My new projekt/bike 55 SQ 4 MK ll

[john.whiting]

a four has constant crankcase volume,so all the vapor coming from the breather is ring blowby containing about 5% water vapor.If I lived in a cold climate,I would hook up a positive ventilation to the highest point of the motor.....and so stop watery sludge from forming in the engine.If you do long runs that heat the engine beyond boiling point,its probably unnecessary.

[rschurr]

Yes agreeded,
what I also meant by that was, that the Morgo has a much larger volume flow rate and that's why there's also a higher airflow. With the mazac/zamac it was not like that under the same conditions!
Rudy

[nevhunter]

Don't know if the higher oil flow has a significant effect, What oil goes in is returned together with some excess air, in the scavenge side of the pump which is higher volume always than the supply side . Once the engine gets quite hot the water and some other volatiles will come out of the breather. Breathers are generally smaller than optimal. Modern engines circulate air using a PC Valve and clean air can come in somewhere else. This is better than the old closed system, Long trips are good for the bike. A series of short ones will contaminate the oil, and require more frequent changes, particularly in winter. Nev

[rschurr]

Luckily the last few days have been good weather, so I was able to really warm up the engine and make smaller adjustments trips, each about 8 to 10 miles. The new filter works perfect and got also really warm, I think due to the location in front of air stream there is no further need for a cooler. The SU carburetor is really great to set and the machine is now running very well with good transitions when accelerating and a stable tick over.

There was a small amount of oil comining out the timing breather, I now had installed a longer tube.

The PCV may be a next step, but then I need a hole for clean air. The location of this hole is not yet clear for me.

Cheers Rudis

P.S: Surprisingly, the front brake has worked really well for a vintage bike......

[rschurr]

Good news, bad news:

Because of the ongoing good weather, I was able to do some larger test drives.

Good:
There was no more oil on the breather tube.

Bad:
If the machine was really hot, I had the problem that misfires occurred. And once (a hill up) the machine even stopped and did not start anymore, had to wait more than 30 minutes until it was cooler, then I came luckily home.
The good old bikers textbook says: valve clearance, ignition, carburetor. So I started my investigation.
Valves checked: ok.
Replaced the coil for a test run. Not better.
Ordered a new capacitor, as the installed one was not original for the DK4.
When I opened the distributor to change the capacitor, I noticed that the connecting link between the capacitor and breaker contact was broken. So it was a sort of bimetallic effect, if the distributor was warm a gap opened here and the capacitor was without function!
I have to say that was really lucky to find that.

Since the part is backordered (as expected) at the Drags, I have soldered a piece of copper sheet, a work around until I find this part.

What else:
noticed that the machine was set very rich. Was a little bit confused as I have in the documents available to me (owner manual and workshop manual) 2 different statements for MC2 settings (3 turns vs 1 ½ turns). Mine is now running with 7 flats open (about 1 1/4 turns). Further test needed to optimize this.

Cheers Rudy

[roger.fellows]

Hi Rudy, the timing chain tensioner looks awkward as you may have noticed. Some body else will correct me maybe, that sort of spring tensioner should fit into the rectangular block near the dynamo sprocket. I would expect there to be a hole in that block and a slot to take the coiled spring. Has there been a repair there? Has somebody converted from duplex to simplex timing chain for some reason?

[rschurr]

" Has somebody converted from duplex to simplex timing chain for some reason?"

Hi Roger,
I had the same suspicion already, I think the simplex system is easier to obtain or cheaper, so some one may have installed it on the last revision.
Rudy

[roger.fellows]

I believe the part that's really difficult to get is the long solid steel tensioner as per Paul Linden's picture.

[paul.jameson]

The timing chain tensioner should have its top end sitting on that nice flat section of the crankcase below and slightly to the left of the dynamo sprocket. It might not be easy to install that way, but it works much better.

[paul_turner]

Hi Rudy
1955 your bike would have been simplex timing chain. The duplex came out late 56. the duplex gears are available from Bruce the square four spares man should you wish to convert.