Boxerworks.com

Thanks Kurt. Currently mid cycle ride but will have another go when I get back this afternoon.

I'm going to prop the swingarm to make it one less task to juggle when spinning the rear wheel. The LHS exhaust pressure is significantly higher than the RHS at idle. The internet says this could be valve clearances or out of sync throttles, so be good to rule out the clearances. I've a vacuum gauge incoming.

Cheers

Ade

Ade B wrote: ↑Sat Aug 02, 2025 3:48 pm Also noticed that the fuel tank filler cap seal has broken.

I have no local parts supplier and have to get everything via mail order so when my filler cap seal fell apart I looked around for a temporary solution while I made up the next mail order. On the shelf I had large O ring 4mm in section and 48mm OD or a little less. It fitted well in the cap groove and sealed nicely. 18 years later that same O ring is still doing the job.

Thanks for reply, fuel filler seal incoming - Motorworks are doing quite nicely out of me at the moment..

So I checked the valve clearances again on both sides, propping the swing arm on an axle stand makes a big difference! Aligning the OT mark after the last valve closes revealed tolerances are bang on from yesterday's efforts.

Had a twiddle with the idle screw on both sides, closing fully and backing off. Both are around 1.25 - 1.5 turns out, tinkering with the throttle idle stop and a bit of fiddling with the cable adjustment got a consistent tickover between 900 - 1000 RPM, when warm. This was me free styling things.

The LHS is definitely pushing more pressure out of the exhaust than the RHS at idle. The LHS plug was much whiter, the RHS came out blacker and wet, not sure what read into this.. other than the LHS appears to be running leaner than the RHS - the header pipes are slightly bluer on the LHS... There is no visible smoke from either exhaust.

LHS
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RHS




Next stop is to attempt to balance the throttles... I'll read up on the correct process once the vacuum gauge arrives.

I've also new throttle cables incoming as the existing outers are past their prime where they connect to the carbs, might also bite the bullet and order new jets and needles...

Hope everyone had a good weekend.. I've not taken it out for a run this evening as I've run out of day and need to spend some time with family. Back to work tomorrow...

Cheers

Ade

Ps. Compression is 130 LHS and 135 RHS according to the vendor.
Note to self... I need to check for air leaks from the airbox to intake...

Always best to warm the bike up via a 20/60 ride before doing the carb tune.

https://bmwr65.org/htdocs/yabbfiles/Att ... by_ear.pdf


Hope that helps...check your carb numbers against the chart for the factory settings. [/color]

Thanks Steve, I've checked the numbers against the info in the Haynes and online and all checks out for the model numbers. Only the needles seemed to have a different finish (LHS looked polished like steel, RHS looked matt like aluminium, my hunch is the LHS is worn more). I need to open them up again as I foolishly didn't check the needle projection length after pulling them out 2 clicks, and I'm going to order new jets and needles anyway..

Took the carbs to bits again and replaced the following based on the Haynes and Steve's list:

• Needle jets
  Main jets
  Main jet washers
  Needles
  O-rings including aux carb
  New throttle springs
  I took off the floats and cleaned the float needle
  Cleaned the pilot jet and mixture screw
  New float bowl gaskets
  New petrol cap o-ring

Reassembled with new throttle cables and a new air filter. Set everything up as standard - needles 2 clicks (46.5-47mm projecting), pilot mixture screw out 1.25 turns, choke as extended as possible (there is still a little bit of movement beyond the closed position on the choke lever I can't seem to adjust out), 2-3mm throttle cable slack, butterfly stop screw set to just touch the butterfly mechanism.

Fired the bike up and it started fine, settled into a tickover and picks up ok. I tinkered with the pilot screw, closing off and backing out and then tweaked the throttle stop screw, all seemed fine and I could get a smooth idle at about 1000 rpm.

Blipping the throttle the engine picks up fine and will rev throughout the range on the centre stand.

I hooked up my ebay vacuum gauge... Tickover seemed balanced, I then managed to burn a hole through one of the tubes on the hot exhaust. The o-ring in the valve on the lhs vacuum gauge doesn't seem to seat properly and after repairing the hole I couldn't get any sensible readings out the thing after a run...

Head out for a run and whilst the bike will rev and isn't particularly lumpy, it is massively down on power. I got it up to an indicated 50mph (probably more like 40mph) at 2k rpm it will pull slowly upward, with larger throttle openings it will accelerate through the rev range without bogging down, but it just won't pull.

To recap. When I picked the bike up a few weeks back, I rode it from Newcastle Upon Tyne to London and it ran fine below 4000rpm.
Following a clean up and some o-ring replacements, it pulled like a train and ran fine over 4000rpm, but badly at lower rpm - I had both pilot jets incorrectly set up (one actually fell out!),

The fact it pulled well before I started to mess things up makes me think this is a fuel thing rather than an electrical thing..

Have I got the needles set incorrectly, is it now running too lean?
Is it possible to mess up the air filter install so it isn't breathing properly?

I've run out of time and we're away for a few days with the kids. I really want to get this running sweetly as Mrs Ade B has a motorcycle camping trip planned when we get back..

A few pics:

Old and new needles


Aux carb assembly, a previous owner had forced a 13mm nut on the spindle mullering the threads. The o-ring was toast and was replaced.


Old and new airfilters


Vacuum gauge with modified tube... (which may get binned) Gauge on the rhs in the pic decided to reset its needle and wouldn't allow me to move it back to the zero point with the screw adjuster, so I reset both just the read the same...


List of parts

You may have all ready done this but both gauges should initially be set off the same carburettor.

I didn't try that. Will do when I get back thanks.

From the internet it would appear I should check the coils, static timing and points clearances as well... And replace the plugs and plug leads.

Feels like trying to tune a moving piano whilst randomly replacing bits..

Back from family hols and a parcel turned up just after we unloaded the car...



Checked the RHS needle setting and confirmed I had it on the correct setting (2 stops in)

Disconnected the battery via the gearbox breather bolt, which appears in good shape and popped the front cover off.

Re-set the points gap, they had closed to the extent I couldn't see them move, I checked with a multimeter to verify they actually opened. Cleaned the points with a bit of paper soaked with contact cleaner. Static timing seemed good which I was pleased about. I replaced the springs on the advance mechanism whilst it was off the bike.

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This whole process felt far from precise scrambling around on the floor, trying to get screwdriver, 0.4mm feeler gauge, head torch and varifocals focal point in the correct relationship... I am looking at ebay bike lifts...

Gapped the new plugs and replaced the existing Denso W22EP-U with a pair of Bosch WR5DC

Put it all back together and it fired up and settled into a fast idle. Tweaked the various screws to settle things down and took it for a local run.

It appears to be running well through the rev range (as much as can be ascertained in SE London suburbia without being completely stupid..). The induction roar is quite addictive..


On returning home I hooked up the Carbtune and with the assistance of Mrs B, had a fiddle with the pilot jet, throttle stop and throttle cable settings. The RHS seems to pull more than the LHS at idle and 3000rpm no matter what I do, but it sounds ok and is responsive and doesn't rattle/shimmy like it did before. I stopped tinkering to avoid overheating, will return to this after a proper run out.

Hopefully all good for a longer run out tomorrow. Spare contact breaker and alternator brushes now live in a sealed bag under the seat.

Now need to work out how to secure the Krauser panniers with straps and load up our camping set up

Post fettle run out revealed a little hesitancy at 2000 - 2500 rpm at low urban speeds but I stopped noticing it after a few minutes and overall the bike appears to be running well.

Still plenty of things need attention but I want to actually ride the thing so off on a short trip with Mrs B, hopefully all works well.