Timing adjustment out of possible range

[FaNaTic]

I wanted to adjust the timing of my Alpina 188 (should be between 2.5 and 2.7 mm BTDC) but the adjustment range is between 4.5 mm and 13.5 mm! Do you have any idea what the possible cause of this problem is?

[feetupfun]

OK based on you posting photos showing the backing plate at both ends of it's rotational adjustment range, I suspect that you might not be approaching the task the right way. Maybe I'm off track here.

How about you say what you have tried doing so far and what the status of the points is? Are they new? Are they the existing points that worked OK earlier?

 

[lorenzo]

2.5-2.7mm. BTDC is the measurement of piston travel at which the points begin to open. First, you need to set the maximum points gap by rotating the flywheel......

How are you determining the opening position ?

[FaNaTic]

It worked before but the bike was very difficult to start (with a brand new Dellorto carb).

So I decided to check the ignition : the points gap was only 0.2 mm and the points were a bit pitted. The timing was out of capacity of my tdc tool (> 4 mm)

I've refresh the points with sand paper and try to set the timing but even at the maximum position (second picture) I still have more than 4 mm.

Just to see I settled at the other end and I get 13.5 mm (roughly with a pencil).

I determine the opening position with a multimeter (I've check once it was really the opening with a paper piece).

Do you think that new points could solve the problem? Does the timing change a lot with their wear?

Thank's for your help.

 

Edited August 23, 2023 by FaNaTic

[konrad]

39 minutes ago, FaNaTic said:

 The timing was out of capacity of my tdc tool (> 4 mm)

Some engines have required me to make an extension for my dial indicator.  All timing specifications assume that you "zero" the dial indicator when the piston reaches TDC.

[lorenzo]

It's quite possible that the fibre heel on the points has worn excessively (particularly if the cam/flywheel centre has been run dry)  ;  this can have a big effect on timing.

Cam  and fibre heel need a light smear of HMP grease to prevent this

[FaNaTic]

I just called the french Hughes Bultaco to order the points.

He told me the same thing : fibre heel worn (and don't forget to oil the felt).

I’ll tell you when it’s done.

[stevem75]

When setting timing on a Bultaco you must always set the point gap first.  It should be between .35-.45 mm or .016”. once the gap is set you can go about adjusting the actual timing by rotating the stator plate.  When looking at the stator if it is rotated clockwise that is advancing the timing.  Counter clockwise retards it.  Take your time to get it spot on.  Don’t make adjustment to the points gap to dial it in.  Use the felt wiper pad as mentioned and also use a very slight amount of dry lubricant on the points cam to help prevent the heel of the points from wearing too quickly 

steve

Edited August 26, 2023 by stevem75

[FaNaTic]

Finally, after changing the points, I managed to have the perfect setting (2.6 mm), just before the limit of the adjustment stop.

I think there were three reasons for the problem (decreasing importance):

First: wear of points and heel,

Second: did not tighten the flywheel nut before measuring the timing. I don't remember who wrote this on this forum but I thank him,

Third: my timing tool was perfectible.

Thank you all.