XS 850 Re Model

[Signal]

Well today I must have had too much time on my hands and the devil put some ideas in my head.
Looking at the motor it is in a sorry state cosmetically and I think the only thing is to pull it apart blast clean it and repaint. So far so good.
Now for the Devils input:
Having made that decision I thought I might as well look at the ports in the head, so I pulled a head of a parts 750 motor to prepare for some preliminary flow testing .
While doing this out of curiosity I measured that the 750 cams and discovered that the inlet has 0.5mm lift than the exhaust. So at this stage as well as a mild clean up of the ports I will investigate using an inlet cam in the exhaust for the extra lift. Driving the tacho is no problem as I have an electronic one.

This is probably too good to be true and I have contacted someone who races an XS850 based sidecar to see what he knows about this.

And since the motor is coming apart I will need a gasket set.
Looking on Cruzin Image for a gasket set I also found a 896 cc kit , well why not throw one of those in as well I mean the motor has done quite a few K's so the stock bore is bound to be worn right ?
Oh dear there is no hope for me, in my defence no money has changed hands yet.

I dropped the seat off at the upholsterers on monday I took in some photos of the sort of look I wanted and selected some fabrics. It should be ready in 2 weeks.

Pretty much finished the number plate holder. The plate holder is huge at some time in its history the bike has been re registered and it lost its desirable black plate and now sports one of the truly gigantic Euro style bike plates that was used for a few years before moving to a smaller style.
I might see if I can get a duplicate plate in the smaller size.

The work continues...

 

[Eugene]

Looking good.
I’ve used the Cruzin Image pistons on two rebuilds, no complaints.
Why go to the max CC size. You can’t adjust the gearing so it’ll only be more torque??? Dunno.
Waste of useable bores unless your barrels are already on +4.
Here’s one to check before you go, the advance and retard pin. After rebuilding the engine I found this pushed in flush. Maybe why the PO gave up. Another kick up the butt.

 

[Eugene]

And just to make it interesting it’s a hardened steel pin. The centre punch just bounces off

 

[Signal]

The overbore is on the back burner for now pistons out of stock next batch in 6 months. I could get a XS1100 big bore kit ( same pistons) from Aussie but dont really wont to pay more than I need to.
With regard to your pin problem, try warming shaft (heat gun) and using one (or more ) of those really strong magnets to pull it out.
I have other ideas but they are a lot more drastic.
The seat is ready will pick it up tomorrow and post photo.

 

[Signal]

I have not had much shed time this week but made some progress.
I picked up the seat and I am very happy with the job the upholsterer did with the pattern sewing but not so happy with my foam shaping.
The seat looks a little high in the rear part and needs to be scalloped more in the riders part. However it will do for now until it becomes so irritating that it must be fixed or becomes acceptable.


I can now proceed to do the final shaping of the sidecovers and rear unit.
I started to measure the 750 cams I have taking measurements every 2 degrees of cam (4 degrees of crank). Then entered this data into Excel and graphed the cam profile.
I have done the exhaust and finished measuring the inlet tonight. The plan is to overlay the graphs to ensure the cams can be swapped.
I will also have to measure the 850 exhaust cam as well. If anyone has a better way of doing this I would like to know as this is the best I could dream up.

 

[Eugene]

Very busy.
From memory I think the 750 cams had slightly different profiles to the 850, maybe worth looking into.

 

[Signal]

Yes I will measure the 850 cams as well with them in situ it will be easier. It might all be for nought but the hope is a bit more lift on the exhaust by using an inlet cam.

 

[Signal]

A quick update
Over easter I spent a lot of time making a front brake line bracket. All was going well until the final fitting check showed that on full lock a line was hitting the oil cooler. Oh well back to the drawing board.
Fed up with that I decided to make some swing arm bobbins for a rear stand, as the centre stand is going to be removed. I was pleased how the ones for the GS turned out so have copied the pattern. The shock mounts are different on each side of the swingarm the brake side has a bolt, and the drive side uses a stud.

I also test fitted the carbs and had two attempts at buying a suitable fuel filter. I plan to de rust the fuel tank again but with nice new carbs I don’t want any preventable debris clogging them.
I found a guide to modifying the vacuum fuel taps to manual on a defunct XS 850 site and did the mod some time ago, the plan is to use one tap. If the tap leaks, I will spring for a Pingle and have done with it but hopefully I wont need to. Pingles are very pricy here.

I also bought a new fuse block and some flashing LEDs; the plan is to use a flashing LED in series with a single Turn pilot LED. The indicators I have are self-flashing and I thought it was silly to run a flash unit just to flash the pilot. I will use a couple of diodes to stop it back feeding.
I did a test with a normal LED in series with the pilot LED and with them in series the pilot is still bright enough.

Spent a bit of time fiddling with the tank and retesting my filler cap soldered insert. It leaked so had another go and no leaks on a second pressure test. I think it will need a small 10mm riser to enable a good cap seal and allow the paint and filler something to finish to. All of this will be an adventure to come.

 

[Eugene]

All looking good and sounding very busy.
I have removed the oil cooler, for now, and run two single lines from the front m/c down.
Where are you mounting the rear bobbins?

 

[Signal]

The bobbins will mount on the rear shock bottom mounts. Will post photos when complete.

 

[Eugene]

Pin partially removed. You can see where my carbide drill snapped and danced.
I tried the punch but as said nfg. So carbide tipped tools on the Dremmel were used. Centred as best as possible then as carefully as possibly kept on grinding using a box of tips. Only slipped a bit off centre. Went in about 5mm, made an ally pin to fit hole and stand out by 4mm.
All lined up nicely now.

 

[Signal]

The bobbins are finished and mountied.
The drive side shock mount has a stud and the brake side uses a bolt for the lower shock mounts.

For those having trouble plating in deep holes here is a photo of one idea to get it done.


Spent more time fiddling with the tank, I made a big mistake in my ignorance I used resin cored solder to solder the panel steel to the tank .
The resin allows for pin holes to form.

After much fiddling cleaning and resoldering I think I have it. Wont be making that mistake again.
Using the inclined manometer from the flow bench in the vertical position and soapy water was the best way to find the leaks. The gauge bought to test two stroke crankcases is calibrated to high.

Still progressing slowly the body work needs a lot of work still.

After that the next job will probably be to convert my compressor from electric to petrol. The electric motor struggles when running the blasting cabinets I have and cleaning the motor cases is going to be a big job.
I have the motor from the 700 paddock starter but need to get a pilot valve, I also want to quieten the compressor intake and motor exhaust.

After watching a video on an XS1100 race bike I liked look of the motor aluminium cases with black rocker, and side covers . So that is todays look, will see how the cases clean up they may be too rough and in that case will be black.

Also want to do a leak down test on the motor, and recheck the feasibility of using an XS750 inlet cam on the exhaust before I pull the motor out and down. So much to do.

 

[Eugene]

I like the bobbins. Was a bit concerned it might look like Boudicca chariot. The rear pegs conceal them nicely. I’m still lifting mine on the rear spindle and plan to use a sand bag and jack under the frame for rear wheel removal. With assistance of course . Not sure if my lift has the height to reach the shock bolts without resorting to bits of wood on the floor. Will find out when she’s off the bench.
Interested in the cam swap tho. Keep us posted.

 

[Jim]

For those having trouble plating in deep holes here is a photo of one idea to get it done.

I like that idea.