XS850 Restoration

First topic message reminder :

Having cleaned out a corner of the shed, I've finally started the work on the XS850.  Not much progress but I've made a start.  Pics to follow.

Makes sense, I'll see if I can work out some plumbing.

I still reckon its float level or a problem with a needle and seat on one of the carbs. It's the only reason a carb vents fuel is too much fuel in the bowl

reddog wrote:I still reckon its float level or a problem with a needle and seat on one of the carbs. It's the only reason a carb vents fuel is too much fuel in the bowl

+1 That's what Scarlett was doing.

Here's hoping for a good day - I seem to have isolated the problem to the centre carb.  It is the only one leaking fuel back into the airbox.  The only other thing I'm curious about are the fuel taps.  They still let fuel out when the tank is on the bench - I thought vacuum operated cocks would not do that, ie the are supposed to fully shutoff when there is no vacuum and open when there is.  Hmm, I see some people have converted their fuel cocks to a simple open and close system with the vacuum lines blocked off.  Might investigate that once I can find (and solve) why the centre carb is misbehaving.  



The further good news is that she's purring like a kitten when running without the fuel tank on, ie sucking fuel only from the carby bowls.  That's a big improvement on how it was running before I started playing around with the carbies. 

You're into black are business with carbs.
The theory is simple...............

Ahh. You're on the home stretch now, mate. 
Pitty it's the piggy in the middle.  
It's just a matter of pulling the bowl, manually lifting the float and blowing down the fuel line. If you can keep blowing then the needle or seat is stuffed. If it seals nicely, then I would look closely at the float. 
Did you say that a carb guru fixed them for you?  
Take the middle one back to him and ask him to check his work.

agreed with @Bosco here.

Good work isolating the problem. BTW a vacuum petcock shoudl definitely shut off when the motor shuts off. Saves fuel everywhere like you have been experiencing, or worst still cylinders full of fuel

Thanks reddog. A bit further research has highlighted that leaking petcocks are a problem on these old machines. Worse, the overhaul kit I put in to the petcocks was bagged badly on the XS Tiples forum, one guy saying that although the kit's diaphragm is ok the rest of the kit's bits introduce leaks - tomorrow I'll put the old bits back in and see what happens.

Some people keep strange pets.

A bit of frustration over the past 24hrs (gotta love project bikes).  The RHS carby started leaking just when I thought the carbs were all done and dusted.  So fiddled with the float and needle and it stopped.  Then I watched the LHS carby like a hawk expecting the worst, but it behaved itself (touch wood).  Carbs done then I hope.  

The XS triples forum had some interesting commentary on the fuel taps.  It appears (a) these XS750/850 vacuum jobs all leak after a bit, (b) the overhaul kits are of varying quality and some have rubber components that swell when exposed to fuel(!) making them useless, and (c) there are several options to 'fix' this problem.  

The best option is to chuck the Yamaha taps and replace them with non-vacuum types at a cost of about $50 each.  Hmm.  Another option is to switch components from the LHS tap with those from the RHS tap, which then changes the tap settings: Prime becomes On, On becomes Off (this mod blocks the fuel feed) and Reserve remains Reserve.  Hmm.  So I did that and presto, LHS works beautifully as just stated.  But the RHS still leaked.  Much time spent trying to solve this and it looks like the tap is worn inside where the rubber o-ring seal is supposed to shut it off, meaning it never shuts off even with the mod.  So I manually blocked that feed inside the tap which stopped the leak and still had Prime working as On (as hoped).  

All of this is reversible but I can't see that I'd ever want to do that unless I replaced all of the components in the LHS tap, including the tap itself.  The comments about the originals and the comments re the poor results from overhaul kits makes me think this solution will do fine.  Any further trouble and I'll be putting non-vacuum after-market taps on - option (a).

So, she's all hooked up and still running nicely - this time without a puddle of fuel. 

Have even ordered some air filter pods since I hate the original airbox!  But, it certainly can be put back on for that original look.

Now to see about that seal on the tacho ....

For ease & peace of mind , I think I would go the after market tap ...........................as long as you can remember to turn it off of course  

Makes you wonder if there is any truth to the rumour that fuel injection was introduced to makes things simplier

Carbs are pretty simple in theory but accelerator pumps, idle circuits, pilot circuits, main circuits (all with jets) and floats all add complexity that complicate problem solving - especially if you don't have the experience to know that leaking (a) means (b) should be adjusted, varying idle means xx, etc.  No experience is not a good starting point, but having said that, no experience with fuel injection would also be daunting (and frustrating) for a newbie. At the end of the day maybe carbs are easier as there is little electronic test equipment to have to worry about and still a lot of old timers willing to help with questions on various forums.  Maybe easier for the do it yourselfer.  

It's interesting that the vacuum operated carbs were hailed as a great thing in their day - people no longer had to think about switching off their fuel taps.  So it's odd that the preferred fix is to 'go backwards' and reinstate a system that was supposedly made obsolete! Pretty ironic.  But the way I'll be going if there is any further trouble.

Cheers guys. 

Great to see that you made progress, buddy. 
Any chance of a video of the triple running?
Go on whack up a YouTube link. You know you want to. 

Yep great work. I knew it was something simple. I now have to get off my arse and get back into fixing an old ct200 in the shed so I can offload it. I just need to find a carb kit for it as it doesn't run right. Backup to the battery start to this bike is a pull start. Quite odd, but actually works well.

Bosco15 wrote:Great to see that you made progress, buddy. 
Any chance of a video of the triple running?
Go on whack up a YouTube link. You know you want to. 

I've managed to get one on my Facebook page - find friend David Steer (pic has a shot of me standing beside the Bandit).  If necessary filter on Traralgon High School and I'll be that one.  Hope that works.  

Utube - I aint gotta clue!

The filter pods arrived today, so of course I installed them.  Because the seller also sells them for the XS11 I had one left over - a spare in the spares box!

That's Horn, mate.

Took it for a run this morning. What a sweet sounds that triple cylinder engine and those pipes make under load. The only bad thing was I had no rear brake - but the run showed up a leaking piston seal so the overhaul kit for the brake cylinder has been ordered (hydraulic brakes front and rear - not bad for 1980). It may also need new pads and a caliper overhaul kit but I'll wait and see. The front brakes were strong, and no leaks. The gearbox is a bit clunky but I didn't detect any problems. It finds neutral easily so I think it is just the way it is.

It keeps me out of trouble.

For what it cost , it may be worth giving the brakes a birthday anyway ..............seeing as we always need them to work when we need them .
The clunky box may get better with regular use .Good to hear it ran well 

I bet you had a grin from ear to ear

We had a wet day here today so I spent some time in the shed, removing the XS850 rear master cylinder and disassembling it.  The remaining fluid that hadn't leaked out had gone a long way to drying up, so not only did the residual fluid look like mud, there were plenty of "snotty" lumps (of varying sizes) in the reservoir and the cylinder.  One of the lager snot blocks can be seen in this pic to the right of the circlip.  Check out more of this stuff on the end of the spring.  This is probably 34 year old brake fluid.

Makes me wonder if I should be pulling the front master cylinder down to have a look.  And both caliper cylinders.

Most excellent, Dave. When its a full goer we better get you together with the guy I was up the mountains this weekend. His current ride is an FJR1300 but he's kept a 1988 FJ1200 that he's owned since new cause he could never bring himself to sell it. The FJR is down so he brought the FJ. And his rego plates are FJ88. You two will make a splendid pair!

Ewok1958 wrote:Makes me wonder if I should be pulling the front master cylinder down to have a look.  And both caliper cylinders.

Most definitely Dave