Boxerworks.com

Gidday,

Ok so the 78 RS is now smokey

Over the last two days I have cheekily (registratation issues) gone out for 2 x 15km runs on the bike to sort of a couple of things with the speedo etc which are now fixed, cruising at 100 -120 kph but I have noticed that when I pull up to stop at the lights, intersection etc, it idles down and then stalls.. I start it up and when revved it is smoking alot of a blue/white smoke from both pipes but a little more on the left.
Over the last six months during the resto I have started it many times in the shed on the lift with the fan running and revved the engine quite a bit and no smoke was present during these shake downs.
I will list a few of the things that I have done to the bike below and could I please get some feedback or direction as to what to do next and what to look for as I am a little worried about this smoke.

• Timing, valve clearances and both carburetors set and running nicely on the bike lift.
  Fuel/air mixture set to specs for a 78
  Fuel tanks cleaned
  New fuel lines added with in line filters
  New push-rod tube seals fitted.
  I removed the heads and pistons to completed the push-rod tube seals job but the rings were left on the pistons and re-installed with a good ring compressor, the ring gaps were lined up at 120 degrees about for each one.
  I removed and rubbed away some carbon on both piston heads etc, not hard or aggressive with sandpaper...would this be cause and they just require a good long hot ride to "bed it back down again"
  Timing checked and set again after the seal job.
  Oil changed to Penrite HPR 30 20w/50w with new oil filter, o-ring etc.
  New sump gasket installed.
  I added a small cap full of mentholated spirits to the tank after cleaning.
  
  The only thing that is annoying me is that I used fuel to fill the bike from a plastic can in the shed that I have spare for the chevy, it may have been there six months

.

I followed the valve clearance procedure by the book, OT mark, feel for loose rockers etc, but just say I got things mixed up a little which I am sure I haven't but you just never know, would this cause the bike to -

• Smoke like this all of a sudden.
  The bike starts cold great and idles well, so if the valves were adjusted wrong would this happen, or would starting be hard.
  The bike pulls away well through all gears, would this happen if something was adjusted wrong.

Any info would be helpful fellas!!

How much oil did you put in it?

Gidday,

Choke lever and cables good and adjusted

Oil is right on the half way mark..

grant81rs wrote: Choke lever and cables good and adjusted .

Can you push the levers at the carb end down any further?

White/blue is usually oil I know.
However the carbs have had a bit of work lately, so worth a quick look to eliminate that reason....black usually mixture.

Gidday

Steve, no they down or out to their limit, this I checked a few times when re-installing the cables..

OK. Simple reason #1 out of the way.

#2.Is it only today that it's smoked? Not on previous rides? Not on the first ride after the top end was reinstalled? Maybe the rings have lined up? Doubt that'd do it though. The top end work was last week, and this was the second ride? Pistons and rings reinstalled dry?

I removed the heads and pistons to completed the push-rod tube seals job but the rings were left on the pistons and re-installed with a good ring compressor, the ring gaps were lined up at 120 degrees about for each one.

SteveD wrote:OK. Simple reason #1 out of the way.

#2.Is it only today that it's smoked? Not on previous rides? Not on the first ride after the top end was reinstalled? Maybe the rings have lined up? Doubt that'd do it though. The top end work was last week, and this was the second ride? Pistons and rings reinstalled dry?

I removed the heads and pistons to completed the push-rod tube seals job but the rings were left on the pistons and re-installed with a good ring compressor, the ring gaps were lined up at 120 degrees about for each one.

I only ran the bike on the lift after the heads went back on last week, with a fan in front to keep things cool, it was given a good few handfuls of throttle also during this time or 8 minutes each time, no excess smoke to be seen.

Yesterday was the first time out on the road at 120kph, for about 15kms, it didn't stall and I didn't notice any smoke but I was not looking for it either Steve.

It is only today that I have noticed the smoke and that was because it stalled at the lights when coming to a stop, I started it again while looking back around behind me for cars and noticed the smoke.. rode back home, it stalled in the driveway, I started it again and it smoked a lot for about 30 seconds..

Two prblems Grant?
1. Smoke
2. Loses power at 120kph...

With all the work done, has it had a single 20 minute ride and then had the carbs tuned whilst hot?

No

The stalling sounds more like carbs than motor. Maybe it needs a good run, then re-tune the carbs again. As the heads were off last week and the valves re-done then, the heads won't be due for re-torque for 600kms. You'll need to do the valves then anyway.

Ok

In my head, I'm still thinking along the lines of simpler things first, ie carbs, despite the white/blue smoke description. Check the diaphragms as we'd discussed, otherwise the valve guides might need a look at, though other than smoke, it should still run.

Diaphragms will get a look at this week, new ones have been ordered tonight!!

Looking at the Fault Diagnosis section in Haynes under "Poor running or lack of power at high speeds" spark plug leads and/or HT leads get a mention. Are the spark plug caps firmly on? Correct plugs? Leads look ok? Have you replaced them?[/color][/quote]

New plugs fitted from BMW supplier, leads and caps on tight but no I have not replaced the leads? can these be brought at the local Supercheap Auto Store or similar? is there a product number or general number for them??