correction of broken link from above

 

xs850 Ignition coil relay mod went smoothly.
I now have really strong spark and starter cranks when even just barely touching the start button.
The coils and solenoid are now seeing battery voltage, instead of a 2-5v drop.

Prior to this mod, jumping the solenoid with a pliers always worked, but starting with the button was intermittent at best.
I could could see voltage and hear some clicking at the solenoid but it would only work & turn the starter occasionally & at random.
I cleaned and polished all the switches, connectors, etc., and still was seeing 2-5v drop depending where I was testing. along the path.
Now with this mod start button works every time and seeing battery voltage at every point in the system that is downstream of the relay.

Side note, I removed the Neutral Relay "in" wire from factory splice #2 (pictured above) and extended it all the way up to the yellow connector (pictured below), so now each component has its own dedicated full length trace back to relay pin 87.

I still need to tidy up and make the fuse arrangement permanent. Really happy with the result so far!

 

@slackard, good job! I have done something similar but simpler for my '84 Moto Guzzi California 2. Factory has the coil power going to the kill switch on the right control. A few years ago that gave up while not at home. A road side jumper got us home. Now with the relay in place it is much more reliable and runs much nicer. Funny what a good hot spark will do for you. I will have to investigate how similar your mod is to the XJ's. Thanks!

 

This is a correction of an earlier version. The 12R-01 relay is for the Neutral Safety circuit described in this bulletin

 

See above note, further correction, clarification, etc.

 

This is a revision to XS850 Service Bulletin #001 - Neutral Safety Circuit... A bunch of research, trial & error got me to this point.

12R-01 is the correct relay for the Neutral Safety circuit described in this bulletin, Yamaha part# 12R-81950-01-00.

This revision of Service Bulletin #001 now incorporates the clutch switch, which is part of this neutral safety circuit, & a corrected internal wire diagram for the 12R-01 relay itself.

Unlike the similar looking Headlight relay, this neutral safety relay's coil is energized by the R/W wire coming directly from the kill switch. In order for the coil to be grounded (and the relay switch closed) 1 or both of 2 conditions must met;
1. Neutral switch is closed (bike in neutral).
2. Clutch switch is closed (clutch lever pulled in)

If ether switch is closed, the neutral safety relay coil is grounded and the start button should work if all other wiring is in order. The diode inside the relay that connects to the Sb wire protects the relay coil from current back flow from the neutral dash light in the event the bike is in neutral (neutral switch closed) while the bike is running.

 

Repost of a corrected/broken link from above.

 

TLDR:
If there is a broken link you are looking for in this thread, keep scrolling as it has been re-posted in an updated / revised / more-accurate form, further down in this thread.

For the literate:
Heads up, clarification, etc.. I am treating this thread like a living-modern-pseudo-service-manual for the xs850 (as much for my own benefit as for the XJ/XS community at large). Above, and below, in this thread, will appear a number of broken image links. These links are INTENDED to be broken, as the original source images have been removed intentionally.

The broken links are on purpose, because, information in the broken links has been superseded, revised, or otherwise updated. This forum's tools don't give me the option to update posts >1h after submission, so by intentionally breaking the image links and reposting superseded information below, I can keep this thread reasonably tidy without also re-displaying inaccurate information as time goes on.

Enjoy!

 

A quick service note on spark plug wires and caps for the XS850..

The Coils are Yamaha part#4GR-81958-00-00 (Hitachi CM11-52A)

The Yamaha diagrams call for 2 different plug wire assemblies:
Long (qty1): 41R-82342-00-00
Short (qty2): 4X7-82341-00-00


The coil harness leads (red/white & orange wires) on my bike had all been cut, spliced and taped with electrical tape. It's a mess, adds resistance, and is definitely prone to failure. So, I got a set of what appeared to be unmolested/used coils off ebay for $35 shipped (Great deal!).

With the new coils I couldnt get any Ohm readings on any of the the 2ndary windings.. (should read 11.1kohm +/- 1.1koh, see the Coil diag graphic further up in this thread.)

Lucky for XS850 owners, the plug wires are replicable on these coils (not molded in like on the XJ). WHen i pulled the wires off and tested at the bare electrode i got good readings on each of the coils ~8kohm, so, wires and plugs shot, coils good!

Instead of searching for OE NOS plug wires for $$$, I just went to Oriley and paid 1.59 per foot of bulk 7mm copper core ignition wire (Oriley part# CC7N) (https://www.oreillyauto.com/detail/...-7mm-100-foot-primary-ignition-wire/std0/cc7n)



The OE plug caps were all pretty trashed too, & I found these caps that match the OE exactly for ~$5 ea. (NGK sku# L05EA, part#6667) (https://www.ngk.com/ngk-6667-l05ea-spark-plug-cap).




Total spend for 3 caps & 6' wire was ~$27.50 including tax, with plenty of wire to spare.

After installing the new wires and caps the 2ndary coils now all reading ~13kohm.. Maybe slightly out of the desired spec.. However after putting the new coils on the bike, my spark is visibly WAY hotter, more bright/white/blue, and girthier/fatter too... the old coils were throwing a noticeably weaker/narrow/yellow/orange spark (either bad plug wires, caps, or those spliced harness leads, or all 3).

I have yet to start or run the engine since I got the bike in Dec., she turns freely tho & has good compression. Since then I have been steadily laying groundwork for an easy start when the time comes.

 

Very exciting news.. NOS cockslap.. er... petcock, now in stock!! Part# 2G2-24500-05-00

Found this little guy NOS/NIB on a Yamaha dealer shelf in Alberta & it had probably been sitting there 40 yrs.



For parts like this, I will typically call a Yamaha dealer & ask them to search the dealer network inventory, then resort to ebay or amazon as needed.

I'm fine with an aftermarket or rebuilt component from amazon or ebay if it matches and fits and works.

In this case, the xs850 has 2 petcocks that are mirror images of each other (left and right) and the fuel/vac nipples need to point toward the engine.

No after market valve was setup as a left/right pair and hose routing would look very stupid with the nipples pointing the wrong way.

So.. although this wasn't cheap, $115USD shipped, I'm ok with it since the only other exact match, left hand valve for this bike is listed north of $200(ebay). Glad I called the dealer first!

 

Side note on the xs850 fuel valves...

There are two. Each are marked on the back with a big R or L.

Fuel Cock Assembly 1 (Right): 2G2-24500-05-00

Fuel Cock Assembly 2 (Left): 2G2-24510-05-00

 

Double side note on Yamaha Dealer pricing. Yamaha is AWESOME!

I also own & fix up an 85 BMW 535i.




Yamaha and BMW are both mASSive companies that have never been bought or sold or broken up. They have epic amounts of warehouse space, and dealer warehouse space in their networks, and have inventory that has been sitting on shelves for decades.

Bmw pricing on old inventory is insane. They sit on decades old, forgotten OE gear on dusty shelves & they refuse to sell for less than a small kingdom....I guess maybe they want to support the aftermarket bros? ¯\_(ツ)_/¯
(Those bros are def getting all my bmw cash, thats for sure!)

Yamaha wants to move inventory and will sell you NOS, OE gear at below aftermarket pricing...so yeah, Yamaha is awesome.