timing problem

[Bill Conquest]

Hi - I've borrowed an inductive type timing light from a friend, powered it from my other vehicle,but...I can't see into the timing hole because the carb is dead in the way! Does anyone have an idea or trick to deal with this?
Thanks, Bill

[Barry]

Bill

The picture of the timing marks I posted on your previous points check thread was taken with the carbs in place. My carbs are flat tops which helps but your 79 should have flat tops too.  The only thing I've done is to make sure the carbs are pushed as far into the head rubbers as they will go. I do that because the annular gap between the head stub and the carb stub is a bad thing from a mixture point of view but it also helps a couple of mm with clearing the timing hole (at the expense of the dipstick clearance). Can't remember for sure but I might have shortened the rubbers a little if that was needed to eliminate the gap.

http://www.bmwr65.org/cgi-bin/yabb2/YaBB.pl?action=downloadfile;file=S_Mark_004.jpg

Only other thing I can suggest is try it in a darkened garage.

[montmil]

A darkened work space is very helpful in regards to seeing the flywheel's timing marks. Have you added some white paint to the flywheel's embossed timing marks? This trick alone seems to ease the degree of difficulty with the timing light chore.

Avoid closing the garage door and running the engine during engine timing! Night time is the right time. We'd like to keep you here on the forum, Bill.

[Bill Conquest]

Thanks for the picture, Barry - I have flat tops, too but for some reason mine are situated right in front of the hole..Hey Monte, i'll try the night time approach & don't worry about the closed garage door danger, the garage has been taken over by my wife as a music room & I am certainly NOT allowed in. So, i'm a tent mechanic - at least the wife can't count how many beers have left the cooler..
Bill

[Barry]

I didn't mention before that my carbs are tilted in at the top by a few degrees to give the throttle cables a straighter run but it might also help with a clearer view of the timing hole.

[Bill Conquest]

Thanks,Barry, i'll take a look at that..and I plan to shorten the rubber collar between the carb & head to gain a little room.And I guess i'll try to reach in with an artist's paint brush & put a touch of white paint on the marks. Thanks again for the ideas.
Bill

[Bob_W]

Beware of changing the carb to head rubber, it could lead to problems. I have had some very dim timing lights, so shaded work space could help. Even with dome tops, the timing plug seems easily viewable.
White paint is a good idea.
Bob

[Barry]

Bob

I agree there might be one problem that could result from shortening the carb rubbers so I ought to explain more clearly why I did it and it wasn't primarily to get good line of sight to the timing hole.

Who knows if all carb rubbers are accurately sized. If due to the length of the carb rubber there is a gap between the carb spigot and the head spigot of 1/4 "" or more that for me is a bad thing that creates some issues.

The inlet tract will have an annular gap or step which is less than ideal for smooth air flow and maximum power but I doubt this is of very great significance.

More important for me is the potential for fuel to condense and pool in the gap at idle and small throttle openings.  This will weaken the mixture while the fuel is condensing out and and then when the throttle is opened up it can cause an off idle stumble due to excessively rich mixture as the pool vapourises again. There's no question of this being an issue once up to speed but the effect is real when slow speed commuting from a cold start.

The potential down side from closing the gap is the loss of a thermal break between the cylinder head and carb but I've never seen any signs of this being a problem possibly because really good metal to metal contact is not being achieved.  

I should mention that this isn't an idea I dreamt up. I need to credit Mike Fishwick who was the Technical Advisor to the UK BMW Club. Mike closed the gap by manufacturing brass spacer rings rather than shortening the rubbers. Although I'm not seeing any problems due to loss of the thermal break perhaps the best solution would have been to make spacers from a thermal insulating material.

[jusgus]

Bill, I made a simple light with an LED that clips onto the timming hole with the LED inside the housing. My bike is a 1980, the light will not work on some bikes because there is not enough clearence. If you would like to try the light, send me your mailing address and I will give you one.

[Bill Conquest]

Hi Jusgus - That light looks like a really good idea!
Thanks, Bill